Lab Report Shell &Tube Heat Exchanger

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1.

ABSTRACT/SUMMARY

We have successfully conducted our experiment of Shell and Tube Heat Exchanger by using Heat Exchanger Training Apparatus (Model; HE 158C). A heat exchanger is a device that allows heat from a fluid (a liquid or a gas) to pass to a second fluid (another liquid or

gas) without the two fluids having to mix together or come into direct contact. In this

experiment, cold water enters the shell at room temperature while hot water enters the tubes in the opposite direction. We then vary the hot water and cold water flow rates and record the inlet and outlet temperatures of both the hot water and cold water streams at steady state. The flow of hot and cold water is counter-current flow. Then the experiment is repeated with co-current shell and tube heat exchanger which is parallel flow of hot and cold water. From the data calculated, shows that counter current flow configuration of heat exchanger is more preferred for practical application.

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2.

INTRODUCTION

SOLTEQ® Heat Exchanger Training Apparatus (Model: HE 158C) is an apparatus that is used to demonstrate the application of heat exchanger in industries. This apparatus consists of four different type of heat exchanger that is Shell and Tube Heat Exchanger, Spiral Heat Exchanger, Concentric Heat Exchanger and Plate Heat Exchanger. In this experiment, type of heat exchanger used is Shell and Tube Heat Exchanger. Inside the shell and tube heat exchanger, there is shell, tubes, baffles, rear-end header and rear-end header. For shell and tube heat exchanger to operate, valves V4, V5,V19 and V20 are open while V6-V11 and V21-V26 are set to be close.

Figure 1: SOLTEQ® Heat Exchanger Training Apparatus (Model: HE 158C)

Figure 2: Shell and Tube Heat Exchanger

Pump Contro

l panel Shell and tube heat exchanger

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There are two types of flow in heat exchanger unit which is counter-current flow and co-current flow. To set a counter-co-current flow, valves V1, V12, V15, V18 and V28 are set to open and valves V16, V17, V27, V29 and V30 are set to close. For co-current flow, the valves V1, V12, V16, V17 and V28 are set to open and valves V15, V18, V27, V29 and V30 are set to close. In the control panel, there is main power switch an also a heater switch. Besides, there is also a digital temperature and pressure reader as shown below:

a)

Flow measurement

FT1: Hot water flow rate (LPM)

FT2: Cold water flow rate (LPM) b)

Temperature Measurement

 TT1: Hot water inlet temperature (°C)

 TT2: Hot water inlet temperature (°C)

 TT2: Hot water inlet temperature (°C)

 TT2: Hot water inlet temperature (°C) Table 1: Control panel symbol

The function of shell is to transport cold water. The water will be inserted into the shell inlet and go out from at the shell outlet whereas tube is used to transport hot water across the tube. Front-end header is where water will enter the tubeside of the heat exchanger. Furthermore, Rear-end header is where the water leaves the heat exchanger. Baffles are installed in order to support the tubes and allow water to flow across the tubes. Besides, baffles also give a higher transfer rate due to the increase of turbulence. The heat exchanger’s dimension is as follows:

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Information about the Shell & Tube Heat Exchanger unit Tube O.D. (do) Tube I.D. (di) Tube Length (L) Tube Count (Nt) Tube Pitch (pt) Tube arrangement Shell O.D. Shell I.D. (Ds) Baffle Count Baffle Cut (Bc) Baffle Distance (lB) Material of Construction : : : : : : : : : : : : 9.53 ×10-3 7.75×10-3 0.5 10 0.018 Triangle 0.1 0.085 8 20 % 0.05 m m m m m m m

316 L Stainless Steel/Borosilicate Glass Table 2: Dimensions of shell and tube heat exchanger

3.

OBJECTIVES

The objectives for conducting this experiment are :

1) To study the working principle of the concentric heat exchanger operating by using co-current flow and counter-co-current fluid flow.

2) Then, another purpose of this experiment is to demonstrate the effect of hot and cold flow rate variations on the performance of the heat exchanger system.

4.

THEORY

The main function of heat exchanger is to either remove heat from a hot fluid or to add heat to the cold fluid. The direction of fluid motion inside the heat exchanger can normally

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categorised as parallel flow, counter flow and cross flow. In this experiment, we study only counter-current and co-current flow. For co-current flow, also known as co-current flow, both the hot and cold fluids flow in the same direction. Both the fluids enter and exit the heat exchanger on the same ends. For counter-current flow, both the hot and cold fluids flow in the opposite direction. Both the fluids enter and exit the heat exchanger on the opposite ends. In this experiment, we focused on the shell and tube heat exchanger.

Heat exchangers with only one phase (liquid or gas) on each side can be called one phase or single-phase heat exchangers. Two-phase heat exchangers can be used to heat a

liquid to boil it into a gas (vapor), sometimes called boilers, or cool a vapor to condense it into a liquid (called condensers), with the phase change usually occurring on the shell side. One of the most common, conductive-convective, heat exchanger types is the concentric tube heat exchanger. These exchangers are built of coaxial tubes placed the ones inside the others.

When both the fluids enter from the same side and flow through the same direction we have the parallel flow (concurrent flow), otherwise, if the fluids enter from opposite sides and flow through the contrary direction we have the countercurrent flow. Usually the countercurrent flow is more efficient from the heat transfer point of view. This type of heat exchangers can also be built with the internal tube made with longitudinal fins which could be placed either in its internal surface or in its external one or both. This configuration is useful mainly if one of the fluids is a gas or a liquid with a very high viscosity and it's very difficult to have a good thermal convection coefficient.

The heats are transfer between the two fluids by convection mode which is from the hot fluid to the wall and also by conduction which is occur within the wall itself and back to the convection which is from the wall to the cold fluid. This concentric tube heat exchanger is the simplest one of heat exchanger between the other types of heat exchanger. This type mainly used for small flow rates of fluid.

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Figure 1 - Diagram of Parallel and Counter Flow Configurations

5.

APPARATUS & MATERIALS 1) Concentric Heat Exchanger 2) Water

6.

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GENERAL START-UP PROCEDURE

1 A quick inspection is performed to make sure that the equipment is in proper working condition

2 All the valves are closed initially except for V1 and V12.

3 Hot water tank is filled up via a water supply hose connected to V27 until it is full.

4 The cold-water tank is filled up by opening V28 and the valve is leaved opened for continues water supply.

5 A drain horse is connected to the cold water drain point.

6 The main power is switch on. The heater is switch on for the hot water tank and the temperature controller is set to 50oC.

7 The water temperature in the hot tank is allowed to reach the set-point.

GENERAL SHUTDOWN PROCEDURE

1. The heater is switched off until the hot water temperature drops below 40oC.

2. Pump, P1 and pump, P2 are switched off. 3. The main power is switched off.

4. All the water in the process line is drained off. The water is retained in the hot and cold water for the next laboratory session.

5. All the valves are closed.

EXPERIMENT A: COUNTER-CURRENT SHELL AND TUBE HEAT EXCHANGER 1 The general started up is performed.

2 The valves (V) for counter-current Shell & Tube Heat Exchanger are switched on. 3 P1 and P2 are switched on.

4 V3 and V14 are adjusted to obtain the desired flow rates for hot water and cold water. 5 The system is allowed to reach steady state for 10 minutes.

6 FT1, FT2, TT1, TT2, TT3 and TT4 are recorded.

7 The pressure drop measurement for shell-side and tube-side are recorded for pressure studies.

8 Steps 4 and 7 are repeated for different combination of flow rate FT1 and FT2. 9 P1 and P2 are switched off after the completion of experiment.

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10 The next experiment is preceded.

EXPERIMENT B: CO-CURRENT SHELL & TUBE HEAT EXCHANGER 1 The general start up is performed.

2 The valves (V) for co-current are switched on. 3 P1 and P2 are switched on.

4 V3 and V14 are adjusted to obtain the desired flow rates for hot water and cold water. 5 The system is allowed to reach steady state for 10 minutes.

6 FT1, FT2, TT1, TT2, TT3 and TT4 are recorded.

7 The pressure drop measurement for shell-side and tube-side are recorded for pressure studies.

8 Steps 4 and 7 are repeated for different combination of flow rate FT1 and FT2. 9 P1 and P2 are switched off after the completion of experiment.

10 The general shut down is performed.

7.RESULT

EXPERIMENT A : COUNTER-CURRENT SHELL & TUBE HEAT EXCHANGER

i. FT1 (HOT) Constant=5 LPM FT1 (LPM) FT2 (LPM) TT1 (oC) TT2 (oC) TT3 (oC) TT4 (oC) DPT1 (mmH20) DPT2 (mmH20 5 1 27.8 38.4 31.6 49.1 5 5 5 2 27.9 39.3 30.7 50.0 5 5 5 3 27.9 40.1 29.9 49.1 5 5 5 4 28.0 40.9 29.3 49.6 5 5 5 5 28.0 41.6 28.7 49.2 5 5

Hot fluid (Tube)

Volumetric Flowrate (LPM) 5 5 5 5 5

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Outlet Temperature,TT2 27.8 27.9 29.8 29.8 29.9

Mass flow rate (kg/s) 0.1647 0.1647 0.1647 0.1647 0.1647

Heat transfer rate, W 3644.33 3919.37 3575.56 4435 4675.74

Pressure drop, mm H2O 5 5 5 5 5

Cold fluid (Shell)

Volumetric Flowrate (LPM) 1 2 3 4 5

Inlet temperature,TT3 31.6 30.7 29.9 29.3 28.7

Outlet Temperature,TT4 49.1 50.0 49.1 49.6 49.2

Mass flow rate (kg/s) 0.033 0.066 0.10 0.13 0.166

Heat transfer rate, W 1214.76 2665.53 1332.76 5636.48 7115

Pressure drop, mm H2O 5 5 5 5 5

Temperature difference

Tlm 8.42 2.07 3.59 3.70 1.93

Heat loss, W 2429.57 1253.84 1783.26 1201.48 2439.26

Efficiency, % 300 68.00 66.72 126.19 152.17

Overall heat transfer coefficient

Total exchange area, m2 0.15 0.15 0.15 0.15 0.15

Overall heat transfer coefficient 86.3 94.99 86.18 106.85 1222 Tube Side

Cross-section area, m2 0.0000472 0.0000472 0.0000472 0.0000472 0.0000472

No.of tubes 10 10 10 10 10

Total cross-section area,m2 0.000472 0.000472 0.000472 0.000472 0.000472

Mass velocity, kg/m2.s 349.13 349.13 349.13 349.13 349.13

Linear velocity, m/s 0.3533 0.3533 0.3533 0.3533 0.3533

Reynolds number,Re 4924.93 4924.93 4924.93 4924.93 4924.93

Prandtl 3.56 3.56 3.56 3.56 3.56

Types of flow Turbulent turbulent turbulent turbulent turbulent Tube coefficient, W.m-2.K 2570.30 2570.30 2570.30 2570.30 2570.30 Shell Side Cross-section area, m2 0.002 0.002 0.002 0.002 0.002 Mass velocity, kg/m2.s 8.3 33.189 24.89 33.189 41.00 Linear velocity, m/s 0.0083 0.0333 0.025 0.033 0.0412 Reynolds number,Re 288.17 1152.31 864.17 1152 1423.50 Prandtl 5.44 5.44 5.44 5.44 5.44

Types of flow Laminar Laminar Laminar Laminar Laminar

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ii. FT2 (COLD) Constant = 5 LPM FT1 (LPM) FT2 (LPM) TT1 (oC) TT2 (oC) TT3 (oC) TT4 (oC) DPT1 (mmH20) DPT2 (mmH20 1 5 28.1 42.1 28.2 50.6 5 5 2 5 28.1 42.4 27.8 49.8 5 5 3 5 28.3 42.9 27.5 50.0 5 5 4 5 28.2 43.3 27.2 49.3 5 5 5 5 28.2 43.7 27.1 49.8 5 5

Hot fluid (Tube)

Volumetric Flowrate (LPM) 1 2 3 4 5

Inlet temperature,TT1 28.1 28.1 28.3 28.2 28.2

Outlet Temperature,TT2 42.1 42.4 42.9 43.3 43.7

Mass flow rate (kg/s) 0.016 0.033 0.049 0.066 0.082

Heat transfer rate, W 962.65 1966.56 3011.73 4153.16 5328.97

Pressure drop, mm H2O 5 5 5 5 5

Cold fluid (Shell)

Volumetric Flowrate (LPM) 5 5 5 5 5

Inlet temperature,TT3 28.2 27.8 27.5 27.2 27.1

Outlet Temperature,TT4 50.6 49.8 50.0 43.9 49.8

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Heat transfer rate, W 7774.46 7635.63 7809.17 7670.34 7878.58 Pressure drop, mm H2O 5 5 5 5 5 Temperature difference Tlm -75.58 -91.60 -108.18 -137.55 -145.09 Heat loss, W -8737.10 -9601.56 -10820.90 -11823.50 -13207.55 Efficiency, % 807.61 388.27 259.29 184.69 147.84

Overall heat transfer coefficient

Total exchange area, m2 0.15 0.15 0.15 0.15 0.15

Overall heat transfer coefficient 18.41 143.09 185.56 206.14 244.89 Tube Side

Cross-section area, m2 0.0000472 0.0000472 0.0000472 0.0000472 0.0000472

No.of tubes 10 10 10 10 10

Total cross-section area,m2 0.000472 0.000472 0.000472 0.000472 0.000472

Mass velocity, kg/m2.s 348.94 348.94 348.94 345.33 341.95

Linear velocity, m/s 0.3533 0.3533 0.3533 0.3533 0.3533

Reynolds number,Re 4924.93 4924.93 4924.93 4875.70 4826.47

Prandtl 3.56 3.56 3.56 3.56 3.56

Types of flow Turbulent turbulent turbulent turbulent Turbulent Tube coefficient, W.m-2.K 2570.36 2570.36 2570.36 2462.58 2437.71 Shell Side Cross-section area, m2 0.002 0.002 0.002 0.002 0.002 Mass velocity, kg/m2.s 16.60 31.55 46.45 60.55 75.50 Linear velocity, m/s 0.01667 0.03173 0.04670 0.06086 0.07583 Reynolds number,Re 576.4 1095.40 1612.73 2102.27 2621.33 Prandtl 5.44 5.44 5.44 5.44 5.44

Types of flow Laminar Laminar Laminar Laminar Laminar

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7.1 EXPERIMENT B : CO-CURRENT CONCENTRIC HEAT EXCHANGER i. FT1 (HOT) Constant = 5 LPM FT1 (LPM) FT2 (LPM) TT1 (oC) TT2 (oC) TT3 (oC) TT4 (oC) DPT1 (mmH20) DPT2 (mmH20 5 1 43.8 44.8 26.6 49.1 4 5 5 2 44.3 45.4 26.6 50.1 10 5 5 3 44.3 44.9 26.4 49.4 5 5 5 4 30.1 33.8 26.2 49.5 5 5 5 5 29.6 32.9 26.2 50.0 5 5

Hot fluid (Tube)

Volumetric Flowrate (LPM) 5 5 5 5 5

Inlet temperature,TT1 43.8 44.3 44.3 30.1 29.6

Outlet Temperature,TT2 44.8 45.4 44.9 33.8 32.9

Mass flow rate (kg/s) 0.0823 0.0823 0.0823 0.0823 0.0823

Heat transfer rate, W -343.80 -378.18 -137.52 -1272.08 -1134.55

Pressure drop, mm H2O 4 10 5 5 5

Cold fluid (Shell)

Volumetric Flowrate (LPM) 1 2 3 4 5

Inlet temperature,TT3 26.6 26.6 26.4 26.2 26.2

Outlet Temperature,TT4 49.1 50.1 49.4 49.5 50.0

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Heat transfer rate, W 1562.35 3263.58 4791.21 6471.60 8263.10 Pressure drop, mm H2O 5 5 5 5 5 Temperature difference Tlm 19.05 20.92 18.31 28.81 24.41 Heat loss, W -1905.63 -3607.38 -5135.01 -6815.40 -8606.90 Efficiency, % 454.28 949.27 1393.60 1960.91 2403.46

Overall heat transfer coefficient

Total exchange area, m2 0.15 0.15 0.15 0.15 0.15

Overall heat transfer coefficient 120.31 109.56 125.18 79.56 93.90 Tube Side

Cross-section area, m2 0.0000472 0.0000472 0.0000472 0.0000472 0.0000472

No.of tubes 10 10 10 10 10

Total cross-section area,m2 0.000472 0.000472 0.000472 0.000472 0.000472

Mass velocity, kg/m2.s 174.36 174.36 174.36 174.36 174.36

Linear velocity, m/s 0.176 0.176 0.176 0.176 0.176

Reynolds number,Re 2459.57 2459.57 2459.57 2459.57 2459.57

Prandtl 3.56 3.56 3.56 3.56 3.56

Types of flow Turbulent turbulent turbulent turbulent Turbulent Tube coefficient, W.m-2.K 1498.20 1498.20 1498.20 1498.20 1498.20 Shell Side Cross-section area, m2 0.002 0.002 0.002 0.002 0.002 Mass velocity, kg/m2.s 8.29 16.60 24.9 33.2 41.5 Linear velocity, m/s 0.00833 0.0167 0.0250 0.0333 0.0417 Reynolds number,Re 288.17 576.35 864.52 1152.69 1440.86 Prandtl 5.44 5.44 5.44 5.44 5.44

Types of flow Laminar Laminar Laminar Turbulent Turbulent

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ii. FT2(COLD) Constant=5 LPM FT1 (LPM) FT2 (LPM) TT1 (oC) TT2 (oC) TT3 (oC) TT4 (oC) DPT1 (mmH20) DPT1 (mmH20 1 5 29.6 31.0 26.2 50.0 4 5 2 5 30.1 31.8 26.2 50.6 5 5 3 5 30.1 32.5 26.1 49.6 8 5 4 5 29.5 32.1 26.1 50.2 4 5 5 5 29.5 32.4 26.1 50.3 3 5

Hot fluid (Tube)

Volumetric Flowrate (LPM) 1 2 3 4 5

Inlet temperature,TT1 29.6 30.1 30.1 29.5 29.5

Outlet Temperature,TT2 31.0 31.8 32.5 32.1 32.4

Mass flow rate (kg/s) 0.0823 0.0823 0.0823 0.0823 0.0823

Heat transfer rate, W 96.27 233.79 495.08 715.1 997.0

Pressure drop, mm H2O 4 5 8 4 3

Cold fluid (Shell)

Volumetric Flowrate (LPM) 5 5 5 5 5

Inlet temperature,TT3 26.2 26.2 26.1 26.1 26.1

Outlet Temperature,TT4 50.0 50.6 49.6 50.2 50.3

Mass flow rate (kg/s) 0.0166 0.0332 0.0498 0.0664 0.0830 Heat transfer rate, W 8260.4 8468.6 8156.24 8364.5 8399.2

Pressure drop, mm H2O 5 5 5 5 5

Temperature difference

Tlm 9.07 9.47 9.02 8.79 8.73

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Efficiency, % 8580.5 3622.3 1647.46 1169.70 842 Overall heat transfer coefficient

Total exchange area, m2 0.15 0.15 0.15 0.15 0.15

Overall heat transfer coefficient 70.76 164.58 366.03 542.30 761.36 Tube Side

Cross-section area, m2 0.0000472 0.0000472 0.0000472 0.0000472 0.0000472

No.of tubes 10 10 10 10 10

Total cross-section area,m2 0.000472 0.000472 0.000472 0.000472 0.000472

Mass velocity, kg/m2.s 174.36 174.36 174.36 174.36 174.36

Linear velocity, m/s 0.176 0.176 0.176 0.176 0.176

Reynolds number,Re 2459.57 2459.57 2459.57 2459.57 2459.57

Prandtl 3.56 3.56 3.56 3.56 3.56

Types of flow Turbulent turbulent turbulent turbulent Turbulent Tube coefficient, W.m-2.K 1498.20 1498.20 1498.20 1498.20 1498.20 Shell Side Cross-section area, m2 0.002 0.002 0.002 0.002 0.002 Mass velocity, kg/m2.s 8.29 16.60 24.9 33.2 41.5 Linear velocity, m/s 0.00833 0.0167 0.0250 0.0333 0.0417 Reynolds number,Re 287.79 578.88 863.90 1151.50 1439.48 Prandtl 5.44 5.44 5.44 5.44 5.44

Types of flow Laminar Laminar Laminar Turbulent Turbulent

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8 CALCULATION Sample Calculation : Hot Water Density 988.18 kg/ m3 Viscosity 0.0005494 Pa.s Thermal condition 0.6436 W/m.K Heat Capacity 4175.00 J/kg.K Cold Water Density 995.67 kg/ m3 Viscosity 0.0008007 Pa.s Thermal condition 0.6155 W/m.K Heat Capacity 0.0008007 Pa.s

Cold Water Flowrate at TT1 = 40.1 oC

Hot fluid (Tube-side) : Water Cold fluid (Shell side ) : Water Volume flow (L/min) 10.0 Volume flow (L/min) 2.0 Inlet Temperature, oC 40.1 Inlet Temperature, oC 47.4

Outlet Temperature, oC

29.7 Outlet Temperature, oC

50.2

1 Calculation On Heat Transfer using heat balance equation : Heat transfer rate for hot water, Q

= mh Cp ∆T =5 min x L 1 m 3 1000 L x 1 min 60 s x 988.18 kg m3 x 4175 J kg .C x (27.8-38.4) ◦C = -3644.33 W

Heat transfer rate for cold water, Q = mc Cp ∆T = 1 min x L 1 m 3 1000 L x 1 min 60 s x 995.67 kg m3 x 4183 J kg .C x (31.6-49.1) ◦C = -1214.76 W Heat loss

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= Qhot-Qcold = -3644.33+1214.76 = -2429.57W Efficiency = QcoldQhot x 100 =300%

2 Calculation of Log Mean Temperature Difference (LMTD) :

∆Tlm = [( Th,in – Tc,out) – (Th,out – Tc,in)] / ln[( Th,in – Tc,out) /( Th,out- Tc,in)]

=

(38.4−49.1)−(27.8−31.6)

¿(38.4−49.1)

(27.8−31.6) =8.42◦C

3 Calculation of the tube and shell heat transfer coefficients by Kern’s method : a Heat transfer coefficient at tube side

i Cross Flow Area,A = ∏ di 2 4 = 3.142 x 0.0077 5 2 4 = 0.0000472 m2

ii Total cross Flow Area, At = At x Nt

= 0.0000472 x 10 =0.000472 m2 iii Mass velocity, Gt

= mtAt

= 0.0004720.1647 = 349.13 kg/ m2 s iv Linear velocity, ut

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= ¿p = 349.13988.18 = 0.3533 m/s v Renolds Number, Re = ¿x deµ = 349.13 x 7.750.0005494 x 10001 = 4924.93

Value shows in range of turbulent flow vi Prandtl No, Pr

= µ x Cpk

= 0.0005494 x 41750.6436 = 3.56

vii Tube Side Coefficient, hi = jh ℜ P r 0.33 k di = 0.004 x 4924.93 x 3.56 0.33 x 0.6436 0.00775 = 2570.36 W m−2 K

b Heat transfer coefficient at shell side i Cross flow area, As

= Shell diameter x (Tube pitch-Tube OD) x Baffle distance / Tube pitch = [0.085 x ( 0.018 – 0.0953) x 0.05 ] / 0.018

= 0.002 m2 ii Mass velocity, Gs

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= 0.01660.002 = 8.3 kg/ m2 s iii Linear velocity, us

= Gsp = 995.678.3 = 0.0083 m/s iv Equivalent diameter, de = 1.1d 0 (pt2 - 0.917d02 ) = 9.53 [ 181.1 2 - 0.917 (9.53)2] = 27.80 mm v Reynolds number, Re = Gs x deµ = 8.3 x 27.800.0008007 x 10001 = 288.17

Value shows in range of laminar flow vi Prandtl No, Pr

= µ x Cpk

= 0.0008007 x 41830.6155 = 5.44

vii Shell Side Coefficient, hs = jh ℜ P r 0.33 k de = 0.025 x 288.17 x 5.44 0.33x 0.6155 0.02053

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= 377.72 W m−2 K

c Overall Heat transfer Coefficient i Total exchange area, A

= Number of tube x ∏ x Tube OD x Length of Tubes = 10 x ∏ x 0.00953 x 0.5

= 0.15 m2

ii Overall heat transfer coefficient,U = A ∆ TlmQhot

= 86.33 W/ m2 K

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0 5 10 15 20 25 30 35 40 45 31.6 30.7 29.9 29.3 28.7 38.4 39.3 40.1 40.9 41.6

Temperature Profile

Cold water Hot water

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1 2 3 4 5 0 500 1000 1500 2000 2500 3000 2570.32570.32570.32570.32570.3 377.72 151.04 1132.73 1510.41 1865.89

Relationship between Heat Transfer Coefficient and Cold Water Flowrate

Tube side Shell side

Cold Water Flow rate (LPM) Heat Transfer Coefficient (W/m2K)

0 1 2 3 4 5 6 0 200 400 600 800 1000 1200 1400

Overall Heat Transfer Coefficient vs Cold Water Flowrate

Cold Water Flowrate(LPM) Overall Heat Transfer Coefficient(W/m2.k)

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9 DISCUSSION

The experiment was carried out to study the working principle of parallel flow and counter flow heat exchangers and also to investigate the effect of fluid temperature on counter and parallel flow heat exchanger performance. There are two types of experiment which is counter-current shell and tube heat exchanger and co-current shell and tube heat exchanger. The different between these two experiments are the counter-current flow is when hot water and cold water flow in opposite direction to each other while co-current flow is where hot and cold water flow in the same direction and also known as parallel flow. For counter-current flow and co-current flow, the experiment is run and all of the temperature and pressure data is recorded

From the data collected, the counter-current and co-current heat exchanger’s exit temperature of the hot fluid is higher than the exit temperature of the cold fluid but due to the equipment error during experiment is done, exit temperature becomes lower than temperature inlet for parallel flow . This cause the experiment cannot be done practically. Instead of

equipment and human error, this may because of the heat loss to the surrounding that can reduce the temperature itself and the flow rates which always easily change during the experiment may also cause this problem. This shows that heat may not spontaneously transfer from a colder body to a hotter body.

The increase in flow rate of one of the stream will results in an increase in the rate of heat transfer. But from calculation, results show that the increase of flow rate, the lower the heat transfer. This is contra to the theoretical result but due to big error from the unit and since the unit does not function properly, we cannot able to avoid this mistake. Theoretically, the amount of heat loss form the hot water should be equal to the heat gain by the cold water.

Based on the calculation done, it is found out that the values of LMTD, which is log mean temperature difference for co-current flow is higher than the counter-current flow. But, the

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overall heat transfer coefficient for counter-current flow is higher than the co-current flow. This mean that counter current flow heat exchanger has a higher effectiveness rather than parallel flow heat exchanger.

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CONCLUSION

So, overall in conclusion, shell and tube heat exchanger follows the basic law of Thermodynamics and fulfilled the study of Heat Transfer. In parallel (co-current) flow

configuration, the exit temperature of the hot fluid is always higher than the exit temperature of the cold fluid. In countercurrent flow configuration, the exit temperature of the hot fluid is also higher than the exit temperature of the cold fluid. But then, in the configuration of counter current flow, the exit temperature of the cold fluid is higher than the exit temperature of the cold fluid in co-curent configuration. So, this stand the statement that counter current flow heat exchanger has a higher effectiveness than the parallel flow configuration. Besides, the

experiment shows that the flow rate of one of the stream is directly proportional to the rate of heat transfer since the rate of heat transfer is increases as the flow rate of fluid increases. Futhermore, the amount of heat loss form the hot water is not equal to the heat gain by the cold water due to the heat loss to the surrounding. From the calculations done, the LMTD (log mean temperature difference) for co-current flow is higher than the counter-current flow. In a nut shell, counter current flow configuration of heat exchanger is more preferred for practical application. One of the application of heat exchanger is oil cooler.

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RECOMMENDATION

Based on the experiment, there are a few recommendations that can be suggested in order to increasing the performance of the concentric heat exchanger and to avoid from the error while recorded the data thus can affect the calculation outwards. Firstly, the most importance is to make sure that the equipment is in good condition so that the flow of the experiment does not disturbing by the inconstant data. Then, while conducting the experiment, make sure that the time taken to collect the data is punctually followed. The relay of the time can affect the data recorded. It is suggested that, the alert alarm system is placed so that it can be easier to record the data on time. Then, while recording the data, make sure that the pressure and temperature is at constant value because this can affect the calculation made.

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REFERENCES

Yunus A.Cengel, 2006, Heat and Mass Transfer: A Practical Approach. Mc Graw Hill,, 3rd

Edition

Christie John Geankoplis, Transport Process AND Separation (includes unit operations) , 4thEdition

Heat Exchanger Lab Report, by Ram Krishna Singh, retrieved from https://www.scribd.com/doc/23106551/Heat-Exchanger-Lab-Report

CONCENTRIC TUBE HEAT EXCHANGER, by amirhazwan,

Retrieved from https://www.scribd.com/doc/27156908/CONCENTRIC-TUBE-HEAT-EXCHANGER

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Figure

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References

  1. Ram Krishna Singh
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