UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA CHEMICAL ENGINEERING LABORATORY (CHE453)

Name : Ahmad Siddiq bin mohd sani (2013467436) Group : eh2203aExperiment : l6 concentric Heat Exchanger date performed : 1st october 2014SEMESTER : 3programme / code : eh220/Che524submit to : puan rabiatul adawiyah Abdol Aziz

No.TitleAllocated Marks (%)Marks

1Abstract/Summary5

2Introduction5

3Aims5

4Theory5

5Apparatus5

6Methodology/Procedure10

7Results10

8Calculations10

9Discussion 20

10Conclusion5

11Recommendations5

12Reference 5

13Appendix 10

TOTAL MARKS100

Remarks:

Checked by:

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Date:

Abstract

This report is done to test the overall learning process that I have learn in classroom and to apply it to the real world engineering The experiment that I done is the concentric heat exchanger which relate to the heat transfer and the thermodynamic subject. The important point in this experiment is the temperature difference and the flow rate and the direction of the flow. However, by doing the calculation after the experiment, we can get other things, such as, the heat emitted, log mean temperature difference, and heat transfer coefficient

Introduction

Heat exchanger is a device designed specifically to transfer heat or exchange heat between two medium whether it is liquid-air or liquid-liquid heat exchange between them. In industry, there many uses for this heat exchanger such as the for the cooling process or to retain heat energy such as in heat recovery steam generator . It come to be common today because of it flexibility and simplicity to operate. In addition, there many types of heat exchanger that can be found today such as shell and tube heat exchanger, plate heat exchanger, concentric heat exchanger and many more. Usually, it is their heat transfer area design or the fitting of its type toward specific process that differ them.In this experiment, we will focus on the heat transfer process by using the concentric heat exchanger. This would be done in the SOLTEQ Heat Exchanger (Model: HE 158c) which is consists of other type heat exchanger which can be used by changing the arrangement. To minimise the water loses, the pipe that channel the water to the heat exchanger is insulated and the hot water flow in the inner tube while the cold water at the outer tube. There are temperature sensor installed at the inlet and outlet tube to measure the temperature difference. The temperature that been investigate and flow rate and be seen at the instrumentation panel. The hot water system is totally self-contained. A hot water storage tank is equipped with an immersion type heater and a temperature controller. Circulation to the heat exchanger is provided by a pump, and water returns to the storage tank via a baffle arrangement to ensure adequate mixing .The heat exchanger uses the heat transfer knowledge in order to understand how it works. Basically, it relate more on convection and conduction in it process. There will a radiation too but due to its small effect. Engineer or scientist usually neglect it in the heat exchanger. The convection occur when heat is transfer from the hot fluid to the wall of the tube. The flow rate will give a significant effect on the process. It will followed by the conduction at the wall of the tube. It will be better if the tube is thin to increase heat transfer rate but strong to withstand high pressure. The convection will occur again when the heat is transfer from the wall of the tube to the coolant. There are factor that effect the heat transfer such as the flow of the fluid, whether it is counter current or co current or the flow rate of the fluid.

Counter-current flow

Co-current flow

Objective-To investigate the heat transfer and the heat loss for energy balance study-To calculate the log mean temperature difference-To calculate the heat heat transfer coefficient-To perform the temperature profile study and the flow rate effects on heat transfer

TheoryThe conservation of energy is First Law Thermodynamics which is the theory that involve in operation of the cooling tower. As we know, conservation energy is the energy that enters the system is same as the energy that exit the system and it can be neither destroyed nor created. Energy just transformed from one form to another.

The important in understanding the theory of this experiment is to know concept of the heat transfer since this experiment involve the transfer of heat between the fluid. As stated in the introduction above this experiment involve mainly on conduction and convection. Therefore, we want to know how to calculate the heat that been transfer into between the fluid. The temperature of hot and cold water at the inlet is the key in calculation of the heat transfer. Both of them are the responding variable data that we collected after manipulating the flow rate of the hot and cold water and the flow direction. So, we will calculate first the heat that been transfer by using the energy balance.

(1)

By assuming there are no phase changes and work done toward the system and the potential and kinetic energy is negligle. We will get the formula of

Where

We will get the the amount of heat emitted by the hot fluid and the heat absorb by the cool waterThe heat transfer coefficient also can be obtain by relation between the amount of heat that been transferred which is calculated by using

whereArea= **L LMTD (Log Mean Temperature Difference)

For counter-current flow For co-current flow

Apparatus-Heat Exchanger Training Apparatus (model:HE158C)

How WaterCold Water TankMotor PumpRotameterControl PanelConcentric Heat ExchangerHe

General Starting ProcedureGeneral Start-up Procedure1. The quick inspection must be done to ensure the equipment in proper working condition2. Except valve 1(V1) and valve 2(V12) all the the other valve must be close3. The water supply hose was connected to V27 to fill up the hot water tank until it full. The valve was closed.4. The water supply hose was connected to V28 to fill up the hot water tank until it full. The valve was left open to ensure continuous water supply5. The drain hose connected to cold water drain point6. After the main power was switch on, the heater for the hot water tank is set by at the temperature controller to 50C7. Leave the apparatus until it reach the temperature of 50C.8. The experiment was ready to run

Experiment A: Counter Current Concentric Heat ExchangerProcedure1. V1,V12,V15,V18, and V28 opened while V16,V17,V27,V29,V30 closed for the counter-current arrangement. The other valve do not involve2. Pump 1(P1) and pump 2(P2) opened3. The flow rates needed obtained by open and adjusting V3 and V14 for cold and hot water streams4. Leave the apparatus for 10 minutes for it to reached steady state5. Record the initial reading FT1,FT2,TT1,TT2,TT3 and TT46. Step 3 to 5 repeated with different combinations of flow rate7. The pump switch off order for the arrangements of the next experiment

Experiment B: Co-Current Concentric Heat ExchangerProcedure1. V1,V12,V16,V17,V28 opened while V15,V18,V27,V29 and V30 closed. The other valve will be leave alone2. Pump 1(P1) and pump 2(P2) opened3. The flow rates needed obtained by open and adjusting V3 and V14 for cold and hot water streams4. Leave the apparatus for 10 minutes for it to reached steady state5. Record the initial reading FT1,FT2,TT1,TT2,TT3 and TT46. Step 3 to 5 repeated with different combinations of flow rate7. After finished the experiment. The shut-down procedure was done

General Shut-down Procedure1. The heater switched off2. When the temperature drop below 40C, both of the pum switched off3. The main power switch off4. All the water in the process line drain off while the water in hot and water tanks retained5. All the valve closed

Result & CalculationCounter-CurrentFT1(LPM)FT2(LPM)TT1(C)TT2(C)TT3(C)TT4(C)

10234.428.348.349.2

10430.928.648.549.9

10630.328.848.249.3

10830.429.248.149.1

101030.529.548.249

Average 31.328.848.349.3

FT1(LPM)FT2(LPM)TT1(C)TT2(C)TT3(C)TT4(C)

21030.329.74649

41030.729.947.549.5

6103130.247.649

81031.130.248.249.3

101031.230.348.249

Table 1(a)

FT1(LPM)FT2(LPMLMTD(K)

10.02.06.10.9-4.2600.12-17.35.22

10.04.02.30.9-1.6000.25-19.191.77

10.06.01.51.1-1.050.453-19.191.16

10.08.01.21-0.840.54-18.800.94

10.010.010.8-0.700.56-18.600.80

FT1(LPM)FT2(LPMLMTD(K)

2.010.00.63-0.082.09-17.470.01

4.010.00.82-0.221.40-18.190.26

6.010.00.81.4-0.330.98-17.700.40

8.010.00.91.4-0.490.98-18.650.56

10.010.00.90.8-0.630.56-17.540.76

Table 1(b)Example temperature profile of counter-current flow: At 10 (LPM) hot water and 2 (LPM) cold water

Co-CurrentFT1(LPM)FT2(LPM)TT1(C)TT2(C)TT3(C)TT4(C)

10230.933.148.849.2

10430.83248.749.2

10630.431.548.549.2

10830.331.148.549.1

101030.331.148.449.2

FT1(LPM)FT2(LPM)TT1(C)TT2(C)TT3(C)TT4(C)

21030.430.746.549.3

41030.530.947.849.3

61030.53147.949.3

81030.431.148.649.6

101030.531.248.849.7

Table 2(a)

FT1(LPM)FT2(LPMLMTD(K)

10.02.02.20.4-1.540.06-16.971.92

10.04.01.20.5-0.840.14-17.541.02

10.06.01.10.6-0.770.25-17.940.91

10.08.00.80.6-0.560.33-18.090.66

10.010.00.80.8-0.560.56-18.090.66

FT1(LPM)FT2(LPMLMTD(K)

2.010.00.32.8-0.041.95-17.300.05

4.010.00.41.5-0.111.05-17.830.13

6.010.00.51.4-0.210.98-17.830.25

8.010.00.71.0-0.380.70-18.330.44

10.010.00.70.9-0.490.63-18.330.57

Table 2(b)Example of temperature profile for co-current:At 10(LPM) hot water and 2(LPM) cold water flow

Sample CalculationConversion of LPM

Assume that density of water along the experiment constant.

Heat capacity of water

Heat Transfer 6.1K

Log Mean Temperature Difference (LMTD)

For counter-current

LMTD= -17.3K

For co-current

LMTD= -16.97 K

Heat Transfer Coefficient

Area= **L

Effect Of Flow Rate On Heat Transfer In Counter-Current Flow

Graph 1(a)

Graph 1(b)

Effect Of Flow Rate On Heat Transfer In Co-Current Flow

Graph 2(a)

Graph 1(b)

DiscussionAs we know, the most important in this experiment is the temperature that been measure is the key to understanding about the heat exchanger.The difference when we manipulate the flow rate whether it it cold or hot water does not give drastic increase in the reading of the temperature. It usually will brought effect ranging from to 0 to 1.0of the reading. For example when we change the cold water flow rate at the counter-current flow from 2(LPM) to 4(LPM), the reading of cold water outlet,TT4 change from 49.2 to 49.9.But we must notice that the temperature of supposed to be cold water is more higher than the hot water. This thing might be due to the error of the apparatus or material. However, the calculation still going through to investigate more things which relate to the heat exchangerFor counter-current flow, when the volumetric flow rate of cold water increase, the amount of emitted release decrease from -4.260(kW) to -0.70 (kW). The negative sign indicate the heat is release. But while volumetric flow rate of cold water increase, the rate of heat absorption increase from (0.12)to (0.25). However, this pattern will be inverted when the flow rate of hot water increase, the heat emitted increase but the amount if heat absorb is decreasing from time to time. The heat emitted and absorb in the co-current also follow the same pattern in the counter-current low. There also a reason why the heat emitted value is negative. When heat is emitted it will carry negative value due to the loss of energy to the surrounding. By calculating the difference between the hot water temperature and cold water temperature inlet and outlet, we can calculate the log mean temperature difference(LMTD). Denote that, the larger the LMTD, more heat is transferred by logically see the difference in the temperature at the inlet and the outlet.Finally, the other thing that we can investigate in this operation of heat exchanger is the effect of the flowrate on the heat emitted and absorb, I choose to relate between the hot water flow rate to heat emitted and cold water flow rate to heat absorb. By referring to the graph 1(b) which is for the counter current we can see that as the hot water flow rate increase, the heat emitted increase, the more negative the value mean, more heat is transferred, and for graph 1(a), the higher the cold flow rate, the higher the amount of heat absorbed. As for the co-current flow, the graph we refereed is graph 2(a) and graph2(b), as the flow rate of hot water increase, the heat emitted decrease, this might be as the co-current mean parallel flow. Therefore increasing the flowrate might decrease the time for heat to transfer. In addition, as the cold water flow rate increase, the heat absorb also increase.ConclusionFrom my point of view, this experiment has slightly error which affect the the result of the experiment. This can be seen on the temperature of hot water which is cooler than the suppose to be cold water, In theory, the heat will transfer from high temperature to the cold temperature. This might happen due to the error in apparatus or it setting. Overall, we can deduce that, by increasing the cold water flow rate will decrease the heat emitted while increasing the hot water flow rate will increase the heat emitted

RecommendationsAll students should be clearly read and understood the manual lab before start the experiment. During experiment, students must wear protective clothing, shoes, helmet and goggles for safety. All students should be serious went carry out the experiments and always run the experiment after fully understand the unit and procedures. To avoid parallax error, the eyes must be perpendicular to the scale when adjusting the hot and cold water flowrate. Make sure the valve of counter-current is closed when doing a co-current flow. Do the same thing when doing a counter-current. This is because to allow the flowing of hot and cold water in the right directions of flowing.

Reference CENGEL.Y , BOLES.M (ed.) Thermodynamic: An Engineering Approach. New York: McGraw-Hill

BBC UK, (n.d) Heat transfer and efficiency. [online] Available from http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/energy/heatrev1.shtml [Accessed on 29th September 2014]

CENGEL.Y,GHAJAR.J,(ed).Heat And Mass Transfer:Fundamental And Application.New York:McGraw Hill

INCLOPERA,DEWITT,BERGMANN,(ed) Principle Of Heat And Mass Transfer.NewJersey:Wiley