ME – 306P Heat and Mass Transfer School of Technology, PDPU

Safety Hazards

HAZARD: Rotating Equipment / Machine Tools Personal Protective Equipment: Safety Goggles; Standing Shields, Sturdy Shoes. Personal Care

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.

HAZARD: Electrical - Burns / Shock

Personal Care: Take Care while doing electrical connections, particularly with grounding; do not use frayed electrical cords.

HAZARD: Water / Slip Hazard

Personal Care: Clean any spills immediately. HAZARD: Noise Personal Protective Equipment: Ear Plugs

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

+=

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

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.

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

ME – 306P Heat and Mass Transfer School of Technology, PDPU