parallel and counter flow heat exchangers
DESCRIPTION
parallel and counter flow heat exchanger experimentTRANSCRIPT
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ME – 306P Heat and Mass Transfer School of Technology, PDPU
Safety Hazards
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1. Do not wear loose clothing, Neck Ties/Scarves; Jewelry (remove). 2. Tie back long hair.
HAZARD: Heating - Burns
Personal Protective Equipment: High temperature gloves; High temperature apron.
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ME – 306P Heat and Mass Transfer School of Technology, PDPU
Experiment No: Parallel Flow and Counter Flow Heat Exchangers
OBJECTIVES
1. To determine the effectiveness of heat exchanger under parallel flow and counter flow condition.
2. To determine the overall heat transfer coefficient of heat exchanger under parallel flow and counter
flow condition.
3. Theoretical estimation of overall heat transfer coefficient for the experiment conditions.
4. Comparison of experimental and theoretical heat transfer coefficient.
5. Determine NTU (no. of transfer unit for outer surface) for parallel flow and counter flow conditions
THEORY
A double pipe heat exchanger consists of two concentric, different diameter tubes with fluid flowing in each
as indicated in Figures 1. If the two fluids travel in opposite directions as illustrated in Figure 1a, the
exchanger is a counter flow type. If the fluids travel in the same direction as shown in Figure 1b, parallel
flow exists. The same apparatus is used for either flow configuration.
Overall Heat Transfer Coefficient (U)
The heat transfer in parallel and counter flow arrangement is given as;
( )0 0 LMTDq U A T= ∆
Where Uo is overall heat transfer coefficient, Ao is outer surface area of tube and ( )LMTD
T∆ is Logarithmic
Mean-Temperature Difference.
The experimental overall heat transfer coefficient can be written as;
( )0,
0
EXP
LMTD
qU
A T=
∆
The heat exchange between the hot and cold water can be written as;
( ),h h w pw hi hoq m c T T= −�
( ),c c w pw co ciq m c T T= −�
The average heat transfer can be written as;
2
h cq qq
+=
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ME – 306P Heat and Mass Transfer School of Technology, PDPU
Log-Mean Temperature Difference:
Parallel Flow:
( ) 1 2
1
2
lnLMTD
T TT
T
T
∆ − ∆∆ =
∆
∆
1T∆ and 2T∆ are shown in Figure 1.
Counter Flow:
( ) 1 2
1
2
lnLMTD
T TT
T
T
∆ − ∆∆ =
∆
∆
1T∆ and 2T∆ are shown in Figure 1.
Effectiveness:
It is defined as the ration of actual heat transfer to maximum heat transfer that could be possibly be
transferred from one fluid to the other.
( )
( )
( )
( )0
min min
h hi h c co ci
hi ci hi ci
C T T C T T
C T T C T Tε
− −= =
− −
Where h
C , c
C and minC represent heat capacity of hot, cold fluid and minimum heat capacity of fluid
respectively.
(a) (b)
Figure 1 Concentric tube heat exchanger (a) Counter flow arrangement (d) Parallel flow arrangement
∆T1
∆T2
∆T1 ∆T2
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ME – 306P Heat and Mass Transfer School of Technology, PDPU
APPARATUS
The apparatus consists of a concentric tube heat exchanger. The hot water is supplied from an electric
geyser passes through the inner tube, while the cold water from over head tank passes through outer tube.
The flow rate of both hot and cold water is controlled by the flow control valve. Inlet and exit temperatures
of hot and cold water are measured using thermocouples. Flow rate of the water is measured by the
rotameter. The outer tube is provided with insulation to minimize the heat loss to the surroundings.
TECHNICAL SPECIFICATIONS
Test Section
� Inner tube material :
� Inner tube diameter
� Outer : 0.0095 m
� Outer tube material :
� Outer tube diameter
� Inner : 0.0127 m
� Length of test tube section : 1.6 m
Thermocouples
� Type : “K” Type
� Numbers : 04
� Range : 0-200 °C
OPERATION PROCEDURE
1. Make all the connections as shown in figure and check valve positions and any leakage through the
system
2. Connect the equipment to the power supply.
3. Switch on the main system.
4. Adjust the desired flow rate of water either parallel/counter flow heat exchanger.
5. Switch on the electric geyser set the hot water temperature say 50 to 60 °C.
6. Allow sufficient time for thermal equilibrium to attain between hot and cold water
7. After reaching to thermal equilibrium conditions, note down the readings of temperature by rotating
knob.
8. Note down the reading of hot and cold water flow rate.
9. Repeat the experiment for different flow rates.
10. Follow the steps 1 to 8 by changing the flow conditions through the test rig.
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ME – 306P Heat and Mass Transfer School of Technology, PDPU
OBSERVATION TABLE
Table 1: Parallel Flow Condition
Sr.
No.
Hot Water Cold Water
Flow rate
(Kg/hr)
Inlet Temp.
(°C)
Outlet Temp.
(°C)
Flow rate
(Kg/hr)
Inlet Temp.
(°C)
Outlet Temp.
(°C)
1
2
3
Table 2 Counter Flow Condition
Sr.
No.
Hot Water Cold Water
Flow rate
(Kg/hr)
Inlet Temp.
(°C)
Outlet Temp.
(°C)
Flow rate
(Kg/hr)
Inlet Temp.
(°C)
Outlet Temp.
(°C)
1
2
3
SHUTDOWN PROCEDURE
1. Turn off the electric geyser.
2. Allow cold water to flow through electric geyser till its temperature goes down to room temperature.
3. Turn off the main switch on the control panel.
4. Turn off the main switch and disconnect the test rig from the power supply.
SAMPLE CALCULATION: (in separate sheet)
RESULTS AND DISCUSSION:
1. Plot results of Overall heat transfer vs Flow rate
2. Plot results effectiveness vs Flow rate
Date of Performance Sign of Faculty
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ME – 306P Heat and Mass Transfer School of Technology, PDPU