Thermal Conductivity Experiment-123

FORCED CONVECTION HEAT TRANSFER

06-92-328-01/02 HEAT TRANSFER

Summer 2015

Graduate Assistant: Prashant Kaliram Pradip

Introduction

Forced convection heat transfer theory is valuable in many engineering fields

Especially heat-exchanger design

This apparatus allows to examine the theory & formulae related to forced convection in pipes

Tuesday, July-14-15 Pradip 2

General Layout


Airflow Speed

The fan runs at a constant speed and draws air through a control valve

The air speed is varied by screwing in the plate over the fan inlet

Do not screw the plate fully in, there must be an airflow!


Orifice Dimensions


Pitot Tube

Pitot tube traverse assembly measures:

Velocity and temperature profile across the test pipe

Outer Diameter of Pitot tube 3 mm


Dimensions and Positions of Thermocouples

Thermocouple selector is adjusted to measure the temperature from thermocouple 1 to 14.

Maximum duct temperature < 150C!


Procedure

Start the fan. When air is flowing through the tube, slowly increase the electrical

current to the heating coil until a suitable value is reached. Run for 15 to 20 minutes, by which it will have reached an equilibrium

temperature. Check this by monitoring one of the thermocouples. Note down the Orifice pressure drop from the manometer. Take readings of temperature distribution across the duct by changing

the thermocouple selector. Set the Pitot tube right against the far side of the duct and take

readings of temperature from 14 in thermocouple selector. Without altering the current setting, traverse the Pitot tube across in

intervals of 2 mm, and not the results. After use, turn off the heater but allow the fan to keep working for

approximately five minutes before you switch it off.


Data collection sheet

THERMOCOUPLES

Number Position Temperature (C)

1

Outer

surface of

copper

tube

2

3

4

5

6

7

8 Inner

surface

insulation

10

12

9 Outer

surface

insulation

11

13

Distance from pipe wall (mm) Temperature (C)

1

3

5

7

9

11

13

15

17

19

21

23

25

27

29


Orifice pressure drop (mm H2O):

Experimental Information

Video conference

Fill the tabular column as the camera is focused on the data

The data to be noted will be shown in the computer screen


Tasks associated with the laboratory

Plot the temperature transverse as a function of distance from pipe wall.

Calculate the heat input to the air through thermocouple 1 to 7 from equation 8.

Determine the heat transfer coefficient from tube to air with equation 4.

Calculate the non-dimensional numbers and compare with Dittus and Boelter empirical relationship.


Instructions for preparation and submission of the lab report

You may work in groups of up to four. Each person will write and sign their name on the

title page of the submitted laboratory report, and provide an e-mail address.

Prepare a short lab report (no more than 3 pages) including the data collection sheet provided above.

Explain your results and complete all tasks as specified above.

Each group should submit a hard copy of the lab report no later than July 22, 2015. No late submissions will be accepted.


THANK YOU


Thermal Conductivity Experiment-123

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Transcript of Thermal Conductivity Experiment-123