Raj Thesis 2003
Transcript of Raj Thesis 2003
TEST ROOM DEVELOPMENT FOR BULK MILK COOLER
By
Solanki Rajkumar D.(090370721001)
Prof. Avdhoot N. JejurkarM.E (Mechanical)Assistant Professor
A Thesis Submitted toGujarat Technological University
in Partial Fulfillment of the Requirements forthe Degree of Master of Engineering
in Thermal Engineering
June 2011
DEPARTMENT OF MECHANICAL ENGINEERINGPARUL INSTITUTE OF ENGINEERING AND TECHNOLOGY
VADODARA-391 760
i
CERTIFICATE
This is to certify that research work embodied in this thesis entitled “TEST ROOM DEVELOPMENT
FOR BULK MILK COOLER” was carried out by Mr. Solanki Rajkumar D. (090370721001) at Parul
Institute of Engineering & Technology (21) for partial fulfillment of M.E. degree to be awarded by
Gujarat Technological University. This research work has been carried out under my supervision and
is to my satisfaction.
Date:
Place:
Supervisor Principal
Prof. A. N. Jejurkar Dr. Vilin P. Parekh
Seal of Institute
ii
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COMPLIANCE CERTIFICATE
This is to certify that research work embodied in this thesis entitled “TEST ROOM
DEVELOPMENT FOR BULK MILK COOLER” was carried out by Mr.Solanki Rajkumar
D. (090370721001) at Parul Institute of Engineering & Technology (37) for partial
fulfillment of M.E. degree to be awarded by Gujarat Technological University. He has
complied with the comments given by the Mid Semester Thesis Reviewer to my satisfaction.
Date:
Place:
Guide
Solanki Rajkumar D. Prof. A. N. Jejurkar
PAPER PUBLICATION CERTIFICATE
This is to certify that research work embodied in this thesis entitled “TEST ROOM DEVELOPMENT
FOR BULK MILK COOLER”, out by Mr. Solanki Rajkumar D. (090370721001) at Parul Institute of
Engineering & Technology (37) for partial fulfillment of M.E. degree to be awarded by Gujarat
Technological University, has been accepted for publication by the Second National Conference on
Emerging Vistas of Technology in 21st Century at Parul Institute of Engineering & Technology during
4-5 December 2010.
Guide
Solanki Rajkumar D. Prof. A. N. Jejurkar
Principal
Dr. Vilin P. Parekh
Seal of Institute
iv
THESIS APPROVAL
This is to certify that research work embodied in this entitled “TEST ROOM DEVELOPMENT FOR
BULK MILK COOLER” was carried out by Mr. Solanki Rajkumar D. (090370721001) at Parul
Institute of Engineering & Technology (37) is approved for award of the degree of Thermal
Engineering by Gujarat Technological University.
Date:
Place:
Examiner(s):
( ) ( ) ( )
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DECLARATION OF ORIGINALITY
I hereby certify that I am the sole author of this thesis and that neither any part of this thesis nor the
whole of the thesis has been submitted for a degree to any other University or Institution.
I certify that, to the best of my knowledge, my thesis does not infringe upon anyone’s copyright nor
violate any proprietary rights and that any ideas, techniques, quotations, or any other material from
the work of other people included in my thesis, published or otherwise, are fully acknowledged in
accordance with the standard referencing practices.
I declare that this is a true copy of my thesis, including any final revisions, as approved by my thesis
review committee.
Date:
Place:
Solanki Rajkumar D.
(090370721001)
Verified
Supervisor
Prof. A. N. Jejurkar
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ACKNOWLEDGEMENT
First of all, I am indebted to Parul Institute of Engineering and Technology for giving me all the
utility that I needs towards the completion of this project.
With great pleasure I wish to express my deep gratitude to Prof. K. B. K. Lamba, (Head of
Department, Mechanical Engineering, Parul Institute of Engineering & Technology, Vadodara) for his
keen interest, constant encouragement and valuable guidance for this work.
I would like to express my deepest appreciation and gratitude to my project guide, Prof. A N
JEJURKAR, Professor, Mechanical Engineering Department, PIET for his guidance, patience for
giving advises and supports throughout the progress of this project.
With deep sense of honor and gratitude, we acknowledge our obligation to Mr. J. P. GOPAL,
Managing Director IDMCL, Mr. K. U. MANGLANI, General Manager IDMCL and Mr. H. R. Patel,
H. R. Manager IDMCL for their immense co-operation, valuable suggestions and encouragement for \
this project. We take precious opportunity to express our gratitude and sincere regards to Mr. Ankit
Gupta, Mr. Saurabh Vyas, Mr. Devendra Gupta, Mr. Vinay Nayak, Mr. N. H. Patel, Mr. Hemant
Kumar, Mr. Kuldeep Sishodhia, Mr. Sourabh Mishra and Mr. Ashok Nangal for their guidance, co-
operation, valuable and constant inspiration during entire period of our training. We are highly
indebted to them for their constant encouragement and able guidance during our training. We also
highly appreciate the co-operation of skilled technical staff of the plant and thank them who all helped
out in my project.
Not forget to my family members for their support, advises and motivation.
Solanki Rajkumar D.
(090370721001)
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TABLE OF CONTENTS
Sr. No. Contents Page No.
Title Page i
Certificate ii
Industrial Certificate iii
Compliance Certificate iv
Paper Publication Certificate iv
Thesis Approval v
Declaration of Originality vi
Acknowledgement vii
Table of Contents viii
List of Tables xiii
List of Figures xiv
Abstract xvi
1 Introduction 1
1.1 Introduction 1
1.2 Installation Objective Behind Bulk Milk Cooler 2
1.3 Advantage using Bulk Milk Cooler 3
1.4 Types of Bulk Milk Cooler 3
1.4.1 Open Type Bulk Milk Cooler 3
1.4.2 Closed Type Bulk Milk Cooler 4
2 Literature Survey 5
2.1 Bulk Milk Cooler 5
2.2 Performance of Bulk Milk Cooler 6
2.3 ISO 5780:1983 Test Set Up for Bulk Milk Cooler 9
2.3.1 Test Set Up for Bulk Milk Cooler 9
2.3.2 Specification for Prefabricated Wall 10
2.4 Heat Load Design 11
2.5 Variable Chiller Flow Pumping 11
2.6 Piping Design 12
2.7 HVAC Control 14
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3 Air Conditioning System 15
3.1 What is Air Conditioning 15
3.2 Air Conditioning Systems Classification 15
3.3 Central Air Conditioning Systems 15
3.3.1 Central Air Conditioning System Components 15
3.3.2 Advantage of Central Air Conditioning System 16
3.3.3 Disadvantage of Central Air Conditioning System 16
3.4 Decentralized Systems 16
3.4.1 Advantage of Decentralized Air Conditioning System 17
3.4.2 Disadvantage of Decentralized Air Conditioning System 17
3.5 Applied Psychometrics 17
3.6 Description of Terms, Process and Factors 18
3.6.1 Sensible Heat Factor 18
3.6.2 Room Sensible Heat Factor 18
3.6.3 Effective Sensible Heat Factor (ESHF) 19
3.6.4 Air Quantities using ESHF, ADP, and BF 20
4 Heat Load Calculation 21
4.1 Summer Season 23
4.1.1 Inside Design Condition 23
4.1.2 Outside Design Condition 23
4.2 Sensible Heat 23
4.2.1 Solar Heat Gain through Glass 23
4.2.2 Heat Gain through Building Structure 24
4.2.3 Transmission Heat Gain except Walls 25
4.2.4 Infiltration and Ventilation Heat 26
4.2.5 Internal Heat 27
4.3 Latent Heat 28
4.3.1 People 28
4.3.2 Outside Air 28
4.4 Outside Air Heat 29
4.5 Apparatus Dew Point and Air Quantity 29
4.6 Prediction of Heat Load 30ix
5 Chiller Plant Design 31
5.1 Chiller Basics 31
5.2 Chiller Arrangement 31
5.2.1 Parallel Chiller System 31
5.2.2 Series Chiller System 32
5.3 Piping Basis 33
5.3.1 Open Loop Piping System 33
5.3.2 Closed Loop Piping System 33
5.3.3 Reverse Return Vs Direct Return Piping 33
5.4 Types of Piping System 35
5.4.1 Two pipe system 35
5.4.2 Three Pipe System 35
5.4.3 Four Pipe System 35
5.5 Flow Calculation 36
5.6 Types of Heat Exchangers 39
5.6.1 Shell and Tube Heat Exchanger 39
5.6.2 Plate Type Heat Exchanger 43
5.7 Selection Criteria of Heat Exchanger 43
5.8 Types of Chiller Compressors 45
5.9 Centrifugal Pump 49
5.10 Flow Control System 52
5.11 Selected Equipment 54
6 Test Room Layout 55
6.1 Cooling Process 55
6.2 Heating Process 55
6.3 Bulk Milk Cooler Test 55
6.4 Bill of Quantities 57
7 Performance of Chiller Heat Exchanger 59
7.1 Heat Transfer and Pressure Drop Calculation 59
7.2 Stepwise Performance Analysis 61
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7.2.1 Required Heat Duties 61
7.2.2 Sizing of Heat Exchanger 61
7.2.3 Heat Transfer Analysis 62
7.2.4 Pressure Drop Analysis 65
7.3 Data Analysis of Thermal Heat Exchanger for Chiller Flow 67
7.3.1 Heat Transfer Trend for Chiller Flow 67
8 Bulk Milk Cooler Test 68
8.1 10KL Closed Type Bulk Milk Cooler Test 68
8.1.1 Room Temperature and Chiller Test 69
8.1.2 Bulk Milk Cooler Test 70
8.1.3 Calculation for Heat Remove from Condenser 70
8.1.4 Total Room Heat Load 71
8.2 5KL Closed Type Bulk Milk Cooler Test 72
8.2.1 Room Temperature and Chiller Result 73
8.2.2 Bulk Milk Cooler Test Result 74
8.2.3 Calculation for Heat Remove from Condenser 74
8.2.4 Total Room Heat Load 75
8.3 2KL Closed Type Bulk Milk Cooler Test 76
8.3.1 Room Temperature and Chiller Result 76
8.3.2 Bulk Milk Cooler Test Result 77
8.3.3 Calculation for Heat Remove from Condenser 77
8.3.4 Total Room Heat Load 78
9 Result and Discussion 79
9.1 10KL Bulk Milk Cooler 79
9.1.1 Compare Actual Chiller Flow and Required Chiller Flow 79
9.1.2 Average Room Temperature Trend 80
9.1.3 Predictable and Experimental Chiller Flow Trend 80
9.2 5KL Bulk Milk Cooler 81
9.1.1 Compare Actual Chiller Flow and Required Chiller Flow 81
9.1.2 Average Room Temperature Trend 82
9.1.3 Predictable and Experimental Chiller Flow Trend 82
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9.3 2KL Bulk Milk Cooler 83
9.3.1 Total Room Load and Chiller Flow Required 83
9.3.2 Compare Actual Chiller Flow and Required Chiller Flow 84
9.3.3 Average Room Temperature Trend 84
10 Conclusion 85
References 86
Appendix – A Heat Transfer Correlation for Plate Heat Exchanger 88
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LIST OF TABLES
Sr. No. Contents Page No.
2.1 Performance of Bulk Milk Cooler 7
2.2 Characteristic of Cooling Tank 8
2.3Comparison of Various Refrigerant used in 5000L Bulk Milk
Cooler8
4.1 Outside Design Temperature 23
4.2 Ventilation Standard 26
4.3 Internal Heat from Person for Various Activities 27
4.4 Load Prediction for Summer and Winter Data 30
5.1 Pipe Size for Required Flow Rate 36
5.2 Standard Steel Pipe Data 38
6.1 Bill of Quantities 58
7.1 Plate Heat Exchanger Data Sheet 59
7.2 Construction Data for Plate Heat Exchanger 60
7.3 Chiller Heat Transfer Analysis 67
8.1 Chiller and Room Temperature Test for 10KL Bulk Milk Cooler 69
8.2 10KL Bulk Milk Cooler \Test 70
8.3 Total Room Load for 10KL Bulk Milk Cooler 71
8.4 Chiller and Room Temperature Test for 5KL Bulk Milk Cooler 73
8.5 5KL Bulk Milk Cooler \Test 74
8.6 Total Room Load for 5KL Bulk Milk Cooler 75
8.7 Chiller and Room Temperature Test for 2KL Bulk Milk Cooler 76
8.8 2KL Bulk Milk Cooler \Test 77
8.9 Total Room Load for 2KL Bulk Milk Cooler 78
9.1 Compare Chiller Flow Rate for 10KL BMC 79
9.2 Compare Chiller Flow Rate for 5KL BMC 81
9.3 Compare Chiller Flow Rate for 2KL BMC 83
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LIST OF FIGURES
Sr. No. Contents Page No.
1.1 Typical Open Type Bulk Milk Cooler 3
1.2 Typical Closed Type Bulk Milk Cooler 4
2.1 Two Piping System In Chiller Arrangement 12
3.1 Sensible Heat Factor Lines 19
4.1 Top View of Test Room 22
5.1 Parallel Flow Chiller 32
5.2 Series Flow Chiller 33
5.3 Reversed Return Piping 34
5.4 Direct Returns Piping 34
5.5 Friction Loss Chart for 40 Schedule Steel Pipe 37
5.6 Counter path in shell and tube heat exchanger 40
5.7U- Tube Shell and Tube Heat Exchanger with Removable Bundle
Assembly and Cast “K” Pattern Flanged Head41
5.8U-Tube Tank Heater with Removable Bundle Assembly and Cast Bonn
Head41
5.9U-Tube Tank Suction Heater with Removable Bundle Assembly and
Cast Flanged Head41
5.10Straight-Tube Floating Tube sheet Shell-and-Tube Heat Exchanger with
Removable Bundle Assembly and Fabricated Channel Heads42
5.11 Flow Path of Gasket Plate Heat Exchanger 43
5.12 Pump Efficiency Curve 50
5.13 Pump Pressure Curve for Parallel Arrangement 51
5.14 Pump Pressure Curve for Series Arrangement 51
5.15 Three Way Bypass and Mixing Valve 52
6.1 Test Room Layout 56
7.1 Dimension View of Plate Heat Exchanger 60
8.1 10KL Bulk Milk Cooler Set Up 68
8.2 Chiller Arrangement 69
8.3 5KL Bulk Milk Cooler Set Up 72
9.1 Average Room Temperature Trend for 10KL BMC 80
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9.2 Chiller Flow Trend for 10KL 80
9.3 Average Room Temperature Trend for 5KL BMC 82
9.4 Chiller Flow Trend for 5KL 82
9.5 Average Room Temperature Trend for 2KL BMC 84
9.6 Chiller Flow Trend for 2KL 84
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ABSTRACT
Bulk milk cooling tank works as an important tool in maintaining the cold chain of milk
between the producers of it at rural area to the processing of it at main dairy plant. It provides
the cooling and holding milk at a cold temperature until it can be picked up by a milk hauler.
For this reason the bulk milk cooling tanks acts as a boon to the dairy industry. Present work
concerned to developed test facility for bulk milk cooler because of variation of ambient
condition affect the performance of bulk milk cooler. Test room is suitable for testing bulk
milk cooler up to maximum capacity under all condition specified in ISO 1983:5708 as far as
cooling test are concerned, the room temperature can be set within the range of 15°C to 50°C
with stability of 0.2°C. For this calculation of heat load and choosing cooling system element
such as evaporator, compressor, condenser for designing test room. Transmission heat,
Infiltration heat, product heat, heat of other sources and unknown and unexpected heat which
is component of heat load are calculated and designed chiller water arrangement based on
heat load calculation. Based on hot and cold water arrangement for different ambient
temperature obtained by controlling three way control valve that install in the system, three
way control valve set as per different type of bulk milk cooler equipment load and room load
for summer and winter weather data and also include one pipe arrangement for getting water
temperature set at 35˚C in bulk milk cooler and cool to 4˚C .After installation of system then
testing different type of bulk milk cooler for different ambient condition .For testing
particular bulk milk cooler set the chiller flow as per calculated design load and compare this
chiller flow with required experiment load to achieve uniform temperature of room and
dispatch the customer as per the said ambient condition. Thesis includes 10KL, 5KL and 2KL
bulk milk cooler test with maintain ambient condition.
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CHAPTER 1: INTRODUCTION
1.1 INTRODUCTION [B5]:
As per the latest Draft Codex International Code of Hygienic Practice for Milk and Milk
Products from Codex Secretariat, if the milk is not processed within two hours of milking, it
is required to be cooled to a temperature below 4oC. Bulk milk cooling tank works as an
important tool in maintaining the cold chain of milk between the producers of it at rural area
to the processing of it at main dairy plant. It provides the cooling and holding milk at a cold
temperature until it can be picked up by a milk hauler. For this reason the bulk milk cooling
tanks acts as a boon to the dairy industry. Thus, the present scenario of collection system of
milk is chilling the milk immediately after milking by Bulk Milk Cooling Tanks. The usage
of such tanks has become popular in the recent past because it not only has helped in
increasing the shelf-life of milk but also provided systematic and simple way of the
procurement of milk. Also ensures procurement of more milk by covering untapped rural
areas for milk collection, where transportation facilities are scarce by providing only one time
transportation in a day and storing the milk of another milking in it.
Bulk milk cooling unit is used to cool raw milk at the village level co-operative milk societies
from the ambient temperature to 4 degree Celsius in conformity to specified ISO standard.
The cooling tank is used for cooling the milk immediately after milking to conserve quality
of milk and check growth of micro-organisms. It is intended for daily collection of milk. It is
a hygienic container built to sanitary standards, which besides cooling also serves as buffer
storage prior to transfer of milk for onward transportation and further processing.
The agitator provided in the cooling tank works intermittently and at a very gentle speed to
avoid damage to the milk fat globules.
The best alternative to present collection system of milk is cooling of milk immediately after
milking by bulk cooling tanks. The usage of such tanks has become popular in the recent past
because it not only helps in increasing the shelf life of milk but also provides a systematic
and simple way, to ensure procurement of more milk by covering untapped areas for milk
procurement.
Refrigeration plays a very vital role in dairy industry as milk and milk products are highly
susceptible to bacteria growth in very short time. Fresh milk does not form any bacteria for 1
the first 40 minutes, after that bacterium multiplies every 20 minutes in unprocessed milk. So
the quality of collected milk is preserved by cooling it as quickly as possible to below 4 °C at
milk collection centers with the help of Milk Coolers before dispatching it daily in insulated
tanks to big plant for further processing. Production of milk in India is very widely scattered
in the rural areas and at vast distances from the places of high consumption in the urban
areas. Dairy Farming as such is not a professional occupation but part of the overall
agriculture operation. The hygienic conditions and environment of milk production in the
rural area are still not up the desired standards. High ambient temperature throughout the year
in a tropical country like India is an additional disadvantage since the bacterial growth is very
rapid if the temp of milk is not brought down immediately after the production. It is very
essential to cool the milk immediately after milking to maintain the quality of milk as final
transporting to processing plant may take 8 hours or more from the time of milking. In fact
the chilling of milk at or near the production centers is the most important factor which has
influenced the growth of milk industry. The chilling of milk to about 4 °C or less is done to
check the growth of bacteria and preserve the quality as produced, until it is subjected to
pasteurization process. This is done at collection centers using Instant Milk Chilling Units
and Bulk Milk Coolers.
A milk cooling tank as a bulk tank or milk cooler, consist of an inner and an outer tank, both
made of high quality stainless steel. For a direct expansion tank, attach to inner tank is a
system of plates and pipes through which refrigerant fluid gas flows. The refrigerant
withdrawn heat from the tanks content (milk in this case). Direct expansion milk cooling tank
come with set of condensing unit which circulate the refrigerant and convey the withdrawn
heat to air.
1.2 OBJECTIVE BEHIND BULK MILK COOLER INSTALLATION:
1. Enhance and maintain quality of milk to avoid economic losses to farmers because of
spoilage/sour age.
2. To produce quality products for export and domestic requirements.
3. To reduce cost by regulating transportation of the milk on alternative days and also
through reduction in expenditure on purchase and maintenance of cans.
4. Flexibility in milk collection time resulting in increase in volume of milk collected at
the centers.
5. Farmers to get better returns for quality of milk.
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6. Energy saving by avoiding chilling at the main dairy
1.3 ADVANTAGE USING BULK MILK COOLER:
1. Compact package unit simple to operate,
2. Power savings, almost trouble free running just like a large domestic refrigerator
3. Milk gets immediately cooled when poured progressively (Cooling Curve)
4. Only to be run during reception hours' and not a three shift operation
5. Can be easily relocated to other potential areas, being a package unit
1.4 TYPES OF BULK MILK COOLER:
1.4.1 Open Type Bulk Milk Cooler:
Figure 1.1: Typical Open Type Bulk Milk Cooler [B5]
It is available in the capacity ranges of 500L, 1000L, 2000L & 3000L, 5000L. Following are
the features of this type of cooler.
Features:
1. Available in horizontal rectangular/vertical circular configuration.
2. Designed as per ISO standards
3. Top cover is openable for direct tipping of milk.
4. Available in single phase as well as three phase electric supply.
5. Cleaning done manually with tank cleaning brush.
3
6. One agitator and one condensing unit up to capacity 1000L and two condensing units
for cap: 2000L and above.
7. Best option for small, remote societies
8. Low initial investment and operating cost
1.4.2 Closed Type Bulk Milk Cooler:
Figure 1.2: Typical Closed Type Bulk Milk Cooler [B5]
It is available in the capacity ranges of 3000L, 4000L, and 5000L. Following are the features
of this type of cooler.
Features:
1. Available in horizontal cylindrical configuration.
2. Designed as per ISO standards
3. Pump feed system for milk loading
4. Available in three phase electric supply.
5. Cleaning done using spray ball.
6. One agitator and two condensing units for all capacity.
7. Best option for large societies.
8. High initial investment and low operating cost.
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CHAPTER 2: LITERATURE SURVEY
2.1 BULK MILK COOLER [P1]:
When refrigeration first arrived (the 19th century) the equipment was initially used to cool
cans of milk, which were filled by hand milking. These cans were placed into a cooled water
bath to remove heat and keep them cool until they were able to be transported to a collection
facility. As more automated methods were developed for harvesting milk, hand milking was
replaced and, as a result, the milk can was replaced by bulk milk cooler. 'Ice banks' were the
first type of bulk milk cooler. This was a double wall vessel with evaporator coils and water
located between the walls at the bottom and sides of the tank. A small refrigeration
compressor was used to remove heat from the evaporator coils. Ice eventually builds up
around the coils, until it reaches a thickness of about three inches surrounding each pipe, and
the cooling system shuts off. When the milking operation starts, only the milk agitator and
the water circulation pump, which flows water across the ice and the steel walls of the tank,
are needed to reduce the incoming milk to a temperature below 40 degrees.
This cooling method worked well for smaller dairies, however was fairly inefficient and was
unable to meet the increasingly higher cooling demand of larger milking parlors. In the mid
1950's direct expansion refrigeration was first applied directly to the bulk milk cooler. This
type of cooling utilizes an evaporator built directly into the inner wall of the storage tank to
remove heat from the milk. Direct expansion is able to cool milk at a much faster rate than
early ice bank type coolers and is still the primary method for bulk tank cooling today on
small to medium sized operations.
Another device which has contributed significantly to milk quality is the plate heat exchanger
(PHE). This device utilizes a number of specially designed stainless steel plates with small
spaces between them. Milk is passed between every other set of plates with water being
passed between the balances of the plates to remove heat from the milk. This method of
cooling can remove large amounts of heat from the milk in a very short time, thus drastically
slowing bacteria growth and thereby improving milk quality. Ground water is the most
common source of cooling medium for this device. Dairy cows consume approximately 3
gallons of water for every gallon of milk production and prefer to drink slightly warm water
as opposed to cold ground water. For this reason, PHE's can result in drastically improved
milk quality, reduced operating costs for the dairymen by reducing the refrigeration load on
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his bulk milk cooler, and increased milk production by supplying the cows with a source of
fresh warm water.
Plate heat exchangers have also evolved as a result of the increase of dairy farm herd sizes in
the US. As a dairyman increases the size of his herd, he must also increase the capacity of his
milking parlor in order to harvest the additional milk. This increase in parlor sizes has
resulted in tremendous increases in milk throughput and cooling demand. Today's larger
farms produce milk at a rate which directs expansion refrigeration systems on bulk milk
coolers cannot cool in a timely manner. PHE's are typically utilized in this instance to rapidly
cool the milk to the desired temperature (or close to it) before it reaches the bulk milk tank.
Typically, ground water is still utilized to provide some initial cooling to bring the milk to
between 55 and 70 °F (21 °C). A second (and sometimes third) section of the PHE is added to
remove the remaining heat with a mixture of chilled pure water and propylene glycol. These
chiller systems can be made to incorporate large evaporator surface areas and high chilled
water flow rates to cool high flow rates of milk.
2.2 PERFORMANCE OF BULK MILK COOLER [P1, P2, B5]:
Direct expansion systems are the most common choice in farm milk cooling systems. In these
systems, the evaporator plates are incorporated in the lower portion of the storage tank, in
direct contact with the milk. Milk cooling takes place within the tank and one or more
agitators move the milk over the evaporator plates for cooling. The refrigerated surface area
is limited by the tank geometry and therefore, in many cases, the ability to remove heat from
the milk fast enough to meet cooling requirements with high milk loading rates is not
possible without reducing evaporator surface temperature to the point where freezing of milk
may occur. Agitating warm milk for long periods of time can also be detrimental to milk
quality. The milk cooling tank is usually not completely filled at once. A two milking tank is
designed to cool 50 % of its capacity at once, a four milking tank is designed to cool 25 % of
its capacity at once, etc. Therefore, the cooling performance depends on the number of
milking it takes to completely fill the tank, the ambient temperature and the cooling time. In
Europe, the EN standard 13732 sets different classes of cooling performance based on these
three parameters (number of milking, ambient temperatures and cooling times) as
summarized in Table. Similar classifications are given by the international standard ISO 5708
or the American standard 3A 13-10.
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1. No. of Milking Class
2. 2-milking tank designed to cool 50% of its capacity at once
4 4- milking tank designed to cool 25% of its capacity once
6 6- milking tank designed to cool 16.7% of its capacity once
2. Ambient temperature class
Class A B C
Performance temperature 38°C 32°C 25°C
Safe Operating temperature 43°C 38°C 32°C
3.Cooling time class( maximum cooling time cool any milk (35 deg to 4 deg )
Class 0 1 2 3
Time 2 hours 2.5 hours 3 hours 3.5 hours
Table 2.1 - Performance of Bulk Milk Cooler [P2]
In 2007 F. Illan, A.Viedma analyzed milk cooling tanks in this work are assumed to be class
2 B II (milking tank designed to cool 50 % of its capacity from 35 ºC to 4 ºC in 3 hours at an
ambient temperature of 32 ºC). Three different tank capacities of 1.5, 5 and 9 m3 were
studied. Both specific heat and density of milk are influenced by its fat content and
temperature. Since the milk directly comes from the cow milking machine, it can be
considered whole milk (3.5 % fat). For a temperature range between 4 and 35ºC, the specific
heat cp of whole milk can be considered constant and equal to 3890 KJ/ kg ˚k, where its
density around 1032 considered constant 1030 kg/m3 Therefore, the cooling capacity required
to cool a n-milking tank of volume V from 35 ºC to 4 ºC in 3 hours can be obtained as:
Q = (ρm v cp ΔT)/(n Δ t) =1023 *V*3890*(35-40) /(n*3*3600) (W)
Usually milk cooling tanks had its own condensing unit, which only produces the
refrigeration effect required to cool the milk stored in one tank. The cooling capacity of any
condensing unit depends on tank volume and class and it must be at least equal to (and
normally higher than) the value obtained applying equation. In this work it had been assumed
that this cooling capacity is strictly equal to the minimum. Summarizes the main
characteristics of the cooling tanks (condensing units included) analyzed in this work.
Model Volume Class Cooling Refrigerant Energy 7
capacity charges consume
1500L 1.5m^3 2B2 8.64 8.16kg 4.39kw
5000L 5m^3 2B2 28.79 19.94kg 14.64kw
9000L 9m^3 2B2 51.82 29.91kg 26.35kw
Table 2.2 - Characteristic of Cooling Tank [P2]
In 2009 hazard chilling centre Bhopal installed 5000 L bulk milk cooler It is bulk milk cooler
with direct expansion cooling system. The cooling unit of bulk cooler adequate design to cool
milk from 35˚ to 4˚ according ISO 5708 norms. The compact condensing unit is simple easy
to install comprise reliable hermetic compressor operating 0˚c evaporator and 50˚condensing
temperature (Alfa level) and charged with 14 kg of Freon 22 which is injected by the
expansion valve in evaporator. For this calculation bulk milk cooler isentropic efficiency
0.80. Compressor and motor efficiency 1.00 and cooling capacity28.64kw this value taken
from Alfa level limited (Replacing harmful refrigerant R22 in bulk milk cooler volume 2
Indian journals of science and technology).
Refrigerant M(kg/sec) P(kW) Qk (kW) R.E (kJ/kg) COP
R22 .207 10.62 39.25 138.41 2.87
R134a .232 10.77 39.40 123.60 2.66
R152a .135 10.08 38.71 212.24 2.84
R717 .028 9.99 38.52 1009.36 2.87
R143a .288 12.83 41.46 99.43 2.23
R32 135 11.41 40.04 212.08 2.51
R290 .125 11.10 39.76 236.60 2.57
Table 2.3 - Comparison of Various Refrigerants used in 5oooL Bulk Milk Cooler [P1]
2.3 TEST SETUP REQUIRED FOR BULK MILK COOLER AS PER ISO
5708:1983 [B5]:8
The test room is suitable for testing the Bulk Milk Coolers up to the maximum capacity of
5000 LPD under 2AII conditions as specified in ISO 5708: 1983, as far as the Cooling Tests
are concerned.
The room temperature can be set within the range of 15ºC to 50ºC with the stability of
±0.2ºC.
2.3.1 The Setup for Bulk Milk Cooler Consists of:
1. An Insulated Room made from Sandwich Panels measuring 4.5 M X 4.5 M X 4 M
Height.
2. A Semi-hermetic Water Chiller of nominal 35HP rating (with water cooled
condenser) or of nominal 40HP rating (if the air cooled condenser is used). The
refrigerant used is R22.
3. Hot & Cold Tank Arrangement for the chiller so that the room temperature is
maintained within ±0.2ºC and the temperature gradient around the test piece is within the
limits of ISO 5708: 1983 section 15.1.
4. A Vertical Inline Pump of Grundfos make, for circulating the water from the cold
tank to the Refrigerant to Water PHE and back.
5. A Vertical Inline Pump of Grundfos make, for circulating the conditioned water from
the hot tank to the water cooling coil located inside the air handling unit and back to the
hot tank.
6. An Air Handling Unit Assembly located at the roof of the room consisting of a blower
of adequate capacity and a water cooling coil and the heaters. The air is delivered thru
the perforated wall and is sucked from the opposite wall. This ensures uniform air
velocity and air temperature across the length, breadth and the height of the room. The
arrangement easily satisfies the temperature uniformity and maximum air velocity
requirements of ISO 5708: 1983 section 15.1.
7. PID Control System for the control of the room temperature consisting of Siemens
make Three Ways Flow Control Valve, Thyrister for modulating the room air heaters,
and a PID controller. The Heat-Cool Control is used so as to keep the running cost to the
minimum.
8. Yokogawa make Data Acquisition System and the sensors like RTD PT100 for
mapping of the air temperature around the tank under test and the condensing unit as per
9
ISO 5708: 1993 section 15.1.2 and 15.1.3, pressure and temperature sensor for the
measurement of the parameters at the evaporator inlet (ISO 5708:1983 section 19.2).
9. Sensors (Transducers) for the measurement of the electrical parameters such as the
voltage, frequency, power consumption and the integrated power for calculating the
power consumption of the bulk milk cooler on per liter basis as per ISO 5708: 1983
section 21.1.1.9. The transducers are connected to Data Acquisition System as
explained in ‘h’ above. Specified starting point such as 35 ºC or 19 ºC, consisting of the
heaters, pump and a PID Controller.
10. A Computer consol and the Data Acquisition software based on National
Instruments, USA LAB View®.
11. The setup is designed to work 24 hours a day and 7 days a week.
12. The setup is user friendly and has the provision to make all the operations from the
computer terminal.
13. A Milk (Water) Heating System, to raise the temperature of the water to the tripping
signals is indicated on the computer monitor whenever a safety device trips or a
parameter exceeds the preset limit. ISO 5708: 1983 requirements such as filling the tank
under test with the correct milk/water quantity within the prescribed time period, etc. are
out of the scope of our supply
2.3.2 Specification of Pre-Fabricated Wall:
The test room is of prefabricated type with tongue and groove joints and silicone sealant at
the joints. Given below are the specifications.
Size of the room : Length 4.5M X Breadth 4.5M X Height 4M
Insulation thickness : 80MM PUF all over, 40 ±2 kg/m3 Density.
Cladding, Inside : Galvanized & pre-coated Steel Sheets, 0.6MM thick
Cladding, Outside : Steel Sheets, 0.6MM thick, percolated galvanized
Flooring : 0.6MM thick pre-coated sheets outside, PUF insulation &
12MM Marine plywood with FRP coating. 1.5MM Stainless
Steel Sheet above.
Door : User to specify the size. Has glass viewing window, one each
for indoor and outdoor rooms. Heavy duty hinges, latches and
gaskets are provided for proper sealing.
Conditioned Air Delivery: From perforated wall.
10
Air Suction : From the opposite wall.
Illumination : 40W X 4 tubes with decorative fittings.
Floor of the room : made from heavy gage SS sheets and can withstand the loading
of 800 kg/m3.
Roof of the room ; The conditioning equipment (AHU) is strategically located
2.4 HEAT LOAD DESIGN [P2, P6, B3]:
According to carrier air conditioning company primary function of air conditioning is to
maintain human comfort or require by product or process within a space. To perform this
function equipment must be installed proper capacity. The purpose of calculating heat load is
important choosing system component such as chiller, pump, air handling unit carrier (1987)
, Aybers (1992) stated that choice of ideal cooling system requires good calculation heat load
and all source of heat must be take into consideration. According to Erol (1993) determines
all inputs of heat load would not be possible for this reason, there may be some deviation in
the heat load and focus point must be minimizing deviation. The capacity of compressor must
be enough to suck and pump cooling gas to compressor ( sava 1987). For calculating heat
load of the environment detailed construction design information used as a testing room.
Anonymous (1998).
2.5 VARIABLE FLOW CHILLER WATER PUMPING [P5, P7]:
The principal objectives of chilled water pumping system selection and design are to provide
the required cooling capacity to each load, to promote the efficient use of refrigeration
capacity in the plant, and to minimize pump energy consumption subject to whatever
budgetary constraints may apply. In the typical design process, such decisions are made on
the basis of economic calculations. Accurate energy use prediction is an essential step in the
development of the operating cost component of such analyses. Typically, flow is at a
constant flow rate or in increments such that flow through active evaporators of chillers is
constant while flows vary in proportion to the cooling load to reduce the part load energy
consumption of pumps. Primary/secondary systems with constant flow have been converted
into variable flow systems by introducing a valve into the bypass line to permit flow only
from supply to return (Avery 1998), a practice that have received universal approval from the
design community (Rishel 1998). Multiple chillers are generally connected in parallel,
although some plants employ series arrangements.
11
2.6 PIPING DESIGN: ASHARE STANDARD 90.1(2001) STATES [B1, B2]:
6.3.2.2.2: two pipe changes over system that use a common distribution system to supply
both heated and chilled water is acceptable provide all the following met system is built.
Many designers consider humidity control through reheat In October of 2000 the Trane
company is said modern two pipe arrangement is arranged for ease of balancing in almost all
area . Modern two pipe system does not vary much changes in load show up as variation in
the system delta T . In this two pipe chiller water system divide the flow of two chillers same
way two condensing unit required for particular one unit chiller and return from air handling
unit suck two unit of chiller, water is recalculated in the system
Figure 2.1 - Two Piping Systems in Chiller Arrangement [B2]
Piping materials and design have a large influence on the system pressure drop, which in turn
affects the pump work. Many of the decisions made in the piping system design will affect
the operating cost of the chiller plant every hour the plant operates for the life of the building.
When viewed from this life cycle point of view, any improvements that can lower the
operating pressure drop should be considered. Some areas to consider are pipe size, pipe
material, valve, direct return vs reverse return. Three pipe systems with a common return for
heating and cooling are not allowed. (6.3.2.2.1)
Pipe joint: According to division 15, 15060 HVAC pipe
1. Threaded joint:
12
a. Thread pipe with tapered pipe threads in accordance with ANSI B2.1. Ream threaded
ends to remove burrs. Apply pipe joint sealant (Rector Seal No. 5) or Teflon tape
suitable for the service for which the pipe is intended on the male threads at each joint.
Teflon tape shall not be used for oil services.
2. Welded Joints
a. Weld pipe joints in accordance with ASME Code for “Power Piping,” B31.1.
b. Whenever welded piping connects to equipment valves or other units needing
maintenance, servicing, or possible removal, flange the connecting joints. Match the
pressure rating of the pipe flanges with the pressure rating of the flanges on the
equipment to which the piping connects. Provide flanged pipe sections to permit removal
of equipment components.
c. Welding Process: Sizes 4 inch and smaller, use either gas welding (oxyacetylene
process) or metallic arc process; sizes above 4 inches, use metallic arc process.
d. Beveling and Welding: All pipe 2½ inches and larger may be purchased mill beveled or
shall be machine beveled on both ends before welding. On odd lengths of pipe, beveling
may be accomplished by means of the oxyacetylene cutting torch provided all paint, rust,
scale and oxide are carefully removed with hammer, chisel or file and bevel left smooth
and clean. Joints shall be prepared and welded to assure thorough fusion of alignment
and the production of a joint that shall develop the full strength of the pipe and that shall
be leak proof in service.
e. Welding Rods: The welding rod used for welding steel and wrought iron shall be
approved welding rod in accordance with ASTM Spec. A233. Electrodes of
Classifications E6012, E6013, E7014 and E7024 shall not be used.
f. Repair of Welds and Weld Defects
1) A weld is considered defective and shall be repaired if it does not meet the acceptance
standard of each applicable non-destructive examination as defined ASME/ANSI
B31.9.
2) Repairs shall be made in accordance with ASME/ANSI B31.9.
3) Brazed Joints: For copper tube and fitting joints, braze joints in accordance with the
AWS “Soldering Manual”, the Contractor’s tested Procedure Qualification Record,
ANSI B31.1 – Standard Code for Pressure Piping, “Power Piping”, and ANSI B9.1 –
Standard Safety Code for Mechanical Refrigeration.
13
4) Soldered Joints: For copper tube and fitting joints, solder joints in accordance with the
AWS “Soldering Manual” and “The Copper Handbook.” Thoroughly clean tube
surface and inside surface of the cup of the fittings, using very fine emery cloth, and
prior to making soldered joints. Wipe tube and fittings clean and apply flux. Flux shall
not be used as the sole means for cleaning tube and fitting surfaces.
2.7 HVAC CONTROL [B9]:
It was only natural that the first HVAC controllers would be pneumatic, as the engineers
probably understood fluid control. Thus mechanical engineer could use their experience with
the properties of steam and air to control the flow of heated or cooled air. There are still
pneumatic HVAC systems in operation in some buildings, such as schools and offices, which
can be a century old.
After the control of air flow and temperature was standardized, the use of electromechanical
relays in ladder logic to switch dampers became standardized. Eventually, the relays became
electronic switches, as transistors eventually could handle greater current loads. By 1985,
pneumatic control could no longer compete with this new technology.
By the year 2000, computerized controllers were common. Today, some of these controllers
can even be accessed by web browsers, which need no longer be in the same building as the
HVAC equipment. This allows some economies of scale as single operations center can
easily monitor thousands of buildings.
14
CHAPTER 3: AIR CONDITIONING SYSTEM
3.1 WHAT IS AIR CONDITIONING?
Heating ventilating and air-conditioning HVAC is one of the building mechanical services
that include plumbing, fire protection, and escalators. Air-conditioning refers to any form of
cooling, heating, ventilation or disinfection that modifies condition of air. the goal of an
HVAC system is to provide an energy efficient, cost effective, healthy and comfortable
indoor environment with acceptable indoor air quality.
3.2 AIR CONDITIONING SYSTEMS CLASSIFICATION:
Corresponding to their related equipment Air conditioning systems may be classified as:
1. Central systems.
2. Decentralized systems;
According to the method by which the final within the space cooling and heating are
attained, air conditioning systems are generally divided into four basic types:
1. All-air system when energy is transferred only by means of heated or cooled air.
2. All-water system when energy is transferred only by means of hot or chilled water.
3. Air-water system when energy is transferred by a combination of heated/cooled air and
hot/chilled water
4. Unitary refrigerant based system when energy is transferred by a refrigerant
3.3 CENTRAL AIR CONDITIONING SYSTEMS:
A central HVAC system serves one or more thermal zones and has its major components
located outside the zone or zones being served in some convenient central location in the
building or near it. District systems serving more than one building revert to central systems
at the single building level.
3.3.1 Central Air Conditioning Systems Components:
Central air conditioning systems basically consist of three major parts:
1. An air system or air handling unit (AHU), air distribution system (air ducts) and
terminals.
2. Water system – chilled water system, hot water system, condenser water system
15
3. Central plant – refrigeration (chiller) plant, boiler plant
3.3.2 Advantages of Central Air Conditioning Systems:
• Allow major equipment components to be isolated in a mechanical room (i.e. Allows
maintenance to occur with limited disruption to building functions, reduce noise and
aesthetic impacts on building occupants).
• Offer opportunities for economies of scale.
• Larger capacity refrigeration equipment is usually more efficient than smaller capacity
equipment; larger systems can utilize cooling towers that improve system efficiencies in
many climates.
• Central systems may permit building-wide load sharing resulting in reduced equipment
sizes, costs, and the ability to shift conditioning energy from one part of a building to
another.
• Central systems are amenable to centralized energy management control schemes; i.e.
reduced building energy consumption.
• A central system may be appropriate for other than climate control perspective; active
smoke control is best accomplished by a central all-air HVAC system.
3.3.3 Disadvantages of Central Air Conditioning Systems:
• As a non-distributed system, failure of any key equipment component mayaffect the
entire building.
• As system size and sophistication increase, maintenance may become more difficult and
may be available from fewer providers if specialists are needed.
• Large centralized systems tend to be less intuitive making systems analysis and
understanding more difficult
3.4 DECENTRALIZED SYSTEMS:
Decentralized systems may be divided into:
1. Individual Systems using self-contained, factory-made air conditioner to serve one or
two rooms.
2. Unitary Systems, which are similar in nature to individual systems but serve more
rooms or even more than one floor, have an air system consisting of fans, coils, filters,
ductwork and outlets (e.g. In small restaurants, small shops and small cold storage
16
rooms). The term packaged air-conditioner is sometimes used interchangeably with the
unitary air-conditioner. The air-conditioning and refrigeration institute ARI defines
unitary air-conditioners one or more factory-made assemblies that normally include an
evaporator/cooling coil and a compressor and condenser combination.
3.4.1 Advantages of Decentralized Air Conditioning Systems:
1. Serving only a single zone, decentralized HVAC systems will have only one point of
control typically a thermostat for active systems.
2. Each decentralized system generally does its own thing, without regard to the
performance or operation of other decentralized systems.
3. Decentralized systems tend to be distributed systems providing greater collective
reliability than do centralized systems
3.4.2 Disadvantages of Decentralized Air Conditioning Systems:
1. Decentralized system units cannot be easily connected together to permit centralized
energy management operations.
2. Decentralized systems can usually be centrally controlled with respect to on-off
functions through electric circuit control, but more sophisticated central control (such as
night-setback or economizer operation) is not possible.
3.5 APPLIED PSYCHOMETRICS:
The practical data to properly evaluated the heating and cooling loads They also recommend
outdoor air quantities for ventilation purpose in area where state city, or local code does not
exist
Description of various terms, process and factor –as encounter in normal air conditioning
application
Dry bulb temperature – The temperature of air is as register by an ordinary thermometer
Wet bulb Temperature – The temperature register by thermometer whose bulb is covered by
wetted wick and exposed to a current of rapidly moving air
Dew point temperature – The temperature at which condensation of moisture begins when
air is cooled
Relative humidity - Ratio of actual water vapor pressure of air to the saturate water vapor
pressure at same temperature
17
Specific humidity or moisture content – The weight of water vapor in grains or pound of
moisture per pound of dry air
Enthalpy –a thermal property indicating quantity of heat in the air above arbitrary datum in
Btu per pound of dry air. The datum for dry air is 0°F and for moisture content, 32°F water
Enthalpy deviation – Enthalpy indication above for any given condition is enthalpy of
saturation, it should be corrected by enthalpy deviation due to air not being saturated state.
Enthalpy in Btu per pound of dry air, Enthalpy deviation applied where extreme accuracy is
required on normal air conditioning system they omitted.
Specific volume – The cubic feet of the mixture per pound of dry air
Sensible heat factor – The ratio of sensible heat to total heat
Alignment circle – Locate 80F dry bulb temperature and 50% relative humidity and used in
conjunction with the sensible heat factor to plot various air condition process line
Pound of dry air – The basic for all psychometrics calculations remains constant during all
psychometrics process The dry bulb, wet bulb, dew point temperature and the relative
humidity are so related that if two properties are known, all other properties shown may then
determined. When the air is saturated dry bulb, wet bulb, and dew point temperature are all
equal.
3.6 DESCRIPTION OF TERMS, PROCESS AND FACTORS:
3.6.1 Sensible Heat Factor:
The thermal properties of air separated from latent heat & sensible heat .the term sensible
heat factor is the ratio of sensible heat to total heat, where total heat is sum of sensible heat
load and latent heat load. This ratio mat be expressed as
SHF = SH/ (SH+LH) =SH/TH
Where SHF = sensible heat factor
SH = sensible heat
LH = latent heat
TH = total heat
3.6.2 Room Sensible Heat Factor:
The room sensible heat factor is the ratio of room sensible heat the summation of room
sensible heat and room latent heat. The ratio is expressed following formula
RSHF = RSH/ (RSH+RLH) =RSH/RTH
18
The supply air to a conditioned space must have the capacity to offset simultaneously both
room sensible heat and room latent heat .The room and supply air condition to the space
may be plotted on the standard psychometrics chart and these point connect straight line ( o-
c) shown in figure 3.1 . The line represents the psychometrics process of the supply air within
condition space and is called sensible heat factor line. The slope of RSHF line illustrates the
ratio of sensible to latent load within the space and is illustrating in fig ∆hs (sensible heat)
and ∆hl (latent heat)
Figure 3.1: Sensible Heat Factor Lines [B3]
3.6.3 Effective Sensible Heat Factor (ESHF);
To relate bypass factor and apparatus dew point to the load calculation, the sensible heat
factor term developed. ESHF is interwoven with BF and ADP and thus greatly simplified the
calculation of air quantities and apparatus selection. The effective sensible heat factor is the
ratio of effective room sensible heat to effective room sensible and latent heats. Effective
room sensible heat is composed of room sensible heat plus the portion of outside air sensible
load which is considered as being bypassed unaltered through condition space. The effective
room latent heat is composed of room latent heat plus the portion of outside air latent heat
load which is considered as being bypassed unaltered through conditioned space. The ratio is
expressed in the following formula
ESHF = ERSH / (ERSH+ERLH) = ERSH/ERTH
3.6.4 Air Quantities using ESHF, ADP, and BF:
19
A simplified approach for determining the required air quantity is to use psychometrics
correlation of effective sensible heat factor apparatus dew point and bypass factor .ERSH, BF
and ADP with GDHF and RSHF, These two factor need not be calculated to determine the
required air quantities, since the use of ESHF, BF and ADP (supply temperature) result in
same air quantities. The formula for calculating air quantities’ using BF and supply
temperature
CFM = ERSH / 1.08(Trm – Tadp) (1-BF)
The air quantities simultaneously offset the room sensible and room latent loads and also
handles the total sensible and latent loads for which the conditioning apparatus is designed
including outdoor air load and supplementary loads
20
CHAPTER 4: HEAT LOAD CALCULATION
The primary function of air condition is to maintain condition that are (1) conductive to
human comfort (2) require by product or process within a space. To perform this function,
equipment of the proper capacity must be installed and control through the year. The
equipment capacity is determined by actual instantaneous peak load requirement; type of
control is determined by the conditions to be maintained during peak and partial load. An
accurate survey of load components of the space to be air conditioned is a basic requirement
for realistic estimate of heating loads. The completeness and accuracy of this survey is the
very foundation of the estimate.
21
Figure 4.1: Top View of Test Room
22
4.1 SUMMER SEASON:
4.1.1 Inside Design Condition:
For this application we have to design heat load as per inside design temperature, humidity
and equipment load for different type of bulk milk cooler.
10˚c DBT 55% RH
Equipment load 21TR Maxi 10, 000 L BMC
4TR Mini 500L BMC
Plant Size 32.31ft (9.85 m)*14.43 ft (4.40 m)*10.48 ft (3.19 m)
4.1.2 Outside Design Condition:
Maximum summer design condition are recommended for laboratories and industrial
applications where exceeding the room design conditions for even short period of time can be
determinate to a product or process. The maximum design dry bulb and wet bulb temperature
is simultaneous peak. E ach of this condition can be expected to be exceeded no more than 3
hours in a normal summer. Data for Anand at 20˚ Latitude.
SUMMER(May) WINTER(January)
DB WB RH% DB WB RH%
˚C 44 25.6 24 15.6 6.1 58
˚F 111.2 78 24 60.08 43 58
Table 4.1 - Outside Design Temperature [B6]
4.2 SENSIBLE HEAT:
4.2.1 Solar Heat Gain through Glass:
For a given application there is a no glass in the system, that area of glass is zero so give no
overall heat transfer through glass.
4.2.2 Heat Gain through Building Structure:
23
Heat gain through the exterior construction (walls and roof) is normally calculated at greatest
heat flow. It is caused by solar heat being absorbed at exterior surface and by temperature
difference between outdoor and indoor air. Both heat source are highly variable thought any
one day and therefore, result in unsteady state heat flow through the exterior construction.
This unsteady state flow is difficult to evaluate for each individual situation; however, it can
be handle heat by means of an equivalent temperature across the structure. The heat flow
through the structure may then be calculated, using the steady state heat flow equation with
equivalent temperature difference.
Q= heat flow, Btu/hr, Watt
U =transmission coefficient Btu/hr (ft^2) (˚F), Watt/m^2˚k
A = area of surface, ft^2, m^2
ΔT= equivalent temperature difference, ˚F, ˚C
Facing Area
ft2 (m2)
U
Btu/hrsqft˚F
(Watt/m^2˚K)
Temp diff
˚F(˚C)
Load
Btu/hr (Watt)
North
151.23
(14.05)
0 .4(2.27)
65(36.09) 3931.98
(1151.33)
East 0.0
South 0.0
West 0.0
North East 0.0
South East 0.0
South West 0.0
North West 0.0
Roof Sun
1. Wall
U = 0.4 Btu/hr ft2 ˚F for 9" brick =2.27 Watt/m^2˚K
= 0.2 Btu/hr ft2 ˚F for building with rigid board insulation
Total Q=3931.98 Btu/hr = 1151.33 Watt
24
4.2.3 Transmission Heat Gain except Walls:
Heat flow through the interior construction (floor, ceiling and partitions) is caused by
difference in temperature of the air on both side of structure. This temperature difference is
essentially constant thought the day and therefore, the heat flow can be determined from
steady state heat flow equation, using the actual temperature on either side.
1. Partition
For partition for 9” brick U= 1.7W/m^2k = 0.29Btu/hrft^2F
For partition for 4” brick U= 2.56 W/m^2 k = 0.45Btu/hrft^2F
For partition for masonry U= 3.97 W/m^2 k =0.69Btu/hrft^2F
2. Floor
For floor without ceiling U=3.41W/m^2 k=0.6Btu/hrft^2F
For floor with ceiling U= 2.27 W/m^2 k=0.4Btu/hrft^2F
For floor on ground U=0
A. Ceiling
B. Partition
ΔT = Outside design-inside design-5
C. Floor
Total Q=14552.17Btu/hr=4261.03 Watt
4.2.4 Infiltration and Ventilation Heat:
25
Infiltration of air and particular moisture into conditioned space is frequently a source of
sizable heat gain or loss. The quantity of infiltration air varies according to tightness of door
and window , building, velocity of air .and no of people, duration of occupancy, nature of
activity , any special concentration ,.At times, it is required to estimate the number of people
on the basis of square feet per person ,or on average traffic given by following equation.
1. Outside air:
We have to consider 1 air charges per hour infiltration in the system.
2. Ventilation standard:
Application SmokingCFM(CMH) per person CFM per sq
ft of floorRecommended Minimum
Hospital none 30(50.97) 25(42.48) .33
Office some 15(25.49) 10(16.99) -
Restaurant considerable 12(20.39) 10(16.99) -
Laboratories some 20(33.98) 15(25.49) -
Kitchen - - - 4.0
Table 4.2 - Ventilation Standard [B3]
Total Q=1007.30Btu/hr =294.95 Watt
26
4.2.5 Internal Heats:
Internal heat gain is the sensible and latent heat released within the air condition by the
occupants, light, appliance and pipe
1. People:
Heat is generated within human body by oxidation called metabolism rate. Metabolism rate
vary with person and his activity level
Q= no of people *heat rate (Btu/hr)
ActivitySensible heat
(Btu/hr)(Watt)
Latent heat
(Btu/hr)(Watt)
Total heat
(Btu/hr)(Watt)
Office work 245(71.74) 205(60.03) 450(131.77)
Standing , light work 255(74.67) 187(54.76) 442(129.43)
Heavy work 580(169.83) 870(254.75) 1450((424.58)
Athletics 716(209.65) 1075(314.77) 1791(524.42)
Table 4.3 - Internal Heat from Person for Various Activities [B3]
We have to take office work condition and there are three people work in the test facility.
2. Light: light conversion of sensible heat by conversion of electric power into light and heat
.The heat is dissipated by radiation surrounding surface by conduction and convection to
surround air
Types Heat Gain Btu/hr
Florescent Total light watt *1.25*3.4
Incandescent Total light watt*3.4
Here this which light is taken in testing room so assume 1 W/ft^2
27
3. Equipment: In the testing room equipment is bulk milk cooler , total heat released from
10kl bulk milk cooler is 21 TR heat from standard table .
4. Appliance: there is no appliance in the system
Total Q=254320.182 Btu/hr =74467.61 Watt
Room subtotal heat Q=273811.64 Btu/hr =80174.92 Watt
10% Safety Q= 27381.16 Btu/hr =8017.49 Watt
Effective room sensible heat Q= 301192.80 Btu/hr= 88192.41 Watt
4.3 LATENT HEAT
4.3.1 People:
Heat is generated within human body by oxidation called metabolism rate. Metabolism rate
vary with person and his activity level.
4.3.2 Outside Air:
Outside heat that bypasses the cooling coil contain moisture give latent heat and this outside
air is calculated from infiltration and ventilation.
Total Q=1296.89Btu/hr =379.74 Watt
5%Safety Q=64.85 Btu/hr =18.99 Watt
Effective room latent heat Q=1361.73Btu/hr=398.73 Watt
4.4 OUTSIDE AIR HEAT:
28
Outside heat is total of outside sensible heat and outside latent heat can be determined by
GRAND TOTAL HEAT= SENSIBLE HEAT+ LATENT HEAT+ OASH+ OALH
GTH Q =314942.005 Btu/hr
=26.24TR
=92.22 kW
4.5 APPRATUS DEW POINT AND AIR QUANTITY:
4.6 PREDICTION ANALYSIS OF HEAT LOAD FOR SUMMER AND WINTER WEATHER DATA WITH
DIFFERENT CAPACITY OF BULK MILK COOLER:
Capacity of
cooler(KL)
Maximum
equipment
load (TR)
Room load (TR) Total load (TR) Chiller flow rate
required (l/s)
Summer Winter Summer Winter Summer Winter
10 21 5.25 2.7 26.25 23.7 4.96 4.48
5 11.5 5.25 2.7 16.75 14.2 3.17 2.68
3 6.5 5.25 2.7 11.75 9.2 2.22 1.74
2 4.5 5.25 2.7 9.75 7.2 1.84 1.36
Table 4.4 - Load Predictions for Summer and Winter Data
29
CHAPTER 5: CHILLER PLANT DESIGN
5.1 CHILLER BASICS:
The chiller can be water-cooled, air-cooled or evaporative cooled. The compressor types
typically are reciprocating, scroll, screw or centrifugal. The evaporator can be remote from
the condensing section on air-cooled units. This has the advantage of allowing the chilled
water loop to remain inside the building envelope when using an outdoor chiller. The chilled
water flows through the evaporator of the chiller. The evaporator is a heat exchanger where
the chilled water gives up its sensible heat (the water temperature drops) and transfers the
heat to the refrigerant as latent energy (the refrigerant evaporates or boils).
5.2 CHILLER ARRANGEMENT:
To provide some redundancy in the HVAC design, most designers will require two or more
chillers. Multiple chillers also offer the opportunity to improve on overall system part load
performance and reduce energy consumption. Parallel chiller plants are straightforward to
design and are easily modified for variable primary flow.
5.2.1 Parallel Chiller System:
Figurer shows a parallel water-cooled chiller plant. Chilled water is circulated by the chilled
water or primary pump through both chillers to the load and back to the chillers. The chilled
water loop can be either constant flow or variable flow. Variable flow systems increase the
complexity but offer significant pump work savings. They also resolve the issue about chiller
sequencing that occurs with parallel chillers, constant flow. Variable flow systems are
covered in Primary/Secondary Systems and Variable Primary Flow Design. A condenser loop
is required for water-cooled chillers. This includes a condenser pump, piping and a cooling
tower or closed circuit cooler. The condenser loop operates whenever the chillers operate.
Pumps can be constant or variable flow. The chilled water pump is sized for the design flow
rate. Figure shows one main chilled water pump providing flow to both chillers. An
alternative method is to have two smaller pumps serving dedicated chillers. Another
possibility is to lower the operating chiller’s set point to offset the mixed water temperature.
This also works but has some difficulties. Lowering the chilled water set point requires the
chiller to work harder, lowering its efficiency.
30
Figure 5.1: Parallel Flow Chillers [B3]
5.2.2 Series Chiller System:
Series chillers are another method of operating more than one chiller in a plant. This design
concept resolves the mixed flow issues found in parallel chiller designs. The chillers can be
preferentially loaded as well, allowing the designer to optimize chiller performance. Series
chiller systems are straightforward to design and operate. The flow rate through each chiller
is the entire system flow, that is, double the individual flow rate of the parallel chillers (two
chillers). This means that the chiller evaporator must accommodate the doubled water
quantity. All things being equal, this result in fewer water passes and decreased chiller
efficiency. However, this efficiency loss is more than offset by increased chiller efficiency
because the upstream chiller operates at warmer temperatures. Also, pressure losses are
additive when the chillers are piped in series. This may increase total system pressure loss
significantly. Another problem in series chiller is break down of on chiller may stop total
system operation.
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Figure 5.2: Series Flow Chiller [B3]
5.3 PIPING BASIS:
5.3.1 Open Loop Piping System:
In open loop piping system water flow through the heat exchanger and exposed to
atmosphere such as cooling tower and air washer.
5.3.2 Closed Loop Piping System:
In closed loop piping system water flow is not exposed to atmosphere at any point but some
time contain a expansion tank that is open to the atmosphere but water area exposed is
insignificant such as chilled water system.
5.3.3 Reverse Return Vs Direct Return Piping:
Reverse return piping is designed such that the path through any load is the same length and
therefore has approximately the same fluid pressure drop. Reverse return piping is inherently
self balancing. It also requires more piping and consequently is more expensive.
32
Figure 5.3 - Reversed Return Piping [B3]
Direct return piping results in the load closest to the chiller plant having the shortest path and
therefore the lowest fluid pressure drop. Depending on the piping design, the difference in
pressure drops between a load near the chiller plant and a load at the end of the piping run
can be substantial. Balancing valves will be required. The advantage of direct return piping is
the cost savings of less piping.
Figure 5.4 - Direct Returns Piping [B3]
5.4 TYPES OF PIPING SYSTEM:
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5.4.1 Two pipe system:
This system is composed central water cooling and heating equipment, pump, distributed
piping system and terminal control. Each terminal connected single supply and single return.
Heating and cooling required according to two pipe change over system. When designing a
system the flow and temperature for the system first calculated. The change over system
design such that high temperature water is not damage evaporator and low temperature
chilled water not damage boiler.
5.4.2 Three Pipe System:
In three pipes system there is two supplies separate for hot and cold arrangement and
common return system. Three way valves are for control supply temperature as per
application required and modulating flow. Three pipe systems many were proved there is
common return hot and cold arrangement will excessive waste energy.
5.4.3 Four Pipe System:
In the four-pipe common load system, load devices are used for both heating and cooling as
in the two-pipe system. The four-pipe common load system differs from the two-pipe system
in that both heating and cooling are available to each load device, and the changeover from
one mode to the other takes place at each individual load device, or grouping of load devices,
rather than at the source. Thus, some of the load systems can be in the cooling mode while
others are in the heating mode. There is a two different pumping system is required for two
different two pipe system. Although many of these systems have been installed, many have
not performed successfully due to problems in implementing the design concepts and high
costly for given system. Another disadvantage of this system is that the loads have no
individual capacity control as far as the water system is concerned. That is, each valve must
be positioned to either full heating or full cooling with no control in between.
5.5 FLOW CALCULATION:
34
For water chilling system flow required to cool sensible heat and latent heat of load (total
load in the system) is calculated by following equation
W = 88.23 GPM=5.56l/s
Select the flow required in the system is 90 GPM =5.67 l/s
For a system we use two pipe arrangement systems so that flow is divided in equal part into
two different chiller that required 45 GPM (2.83 l/s)/45 GPM (2.83 l/s) in two pipe
changeover system.
Recommended pipe size according to calculated flow required in the system
Design water quantity
GPM (l/s)
Required pipe
nominal size (in)
240(15.12) 4
227(14.30) 4
214(13.48) 4
160(10.08) 3
142(08.95) 3
060(03.78) 2
040(02.52) 2
Table 5.1 - Pipe Size for Required Flow Rate [B3]
Form chart calculate friction loss feet /100 feet using 40 schedule steel pipe 2 in and 45 GPM
water flow 3.6 feet /100 feet of water as limit of ASHARE recommended friction loss rate 1
to 4 feet/100 feet chilled water system. Most of system is design 2.5 feet/100feet friction loss
wand velocity from graph 5.2ft/s. this is within the limit of so system selected pipe size is ok.
35
Figure 5.5: Friction Loss Chart for 40 Schedule Steel Pipe [B3]
36
For a Standard Data for Steel Pipe
U.S
Nominal
size (in)
Nominal
size in
mm
Schedule Wall
thickness
t, mm
Inside
diameter
d, mm
Surface
area
m2/m
Working
pressure kPa
(gauge)
1/4 8 40ST 2.24 9.25 0.029 1296
80XS 3.20 7.67 0.024 6006
3/8 10 40ST 2.31 12.52 0.054 1400
80XS 3.20 10.74 0.054 5654
1/2 15 40ST 2.77 15.80 0.050 1476
80XS 3.73 13.87 0.044 5192
1 25 40ST 3.38 26.64 0.084 1558
80XS 4.55 24.31 0.076 4427
2 50 40ST 3.91 52.50 0.165 1586
80XS 5.54 49.25 0.155 3799
Table 5.2 - Standard Steel Pipe Data [B2]
Pressure Calculation:
For a centrifugal pump 25 mwc pressure required in the system is given by following
equation
Head (ft) = Pressure (psi)*2.31/specific gravity
Newtonian liquids have specific gravities typically ranging from 0.5 (light, like light
hydrocarbons) to 1.8 (heavy, like concentrated sulfuric acid). Water is a benchmark, having a
specific gravity of 1.0.
Head (ft) = Pressure (psi)*2.31/specific gravity
82 =P*2.31/1.0
P=2.45 bar
5.6 TYPE OF HEAT EXCHANGERS:
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Most heat exchangers for HVAC&R applications are counter flow shell-and-tube or plate
units. While both types physically separate the fluids transferring heat, their construction is
very different, and each has unique application and performance qualities.
5.6.1 Shell and Tube Heat Exchanger:
Figure 5.6 shows the counter flow path of a shell-and-tube heat exchanger. The fluid at
temperature T1 enters one end of the shell, flows outside the tubes and inside the shell, and
exits at the other end at temperature T2. The other fluid flows inside the tubes, entering one
end at temperature t1 and exiting at the opposite end at temperature t2. In a shell-and-tube
heat exchanger, a tube bundle assembly is welded or bolted inside a tubular shell. The bundle
is constructed of metal tubes mechanically rolled or welded at one (U-tube) or both ends
(straight-tube) into tube sheet(s) that function as headers. The shell is usually a length of pipe
that has inlet and outlet connections located along one or more of its longitudinal centerlines.
The shell is flanged at one or both open ends to accommodate a head assembly. The tube
bundle is positioned between the shell and head assemblies such that the tube wall of the
bundle mechanically separates the two flow paths. The tube bundle is assembled with tube
supports, which are held together with tie rods and spacers. Units with liquid on the shell side
have baffles for tube supports that direct the flow. Condensers must have baffles that have
been notched on the bottom to allow the liquid condensate to flow freely to the exit nozzle.
The head assembly directs the other fluid across the tube sheet(s) into and out of the tube
bundle. Head assemblies are designed with pass partitions to isolate sections of the tube
bundle such that the fluid must traverse the length of the unit one, two, four or more times
before exiting. One of two types of head assemblies is mechanically attached to the shell.
Units with multiple tube-side pass construction have a head with both an inlet and outlet
connection bolted at one end with a welded cap (U-tube) or bolted reversing head (straight-
tube) at the opposite shell end. Single-pass units have an inlet head attached atone shell end
and an outlet head attached at the other end. Many variations of the shell-and-tube design are
available, some of which are described in the following paragraphs. U- Tube. Figure 5.7
shows a U-tube removable-bundle shell and-tube heat exchanger. These units are commonly
called converters. Illustrate modifications of the U-tube design. Tank heaters are U-tube heat
exchangers with the shell replaced by a mounting collar, which is welded to a tank. A hot
fluid or steam flows inside the tubes heating the fluid in the tank by natural convection. The
tank heater manufacturer should be consulted about optimizing the bundle length. While it is
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desirable for the bundle to significantly extend into the tank the designer must consider the
need for additional bundle support. Tank suction heaters differ from tank heaters because
they have an additional opening that permits the fluid being heated to be pumped across the
outside tube wall resulting in improved thermal performance. Figure 5.10 shows two
common designs of straight-tube, shell-and-tube exchangers, one with a fixed and the other
with a removable tube bundle assembly .Some straight-tube, shell-and-tube heat exchangers
have a floating head bolted with a gasket to a floating tube sheet or a shell-side expansion
joint. This configuration is expensive and is rarely specified in HVAC applications. The tubes
in this heat exchanger are coiled in a helical configuration around a small core. A spacer is
placed between the tube layers. In some designs the tubes have an oval cross section. These
heat exchangers are very compact and have a relatively large surface area for their size.
Figure 5.6: Counter Path in Shell and Tube Heat Exchanger [B2]
39
Figure 5.7: U- Tube Shell and Tube Heat Exchanger with Removable Bundle Assembly
and Cast “K” Pattern Flanged Head [B2]
Figure 5.8: U-Tube Tank Heater with Removable Bundle Assembly and Cast Bonn
Head [B2]
Figure 5.9: U-Tube Tank Suction Heater with Removable Bundle Assembly and Cast
Flanged Head [B2]
Figure 5.10: Straight-Tube Floating Tube sheet Shell-and-Tube Heat Exchanger with
Removable Bundle Assembly and Fabricated Channel Heads [B2]
5.6.2 Plate Type Heat Exchanger:
Plate heat exchangers consist of metal plate pairs arranged to provide separate flow paths
(channels) for two fluids. Heat transfer occurs across the plate walls. The exchangers have
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multiple channels in series that are mounted on a frame and clamped together. The
rectangular plates have an opening or port at each corner. When assembled the plates are
sealed such that the ports provide manifolds to distribute fluids through the separate flow
paths. Illustrates the flow paths the multiple plates, called a plate pack, are supported by a
carrying bar and contained by pressure plates at each end. The design of the carrying bars and
pressure plate permit the units to be opened for maintenance or the addition or removal of
plate pairs. The adjoining plates are gasket, welded, or brazed together.
Gasket plate heat exchangers are typically limited to design pressures of 2 MPa. The type of
gasket material used limits the operating temperature. Brazed plate units are designed for
pressures up to 3 MPa and temperatures up to 260°C.
The most common plate heat exchanger is the gasket plate unit. Typically, nitride butyl
rubber (NBR) gaskets are used in applications up to 110°C. Ethylene-propylene terpolymer
(EPDM) gaskets are available for temperatures up to 160°C. The gaskets are glued or clipped
onto the plates. The gasket pattern on each plate creates the counter flow paths illustrated in
Figure 5.11: Flow Path of Gasket Plate Heat Exchanger [B2]
5.7 SELECTION CRITERIA OF HEAT EXCHANGER:
Selection of heat exchanger depend upon list of parameter as mentioned below
41
5.7.1 Thermal Performance:
The thermal performance of a heat exchanger is a function of the size and geometry of the
heat transfer surface area. Different heat transfer surface materials also affect performance—
copper has a higher coefficient of heat transfer than stainless steel.
Flow rates (velocity), viscosity, and thermal conductivity of the fluids are significant factors
in determining the overall heat transfer coefficient U. In addition, the fluid to be heated
should be on the tube side because the overall U of a shell-and-tube unit is often reduced if
the fluid to be heated is on the shell side. Properly selected shell-and-tube heat exchangers
use tube pass options and shell-side baffle spacing to maximize velocity (turbulence) without
causing tube erosion. The ability to maximize velocity on each side of a heat exchanger is
particularly important when the flow rates of the two fluids are dissimilar. However, fluid
velocity in shell-and-tube heat exchanger is limited to avoid tube erosion. U-tube exchangers
have lower tube-side velocity limits than straight-tube units due to the thinner tube wall in the
U bends.
Plate heat exchangers typically have U-factors 3 to 5 times higher than shell-and-tube heat
exchangers. The high turbulence created by the corrugated plate design increases convection
and increases the U-factor. The plate design achieves a large temperature cross at a 1 K
approach because of the counter flow fluid path and high U-factor.
5.7.2 Pressure Drop:
Fluid velocity and normal limitations on tube length tend to result in relatively low pressure
drops in shell-and tube heat exchangers. Plate units tend to have larger pressure drops unless
the velocity is limited. Often a pressure drop limitation rather than a thermal performance
requirement determines the surface area in a plate unit.
5.7.3 Fouling:
Often excess surface area is specified to allow for scale accumulation on heat transfer
surfaces without a significant reduction of performance. This fouling factor or allowance is
applied when sizing the unit. Fouling allowance is better specified as a percentage of excess
area rather than as a resistance to heat transfer. Shell-and-tube exchangers with properly sized
tubes can handle suspended solids better than plate units with narrow flow channels. The high
fluid velocity and turbulence in plate exchangers make them less susceptible to fouling. The
42
addition of surface area (tube length) to a shell-and-tube exchanger does not affect fluid
velocity, and, therefore, has little. This characteristic makes a fouling allowance practical.
This is not the case in plate units. The number of parallel flow channels determines velocity
in a plate heat exchanger. This means that as plate pairs are added to meet a load (heat
transfer surface area) requirement, the number of channels increases and results in decreased
fluid velocity. This lower velocity reduces performance and requires additional plate pairs,
which further reduces performance.
5.7.4 Cost:
On applications with temperature crosses and close approaches, plate heat exchangers usually
have the lowest initial cost. Wide temperature approaches often favor shell-and-tube units. If
the application requires stainless steel, the plate unit may be more economical.
5.7.5 Serviceability:
Shell-and-tube heat exchangers have different degrees of serviceability. The type of header
used facilitates access to the inside of the tubes. The heads illustrated in figure 5.7, 5.9, and
5.10 can be easily removed without special pipe arrangements. The tube bundles in all of the
shell-and-tube units illustrated, except the fixed-tube sheet unit (figure 5.10), can be replaced
after the head is removed if they are piped with proper clearance. The diameter and
configuration of the tubes are significant factors in whether the inside of the tubes of straight-
tube units can be mechanically cleaned. Figure 5.11 shows a type of head that permits
cleaning or inspection of the inside of tubes after the channel cover is removed.
Plate heat exchangers can be serviced by sliding the movable pressure plate back along the
carrying bars. Individual plates can be removed for cleaning, regasketing, or replacement.
Plate pairs can be added for additional capacity. Complete replacement plate packs can be
installed.
5.7.6 Space Requirements:
Cost-effective and efficient shell-and-tube heat exchangers have small diameter, long tubes.
This configuration often challenges the designer when allocating the space required for
service and maintenance. For this reason, many shell-and-tube selections have large
diameters and short lengths. While this selection performs well, it often costs more than a
43
smaller diameter unit with equal surface area. Caution should be taken to provide adequate
maintenance clearance around heat exchangers. In the case of shell-and-tube units, space
should be left clear so the tube bundle can be removed. Plate heat exchangers tend to provide
the most compact design in terms of surface area for a given space.
5.7.7 Steam:
Most HVAC applications using steam are designed with shell and-tube units. Plate heat
exchangers are used in specialized industrial and food processes with steam.
5.8 TYPES OF CHILLER COMPRESSORS:
Most cooling systems, from residential air conditioners to large commercial and industrial
chillers, employ the refrigeration process known as the vapor compression cycle. At the heart
of the vapor compression cycle is the mechanical compressor. Its function is: 1) to pump
refrigerant through the cooling system and 2) to compress gaseous refrigerant in the system
so that it can be condensed to liquid and absorb heat from the air or water that is being cooled
or chilled.
5.8.1 Reciprocating Compressors:
Reciprocating compressors are positive displacement machines that use the reciprocating
action of a piston inside a cylinder to compress refrigerant. As the piston moves downward, a
vacuum is created inside the cylinder. Because the pressure above the intake valve is greater
than the pressure below it, the intake valve is forced open and refrigerant is sucked into the
cylinder. After the piston reaches its bottom position it begins to move upward. The intake
valve closes, trapping the refrigerant inside the cylinder. As the piston continues to move
upward it compresses the refrigerant, increasing its pressure. At a certain point the pressure
exerted by the refrigerant forces the exhaust valve to open and the compressed refrigerant
flows out of the cylinder. Once the piston reaches it top-most position, it starts moving
downward again and the cycle is repeated. These compressors are available in 3
configurations namely 1) Hermetic; 2) Semi hermetic and 3) Direct driven versions.
In a hermetic unit, the motor and compressor are enclosed in a common housing, which is
sealed. Because the components are not accessible for repair, the entire compressor unit must
be replaced if it fails. The hermetic sealed units are most common in small capacities.
44
In the semi-hermetic unit the motor is also part of the unit, however it is not sealed. Semi
Hermetic compressors have the advantage over hermetic compressors in that they can be re-
built a number of times if necessary giving a much longer service life.
In a direct drive unit the motor and compressor are separated by a flexible coupling. These
types of units utilize older technology and are not commonly used today
The main factors favoring reciprocating compressor is low cost and efficiency when applied
in low capacities. Multiple reciprocating machines can be installed for higher building loads.
Further advantages include simple controls and the ability to control the speed through the
use of belt drives. Available in both air-cooled and water cooled heat rejection
configurations, these chillers are available from 0.5 to 150 tons of refrigeration (TR).
A major drawback of reciprocating chillers is their high level of maintenance requirements in
comparison with other chiller types. Reciprocating chillers have more moving parts than
centrifugal or rotary chillers, resulting in an increased need for wear-related maintenance
activities. Reciprocating chillers also generate high levels of noise and vibration. Special
precautions must be taken to isolate the chillers from the facility to prevent transmission of
machine-generated vibrations and noise. Finally, reciprocating chillers are not well suited for
applications with cooling loads in excess of 200 tons. As the units grow in capacity, their
space requirements and first costs exceed those of other chiller types. In addition, the energy
requirements for larger units exceed that of other chillers types.
5.8.2 Screw Compressor:
Screw compressors are positive displacement machines that use helical rotors to compress the
refrigerant gas. As the rotors rotate they intermesh, alternately exposing and closing off
interlobe spaces at the ends of the rotors. When an interlobe space at the intake end opens up,
refrigerant is sucked into it. As the rotors continue to rotate the refrigerant becomes trapped
inside the interlobe space and is forced along the length of the rotors. The volume of the
interlobe space decreases and the refrigerant is compressed. The compressed refrigerant
exists when the interlobe space reaches the other end. There are two types: 1) Single and 2)
Twin screw configuration.
A single-screw compressor uses a single main screw rotor meshing with two gate rotors with
matching teeth. The main screw is driven by the prime mover, typically an electric motor.
A twin-screw compressor consists of accurately matched rotors (one male and one female)
that mesh closely when rotating within a close tolerance common housing. One rotor is
45
driven while the other turns in a counter rotating motion. The twin-screw compressor allows
better control and variations in suction pressure without much affecting the operation
efficiency. Available in air-cooled and water cooled configurations, screw chiller is available
up to 750 tons of refrigeration.
With a relatively high compression ratio and few moving parts, screw chillers are compact,
smaller and lighter than reciprocating and centrifugal chillers of the same cooling capacity.
These also offer quieter, vibration-free operation and are well known for their robustness,
simplicity, and reliability. They are designed for long periods of continuous operation,
needing very little maintenance. Screw compressors can overcome high lift when speed is
reduced, allowing energy savings without the possibility of surge as the compressor unloads.
The major drawback of screw chillers is their high first cost. For small cooling loads,
reciprocating chillers are less expensive to purchase and install; for large loads, centrifugal
chillers cost less.
5.8.3 Centrifugal Compressor:
Centrifugal compressor is a dynamic machine that uses the rotating action of an impeller
wheel to exert centrifugal force on refrigerant inside a round chamber (volute). Refrigerant is
sucked into the impeller wheel through a large circular intake and flows between the
impellers. The impellers force the refrigerant outward, exerting centrifugal force on the
refrigerant. The refrigerant is pressurized as it is forced against the sides of the volute.
Centrifugal compressors are well suited to compressing large volumes of refrigerant to
relatively low pressures. The compressive force generated by an impeller wheel is small, so
chillers that use centrifugal compressors usually employ more than one impeller wheel,
arranged in series. Centrifugal compressors are desirable for their simple design and few
moving parts.
Centrifugal chillers are categorized either as positive pressure or negative pressure machines
depending on the evaporator pressure condition and the type of refrigerant used. A chiller
using refrigerant R-22 and R-134A is a positive-pressure machine, like reciprocating chillers
centrifugal units are available in both hermetically sealed and open construction. Despite its
lower operating efficiency, the hermetically sealed unit is more widely used. Due to their
very high vapor-flow capacity characteristics, centrifugal compressors dominate the 200 ton
and larger chiller market, where they are the least costly and most efficient cooling
compressor design. Centrifugals are most commonly driven by electric motors, but can also
be driven by steam turbines and gas engines.
46
A serious drawback to centrifugal chillers has been their part load performance. When the
building load decreases, the chiller responds by partially closing its inlet vanes to restrict
refrigerant flow. While this control method is effective down to about 20 percent of the
chiller's rated output, it results in decreased operating efficiency. For example, a chiller rated
at 0.60 kW per ton at full load might require as much as 0.90 kW per ton when lightly loaded.
Since chillers typically operate at or near full load less than 10 percent of the time, part load
operating characteristics significantly impact annual energy requirements.
5.8.4 Scroll Compressor:
The scroll compressor is a positive displacement machine where refrigerant is compressed by
two offset spiral disks that are nested together. The upper disk is stationary while the lower
disk moves in orbital fashion. The orbiting action of the lower disk inside the stationary disk
creates sealed spaces of varying volume. Refrigerant is sucked in through inlet ports at the
perimeter of the scroll. A quantity of refrigerant becomes trapped in one of the sealed spaces.
As the disk orbits the enclosed space containing the refrigerant is transferred toward the
centre of the disk and its volume decreases. As the volume decreases, the refrigerant is
compressed. The compressed refrigerant is discharged through a port at the centre of the
upper disk. Scroll compressors are a relatively recent development that is rapidly overtaking
the niche of reciprocating chillers in comfort cooling. They provide small size, low noise and
vibration and good efficiency. Available in air-cooled and water cooled configurations, scroll
chiller capacity can reach approximately 30 tons or less, which makes them good candidates
for spot cooling or make-up cooling applications.
The biggest drawback is that these cannot be repaired and there have been issues of scroll
compressors losing oil at low temperatures. On relatively small sizes, these do not affect the
life cycle economics drastically
5.8.5 Recommendations:
Chillers use one of four types of compressor: reciprocating, scroll, screw, and centrifugal.
The choice leans towards reciprocating compressors for peak loads up to 80 to 100 tons.
Between 100 and 200 tons peak cooling load, two or more reciprocating compressor chillers
can be used.
47
Above 200 tons, screw compressor systems begin to become cost effective. The screw
chillers are well suited for applications demanding up to 750 TR. Above these capacities,
centrifugal chillers are generally more cost effective where water is available for heat
rejection.
Centrifugal compressors traditionally provide larger capacities typically above 750 tons. The
centrifugal machines offer highest peak load efficiency and operate reliably for applications
demanding a steady state operation. The machines are only recommended with water-cooled
condenser option.
5.9 CENTRIFUGAL PUMP:
Centrifugal type pumps are used for both condenser water and chilled water systems. They
can be either inline or base mounted. The pumps must be sized to maintain the system
dynamic head and the required flow rate. Normally, the pumps are located so they discharge
into the chiller heat exchangers.
Centrifugal pumps are non-positive displacement type so the flow rate changes with the head.
The actual operating point is where the system curve crosses the pump curve. In systems with
control valves, the system curve changes every time a valve setting changes. This is
important because the pump affinity laws cannot be used to estimate a change if the system
curve is allowed to change. Identical pumps in parallel will double the flow at the same head.
Identical pumps in series will double the head. .Basic pump curve from manufacturer decide
pump impeller size and impeller speed.
Figure 5.12: Pump Efficiency Curve [B3]
48
5.9.1 Arrangement of Pump:
In a large system, a single pump may not be able to satisfy the full design flow and yet
provide both economical operation at partial loads and a system backup. The designer may
need to consider the following alternative pumping arrangement.
1. Parallel Arrangement:
When pumps are applied in parallel, each pump operates at the same pressure and provides its
share of the system flow at that pressure. Generally, pumps of equal size are recommended,
and the parallel pump curve is established by doubling the flow of the single pump curve.
Plotting a system curve across the parallel pump curve shows the operating points for both
single and parallel pump operation single pump operation does not yield 50% flow. The
system curve crosses the single pump curve considerably to the right of its operating point
when both pumps are running.
Figure 5.13: Pump Pressure Curve for Parallel Arrangement [B3]
2. Series Pump Arrangement:
When pumps are applied in series, each pump operates at the same flow rate and provides its
share of the total pressure at that flow. A system curve plot shows the operating points for
both single and series pump operation single pump can provide up to 80% flow for standby
and at a lower power requirement.
49
Figure 5.14: Pump Pressure Curve for Series Arrangement [B3]
5.10 FLOW CONTROL SYSTEM:
Three way valves are used for regulating water liquid / water flow through heat exchanger
like cooling and heating coils, air washer etc. They have single disc on the valve stem
operating between two seats and have three ports. There are two type divesting (mixing)
valve and mixing valve. In divesting valve one connecting port is the inlet and other two are
outlet port, while in the mixing valve there two inlet ports and third one is outlet port.
5.10.1 Diverting Valve:
The diversity valve can operate as a two (open and shut) position valve and also as a
modulating valve, by changing the type of control. The bypass of the chilled water ensure
continuous water flow the chiller even if number of zone in the system do not call for cooling
and so the chilled water respective coil is stopped . A two way solenoid valve is used instead
of diversity valve, but this will be drawback of (I) when the solenoid valve goes off on room
thermostat, there is no bypass chilled water and affect the chiller and chiller will be freeze up
water. (ii) When solenoid valve goes off disturbing noise is produced as its plunger drop
down. The diverting does not produce such type of noise .so that most of system uses three
way valves instead of two way valve. If the full load valve motor move the valve to the fully
open position. As the load is come down valve motor modulate the flow. Thus chilled water
flow through cooling coil and so its capacity is modulate according to load.
50
Figure 5.16: Three Way Bypass and Mixing Valve [B2]
This valve has two inlet and one outlet port and Chilled water supply line is connected to one
inlet port and the second inlet port is connected to the return water line from cooling coil and
third port is connected to two mixing outlet . At full load there is no mixing of water and
according to load mixing process is done
In most cases, a mixing valve can perform the same function as a diverting or bypass valve if
the companion actuator has a very high spring rate. Otherwise, water hammer or noise may
occur when operating near the seat.
5.11 SELECTED EQUIPMENT:
According to design we required 30 TR chiller, Apparatus temperature 2 ˚C,
dehumidification 4 ˚C temperature required and 45 GPM (10368 LPH) flow .we selected
Plate heat exchanger have a higher overall heat transfer compare to shell and tube type heat
exchanger, lower initial cost, for a compact design space requirement is lower, and easy to
service compare to shell and tube heat exchanger and for recommended choice of compressor
30TR capacity choose reciprocating compressor. According to ASHARE 6.3.2.2.2 two
change over more efficient now day select two piping arrangement, parallel pumping and
chiller arrangement
Specification of chilled heat exchanger
Plate heat exchanger (stainless steel) IDMC made and 10.65 m2 heat transfer area
15 TR DX Chillers
51
Cold fluid Hot fluid
Flow rate 6200 LPH 11290 LPH
Inlet temperature -2˚C 6˚C
Outlet
temperature
-2˚C 2˚C
Hydrostat
pressure
9 kg/cm2 9 kg/cm2
Specification for condensing unit
Condensing unit made by Danfoss
15 TR capacity
Model HGM 160A06
Refrigerant = R22
High pressure =25 bar
Low pressure =8 bar
400V3 -50Hz
Specification of pump
Kirlosker brother made centrifugal pump
Head = 15 to 25 m
RPM = 2844
Flow= 3.1 lps
KW/HP=1.5/2.0, Bronze Impeller diameter =138 mm
Specification of measuring instrument
Pressure transmitter for pressure measuring
WIKA made 0-25 bar
Current 4 -20mA
RTD Temperature measuring device
PT 100 Yokogawa
0˚C to 100˚C
Flow switch to measure water flow
FM4WP Mukund electrical
Max temperature 150˚C
Max pressure 11 Kg/cm2, nominal diameter 50mm, Normal flow 170
52
CHAPTER 6: TEST ROOM LAYOUT
Testing room for bulk milk cooler is to test at different ambient temperature and maintain
ambient temperature .In these arrangement chillers arrange so that heating and cooling room.
As per ISO 1983:5708 bulk milk cooler company work on that basis we required 15 ˚ to 50˚
with stability of 0.2˚c around the surface of bulk milk cooler.
6.1 COOLING PROCESS:
In the cooling arrangement used direct expansion chiller (plate heat exchanger) by company
made. cooling system comprise vapor compression system evaporator , condensing unit
(receiver , compressor , condenser , expansion valve ) and their capacity on the basis of
calculation 30TR .In two pipe arrangement use two PHE chiller and for one PHE used two
condensing unit so there are two PHE chillier 15 TR and four condensing unit . We used two
centrifugal pumps for water circulation 3.13 l/s capacity .Pump suck water from sump
500liter syntax tank and two PHE outlet, discharge water goes to air handling unit and
recirculation through PHE. As same way refrigerant cycle comprise evaporator (PHE),
receiver, compressor, condenser, expansion valve, solenoid valve. R22 refrigerant extract
heat from water and cool water.
6.2 HEATING PROCESS:
In heating process of room used solar water heating system 300 liter and boiler 2 kg steam /
hr capacity company available unit circulate water from solar heating or boiler to hot tank
arrangement. At the time of heating application steam or warm water delivered with help of
hot water tank, pump suck hot water at the time suction of chiller water closed and open the
hot water valve and same during the time received from air handling unit PHE suction close
and hot water tank valve open .This system is made up to 50"c temperature condition.
6.3 BULK MILK COOLER TEST:
In the test room testing of bulk milk cooler by using water and cool the water 35˚C to
4˚C .System also comprise one pipe connection for bulk milk cooler set 35˚C hot water
temperature and fill up water according requirement after completion of test water back to
cold water tank.
53
Figure 6.1: Test Room Layout
6.4 BILL OF QUANTITIES:
54
Condensing Unit Qty
CDU Model - HGM 160 / Danfoss with controls 4
MS Stand for CDU 1
Copper piping 1 lot
Cabling 1 lot
Installation material 1 lot
Chilled water pump
45 GPM at 25 MWC, monoblock/bronze impeller 2
Steel pipe Pipe 50 NB 1 lot
Nitrile Rubber insulation 1 lot
Ball Valve 6
Non Return Valve 17
Strainer 1
3 way valve 2
Temperature Indicator 2
Pressure indicator 2
Flow switch 2
Temperature sensor 1
Expansion tank 1000 liters (syntax tank) 1
Installation material 1 lot
AHU
Ceiling suspended cooler 2
13 TR / 33000 CMH
De-super heater 1
Solar water heating system 1
Installation material 1 lot
Automation
Scada 1
Pressure transmitter 20
Temperature transmitter 34
Installation material 1 lot
Electrical Panel
55
MCC 1
Servo voltage stabilizer 50 KVA 1
Lighting 1 lot
Cabling 1 lot
Installation material 1 lot
PHE Chiller
15 TR DX PHE/R22 - SW 40 2
Installation material 1 lot
PUF Panel
PCGI 0.63mm PUF 40kg/m3 1 lot
Installation material 1 lot
Sliding Door
Sliding Door - 4.3m (w) x 3.2m (h) 1
Installation material 1 lot
Labour Work
AHU 1 lot
Door 1 lot
PUF Panel 1 lot
SCADA 1 lot
Cabling 1 lot
Water Piping 1 lot
CDU 1 lot
Total cost 42,00 ,000
Table 6.1 - Bill of Material
56
CHAPTER 7: THERMAL PERFORMANCE OF CHILLER
HEAT EXCHANGER
7.1 HEAT TRANSFER AND PRESSURE DROP CALCULATION:
The designed for gasketed –plate heat exchanger is highly specialized in nature considering
the variety of designs available for the plate and arrangements that may possibly sits various
duties. Manufacture has developed their own design procedure applicable to the exchangers
that they market. Here IDMC LIMITED made own plate heat exchanger for various
application fluids exchanges. For this company used plate data that mentioned below table
from standard plate data we select the no of plate and calculate the no of plates required for
given heat duty required and analyze heat transfer and pressure drop calculation as per
requirement of flows and refrigerant check the heat transfer and pressure drop within
acceptable limit or not. There is a parallel flow heat exchanger and data from required design.
Data sheet for Plate heat exchanger:
Items Hot Fluid Cold Fluid
Fluids Cooling water R22
Flow rates (kg/s) 3.13 1.72
Temperature in (0C) 6 -2
Temperature out (0C) 2 -2
Total fouling resistance (m2K/W) 0.000086 0.000044
Specific heat (J/kg.K) 4178 1.171X103
Viscosity (N.s/m2) 7.66X10-4 2.67X10-4
Thermal conductivity (W/m.K) 0.617 0.0977
Density (kg/m3) 995 1.285X103
Table 7.1 – Plate Heat Exchanger Data Sheet [B7]
57
The Construction Data for Proposed Plate Heat Exchange:
Plate Material SS316
Plate thickness, t (mm) 0.6
Chevron angle , β(degree) 60
Total number of plates, Nt 26
Enlargement factor, Φ 1.36
No of passes, Np One pass/one pass
Port diameter, Dp(mm) 100
Pack length, Lc(mm) 8.2
Vertical port distance , LV(mm) 1055
Horizontal port distance, Lh(mm) 225
Thermal conductivity (w/m.K) 16.5
Table 7.2 – Construction Data for Plate Heat Exchanger
Figure 7.1: Dimension View of Plate Heat Exchanger [B7]
7.2 STEPWISE PERFORMANCE ANALYSIS:
58
7.2.1 Required Heat Duties:
For a given application of heat exchanger required a cool water dehumidification temperature
and apparatus dew point. Here for capacity of bulk milk cooler required chiller water flow
rate 3.13l/s , cool water at apparatus dew point and required dehumidification so that from
heat capacity equation required heat exchanger duty for temperature 6˚C to 2˚C with specific
heat of water assume city water 4178J/kg K.
7.2.2 Sizing of Heat Exchanger:
The temperature difference for parallel flow heat exchanger at inlet and outlet is determined
by temperature difference of two fluids at inlet and outlet.
The effective number of plates is total no of plate subtract two plate for use holding heat
exchanger.
The effective flow length between the vertical ports is
Plate pitch can be determined by total pack length of heat exchanger divided no of plates
Mean channel flow gap for one plate can be determined by plate pitch subtract by thickness
of plate
59
The one Channel flow area is multiplication of width of plate and mean channel flow gap
Single Plate heat transfer area is determined by effective area of one plate that given by plate
manufacturer divided by effective no of plate
The projected area A1p is determined by
The enlargement factor specified by manufacturer but it can be verified by single plate area to
projected area of plate
The Channel hydraulic/equivalent diameter is determined by
The number of Channel per pass is
60
7.2.3 Heat Transfer Analysis:
Mass flow rate per channel for cold fluid total mass flow rate for cold fluid for maximum
flow rate of cooling water divided by no of channel per pass of particular cooling fluid
Mass velocity Gch
The hot fluid Reynolds number
Flow rate per channel for cold fluid
Mass velocity Gcc
Reynolds Number for cold fluid
61
The hot fluid convective heat transfer coefficient hh can be determined using Nusselt number
correlation suggest McAdams for Laminar flow 2*103<Re<1*106. Nusset number based on
hydraulic diameter of plate that convective heat transfer to conduction heat transfer
The Cold fluid heat transfer coefficient hc can be determined by.
For clean overall heat transfer UC determined by
The fouled overall heat transfer
The corresponding cleanliness factor is
The actual heat duties for clean and fouled condition can be determined by
62
Actual heat transfer given by
Percentage of over surface design
7.2.4 Pressure Drop Analysis:
The fluid friction co-efficient for hot and cold fluid determined by
The frictional pressure drop from hot & cold streams
The Pressure drop in port is calculated by
63
Total pressure drop can be determined by summation of friction and port pressure drop
Hot fluid side pressure drop
Cold fluid side pressure drop
As per calculation of heat transfer and pressure drop heat exchanger is sufficient for chiller
plant to achieve an ambient condition in bulk milk cooler testing laboratory and also 21%
over surface design allow due to cleaning of plate which is acceptable.
64
7.3 DATA ANALYSIS FOR HEAT TRANSFER WITH DIFFERENT CHILLER
FLOW RATES:
Chiller flow
rates(l/s)
Required heat duties
Q(Watt)
Actual heat capacity
Qact(Watt)
1.0 16748 67072
1.5 25122 70800
2.0 33496 73154
2.5 41780 74700
3.0 55436 76500
3.5 58618 76800
Table 7.3 – Chiller Heat Transfer Analysis
7.3.1 Heat Transfer Trends for Chiller Mass Flow Rates:
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
1 2 3 4 5 6
Chiller flow (l/s)
Hea
t ex
chan
ge
(Wat
t) Chiller flow
Required heatduty
Actual heatcapacity
Figure 7.2: Heat Transfer Trends for Chiller Flow Rate
CHAPTER 8: BULK MILK COOLER TEST
8.1 10 KL CLOSED TYPE BULK MILK COOLER TEST:
Standard cooling capacity for 10kl bulk milk cooler using two condensing unit hermetic type
by Danfoss made 28.64 KW capacities each.
65
Figure 8.1: 10KL Bulk Milk Cooler Set Up
8.1.1 Room Temperature and Chiller Test:
66
Figure 8.2: Chiller Arrangement
Time
(min)
Chiller 1 Flow
rate GPM (l/s)
Chiller 2 Flow
rate GPM (l/s)
Supply
temperature
(˚C)
Average room
temperature (˚C)
4:00 39.79(2.507) 39.43(2.485) 7.50 10.30
4:15 39.81(2.508) 39.57(2.493) 5.48 10.21
4:30 39.76(2.505) 39.62(2.497) 5.46 10.13
4:45 39.73(2.503) 39.64(2.498) 5.47 10.30
5:00 39.82(2.509) 39.55(2.492) 5.44 10.20
5:15 39.77(2.506) 39.51(2.490) 5.49 10.16
5:30 39.79(2.507) 39.56(2.493) 5.41 10.29
5:45 39.76(2.505) 39.60(2.495) 5.39 10.24
6:00 39.80(2.508) 39.58(2.494) 5.42 10.18
6:15 39.75(2.505) 39.56(2.493) 5.40 10.15
6:30 39.73(2.503) 39.52(2.490) 5.38 10.10
Table 8.1 - Chiller and Room Temperature Test for 10KL BMC
8.1.2 Bulk Milk Cooler Test:
67
Time
(min)
Suction
pressure
(Bar)
Discharge
pressure
(Bar)
Evaporator out
temperature
(˚C)
Liquid line
temperature
(˚C)
Water
temperature
(˚C)
4:00 4.86 19.24 33.31 43 35
4:15 5.00 20.24 32.53 48 31.2
4:30 5.16 21.00 29.81 52 27.6
4:45 5.06 21.33 27.01 51 24.4
5:00 5.20 21.32 24.21 50 21
5:15 5.13 21.20 21.28 51 17.7
5:30 4.78 20.68 16.21 52 14.6
5:45 4.56 20.44 10.26 50 11.6
6:00 4.41 19.89 5.01 47 8.9
6:15 3.99 18.95 1.12 41 6.3
6:30 3.59 18.26 0.5 41 3.9
Table 8.2 - 10KL Bulk Milk Cooler Test
8.1.3 Calculation for Heat Removed from Condenser:
(1) At 4:00 PM
Suction Pressure P0 =4.86 bar,
Discharge Pressure P1 = 19.24 bar,
Evaporator out temperature Te= 33.31 ˚C
Liquid line temperature T3=43˚C
Using this data from p - h chart getting Enthalpy values
h1 =274 kJ/kg, h2=335 kJ/kg, h4=103 kJ/kg= h3,
Q = m*(h1- h4) kJ/s
28.67=m*(274-103)
m = 0.167 kg/s
So heat rejected from compressor
Qrej = m*(h2- h3) kJ/s
= 0.167*(335-103)
=38.74 kW
8.1.4 As Per Calculation at 4:00 PM Heat Removed from Condenser Same
Procedure for Another Time .Total Room Load the Time of Testing and Required 68
Chiller Flow Rates:
Time (min) Product load TR Total load
TR
Flow GPM(L/s)
(TR*3)
4:00 22.05 26.87 80.64(5.08)
4:15 21.21 26.00 78.00(4.91)
4:30 21.47 26.28 78.84(4.97)
4:45 21.85 26.71 80.13(5.05)
5:00 21.12 25.90 77.70(4.90)
5:15 21.26 25.19 75.57(4.76)
5:30 22.75 27.70 83.10(5.24)
5:45 22.56 27.49 82.47(5.20)
6:00 21.26 26.06 78.18(4.93)
6:15 20.77 25.45 76.35(4.81)
6:30 21.28 26.09 78.27(4.93)
Table 8.3 - Total Room Load for 10KL BMC
8.2 CLOSED TYPE BULK MILK COOLER TEST:
69
5KL bulk milk cooler test at outside ambient temperature 39˚C and inside design temperature
10˚C. Bulk milk cooler installed with two hermetic compressors with capacity of 14.66 KW
each unit as shown in below.
Figure 8.3: 5KL Bulk Milk Cooler Set Up
70
8.2.1 Room Temperature and Chiller Test:
Time
(min)
Chiller 1 Flow
rate GPM (L/s)
Supply
temperature
(˚C)
Average room
temperature (˚C)
2:00 50.79(3.201) 10.02 10.30
2:15 51.29(3.232) 8.29 10.21
2:30 51.43 (3.241) 6.35 10.13
2:45 51.39(3.238) 5.25 10.30
3:00 51.36(3.236) 5.21 10.20
3:15 51.42(3.240) 5.18 10.16
3:30 51.34(3.235) 5.05 10.29
3:45 51.37(3.237) 4.87 10.24
4:00 51.40(3.239) 4.63 10.18
4:15 51.42(3.240) 4.57 10.15
4:30 51.45(3.242) 4.39 10.10
Table 8.4 - Chiller and Room Test for 5KL BMC
71
8.2.2 5KL Bulk Milk Cooler Test:
Time
(min)
Suction
pressure
(Bar)
Discharge
pressure
(Bar)
Evaporator
out
temperature
(˚C)
Liquid line
temperature
(˚C)
Water
temperature
(˚C)
2:00 6.21 20.34 23.1 46.0 35.0
2:15 6.20 19.65 19.0 45.1 30.7
2:30 6.07 18.62 16.2 44.2 26.9
2:45 5.52 18.96 13.8 43.4 23.5
3:00 5.17 18.61 09.4 43.1 20.2
3:15 4.83 17.93 07.2 42.8 17.0
3:30 4.48 17.58 05.4 42.0 14.0
3:45 3.79 16.21 04.0 40.7 11.5
4:00 3.45 15.86 02.2 40.2 9.1
4:15 3.10 15.52 01.5 39.0 6.5
4:30 3.08 15.23 0.50 38.6 4.1
Table 8.5 - 5KL Bulk Milk Cooler Test
8.2.3 Calculation for Heat Removed from Condenser:
(1) At 2:00 PM
Suction Pressure P0 =6.21 bar,
Discharge Pressure P1 = 20.34 bar,
Evaporator out temperature Te= 20.34 ˚C
Liquid line temperature T3 =46 ˚C
Using this data from p - h chart getting Enthalpy values
h1 =271 kJ/kg, h2=319 kJ/kg, h4=110 kJ/kg= h3,
Q = m*(h1- h4) kJ/s
14.66=m*(271-110)
m = 0.091 kg/s
So heat rejected from compressor
Qrej = m*(h2- h3) kJ/s
= 0.091*(319-110)
=19.031 kW72
8.2.4 As Per Calculation of 2:00 PM Same Calculation for Another Time. Total
Room Load at the Time of Testing and Required Chiller Flow Rates:
Time (min) Product load
TR
Total load
TR
Flow GPM(L/s)
(TR*3)
2:00 10.82 14.69 44.07(2.78)
2:15 10.64 14.50 43.50(2.74)
2:30 10.33 14.15 42.45(2.67)
2:45 10.32 14.14 42.42(2.67)
3:00 10.21 14.02 42.06(2.65)
3:15 10.48 14.32 42.49(2.71)
3:30 10.55 14.40 43.20(2.72)
3:45 10.86 14.73 44.19(2.78)
4:00 11.27 15.19 45.57(2.87)
4:15 11.26 15.18 45.54(2.86)
4:30 11.26 15.18 45.54(2.86)
Table 8.6 - Total Room load for 5KL BMC
8.3 2KL CLOSED TYPE BULK MILK COOLER TEST:
73
For 2KL bulk milk cooler tested under average outside ambient temperature
40˚C and inside ambient 38˚C. Bulk milk cooler installed with two hermetic type
compressors capacity of 6.23 KW of each unit.
8.3.1 Room Temperature and Chiller Result:
Time
(min)
Chiller Flow
rate GPM (l/s)
Supply
temperature
(˚C)
Average room
temperature (˚C)
03:55 1.12 21.00 38.34
04:10 1.15 18.25 38.21
04:25 1.13 15.24 38.24
04:40 1.20 14.20 38.17
04:55 1.18 13.25 38.24
05:10 1.14 11.78 38.31
05:25 1.12 11.25 38.18
05:40 1.16 10.49 38.16
05:55 1.19 10.25 38.22
06:10 1.18 09.80 38.28
06:25 1.20 09.50 38.15
06:40 1.17 09.10 38.02
Table 8.7 - Chiller and Room Test for 2KL BMC
8.3.2 2KL Bulk Milk Cooler Test:
74
Suction
pressure
(Bar)
Discharge
pressure
(Bar)
Evaporator
out
temperature
(˚C)
Liquid line
temperature
(˚C)
Water
temperature
(˚C)
03:55 18.97 32.4 47.7 35.0
04:10 18.97 25.0 48.0 30.9
04:25 18.62 19.4 46.4 26.9
04:40 17.93 13.6 44.9 23.5
04:55 17.24 10.3 43.8 20.4
05:10 17.24 8.0 43.0 17.4
05:25 16.55 6.2 41.8 14.7
05:40 15.72 5.4 40.9 12.5
05:55 15.52 3.8 39.7 10.4
06:10 15.17 2.3 38.9 8.4
06:25 15.17 1.5 37.9 6.4
06:40 14.83 0.4 37.8 4.0
Table 8.8 - 2KL Bulk Milk Cooler Test
8.3.3 Calculations for Heat Removed from Condenser:
(1) At 3:55 PM
Suction Pressure P0 =6.55 bar,
Discharge Pressure P1 = 18.96 bar,
Evaporator out temperature Te= 32.4 ˚C
Liquid line temperature T3 =47.7˚C
Using this data from p - h chart getting Enthalpy values
h1 =281 kJ/kg, h2=318 kJ/kg, h4=111 kJ/kg= h3,
Q = m*(h1- h4) kJ/s
6.23=m*(281-111)
m = 0.037 kg/s
So heat rejected from compressor
Qrej = m*(h2- h3) kJ/s
= 0.037*(318-111)
=7.59 kW75
8.3.4 Total Room Load at the Time of Testing and Required Chiller Flow Rates:
Time (min) Product
load TR
Total load
TR
Flow GPM(L/s)
(TR*3)
07:55 4.31 5.391 16.17(1.02)
08:10 4.31 5.391 16.17(1.02)
08:25 4.83 5.964 17.89(1.13)
08:40 4.31 5.391 16.17(1.02)
08:55 4.36 5.446 16.34(1.03)
09:10 4.42 5.512 16.54(1.04)
09:25 4.54 5.644 16.93(1.07)
09:40 4.67 5.787 17.36(1.09)
09:55 4.64 5.754 17.26(1.08)
10:10 4.63 5.743 17.23(1.08)
10:25 4.70 5.820 17.46(1.10)
10:40 4.70 5.820 17.46(1.10)
Table 8.9 - Total Room Load for 2KL BMC
76
CHAPTER 9: RESULT AND DISCUSSION
9.1 For 10 KL BULK MILK COOLER:
10KL bulk milk cooler testing at outside temperature 39˚C and inside temperature 10˚C. We
obtained almost uniform temperature as per ISO 5708:1983 mentioned. For room average
temperature installed six number of RTD sensor use three for left wall and three for right wall
and equally spaced from air handling unit . For 10KL and 10˚C inside temperature three way
controls valve is fully open and achieve full chiller flow rate that maintain room temperature.
9.1.1 Comparison of Chiller Flow Rate and Required Flow Rate:
Time
(min)
Predict Flow
GPM(L/s)
(TR*3)
Chiller 1 Flow rate
GPM (L/s)
Chiller 2 Flow rate
GPM (L/s)
4:00 80.64(5.08) 39.79(2.507) 39.43(2.485)
4:15 78.00(4.91) 39.81(2.508) 39.57(2.493)
4:30 78.84(4.97) 39.76(2.505) 39.62(2.497)
4:45 80.13(5.05) 39.73(2.503) 39.64(2.498)
5:00 77.70(4.90) 39.82(2.509) 39.55(2.492)
5:15 75.57(4.76) 39.77(2.506) 39.51(2.490)
5:30 83.10(5.24) 39.79(2.507) 39.56(2.493)
5:45 82.47(5.20) 39.76(2.505) 39.60(2.495)
6:00 78.18(4.93) 39.80(2.508) 39.58(2.494)
6:15 76.35(4.81) 39.75(2.505) 39.56(2.493)
6:30 78.27(4.93) 39.73(2.503) 39.52(2.490)
Table 9.1 - Compare chiller flow rate for 10KL BMC
77
9.1.2 Average Room Temperature Trend:
Figure 9.1: Average Room Temperature Trend for 10KL BMC
9.1.3 Predictable and Experimental Chiller Flow Trend:
4.2
4.4
4.6
4.8
5
5.2
5.4
4:00
4:30
5:00
5:30
6:00
6:30
Time (min)
Flo
w r
ate
(l/s
)
Predict flow
Experimentflow
Figure 9.2: Chiller Flow Trend for 10KL
9.2 For 5KL BULK MILK COOLER:
78
For 5KL bulk milk cooler test at outside room average temperature 39˚C and inside
temperature 10˚C we obtained uniform room temperature at the time of test three way control
valve 70 % open and flow rate is decrease that meet the required chiller water flow and for
this only one.
9.2.1 Comparison of Chiller Flow Rate and Required Flow
Rate:
Time (min) Predict Flow
GPM(L/s) (TR*3)
Chiller 1 Flow
rate GPM (L/s)
2:00 44.07(2.78) 50.79(3.201)
2:15 43.50(2.74) 51.29(3.232)
2:30 42.45(2.67) 51.43 (3.241)
2:45 42.42(2.67) 51.39(3.238)
3:00 42.06(2.65) 51.36(3.236)
3:15 42.49(2.71) 51.42(3.240)
3:30 43.20(2.72) 51.34(3.235)
3:45 44.19(2.78) 51.37(3.237)
4:00 45.57(2.87) 51.40(3.239)
4:15 45.54(2.86) 51.42(3.240)
4:30 45.54(2.86) 51.45(3.242)
Table 9.2 - Compare Chiller Flow Rate for 5KL BMC
79
9.2.2 Average Room Temperature Trend:
Figure 9.3: Average Room Temperature Trend for 5KL
9.2.3 Prediction and Experimental Chiller Trend
Figure 9.4: Chiller Flow Trend for 5KL
80
9.3 FOR 2KL BULK MILK COOLER:
For a 2kl bulk milk cooler test outside temperature 40˚C and inside temperature 38˚C for this
condition 35% three way control valve open and achieve temperature and flow rate as per
requirement of test.
9.3.1 Comparison of Chiller Flow Rate and Required Flow
Rate:
Time (min) Predict Flow GPM(L/s)
(TR*3)
Chiller Flow rate
GPM (L/s)
03:55 16.17(1.02) 1.12
04:10 16.17(1.02) 1.15
04:25 17.89(1.13) 1.13
04:40 16.17(1.02) 1.20
04:55 16.34(1.03) 1.18
05:10 16.54(1.04) 1.14
05:25 16.93(1.07) 1.12
05:40 17.36(1.09) 1.16
05:55 17.26(1.08) 1.19
06:10 17.23(1.08) 1.18
06:25 17.46(1.10) 1.20
06:40 17.46(1.10) 1.17
Table 9.3 - Compare Chiller Flow Rate for 2KL BMC
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9.3.2 Average Room Temperature Trend:
Figure 9.5: Average Room Temperature Trend for 2KL BMC
9.3.3 Prediction and Experimental Chiller Trend:
0.9
0.95
1
1.05
1.1
1.15
1.2
1.25
Time(min)
Ch
ille
r fl
ow
(l/s
)
Prediction flow
Experimentflow
Figure 9.6: Chiller Flow Trend for 2KL BMC
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CHAPTER 10: CONCLUSION
From designing and experimental point of conclude that for any air condition system
complete information require where it is installed after getting primary information
calculation of heat load is important based on required application that include all heat source
.Based on heat load calculation find chiller flow required to achieve temperature and
selection of cooling equipment as per heat load .In this case different capacity of bulk milk
cooler test so that equipment load vary set the control valve system as per predict load for
different capacity of bulk milk cooler and weather data for summer and winter condition.
From experiment view we tested different types of bulk milk cooler chiller heat exchanger is
enough to maintain ambient condition as we set three way control valve according design
heat load calculation so that water flow rate change for different types of bulk milk cooler
and outside design temperature as we calculated that achieve uniform temperature as
customer said where bulk milk cooler will use. Achieve uniform ambient temperature as
mentioned ISO 5708:1983 bulk milk cooler section and dispatch to customer as they told
ambient condition.
83
REFERENCES
PAPERS:
1. Alka Bani Agrawal, R.K. Dave and Vipin Shrivastava, “Replacing harmful refrigerant
R22 in bulk milk cooler”, Indian Journal of Science and Technology. Vol.2 No. 9 (Sep
2009), ISSN: 0974- 6846
2. F. Illan and A.Viedma, “Using ice slurry as a secondary refrigerant for charge reduction
in industrial facility”, Universidad Politecnica de C artegena, Spain,
3. F.A. Ansari, A.S. Mokhtar, K.A. Abbas and N.M. Adam, ”A Simple Approach for
Building Cooling Load Estimation”, American Journal of Environmental Sciences 1 (3):
209-212, 2005, ISSN 1553-345X
4. F.C.Houghten, “Heat and Moisture Losses bi Human Body and Their Relation to Air
Conditioning Problem, American Journal of Physiology, Vol 88, 1929
5. Hartman, Thomas, “All Variable Speed Centrifugal Chiller Plants” ASHRAE Journal,
September 2001. ASHRAE, Atlanta Ga
6. S.Akdemir, ”Designing of cold stores and choosing of cooling equipments”, Journal of
applied sciences 8(5):788-794, 2008
7. William P. Bahnfleth, Eric B. Peyer,”Energy use characteristic of variable primary flow
chiller water pumping system”, Grumman/Butkus Associates, Evanston, IL, USA,
BOOKS:
1. ASHRAE Fundamentals Handbook ASHRAE. Atlanta, 2000
2. ASHRAE HVAC Systems and Equipment Handbook ASHRAE. Atlanta, 2001
3. Carrier, Handbook of Air Conditioning System Design, A Mei Ya Taiwan
Edition ,Mcgraw –Hill Company New York
4. C. P. Arora, Refrigeration and Air Conditioning, 2nd Edition, Tata McGraw-Hill
Company, 2007
5. ISO 5708:1983, Bulk Milk Cooler, 1st Edition, 2010
6. P.N.Ananthnarayanan, Basic Refrigeration and Air Conditioning, 3rd Edition, Tata
McGraw-Hill Company, 2005
84
7. R. K. Shah, Fundamental of Heat Exchanger Design, John Wiley & Sons, 2003
8. R.K. Rajput, Refrigeration and Air Conditioning, 1st Edition, S.K.Kataria and Sons, 2004
9. Ross Montgomery, Fundamental HVAC Control System, 2nd Edition, Elsevier, 2003
85
APPENDIX -A
Friction Factor and Nusset Number Correlation for Gasket-Plate Heat Exchanger with Chevron Plates [B7]:
1. Tait etal, β=60˚ chevron plates:
f =12.065Re-0.74 10< Re<80
=0.3323 Re-0.042 1450< Re<11460
Nu=0.2 Re0.75 Pr0.4 10< Re<720
=0.248Re0.7 Pr0.4 1450< Re<11460
2. Muley and Maglik, β=60˚ chevron plates:
f =51.5/Re Re<16
=17.0Re-0.6 16< Re<100
=2.48Re-0.2 Re>800
Nu=0.572 Re0.5 Pr1/3 20< Re<210
=0.1090Re0.78 Pr1/3 Re>800
3. Muley and Maglik, Mixed chevron plate with β=30˚ & 45˚ angle:
f= {(40.32/ Re) 5+ (8.21 Re-0.5)5}0.2 2< Re<200
= 1.27 Re-0.15 Re>1000
Nu=0.471 Re0.5 Pr1/3 20< Re<400
=0.10Re0.78 Pr1/3 Re>1000
4. McAdam Correlation for 2*103< Re<1*106 for β=60˚ chevron angle:
f= 1.441/( Re)0.206
Nu=0.3(Re) 0.663(Pr) 1/3(µb/µw)0.17
86