Thermalfluids Lab-MEC 554/ LS 5/ THOMAS Rev. 01-2007

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UNIVERSITI TEKNOLOGI MARA

FACULTY OF MECHANICAL ENGINEERING ________________________________________________________________________ Program : Bachelor Of Engineering ( Hons ) Mechanical Course : Thermalfluids Lab Code : MEC 554

LAB SHEET NO : 5

HEAT TRANSFER LABORATORY SHEET

TITLE : HEAT CONDUCTION SIMPLE BAR 1. OBJECTIVE Investigate Fourier’s law for linear conduction of heat along a simple bar.

2. THEORY

If a plane wall of thickness (x) and area (A) and thermal

conductivity (k) supports a temperature difference (T) then the heat transfer rate by conduction is given by the equation:

dx

dTAkQ

Assuming a constant thermal conductivity throughout the material and a linear temperature distribution, this is:

x

TAkQ

Thermalfluids Lab-MEC 554/ LS 5/ THOMAS Rev. 01-2007

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3. EQUIPMENT The equipment is shown in the figure below.

4. READINGS TO BE TAKEN Select an intermediate position for the heater power control (e.g. 10 W) and allow sufficient time for a steady state to be achieved before recording the temperature (T) at all 9 sensor points and the

input power reading on the wattmeter ( Q ). This procedure should be repeated for other input

powers (e.g. 20 W and 30W) up to the maximum setting of the control. After each change, sufficient time must be allowed to achieve steady conditions.

5. RESULTS

HEATER

BRASS SAMPLE REGION COOLER

x (mm) 0 10 20 30 40 50 60 70 80

x (m) 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Test

#

Q

(W)

T1

(°C)

T2

(°C)

T3

(°C)

T4

(°C)

T5

(°C)

T6

(°C)

T7

(°C)

T8

(°C)

T9

(°C)

A

B

C

Thermalfluids Lab-MEC 554/ LS 5/ THOMAS Rev. 01-2007

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1. Plot the temperature profile along the entire length. This should reveal three distinct sections of straight lines (corresponding to the heater, brass sample, and cooler) having

a slope of approximately T/x. 2. Convert the measured temperatures to degrees Kelvin by the following formula:

15.273 CTKT

3. Calculate the cross-sectional area (A) of the circular cylinder by using the equation:

2

4dA

4. The brass sample region is the region of interest. Ignore all other temperature

measurements except T4, T5, and T6 and calculate the thermal conductivity of the brass. This is the slope of the straight line in the brass sample region alone (plotted in 1), given by the equation:

Km

Wunits

T

x

A

Qk

5. Find published values of brass in books or on the Internet. Compare the value you obtained with these values. Which type of brass does your results best compare with (e.g. yellow brass, red brass etc.)? Discuss any source of error in your measured results. Students should comment on how changing the average temperature affects the thermal conductivity.