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Study of Automation of HVAC System and Component
Improvements for Improved Performance
A Graduate Project Report submitted to Manipal Univeristy in partial fulfilment
of the requirement for the award of the degree of
Bachelor of Engineering
In
Mechanical Engineering/Industrial and Production Engineering
by
Nikhil Mohan
Under the guidance of
Dr. U. A. Kini
Department of Mechanical &Manufacturing Engineering
MANIPAL INSTITUTE OF TECHNOLOGY
DEPARTMENT TOF MECHANICAL AND MANUFACTURING ENGINEERING
MANIPAL INSTIITUTE OF TECHNOLOGY
(A constituent Institute of MANIPAL UNIVERSITY)
MANIPAL 576104, KARNATAKA, INDIA
January 2014
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DEPARTMENT TOF MECHANICAL AND MANUFACTURING ENGINEERING
MANIPAL INSTIITUTE OF TECHNOLOGY
(A constituent Institute of MANIPAL UNIVERSITY)
MANIPAL 576104, KARNATAKA, INDIA
January 2014
CERTIFICATE
This is to certify that the project titled Study of Automation of HVAC System and
Component Improvements for Improved Performanceis a record of the bonafide work
done by Nikhil Mohan (090909094) submitted in partial fulfilment of the requirement for
the award of the degree of Bachelor of Engineering in Mechanical Engineering of
Manipal Institute of Technology, Manipal, Karnatak (a constituent of Maipal University)
during the year 2013-2014
Dr. U Achyuth Kini
Project guide
Dr Divakar Shetty
Head Of Department
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ACKNOWLEDGMENTS
I would like to express my deepest appreciation to all those who provided me the possibility to
complete this report. A special gratitude I give to my project guide, Dr. U A Kini, whose
guidance and encouragement have helped me coordinate and complete this project.
Furthermore I would also like to thank the staff of the Mechanical Department, without whose
help, guidance and permission to use the instruments this project could not be completed. I
would like to thank every professor who helped provide guidance and aid to this project.
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ABSTRACT
In todays ever environmentally conscious world energy conservation has become a very
important issue. In smaller house holds the air-conditioner uses up a major portion of the total
monthly energy consumed. The same way in larger structures and spaces, a large amount of
energy is consumed by Heating Ventilation and Air Conditioning units. These large systems
are often put into place to handle large loads for large numbers of people and maintain a space
at a habitable condition. However a lot these system do not have optimised capacity for
handling lower loads and often consume extra energy when faced with these low loads.
These systems however also, when considered in a work environment, have patterns and
characteristics of usage. With the use of these patterns of usage and minimum load instructions
the systems energy consumption can be optimised to conserve energy and thereby also cost.
LIST OF NOTATIONS AND ABBREVIATIONS
HVAC Heating Ventilation and Air Conditioning
BMS Building Management System
AHU Air Handling Unit
RF-id Radio Frequency Identification
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LIST OF FIGURES
Figure Number Title of Figure Page Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Chiller Plant
Plant Layout
Cooling tower
Cooling Tower Layout
Air Handling Unit
AHU layout Library
AHU layout IC + NLH
No. of people/room temperature 1
AHU cut-off
No. of people/room temperature 2
AHU with cooling
Surface Temperature
Library Main Hall
TBS Temperature/no. of people
2ndFloor Library Heat zones
Innovation centre heat zones
Temperatures + No. of People NLH
11
12
13
13
14
15
16
24
24
25
25
27
28
29
29
30
31
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LIST OF TABLES
Figure Number Title of Figure Page Number
1
2
3
4
5
6
7
8
9
10
11
12
13
The Library Time/room temp/no of people 1
The Library Time/room temp/no of people 2
Time/Cooling Tower
Time/Inner/Outer/Glass Temp
Main hall time/no of people/vent temp/ext temp
NLH 203
NLH 205
NLH 403
NLH 404
Computer Lab 3rdFloor IC
4th Floor Public Area IC
4th Floor 04 Classroom IC
Time/Inlet/Outlet
24
25
26
27
28
31
32
32
33
34
34
34
35
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CONTENTS
ACKNOWLEDGEMENTS
ABSTRACT
LIST OF NOTATIONS AND ABBREVIATIONS
LIST OF FIGURES
LIST OF TABLES
3
4
4
5
6
Chapter 1
1.11.2
INTRODUCTION
Problem StatementIdeology of Solution
Chapter 2
2.1
2.2
2.3
2.4
LITERATURE REVIEW
Central HVAC Plant
AHU Systems
Design Parameters
Energy Consumption
Chapter 33.1
3.2
OBJECTIVES AND METHODOLOGYObjectives
Methodology
Chapter 4
4.1
4.2
4.3
RESULT AND ANALYSIS
Design Parameters
Current System
Trends and Patterns
Chapter 5
5.1
5.2
5.3
CONCLUSIONS AND SCOPE OF FUTURE WORK
Inferences
Improvements and Future Design Considerations
Scope for Future Work
8
89
11
11
14
16
17
1818
18
20
20
23
24
36
36
38
41
REFERENCES 42
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1. Introduction
1.1 Problem Statement
Air conditioning is the process of treating air so as to control simultaneously its temperature,
humidity, purity, distribution, air movement, and pressure to meet the requirements of the
conditioned space. In a buildings, it provides conditions to people so that they can live and
work in comfort, safely, and efficiently. In common perspective, air conditioning is generally
associated to cooling and dehumidification during the summer and monsoon seasons when heat
is extracted from the space.
For larger spaces, HVAC units or plants are set up to manage the cooling and dehumidification
of spaces occupied by a large number of people. These spaces can be either places of low
activity like houses, hotel rooms, and other residential areas, or hubs of activity like offices,
work places, gyms, libraries, etc. These systems manage and handle the air conditioning for
sustained periods of time and function under all environmental conditions.
These systems are first designed on specific parameters around which they would be
functioning. These parameters and factors that are used for the design of such systems are
usually very linear in their approach and are based on environmental factors, required condition
of the air, tonnage of air to be cooled, humidity, etc. These factors are set into place and used
to define the design parameters for the system. A system is then selected to meet these
requirements and installed with recommendations from manufacturers. Even though these
systems account for load requirements and have redundancies in case of excessive load, they
do not have any systems in place for reduction in consumption of energy at times when the
load is low. They have cut-off triggers and actuators for system standby till the load the
surroundings being conditioned reach an upper threshold at which the system will resume
working.
This type of system working is very linear and does not account for variation in loads by set
patterns of weather, day time, number of people, air swapping, etc, and hence cannot be
completely efficient in its energy use. This poses a problem as a system that could hence be
saving energy at lower load times continues to run at near full capacity to provide for a fraction
of the load. In light of that even Schneider Electric released a problem statement for devising
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an automation system of HVAC systems of large office buildings to optimise their
performance. This is also a major factor in international environment friendly protocols for
building construction and maintenance practices. In terms of energy efficiency, older systems
fall behind compared to more recent ones as concerns for these factors, environmental or
otherwise were not used to design them.
Also these systems have certain components and subsystems that can be optimised to increase
their performance. These factors sometimes go overlooked and can be a source of
improvement, if only minor, of the performance of these systems. The components that come
under the purviews of improvements are often ducts, their placements, the distribution system,
heat exchangers, cooling towers, etc. Placement of ducts, leakages, exposure to heat, insulation,
draft types in cooling tower, water loss, etc all can reduce the actual energy transfer and
especially if the mass of air or water has to travel larger distances to the place where the cooling
must be provided the energy loss increases.
1.2 Ideology of Solution
Here, in this study, the Library at MIT Manipal has been chosen as one such system. The age
of the system is significant compared to recent systems and has loads that vary to a great degreeover the course of a day and over the course of the week. The climatic conditions around the
system also have somewhat regular patterns. This system also has many older components, that
though have been serviced could possibly have scope for improvement. This system provides
cooling and working to a series of buildings that significantly represent an office space i.e. a
large number of people enter and leave these spaces and the trend for their presence can be
tracked for a long period of time. These buildings face regular and patterned solar exposure
and hence have measurable and patterned solar gain.
One final factor that plays an important role in the proper and efficient functioning of any
system is maintenance and care. If the system has suffered decay, corrosion, and
eutrophication, which HVAC units are prone to, they will suffer energy and in turn efficiency
losses. Broken components like thermostats, thermal sensors, actuators, etc. will cause also
hinder the functioning of the system as the values and inputs required for cut-off at threshold
and consume energy unnecessarily.
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Large HVAC systems also have a centralised control system called a BMS or a building
management system that measures checks, acts as a centre for controlling the system, virtual
switchboard for functions in the system and a feed for all data from the different sensors in the
system. These systems require constant checks and monitoring and need an operator at all times
to manually turn off and on the systems that need to run and that should be turned off. An
automation system would allow the BMS to work on a learning algorithm that understands and
matches patterns to those already input by the designers based on the building requirements.
This would allow the system to save energy by automatically and efficiently regulating the
required parameters to meet the desired load. The system itself would have full manual control
over the working of the unit in case required.
This project is a study of all these factors coming together to make HAVC systems more
efficient using the case of a preinstalled, the HVAC unit for the academic blocks of MIT, to
study where the system has scope for improvement. The study hopes to reveal trends and
patterns for peak loads and how to direct the system to intuitively learn maximum load timings
and variations in order to improve performance.
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2. Working of the Present System / Literature Review
2.1 Central HVAC Plant
The current HVAC plant installed is put in place behind the library and comprises of 2 screw
type and one centrifugal chillers. These are connected to 4 cooling tower, out of which one is
a redundant failsafe. This plant cools 3 buildings out of which one is currently under study by
this project.
2.1.1 Chiller System
The current chiller system employed utilises 3 discrete chiller plants, two screw type
compression chillers and one centrifugal type compression chiller. All these systems are
installed and were designed by Carrier Corporation. As any chiller system, they have 4 major
components, the compressor, the condenser, the throttle valve and the chiller.
1ChillerPlant
The compressors in these systems define the capacity and extent of load handled. The screw
type chillers take less load, while the centrifugal chiller takes more load.
Each chiller however has the same set of inlets and outlets.
1. Water returning to the chiller from AHUs in the buildings
2. Water going from the chiller to the AHUs in the buildings
3.
Water going to the cooling towers from the condenser
4. Water returning from the cooling towers to the condenser
These form 2 separate cycles of water that acts as a working fluid for transfer of heat. One
that transfers cold water to the AHUs for cooling the building spaces. A 3 pump system is
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used to ensure uniform distribution to each of the required spaces, i.e. the NLH, IC, and
Library. The same is applied with 4 pumps for the return of used water to the chillers. This
water is usually in a temperature range of 7.5 to 13 degrees Celsius and is cold enough to
allow the temperature from the vents of the rooms and halls to be 16 degrees Celsius which is
usually the lowest set point for cooling of any HVAC system. The temperature of the water
going out depends also on the temperature of the water coming into the plant. If the load on
the plant is extremely high then the water entering the chiller is too warm to be cooled
sufficiently enough to meet the requirements of the temperature set point of the water leaving
the chiller. The load on the plant reduces both as the area being cooled loses heat and the
actual sources of heat i.e. people and solar exposure reduce. At this point the chiller water
cycle comes back to an equilibrium of set temperature and the plant comes back to normal
load functioning.
At other times the plants must be manually turned off to prevent work from being done for an
almost no load requirement environment in the areas being cooled. At this point the room or
hall can become too cold even after cut-off as the of cold air remains to the AHUs. Even if
the AHUs cut-off cooling, with no heat loss to surroundings the room grows colder and often
uncomfortable. Thus chiller plant energy consumption is wasted in maintaining an area
cooled without requirements.
PlantLayout
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2.1.2 Cooling Towers
The cooling towers employed by this plant to remove heat from the gas in the condenser are an
upward induced draft type. This means that a powerful fan is used to suck air from the bottom
of these towers.
The water falls from the top of the tower and
is forced to interact with upward flowing air.
This interaction causes the water evaporate
and hence cool the surrounding falling water
by a few degrees. Though this method is
effective, there is a certain amount of loss of
water due to vaporisation. This means that
water must constantly be replenished into the
system. The water entering the cooling tower
is usually at 36 to 38 degrees Celsius.
Coolingtower
Cooling
tower
layout
The water that exits the cooling tower can be between 31 to 27 degrees Celsius. This allows
one to judge the load on the plant as the higher the temperature of water leaving the cooling
tower, the higher the load on the plant. A lower temperature of water leaving the cooling tower
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also means that the effectiveness of the condenser increases and hence can directly improve
the performance of the system. Though these towers are designed based on given
environmental and load parameters the effectiveness can vary and still be increased as
conditions and loads vary. Also the condition of the tower itself can mandate the effectiveness.
If the tower has algae or corrosion effecting the inner lining the effectiveness of the system is
reduced and can also cause damage to the piping and cooling of the entire system as a whole.
Thus this must be taken care of with great importance.
The piping of this system also plays a major role in how efficiently this system works as if the
piping and layout is not placed correctly the heat loss and gain to the surroundings can increase
and hence decrease the efficiency of the system as a whole. The piping if too long and exposed
to the sun for long periods of time, even after being insulated, can absorb heat and reduce the
effectiveness.
2.2 Air Handling Unit
Airhandlingunit
The air handling unit utilises water that comes from the chiller to cool the air for a certain area.
Usually each segregated area has an AHU allotted to it for cooling and maintaining air quality.
AHUs not only provide cooling but also maintain humidity, maintain Carbon Dioxide and
Carbon Monoxide levels in parts per million so as to not allow an area to become toxic.
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These systems consist of a centrifugal blower that directs the air and blows it into the ducts and
into vents. This starts a draft and current in the room to provide cooling. The fans usually suck
in air from one inlet that faces a mesh where water flows as a cooling medium. The water flows
through the mesh and cools it. Once the water supply to the AHU is cut-off the air passes
through an un-cooled mesh and doesnt get cooled itself enough to cool the surroundings and
thus the systems cut-off is controlled by thermostats that turn-off and on the AHU cold water
supply. If the amount and mass flow rate of cold water onto the AHU mesh is controlled by the
use of an actuator or digitally operated valve, the required amount of cooling can be provided
in smaller burst when need rather than having the entire system be active to provide cooling in
times of low load.
The following diagrams show the Layout for the AHU in the Library, the Innovation centreand the New lecture Halls. It shows the segregation and direction of usage of these AHUs and
how theyre linked to the central system.
AHUlayoutLibrary
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2AHUlayoutIC+NLH
As the AHUs act as distributers of the cold air, they are the central source of consumption of
the load to the chiller plant and thus directly impact the final and total load on the system as a
whole. Knowing this design parameters for AHUs can be altered and guided to allow for a
maximum efficiency of load distribution.
2.3 Design Parameters
Usually the design parameters for an HVAC system based on load are as follows:
1. Volume Tonnage: The volume of air to be cooled or the size of the area to be
conditioned.
2.
Humidity Regulation: Based on the humidity of the ambient air, the humidity in the
enclosed space can be set and regulated to maintain a comfortable environment.
3.
Heat Sources: The sources of heat around the area to be cooled, such as the heat from
the lighting, from people, from walls, etc. must be managed efficiently.
4. AHU Fan power: To ensure a continuous draft for the flow of air to be constant and
directed correctly for optimum comfort.
5. Sensor placement: The placement of sensors in the system can and often dictate how
the reading and how the system responds to the information.
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6. Air Change rates: This is used to ensure that stale air does not get cycled over and over
and that fresh air gets swapped into the system so the CO2levels do not rise.
7. Mass Flow rates: The amount of water required to be flowing in both the condenser and
the chiller cycles to ensure optimum transfer and flooding of pipes.
These parameters put together with many smaller others are used to design the initial scope and
usage of the system. As mentioned earlier these parameters are fixed when the design is drawn
up and are designed for maximum load centric performance. They can be optimised to allow
the system to conserve energy.
2.4 Energy Consumption
The energy consumed by the system is directly linked to the cost associated with running the
system. A system running in its peak and optimum condition will have a noticeably lower
running cost than one that is inefficient. The current system has an energy meter to track its
energy usage per day and is logged for everyday to check for tracking its usage and energy
requirements.
A significant portion of the energy consumed by these systems is by the central chiller plants.
Hence if the total energy in the system is to be reduced the total load on the plants must also
be directly be reduced. The following table shows the average daily consumption of energy of
the system on the given days of the week.
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a. Piping
b. Ducts
c. Cooling tower
d.
Pumps
5. Check components for scope of better maintenance. Check for corrosion, leakage,
breaking etc.
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4.1.2 Solar Exposure and Time of Day
Depending on the buildings location it can have varying degrees of exposure to sunlight
during the day. A building in the northern hemisphere above the Tropic of Cancer, if aligned
along the east-west direction will get the brunt of the sunlight from sunrise to sunset. The
same way, a building aligned along the north-south direction on any latitude will face
sunlight on one side in the morning and one side in the evening.
A building surrounded by other buildings is greatly protected from the direct radiation of the
sun. This allows the building to retain a large amount of heat and not lose energy to heat from
the sun.
The alignment of the building also dictates how the different heat zones will form across thebuilding. These heat zones, if tackled properly- can significantly reduce the amount of energy
lost to solar exposure.
Heat gain from solar energy and external air is one of the most significant causes of increased
energy consumption by the HVAC System.
Directed cooling at these heat zones created by solar exposure can greatly improve the
performance of a system as the heat generated by the walls and windows is directly and
cleanly absorbed; thereby helping the system maintain a comfortable temperature in space.
4.1.3 Climatic Variations
Weather and climate directly control the external conditions that the system must overcome
to maintain the specific conditions within the space. The climate of any given place follows a
yearly pattern that does not vary significantly. These conditions can therefore be mapped out
and a trend can be generated to allow the system to intuitively understand the needs of the
space being conditioned.
Though the weather changes daily it still follows the general trend of the climate of the
location. Since weather directly influences the conditions the plant must overcome, it
becomes an important factor to consider in making an intuitive system.
Climatic data over the last few years of any location can be used as a reference to map its
trend and teach the system the variations in load over the months. For example, a system can
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be instructed to understand that during summer, due to high external load, a more lax
approach to energy conservation can be put in place. However in months of rain and winter,
the system can learn that since climatic conditions outside are closer to the ones needed to be
maintained within the space, a stricter regime of energy conservation must be followed.
This also allows the concept of free cooling to aid the system in reducing its energy
consumption. Free cooling is when the air outside the space to be cooled is very close to the
temperature to be maintained within. This allows the system to swap fresh air directly from
the surroundings with a small level of cooling and maintaining humidity to condition the
space to a comfortable level. Free cooling allows the system to not use the chilled water from
the plant and thereby save energy.
4.1.4 Insulation and Reflective Shielding
Materials that are used for the faade of the building dictate how much heat the building will
gain. Buildings made of brick and concrete have a greater factor of insulation to the heat as
compared to buildings with the faade of glass.
For walls the insulation materials can be added directly in the mortar and thereby increase the
capacity of insulation. Recently, new materials such as astrofiber, which are extremely light
and highly insulated, can be mixed in the mortar and bricks. Even using waste plastic directly
in the mortar makes for cost effective insulation for buildings.
Since most buildings today utilize artificial lighting indoors the need for natural light has
reduced significantly. Therefore, reflective surfaces can be added to glass, which reduce the
infrared radiation entering the building. These reflective surfaces therefore directly reduce the
amount of heat gained by the buildings through the glass.
4.1.5 Thermal zoning
In any active space, there are always zones or areas that generate the most heat and hence are
centers for the maximum load to the system. It becomes very important to identify these
zones and thereby provide effective cooling to reduce the overall effect they have on the
system.
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The hubs of high activity, large computing centres, windows and walls exposed to sunlight,
cooking spaces and areas next to doors can be easily be identified as high heat zones.
Pantries, places of high activity, computer zones can usually be effectively cooled by
providing high output diffusers or vents that provide high levels of circulation. This cools the
area, thereby significantly reducing the heat it spreads to the entire system.
Walls, windows and cooking areas should preferably have vents over them to suction out the
hot air, so as to effectively reduce the heat immediately from the system. This allows cool air
to be circulated into the region faster and the hot air to be removed and thereby maintaining
the conditions required for the area.
As a general principle, doors that open out to the outside environment usually have a high
power blower generating an air wall that prevents hot air from the outside from mixing with
the cool air inside.
4.2 Current System
The current system is designed with the basic design parameters in mind and has been
designed to handle a redundantly high load if the need arises. However this system itself does
not prepare for low loads and has issues with circulation. This entails that the system isdirectly consuming large amounts of energy that can thus be conserved.
Most systems in place in buildings, the direct set of design parameters, ensures cooling and
maintaining a specific condition in the given space however it does not always aim at energy
conservation.
The current systems are not smart and often need direct or complete supervision to run
efficiently and run without a hitch. This increases the effective cost of the system and also
leaves room for negligence in monitoring the system. Though a BMS manages a system
fairly well it only regulates basic supply and demand parameters for the system and does not
monitor the actual load on the system.
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Time Room temp No. of people
09:00 AM 25.3 8
09:30 AM 25.3 48
10:00 AM 25.0 60
10:30 AM 24.5 62
11:00 AM 25.0 94
11:30 AM 24.2 80
12:00 PM 24.9 112
12:30 PM 24.8 118
01:00 PM 24.2 8401:30 PM 24.5 90
02:00 PM 24.9 100
02:30 PM 25.2 98
03:00 PM 24.7 100
03:30 PM 24.8 109
04:00 PM 24.3 82
04:30 PM 23.6 85
05:00 PM 23.5 89
05:30 PM 23.6 91
06:00 PM 24.4 93
06:30 PM 24.9 110
07:00 PM 24.7 95
07:30 PM 24.9 98
08:00 PM 24.7 80
08:30 PM 24.3 80
09:00 PM 24.1 32
09:30 PM 23.8 30
10:00 PM 23.3 22
10:30 PM 23.1 11
11:00 PM 22.5 8
24.36 74.34
15
15.5
16
16.5
17
17.5
18
18.5
19
19.5
09:00AM
10:00AM
11:00AM
12:00PM
01:00PM
02:00PM
03:00PM
04:00PM
05:00PM
06:00PM
07:00PM
08:00PM
09:00PM
10:00PM
11:00PM
AHUwithCooling
Airtempfromventlefton
09:00AM
10:00AM
11:00AM
12:00PM
01:00PM
02:00PM
03:00PM
04:00PM
05:00PM
06:00PM
07:00PM
08:00PM
09:00PM
10:00PM
11:00PM
Room
Temperature
2
Roomtemp
0
20
40
60
80
100
120
140
09:00AM
10:00AM
11:00AM
12:00PM
01:00PM
02:00PM
03:00PM
04:00PM
05:00PM
06:00PM
07:00PM
08:00PM
09:00PM
10:00PM
11:00PM
No.ofPeople
No.ofPeople
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The above data represents measurements from a day when the air conditioning in the hall was
active throughout the day and hence can be seen that the room temperature falls where the
number of people in the hall reduce. The same way when the AHU is cut-off the temperature
rises in the hall and makes it uncomfortable. The thermostat setting for the hall is 24degrees
Celsius and thus can be seen to vary around it.
At the same time the cooling tower water temperatures were checked to map load on the
system and corresponded with the load given by the number of people and the heat the
building faade received during the day.
Time Cooling Tower Out
09:00 AM 29.35
10:00 AM 30.5
11:00 AM 29.7
12:00 PM 30.5
01:00 PM 30.2
02:00 PM 30.8
03:00 PM 30.9
04:00 PM 31.1
05:00 PM 30.8
06:00 PM 29.4
07:00 PM 29.35
08:00 PM 31.9
09:00 PM 28.1
10:00 PM 27.9
11:00 PM 27.5
The AHU cut-off functioning blower air temperature is approximately 19 degrees Celsius and
can be seen in the above graphs. This shows and explains the marked increase in the room
temperature as the heat from the walls and the people could not be compensated enough to
maintain the room at a comfortable temperature. Increasing the performance of the system is
a major factor but human comfort cannot be ignored. Thus the automation system would
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balance the needs of both together and essentially allow the system to be cost effective and
useful.
The following data shows glass temperature and exposure to the hall to heat from the glass.
Time Inner outer glass temperature
09:00 AM 27.1 30.1 28.28571429
09:30 AM 27.2 34.9 28.6
10:00 AM 26.88 36 28.81428571
10:30 AM 26.7 36.6 29.48571429
11:00 AM 27.11 36.2 29.9
11:30 AM 27.3 36.4 30.1
12:00 PM 27.3 36 30.2
12:30 PM 27.5 34.6 29.8
01:00 PM 26.8 35.2 28.7
01:30 PM 27.4 34.4 29.5
02:00 PM 27.3 34.5 30
02:30 PM 27.2 34.3 30
03:00 PM 27.3 34.3 29.5
03:30 PM 27.4 34 29.1
04:00 PM 27.2 34 29
04:30 PM 27.4 33.2 28.2
05:00 PM 27.3 32.8 28
05:30 PM 27.3 31.6 28.3
06:00 PM 27.4 31.6 27.2
06:30 PM 28.4 31.6 28.6
07:00 PM 28 30.9 28.2
07:30 PM 28 30.3 2808:00 PM 27.8 30.3 27.8
08:30 PM 27.2 30.3 27.3
09:00 PM 27.3 29.5 27
09:30 PM 26.9 29.2 27.5
10:00 PM 26.6 28.8 27.1
10:30 PM 26.4 28.4 26.98
11:00 PM 26.1 28 26.86
27.23413793 32.68965517 28.55261084
20222426283032343638
09:00AM
09:30AM
10:00AM
10:30AM
11:00AM
11:30AM
12:00PM
12:30PM
01:00PM
01:30PM
02:00PM
02:30PM
03:00PM
03:30PM
04:00PM
04:30PM
05:00PM
05:30PM
06:00PM
06:30PM
07:00PM
07:30PM
08:00PM
08:30PM
09:00PM
09:30PM
10:00PM
10:30PM
11:00PM
SurfaceTemperature
InnerWall OuterWall WindowGlass
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The heat given off by the lighting in the library hall was also considerable as the grill holding
it showed a temperature of nearly 42degrees in an air condition environment. These fixtures
were also active throughout the day and hence contribute to the heat gained by the system.
However, during day time, in the presence of sufficient natural light the system would lose
less energy to these fixtures. If however these fixtures must be kept active, tinting of the
windows would serve as an alternative to reduce heat loss from the glass.
The Following data represents the Main hall of the Library.
Time Room Temp No. of People Vent Temp External Temp
09:00 AM 24 16 17.2 27.8
10:00 AM 23.8 22 16.7 33.8
11:00 AM 23.9 21 17 34
12:00 PM 24.1 32 16.8 34.5
01:00 PM 24.2 35 17.2 35
02:00 PM 23.9 28 17.5 34.5
03:00 PM 23.9 27 16.9 34
04:00 PM 24 25 16.6 32.7
05:00 PM 23.8 30 16.9 30.5
06:00 PM 23.7 40 17 30
06:30 PM 23.7 34 17 27.9
07:00 PM 23.6 5 17 27.5
23.88333333 26.25 17.16363636 31.85
The above data shows the how since the hall is significantly isolated and does not have a
very large number of people and the variation in the number of people does swing greatly
LibraryMainHall
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over the day the hall temperature does not vary too much. The hall however does get colder
as the lower levels do not have complete and proper circulation. The temperature therefore
continues to fall and the thermostat does not cut off appropriately and keeps consuming
energy.
In a similar way one of the larger more actively used halls has the following trend.
The black line represents the number of people, and the blue the room temperature. The trend
still has a similar pattern where it follows the load that trails behind the number of people in
the room. As the people in the room fall, as expected, the room temperature falls. It also
happens at the end of the day when the heat from the air is reduced.
The following diagram represents the zones for heating as noticed in the library on the second
floor where the GSH and the TBS are located.
2nd
floor
heat
zones
TBSTem erature no.of eo le
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These halls also have artificial lighting that remains on throughout the day and thus have no
special need of natural light. The light not only act as a source of heat themselves with the
mesh covering them reaching temperatures of 54oC and acting as significant sources of heat.
Also this makes clear windows a little redundant and therefore one or the other can be done
away during the day, i.e. either the lights be turned off and natural light be allowed to
illuminate the room or use reflective films on the glass to reduce heat transfer and use
artificial light in the hall.
4.3.2 New Lecture Hall and Innovation Centre
The central plant provides cooling to 2 other buildings, i.e. the New lecture halls and the
Innovation centre. The following diagram shows the heat zones in the Innovation centre.
3Innovation
centre
heat
zones
These zones shift during the day and time of day. The faade receives a significant amount of
heat from the morning sun and heats the building to a temperature near almost 27.2 27.6
degrees during the morning. The heat persists as there are no AHUs dedicated to the entire
area. The dround floor is kept cool by a single AHU and due to natural convection remains
that way. This area is a significant source of load.
The innovation center however in terms of human load has significantly lower loads than the
NLH. The NLH as a host to classes during the period of the day has a populous load of near
750-850 people every day. The load of people entering these classes does not vary
significantly from a norm as the time tables of most classes are set in advance and can thus be
used to generate a pattern for the usage of the halls. The halls themselves have a tendency,
however, to get cold over a period of time as again the circulation of air across them is not
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NLH 205
TimeRoom
TemperatureNumber of
PeopleGlass Temperature
(with Curtain)Glass Temperature(without Curtain)
Air fromvent
08:00:00 23.8 62 25.7 26.8 17.1
09:00:00 23.4 66 25.6 27 17.2
10:00:00 23.1 66 26 27.2 17.1
10:15:00 22.9 45 26.1 27.3 17
10:30:00 23.2 61 26.1 27.3 17
11:30:00 22.8 61 25.8 27.1 16.9
12:30:00 22.6 63 26 27.4 17.2
12:45:00 22.3 3 26.2 27.5 17.1
13:00:00 21.8 0 26.3 27.9 17.1
14:00:00 21.7 0 27.5 28.3 16.9
15:00:00 21.9 0 28.4 30.1 17
15:15:00 21.9 0 28.5 30.2 17.1
15:30:00 22 0 28.5 30.2 17.2
16:30:00 21.9 0 30.1 32.3 17.1
17:30:00 21.6 0 30.9 34 16.9
18:00:00 22.3 17 29.9 33.8 17.3
19:00:00 21.9 16 28.6 32.6 17.1
20:00:00 21.8 19 27.7 31.3 16.9
NLH 403
TimeRoom
TemperatureNumber of
PeopleGlass Temperature
(with Curtains)Glass Temperature(without curtains)
Air fromvent
08:00:00 24 59 29.3 35.4 16.9
09:00:00 23.7 62 34.5 42 17.1
10:00:00 23.4 62 34.4 42 17.2
10:15:00 23.2 23 34.3 42 17.2
10:30:00 23.8 61 34.7 42.1 17.2
11:30:00 23.7 61 34.9 42.2 17.1
12:30:00 23.5 62 34.6 41.9 17
12:45:00 23 4 34.6 41.8 1713:00:00 25.7 58 34.4 41.6 17
14:00:00 24.2 64 33.6 39.9 16.8
15:00:00 23.9 64 32.7 37.6 16.9
15:15:00 23.5 39 32.6 37.6 17
15:30:00 24.1 63 32.6 37.4 17
16:30:00 23.7 63 31.3 35.1 17.2
17:30:00 23.2 62 30.6 33.9 16.9
18:00:00 21.7 4 29.5 32.3 17
19:00:00 21.4 0 28 31.2 16.8
20:00:00 21.3 0 27.8 29.3 16.9
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Computer Lab 3rdFloor IC
Time Room Temperature Number of People Glass Temperature Air from vent
08:00:00 24.2 7 26.4 17.1
09:00:00 25.1 72 26.6 16.9
10:00:00 24.8 71 27 17.111:00:00 24.5 67 27.5 17
12:00:00 24.1 3 28.2 17.2
13:00:00 24.1 0 31 16.9
14:00:00 26.2 69 33.2 17.1
15:00:00 24 69 34.6 17
16:00:00 24.3 63 34.9 17.2
17:00:00 23.8 4 35.9 16.9
18:00:00 23.6 0 35.4 17.1
4thFloor Public Area IC
Time Room Temperature Number of People Glass Temperature Air from vent
08:00:00 24.1 7 38 18.8
09:00:00 24.4 6 40.1 19.1
10:00:00 24.7 9 42.3 19.2
11:00:00 25.2 4 42.5 19
12:00:00 25 7 42.4 18.9
13:00:00 24.9 8 41.8 18.9
14:00:00 24.7 11 41.1 18.8
15:00:00 24.2 3 40.4 19.2
16:00:00 24.1 1 39.2 19.1
17:00:00 24 1 38.4 19
18:00:00 23.9 1 37.1 18.8
19:00:00 23.7 5 35.2 18.5
20:00:00 23.5 1 31.5 18.4
21:00:00 23.1 1 28.4 18.3
4thFloor 04 Classroom IC
Time Room Temperature Number of People Glass Temperature Air from vent
08:00:00 25.2 56 38 17.3
09:00:00 26.1 57 40.1 17.1
10:00:00 25.8 57 42.3 16.910:15:00 25.4 5 42.3 17
10:30:00 26 53 42.4 17
11:30:00 25.8 53 42.5 16.8
12:30:00 25.7 54 42.2 17.1
12:45:00 25.4 0 42 17
13:00:00 26 48 41.8 17.1
14:00:00 25.4 48 41.1 17.2
15:00:00 25.2 49 40.4 17.1
15:15:00 24.9 17 40.3 17
15:30:00 25.1 47 40.1 17.1
16:30:00 24.8 45 39 17
17:30:00 24.6 37 38.1 16.9
18:00:00 23.9 0 37.1 17
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In the Innovation centre- the most significant source of heat is the sun. The number of people
in this building on any given day rarely exceeds 150. And the days the loads are high it is due
to classes on the 5thfloor where the trend can again be mapped. The zones of heat therefore
are clearly the glass faades that are exposed to sunlight through almost all the day as the
building is aligned along the north-south direction. Each side of the building gets nearly 6
hours of direct heat from the sun, sending the glass temperature to 43oC and more sometimes.
This temperature can be felt as the spaces heat up noticeably and only cool down once the
sun has set. The east facing faade though tends to get warmer as the brunt of the morning
sun heats it. Also though the NLH covers for a small part of the morning, it is not significant
in the grand scheme of the trends.
The data below shows the water temperature from the inlet and outlet of the chiller plants and
shows a direct correlation with the above data, proving a trending pattern of loads
Time Temp Inlet Temp Outlet
09:00AM13.5 10.8
11:00AM12.1 9.4
01:00PM
11.1 8.4
03:00PM10.9 8.7
05:00PM10.2 8.2
07:00PM9.5 7.9
09:00PM8.9 7.4
While studying and measuring these systems, it was noticed that certain parts of the system
needed thorough maintenance and the piping did in fact have scope for improvement. ThePlant is located behind the library and is also exposed to sunlight till almost 2:00pm. The
cooling towers, which are on top of the plant thus take direct heat from the sun for a
significant portion of the day, also when the load inside in maximum. The piping from the
towers that leads into the plant housing, though insulated, is painted black. The outer
temperature of this piping, when measured, was nearly 48 degrees Celsius which leads to the
conclusion that heat lost by the water in the tower would be slightly regained in the piping.
This was confirmed by the temperature difference in the water in the tower and the
temperature sensor checking the water as it enters the condenser and showed a difference of
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about 0.2-0.4 degrees. As the length of the piping is not significantly long enough for such
losses, the insulation is therefore not effective.
The cooling towers were also facing corrosion and had a great degree of eutrophication lining
the upper and lower tank. This was noticeable in the first and less in the consecutive tank.
The algae in the system would causing clogging and lining along the pipes would corrode and
also become ineffective for heat transfer in the system.
5. CONCLUSIONS AND SCOPE OF FUTURE WORK
5.1 InferencesThe following inference can be drawn from the above data and trends:
5.1.1 Load and Number of People
The load a system bears and therefore the room temperature rise in a system is a direct
function of the number of people in the room or hall. This is a fairly obvious inference
however the behaviour of the pattern is worth taking notice of.
The pattern itself goes to show the actual temperature of the surrounding directly trails behind
the appearance of load, i.e. the room gains heat as the number of people increase. This sudden
rise can be directly countered by altering when and how the system cuts off.
At low load times the system cuts off as the room has reached a desirable temperature and
allows the room to heat up so as to allow the cooling to start up again. However when a
sudden increase in load happens at time like this the system has to work twice as hard to
ensure the room/hall return to regular comfortable temperature. Therefore increasing the
energy consumed. The same way once the load suddenly drops the room cools more rapidly
and often beyond the set point to a colder temperature, before the cut-off kicks in. therefore
extra work is again consumed.
5.1.2 Solar Gain
The relation between heat gained and solar exposure is a direct one and one that does not
need noting. However it the location and the generation of increased heat zones that must be
noted.
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Solar gain does not affect the entire building in one go. It effects the side of the building that
is directly exposed to sun light. This allows for us to realise that a direct pattern for the
generation of heat zones based on time can be made so as to effectively counter the heat and
ensure maximum cooling. The system can also be taught to understand the shift in solar
pattern with seasons and time of year so as to know where the zone of heating will will shift
and increase during certain months.
Also cooling during day requires higher energy while the need reduces after sunset as the air
surrounding the area to be condition cools down as well. All of these things can be taken into
consideration to create a pattern for solar gain and loads.
5.1.3 Climatic Variation
The climate of an area also plays a key role in how much load the system must endure. The
current climate that the given system must endure is one of sever heat. This directly reduces
the performance of the system as external temperature to be overcome is higher and also the
temperature the condenser and cooling towers must combat is higher as well.
During the next semester however, once the rains start the system will have a lower loads as
the outside air will be much cooler and also damper. The system can thus learn when the
climate is forbidding and when it aids the system as a whole. Under this parameter the
laxities of how much energy can be conserved can be wither strict during low load times or
lenient during high load times such as summer.
The weather also helps play a significant role in the load on the system. Though it follows a
pattern the climate sets it has a very many random variables such as winds, cloud, sparse or
sudden rain, etc. that cannot be tracked easily and even if data is sent directly to the system
via the internet, the actual weather over the current location cannot be accurately mapped or
made a trend of. Though the current conditions can be easily sensed through appropriate
sensors placed strategically.
5.1.4 Insulation and System Maintenance
The systems current situation went show that it required strict maintenance. The cooling
towers need cleaning. The piping can be directed better to reduce solar exposure and
environmental exposure. The thermostatic sensors placed in the AHU can be made more
effective or in the case they are broken should be replaced.
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The building of glass and dark coloured paint are more susceptible to heat from the outside
and more likely to retain heat as well. All of these factors play a key role in how the tangible
and fixed characteristics of the building itself can reduce the effectiveness of the system and
increase load on it.
5.2 Improvements and Future Design Considerations
The following list of improvements and design considerations can help reduce the energy
consumption by the HVAC system. These use both direct solutions to tangible problems in
the system as well the trends and algorithms to be set in place in the software.
5.2.1 Improvements
The following improvements can be implemted on HVAC systems in general:
Graduated control valves for chilled water delivery to building and AHUs
o This allows for a controlled amount of chilled water to enter the cooling grate
of an AHU instead of a complete cut-off. These will allow for a cooling to be
provide to an area at controlled fractions so as to optimise energy usage. The
same way depending on the load on the building a supply valve can control the
amount of chilled water being directed towards it.
Speed controller for fans in AHUs
o These allow the system to maintain a changeable air delivery system that on
peak loads can deliver the maximum supply of air and cool the area rapidly
and also increase circulation. However at lean time it can be used coupled with
the graduated chilled water valve to deliver controlled cooling.
Reflective Surfaces on glass to reduce IR heat gain.
Load segregation in air ducts leading from AHU
o Some spaces are often divided into smaller spaces occupied by fewer people,
this causes these smaller spaces to cool faster. However since they have a
centralised AHU for these places the cut-off cannot be made on the whole
system on account of one smaller space. Therefore a simple load segregation
system can control either dynamically or statically the cooling being provided
to such an area. A static system would involve using smaller pipes that are
baffled to reduce flow and provide accurate cooling
Arrangement to allow Free cooling
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o Free cooling can easily reduce the amount of energy consumed by the system
and help drastically improve performance. A simple inlet from the outside
surroundings with humidity control can be used to create the use of free
cooling.
Directing pipes underground to act as heat sink
o Pipes directed underground from the cooling towers can lose some extra heat
thereby increasing the effectiveness of the cooling towers. This extra length of
pipe can help improve the performance of the system as the extra heat can be
given away to the ground. Also this improves the insulation capacity of the
pipes they dont gain heat from direct sunlight or hot air it comes in contact
with.
Array of sensors to check weather
o This array of sensors would directly guide the system in real time as where the
load will shift and if the weather will permit for any saving of energy. The
sensors in play would be, a radiosity sensor to check solar exposure and
clouds, humidity and wind gauge to check for wind, chance of rain and a
thermometer to check ambient temperature. These sensors would be placed on
top of the buildings to prevent any obstructions and for clear and direct
measurements.
RF-Id tag on people suing the space
o This measure is usually possible in a work place where employees/students are
given ids and can be used to track real time the presence of people in an area.
Coupled with the algorithms for trends of personnel usage, updates to the
current loads can be made adequately.
Locating vents and thermostats appropriately
o
This allow the system to channel the cold air and suck warm air most
effectively. A good pattern of circulation the takes into account significant
heat zones can increase performance of the system. Also the thermostats
placed in the correct inlet valves give a correct reading of the room
temperature and thereby reduce unnecessary cooling or heating of the room. It
also prevents heat zones from developing when placed strategically.
Manual over-ride in the Space being conditioned and in the BMS
Strict regime of system maintenance and redundancy
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o Proper and appropriate maintenance of any system can
5.2.2 Algorithms and Trends
With the above tangible improvements in place the following algorithms can be put in place
to ensure the system conserves maximum energy.
People
o The trend for the number of people as shown in the report can easily be
mapped for a space that is used every day. With this trend the system can
predict when a load might appear and when the loads will most likely reduce.
Based on the above trend the BMS can control the graduated AHU valve for agiven space and provide the optimum cooling needed. It would pre-emptively
cool areas expecting high load and reducing cooling in areas expecting a
reduction in load. If RF-id tags are available for tracking, the algorithm would
have real-time support for accurately changing and the needs for the given
space.
Solar gain
o
The algorithm for the above would dictate the extent of cooling given y thecontrolled fan so as to circulate a major portion of the air towards the heat
zone and sweep away the heat and all-round cool the area faster while
removing the liable heat zone from increasing direct load on the cooling grate.
This coupled with the trend from personnel usage would allow the system to
judge the peak loads acting on the system and accordingly allocate cooling
water better to the appropriate areas i.e. the graduated valves for buildings can
be used to direct flow to a specific building in high use while away from a
building in low use.
Climate
o This algorithm would dictate the need for free cooling or the need to shift the
strictness of the energy saving algorithms. As mentioned above this would
direct based on a pattern of climate noticed before
Weather
o Using the sensors and climatic patterns an algorithm in place can directly use
the given data to shift usage and requirement patterns to conserve energy, e.g.
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if the sensors dictate long term cloudy weather the cooling directed at
windows can be reduced so as to direct the system to respond to real time load
changes.
Over-ride requests
o Any system that has a high level of automation must have secure and
important over-rides in place in case the system has predicted the pattern for
usage in the wrong manner or has malfunctioned. These over-ride requests can
be handled by the operator of the BMS and manually over-ride the system to
meet the requested requirements.
5.3 Scope for Future Work
A deeper more thorough study of HVAC systems usage and components could lead to better
design considerations for future systems. This could help benefit current systems and the
study can extend to help improve pre-installed systems. Since changing systems currently in
place is difficult and more expensive the study can extend to understand more cost effective
ways to improve pre-installed systems.
The study can also extend to other systems such as lighting, hot water supply, etc to see the
maximum possible energy conservation and aim to make systems in large spaces such as
offices most efficient and save on costs of energy.
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References
http://www.brighthubengineering.com/hvac/859-factors-affecting-hvac-designing-and-heat-
load-calculations/
http://www.teriin.org/ResUpdate/reep/ch_5.pdf
http://www.intertek.com/hvac/performance-testing/
http://built-envi.com/portfolio/hvac-system-operational-characteristics/
http://www.brighthubengineering.com/hvac/26100-hvac-system-what-is-a-zone-part-
one/?cid=parsely_rec#imgn_1