ABSTRACTHeat exchanger experiments were carried out to demonstrate the working principles of a concentric tube heat exchanger operating under co-current flow which V1 &V3 switched on, V2 & V4 off. Also for counter flow conditions, the V1 & V3 off, V2 & V4 were being on. Besides, the effect of hot water temperature variation on the performance characteristics of a concentric tube heat exchanger were evaluated for counter flow condition which V1 & V3 off, V2 & V4 on. The variation of flow rate was conducted for counter-current flow conditions whereby the V1 & V3 off, V2 & V4 were being off. From the experiments, the results were varied according to type of flow arrangement which were co-current flow and counter flow conditions. The power lost by co-current flow was 206.14W which greater than counter current conditions which was 17.94W. As the temperature increased, the power lost became fluctuated and it same went to flow rate variation. The results will be increased and decreased back. The percentage error had shown the human error while doing the experiments. Error percentages were -61.85%% and --74.07%for experiment A and B respectively.

Abstract... Table of Contents Introduction Objectives....... Theory..... Diagram and Description of Apparatus.. Experimental Procedures Results and Discussions.. Sample Calculations... Conclusions and Recommendations... References.. Appendices.123459141622313334

TABLE OF CONTENTS

INTRODUCTIONHeat exchangeris a system designed to transfer heat between two fluids to control the temperature of one of the fluids. Our experiment was started by using the SOLTEQ HE104-PD Concentric Tube Heat Exchangers which has been deliberated to demonstrate the working principles of industrial heat exchangers. Main apparatus required was the cold water supply. The equipment consists of a concentric tube exchanger was in the form of a U mounted on a support frame and it was designed with insulated at the external surface. [1]In concentric tube heat exchanger device the hot water flows inside the inner tube and the cold water flows in the annulus. The cold water flows through the heat exchanger was using the available pressure. The control valves were incorporated in each of the two streams to regulate the flow and two flow meters were employed to measure the volume flow rate. [2]Also to measure the fluid temperatures accurately, three temperature measuring devices were installed in the inside and outside the tubes. Measurements will be performed of the volume flow rates of the hot and cold water as well as the inlet, outlet and bath temperatures of hot and cold water. [2]The hot water system was totally self-contained. A hot storage tank was equipped with an immersion type heater and an adjustable temperature controller which can maintain a temperature to within approximately 10 C. Circulation to the heat exchanger was provided by a pump and hot water returns to be reheated. The valve was set to identify the flow whether it co- or counter-current flow. [1] Heat exchangers find widespread use in power generation, chemical processing, electronics cooling, air-conditioning, refrigeration, and automotive applications. In food industry it has been used to make a dairy, brewing, soft drink and fruit processing. It was applied from heating and air-conditioning system to chemical processing and power production in large plants. Heat exchangers are widely used in industry both for cooling and heating large scale industrial processes. [3]In reference section: [1] Chemical Engineering Laboratory Manual, Heat Exchanger., Pulau Pinang: UiTM Permatang Pauh,.,pp 83-102.[2] Cengel, Y. A. Heat Transfer, McGraw-Hill Education (Asia), 4th ed.[3] Perry, J.H.(Ed): Chemical Engineers Handbook, 4th ed., McGraw-Hill Book Company, New York, 1963.OBJECTIVEThe objectives of this experiment are to investigate the working principles of concentric tube heat exchanger operating under co-current flow and counter-current flow arrangement. Other than that it aims to demonstrate the effect of hot water temperature variation on the performance characteristics of a concentric tube heat exchanger. Also to demonstrate the effect of flow rate variation on the performance characteristics of a concentric tube heat exchanger operating under counter-current flow conditions.

THEORYThere are two possible types of concentric tube heat exchanger which are parallel flow and counter current flow. In a parallel-flow heat exchanger, the working fluids flow in the same direction. In the counter flow exchanger, the fluids flow in parallel but opposite directions.

Figure 1: The different type of flow for the co-current and counter-current flows

Co-current flow Counter-current flowThe variables that affect the performance of a heat exchanger are the fluids physical properties, the fluids mass flow rates, the inlet temperature of the fluids, the physical properties of the heat exchanger materials, the configuration and area of the heat transfer surfaces. In experiment A and B, in order to create the working principles of concentric tube heat exchanger operating under co-current flow and counter-current flow condition, used all these formulas:

Power emitted = QH H CpH (THin THout) (1)QH = Hot water flow rate (m3/s)H = Density of hot water (kg/m3)CpH = Specific heat capacity for hot water (J/kg.K)(THin THout) = Temperature different between hot waters (K)Power absorbed = QC C CpC (TCin TCout) (2)QC = Cold water flow rate (m3/s)C = Density of cold water (kg/m3)CpC = Specific heat capacity for cold water (J/kg.K)(TCin TCout) = Different temperature between cold waters (K)

Power lost (W) = power emitted (W) power absorbed (W) (3)The efficiency of heat exchanger is based on the second law of thermodynamics.System efficiency, = (4)The log mean temperature difference (LMTD) is derived in all basic heat transfer texts. It may be written for a parallel flow or counter flow arrangement. The LMTD has the form: Log mean temperature difference, Tm = (5)Where T1 and T2 represent the temperature difference at each end of the heat exchanger, whether parallel flow or counter flow.

The overall heat transfer coefficient always relate to LMTD. So it can be determined as:

Overall heat transfer coefficient, U = (6)Where, area = Surface area of contact = pi ODinner pipe Length = (3.142 0.015 1.36) m2 = 0.0641 m2Theoretical heat transfer coefficient can be obtained by determination of the flow type of the water either laminar or turbulent. In order to get that, the Reynolds number, Nusselt number, Prandtl number and surface heat coefficient are determine first. Reynold number, Re = = = (7)Where, is density, V is velocity of water, d is diameter of pipe and is dynamic viscosity. These parameters are depends on the fluids either hot or cold.Prandlt number, Pr = cp / k = H cpH / kH = C cpC / kC (8)Where, is dynamic viscosity, cp is specific heat and k is thermal conductivity which all these parameters are depends on the fluid either hot or cold.Nusselt number (for turbulent flow) = ... (9)Nusselt number (for laminar flow) = (10)Surface heat transfer coefficient, h = Nu k / d = Nu kH / Di = Nu kC / Do ... (11)Theoretical Heat Coefficient = (12)Where, Cross-sectional area of outer diameter, = (13)Cross-sectional area of inner diameter, = (14)Average velocity of hot water: (15)Hot water flow rate, = Average velocity of cold water: (16)Cold water flow rate, =

DIAGRAM AND DESCRIPTION OF APPARATUS Figure 2: Rear view of the concentric tube heat

Figure 3: Front view of the concentric tube heat1. Loose cover16. Hot water inlet2. Level switch17. Selector valve3. Heating element18. Flow meter4. Storage tank19. Control valve5. Bypass valve20. Cold water inlet6. Pump inlet21. Cold water outlet7. Pump22. Temperature sensor8. Temperature sensor9. Bleed valve10. Flow rate indicator11. Temperature indicator12. Concentric tube13. Temperature controller14. Main switch15. Temperature sensor

1. Loose cover:The storage tank is fitted with a loose cover to prevent ingress of dust and reduce loss of water due to evaporation. 2. Level switch:Automatic switch that will off if the water level is below than it to prolong the heater life3. Heating element:Heating coil which is located in the storage tank that will heating the water4. Storage tank:Tank which is use to maintain the supplier of hot water 5. Bypass valve:Set accordingly with the desired hot water flow rate to prolong the life ot the pump6. Pump inlet:Flow the hot water into the pump from the storage tank7. Pump:Recirculated the water through the tank continuously8. Temperature sensor:Monitor the temperature of the water9. Bleed valve:Permit air to be bled from the system and facilitate drainage10. Flow rate indicator:Show the flow rate of the water11. Temperature indicator:Show the temperature of the water12. Concentric tube: Hot water and cold water for the exchanger is taken and passes through the concentric tube arrangement.13. Temperature controller: Set the desired temperature for initial hot water temperature.14. Main switch: Turn on/off the heat exchanger.15. Temperature sensor:Monitor the temperature of the water16. Hot water inlet:Inlet of the exchanger hot water circuit17. Selector valve: To obtain co-counter flow configuration by appropriate setting of the selector valve. For co-current flow, valves V1 and V3 are opened, valves V2 and V4 are closed. For counter-current flow, valves V1 and V3 are closed, valves V2 and V4 are opened.18. Flow meter:Flow through this circuit is indicated on it19. Control valve:Flow through this circuit is regulated by it20. Cold water inlet: The cold water for the exchanger is supplied from an external source to the concentric tube arrangement by cold water inlet.21. Cold water outlet: After heating in the exchanger, the cold water leaves by cold water outlet.22. Temperature sensor:Monitor the temperature of the water

EXPERIMENTAL PROCEDURESSTART UP PROCEDURE1. The drain valve underneath the water storage tank was checked fully closed2. The cover of the storage tank was removed and the tank was filled with clean water within 40 mm from the top. After that, the cover was replaced on the tank3. The air bleed valves on the top of heat exchange was closed4. The cold water inlet was connected to a source of cold water and the outlet was connected to a suitable drain5. The pump and heater was switched on for the experiment

EXPERIMENT A: CO-CURRENT FLOW ARRANGEMENT1. The selector valve was set to co-current position (V1 & V3 on, V2 & V4 off).2. The temperature controller was set to the desired hot water inlet temperature, 60 C.3. The hot water flow rate, was set to 2.0 L/min and the cold water flow rate, was set to 1.5 L/min. Both of the flow rate were kept constantly.4. The readings for hot and cold temperatures at inlet, mid-point and outlet was recorded in a table (TT1,TT2,TT3,TT4,TT5,TT6) after the flow rate had stable and the temperature of inlet hot water reached 60 C.

EXPERIMENT B: COUNTER-CURRENT FLOW ARRANGEMENT1. The selector valve was set to counter-current position (V1 & V3 on, V2 & V4 off).2. The temperature controller was set to the desired hot water inlet temperature, 60 C.3. The hot water flow rate, was set to 2.0 L/min and the cold water flow rate, was set to 1.5 L/min. Both of the flow rate were kept constantly.4. The readings for hot and cold temperatures at inlet, mid-point and outlet was recorded in a table (TT1,TT2,TT3,TT4,TT5,TT6) after the flow rate had stable and the temperature of inlet hot water reached 60 C.

EXPERIMENT C: WATER TEMPERATURE VARIATION1. The selector valve was set to counter-current position (V1 & V3 on, V2 & V4 off).2. The temperature controller was set to the desired initial hot water inlet temperature, 50 C.3. The hot water flow rate, was set to 2.0 L/min and the cold water flow rate, was set to 2.0 L/min. Both of the flow rate were kept constantly.4. The readings for hot and cold temperatures at inlet, mid-point and outlet was recorded in a table (TT1,TT2,TT3,TT4,TT5,TT6) after the flow rate had stable and the temperature of inlet hot water reached 50 C.5. The experiment was repeated with different hot water temperature (50 C, 55 C, 60 C, 65 C).

EXPERIMENT D: FLOW RATE VARIATION1. The selector valve was set to counter-current position (V1 & V3 on, V2 & V4 off).2. The temperature controller was set to the desired hot water inlet temperature, 60 C.3. The initial hot water flow rate, was set to 2.0 L/min and the cold water flow rate, was set to 1.5 L/min. Both of the flow rate were kept constantly.4. The readings for hot and cold temperatures at inlet, mid-point and outlet was recorded in a table (TT1,TT2,TT3,TT4,TT5,TT6) after the flow rate had stable and the temperature of inlet hot water reached 60 C.5. The experiment was repeated with different ho water flow rate (2.0 L/min, 3.0 L/min, 4.0 L/min, 5.0 L/min).

RESULTS AND DISCUSSIONEXPERIMENT A : CO-CURRENT FLOW ARRANGEMENTReadingsTT1(tHin)CTT2(tHmid)CTT3(tHout)CTT4(tCin)CTT5(tCmid)CTT6(tCout)C

60.056.551.230.034.539.8

Table 1.0: Reading of Difference Temperature

CalculationsPower Emitted,WPowerAbsorbed,WPowerLost,WEfficiency,%,CU,

1141.24935.10206.1481.9419.222275.93

Table 1.1: Power Emitted, Power Absorbed, Power Lost, Efficiency, Log Mean Temperature, and Overall Heat Transfer CoefficientTemperature,T (C)Flow Rate,Q (Reynolds Number,ReNusselt Number,NuSurface Transfer Coefficient,H (

HotWater55.61.89613136.241810.88

Cold Water34.91.38806851.666435.18

Theoretical U,(Experimental U,()PercentageError, %Type of flow

Hot Water783.872275.93-190.35turbulent

Cold Waterturbulent

Table 1.2: Difference Reading for Hot Water and Cold Water

Figure 2: Graph for parallel flowEXPERIMENT B : COUNTER-CURRENT FLOW ARRANGEMENTReadingsTT1(tHin)CTT2(tHmid)CTT3(tHout)CTT4(tCin)CTT5(tCmid)CTT6(tCout)C

61.256.852.641.633.230.1

Table 2.0: Difference reading temperature

CalculationsPower Emitted,WPowerAbsorbed,WPowerLost,WEfficiency,%,CU,

1114.841096.9017.9498.421.022440.93

Table 2.1: Power Emitted, Power Absorbed, Power Lost, Efficiency, Log Mean

Temperature, and Overall Heat Transfer CoefficientTemperature,T (C)Flow Rate,Q (Reynolds Number,ReNusselt Number,NuSurface Transfer Coefficient,H (

HotWater56.91.89619836.301817.51

Cold Water34.71.38729649.296136.80

Theoretical U,(Experimental U,()PercentageError, %Type of flow

Hot Water1402.222440.93-74.07turbulent

Cold Waterturbulent

Table 2.2: Difference Reading for Hot Water and Cold Water

Figure 3: Graph for counter-current flowEXPERIMENT C : WATER TEMPERATURE VARIATIONReadingsTemp set, CTT1,(tHin), CTT2, (tHmid), CTT3, (tHout), CTT4, (tCout), CTT5, (tCmid), CTT6,(tCin), C

5051.347.853.533.930.927.5

5555.551.347.636.534.027.6

6060.856.153.449.132.627.7

6566.058.055.138.032.127.9

Table 3.0: Difference reading with variation of temperature

CalculationsTemp set, CPower emitted, WPower absorbed, WPower lost,WEfficiency,%tmCU,

50403.03612.37-209.34151.9421.211349.15

551027.28851.11176.1782.8518.232181.65

60959.662041.75-1082.09212.7614.116761.79

651141.53965.52176.0184.5826.211721.40

Table 3.1: Power Emitted, Power Absorbed, Power Lost, Efficiency, Log MeanTemperature and Overall Heat Transfer Coefficient in variation of TemperatureEXPERIMENT D : FLOW RATE VARIATIONReadingsQH

TT1,(tHin), CTT2, (tHmid), CTT3, (tHout), CTT4, (tCout), CTT5, (tCmid), CTT6,(tCin), C

2.060.655.251.128.433.537.3

3.060.456.056.328.034.238.0

4.060.056.554.127.734.739.1

5.060.157.055.227.835.239.9

Table 4.0: Reading of Difference Temperature with Variation of Hot Flowrate

CalculationsQHL/minPower emitted, WPower absorbed, WPower lost,WEfficiency,%CU,

2.01229.29-1146.782376.07-93.2921.722467.21

3.0878.59-1288.462167.05-146.6524.682439.56

4.0944.20-1468.602412.80-155.5422.553043.29

5.01053.14-1558.772611.91-147.9222.753201.75

Table 4.1: Power Emitted, Power Absorbed, Power Lost, Efficiency, Log Mean Temperature, and Overall Heat Transfer Coefficient in Variation of Hot Flow rate

SAMPLE OF CALCULATIONSThe diameter of inner pipe (hot water), and The diameter of outer pipe (cold water), and (All the properties of hot water are evaluated from Table B1 in lab manual and Table A-9 from reference book)EXPERIMENT A(co-current flow)Hot water:THavg = = C

Cold water:TCavg = = 34.9 CLinearized value for hot water and cold water:QH= 1.89 L/min and QC = 1.38 L/minConvert into m/s:QH = =3.15 X 10-5 m3/sQC = = 2.3 X 10-5 m/sInterpolation of , Cp, k, at TH:Temperature ( C) (kg/m)Cp (J/kg.K)k (W/m. K) (kg/m. s)

55985.241830.6490.504 x 10-3

55.60X1X2X3X4

60983.341850.6540.467 x 10-3

value of x1:value of x3: x1 = 984.972 kg/m x3 = 0.6496 W/m. KValue of x2 : value of x4: x2 = 4183.24 J/kg.K x4 = 4.9956 x 10-4 kg/m. s Power emitted using equation (1) = (3.15 x 10-5) (984.972) (4183.24)(60.0-51.2) = 1142.168 WPower absorbed using equation (2) = (2.3 x 10-5) (994.04) (4178)(39.8-30) = 936.109 WPower loss using equation (3) = 1142.168 W - 936.109 W = 206.059 WEfficiency using equation (4) = = 81.96%t1 using equation (5-1) = (60- 30) C = 30.0 Ct2 using equation (5-2) = (51.2 -39.8) C = 11.4 CLog mean temperature using equation (5), tm = = = 19.22 CUexp using equation (6) = = 759.83 W/m. CCold water:Interpolation of , Cp, k, at TC :Temperature ( C) (kg/m)Cp (J/kg.K)k (W/m. K) (kg/m. s)

30.0996.041780.6150.798 x 10-3

34.9Y1Y2Y3Y4

35.0994.041780.6230.720 x 10-3

Value of y1:value of y3: y3 = 0.6228 W/m. K value of y4:y1 = 994.04 kg/m Value of y2: y4 = 7.2156 x 10-4 kg/m. s y2 = 4178 J/kg.K Overall mass transfer coefficient value for theoretical:Hot water,, Cold water, ,

= =1.327

= =1.374

=

,Where =

=8068> 4000 turbulent

The flow of hot water is turbulent. Assuming the flow to be fully developed, the Nusselt number can be determine from

= = 36.01The flow of hot water is turbulent. Assuming the flow to be fully developed, the Nusselt number can be determine from

= = 51.66

=

=

Theoretical overall mass transfer coefficient =

=

= ,Where, area = Surface area of contact = = = = = Percentage Error = X 100% = X 100% = -61.85%DISCUSSIONHeat exchanger is equipment that has been designed to exchange the heat between hot and cold fluids at different temperature. In the experiment, the fluids properties and flow rates are constant throughout the experiment. This experiment was conducted in two different flow which is in co-current flow and counter - current flow. Co-current flow is both the hot and cold fluids enter the heat exchanger at the same end and move in the same direction. For counter-current flow the hot and cold fluids enter the heat exchanger at opposite ends and move in opposite directions.In this experiment, there a four different experiment that was conducted according to their objective.From the result obtained in experiment A and B, the power emitted and absorbed is1142.17 W and 936.11 W and for the counter-current flow the power emitted and absorbed is 1114.84 W and 1096.90 W. This shown that the power emitted in the co-current flow is bigger than the power emitted in counter-current flow but the power absorbed in the co-current flow is smaller than power absorbed in counter-current flow. The power lost of co-current flow is 206.06W which is greater than power lost in counter-current flow arrangement. The power lost in counter-current power arrangement is 17.94 W. In order to get higher efficiency, the power that absorb must be smaller than power emitted and the power that losses should be in the small amount. This is proven in counter-current flow arrangement which the result have smaller value of power absorbed than power emitted and the power lost also smaller. This experiment show that the counter-current flow is more efficient than co-current flow.The log mean temperature difference, tm for counter-current flow arrangement is always higher than that for a co-current arrangement. The tm for counter-current flow is 21.02C which is greater than co-current flow is 19.22C thusit is an acceptable result that follows the theory.TheReynold number (Re) is used to determine the type of flow whether in laminar, transition or turbulent flow by using the formulas. Based on the result obtained, the type of the flow for the co-current and counter-current flow is turbulent because the Reynold number (Re) is greater than 4000. For hot water in experiment A, the Reynold number (Re) is 6082 and for cold water is 8068. In experiment B, theReynold number for hot water is 6198 and for cold water is 7296.Reynold number is related to heat transfer coefficient, h because in order to find the heat transfer coefficient, h, Reynold number is used in the formula for Nusselt number and by Nusselt number general formula, the heat coefficient, h can be obtained. When the flow is turbulent, it will give the bigger value of surface heat transfer coefficient because the higher the Reynoldnumber, the higher the heat transfer coefficient. The theoretical heat transfer coefficient for co-current flow is which is smaller than experimental overall heat transfer coefficient which is 2275.93 with the percentage error -61.85. In counter-current flow, the experimental overall heat transfer coefficient is 2440.93 and the theoretical heat transfer coefficient is 1402.22 which is smaller than experimental overall heat transfer coefficient. From the results obtained, the percentage error for counter-current flow is -74.07.This shown that there is no error in this experiment because the percentage error in negative sign. The heat exchanger is an efficient equipment and also because the experimental data is higher than the theoretical data as a result of negative sign in the percent error. Hence, to get the satisfied result, the pipes material must be isolated so that there is no mass and energy transferred through the pipes.

CONCLUSION AND RECOMMENDATIONThese experiments consist of four different objectives. For experiment A, it was conducted to demonstrate the working principle of a concentric tube heat exchanger operating under co-current or parallel flow conditions. The results obtained were 81.96 % of efficiency and power lost was 206.103 W. For the type of flow, both were turbulent for hot and cold water. The percentage error was -61.85%.. The theoretical overall heat transfer coefficient, U is smaller than the experimental which was W/m2.K and W/m2.K. For experiment B, the objectives was same to Experiment A but different in type of flow which was operating under counter-current flow condition. The types of flow for both hot and cold water were turbulent. The percentage of error was -74.07%. Besides, the theoretical U is lower than the experimental U which were 1402.22 and 2440.93 W/m2.K. Experiment C was carried out to demonstrate the effect of hot water temperature variation on the performance characteristics of a concentric tube heat exchanger. The flow rates of hot and cold water were being constant to 2.0 L/min. The value for log mean temperature differences were increased if the temperature increased but the overall heat transfer coefficient were increasing and decreased back. The power emitted was increasing throughout the experiment. The experiment D, the variable was the hot water flow rates which setting from 2.0 L/min until 5.0 L/min and the cold water flow rate was remain constant which was 2.0 L/min. The power emitted was fluctuated because when the flow rate increased, the power emitted will be decreased and increased back. It same went to the power lost and power absorbed. The overall heat transfer coefficient also varied according to the different flow rates.

RECOMMENDATION1) The readings of temperature must be taken by the same person to ensure the balanced readings.2) The duration of taking the temperature readings must be equal which is not too fast or too slow.3) The temperatures must be taken right after the conditions of water have stabilized and the students must be alert to the temperature readings.4) The hot and cold water flow rate must be constant according to types of experiment throughout the experiments.5) The devices must be checked to ensure there is no leakage that can affect the results of the experiments.6) The students must ensure the valves that are to be open or close to conduct the variation of experiments objectives for example, co-current and counter-current flow arrangement.7) Before conduct the experiment, maintenance should be done on the concentric heat exchanger equipment. This is because to ensure that there is no accumulation of deposits on heat transfer surfaces and to ensure that theres nothing block the flow in the heat exchanger. This is because these problems will lead to existence of fouling factor. The deposits layer will give the pipe surfaces an additional resistance thus it lowers the rate of heat transfer in the heat exchanger.8) The experiment should be repeat for three times for best accuracy by calculating the average of the temperature readings.

REFERENCES[1]. Chemical Engineering Laboratory Manual, Heat Exchanger., Pulau Pinang: UiTM Permatang Pauh,.,pp 83-102.[2] Cengel, Y. A. Heat Transfer, McGraw-Hill Education (Asia), 4th ed.[3] Perry, J.H.(Ed): Chemical Engineers Handbook, 4th ed., McGraw-Hill Book Company, New York, 1963.

APPENDIX

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