Date of Experiment:Report due date:Report submission date:Checked by:

Item/marksFormat/10Abstract and Introduction/10Figures and Diagrams/15Materials and Method/10Results Discussions/45References/10Total

Thermal Radiation Study BenchCaleb Tee Li Jun

0318976

School of Engineering Taylor’s University

17 September 2014

Group MembersNg Vui LoongLee Man Chee

Kalaichelvan A/L ArugamShivani Amish Kumar Pandya

1

2

Table of ContentABSTRACT 3

1.0 INTRODUCTION 3

2.0 EXPERIMENTAL DESIGN2.1 Materials 42.2 Methods 52.3 Procedures 5,6

3.0 RESULT AND DISCUSSION

3.1 Data Tabulation 7

3.2 Graphs 8

3.3 Calculation3.4 Discussion

9 10

4.0 ERROR ANALYSIS 11

5.0 CONCLUSION 12

6.0 REFERENCES 12

AbstractThis experiment is done in two parts which is experiment A and experiment B.

During experiment A, the power we use is constant while the one which is changing is

the distance of the radiometer and the heat source. While, in experiment B, the distance

of the radiometer and the heat source is constant but the power is changing to minimum,

medium and maximum power. From experiment A, result shows that the intensity of the

radiometer is inversely proportional to the distance of the radiometer and the heat source.

This shows that the distance affect the reading of the intensity of the radiometer. In

experiment B, we can see that the intensity of the radiometer increases as the power

increase that makes the temperature increase. This shows that the power that control the

temperature affects the intensity of the radiometer. In this experiment, both random error

and systematic error occurs as the result is slightly different from the theoretical value.

But still, Stefan-Boltzmann law has been proven true in this experiment.

1.0 Introduction

The main objective in conducting this experiment is to prove that the intensity of

the radiometer is inversely proportional to the distance between the radiometer and the

heat source. For the 2nd experiment, it proves that the intensity of the radiation is also

affect by the power of the heat source which is the temperature. Thermal radiation is

different from conduction and convection, thermal radiation requires to have the presence

of an intervening medium while conduction and convection does not have to. Therefore,

thermal radiation is much faster compare to conduction and convection. Example for

thermal radiation is a radiant grill in an oven heating food. The occurrence of the thermal

radiation is due to the radiation emitted by bodies because of their temperature. So this

proves that all things which have a temperature over zero will have thermal radiation.

Stefan-Boltzmann Law states that the thermal energy radiated by a blackbody radiator per

3

second per unit area is proportional to the fourth power of the absolute temperature is

given by q̇b=σ [T S4−T A

4 ] where,

qb = Energy emitted by unit area of a black body surface (Wm-2)

σ = Stefan-Boltzmann constant equal to 5.67 × 10-8 (Wm-2K-4)

TS = Temperature of black plate (K)

TA = Temperature of the radiometer and surroundings (K)

2.0 Experimental Design

2.1 Materials

Diagram 1. Thermal Radiation apparatus

A- Power control

B- Radiometer reading

C- Heat source

D- Radiometer

E- ‘ON’ switch

4

F- Temperature reading

1) Thermal Radiation Apparatus ( A, B, C, D, E, F)

2) Protective cover

3) Black plate

2.2 Methods

A thermal radiation apparatus is placed on a flat table. The switch us turned to

‘ON’ button as the temperature increase as shown on the temperature reading. As time

goes by, the reading of the temperature will be stabilized at a certain amount. The

radiometer reading is also observed by us as the temperature increases. The radiometer is

covered by a rubber cover to prevent the heating of the radiometer. Distance of the

radiometer and the heat source is by a scale on the track. The measurement of the

distance is used using parallel to the eyes level to avoid parallax error. To avoid the

inaccuracy of the radiometer reading, the experiment is start from the furthest to the

nearest between the radiometer and the heat source.

2.3 Procedure

Experiment A: Inverse Square Law of Heat

1. Main switched is turned ‘ON’ to enable the power to flow into the apparatus.

2. The radiometer is covered with a rubber protector.

3. The power control is set to the mid position as constant to conduct the whole

experiment.

5

4. As time goes by, the temperature is set to a stable state before noticing the

radiometer reading.

5. The radiometer is placed away from the heat source within 500mm, 400mm,

300mm, 200mm and 100mm respectively.

6. As the temperature is stabilized, the rubber cover and the black plate is taken off

to conduct the experiment.

7. Radiometer reading then is recorded and is written into the table prepared.

8. The experiment is made respectively by changing the distance of the radiometer

and the heat source.

9. Results is taken and recorded in the table prepared.

Experiment B: Stefan-Boltzmann Law

1. Main switched is turned ‘ON’ to enable the power to flow into the apparatus.

2. The radiometer is covered by a rubber protector.

3. The power control is set to the minimum to conduct the 1st part of the experiment

4. As times goes by, the temperature shown on the temperature reading is then

stabilized.

5. The distance of the black plate and the heat source is 50mm and it stays constant.

6. The rubber cover and the black plate is then taken off after the temperature is

stabilized.

7. The results shown on the radiometer reading is then recorded in the table.

8. Experiment is repeatedly done by changing the power to the minimum, medium

and maximum.

9. Results shown in the experiment is taken and tabulated.

6

3.0 Results and Discussion

3.1 Data Tabulation

Experiment A:

Table 1: Radiometer Reading, R and Distance from the Heat Source, X

Distance X (mm) 100 200 300 400 500

Radiometer Reading R (Wm-2) 1042 446 220 125 80

Table 2: Logarithm Values of the Data Taken

Log10 X 2.00 2.30 2.48 2.60 2.70

Log10 R 3.00 2.65 2.34 2.10 1.90

Experiment B:

Table 3: Readings for Source Temperature, Ambient Temperature, Radiometer and

7

Energy Emitted by Unit Area of a Black Body Surface

READINGS CALCULATIONS

Source

Temperature

Reading (TS)

Ambient

Temperature (TA)

Radiometer

Reading (R)TS TA q̇b=σ [T S

4−T A4 ]

α=q̇b

R

oC oC Wm-2 K K Wm-2

30 27 160 303 300 18.65 0.117

39 27 575 312 300 78.01 0.136

77 27 1999 350 300 391.58 0.196

3.2 Graphs

Graph 1: Graph of Radiometer Reading R against Distance X

8

Graph 2 : Log-log Plot of Radiometer Reading against Distance

3.3 Calculation

Conversion of oC(celcius) to K(Kelvin)

K= oC +273

=77+273

=350 K

Gradient of the slope between log10 R and log10 X

m=2.70−2.00

1.9−3.0

=-0.64

9

Calculation of thermal energy radiated by a blackbody radiator per second per unit area,

q̇b

q̇b=σ [T S4−T A

4 ] = 56.7 × 10-9 (3124 - 3004)

= 78.01 Wm-2

Calculation for

α

α=q̇b

R

= 78.01575

= 0.136

3.4 Discussion

By looking at the graph, we can see that the intensity of the radiation is inversely

proportional to the distance between the heat source and the radiometer in graph1. This

has shown that the intensity of the radiometer depends on the distance of the radiometer

and the heat source. The further the radiometer is away from the heat source, the lower

the intensity of the radiometer. As shown in graph 2 as well, we can see that Log10 R is

10

inversely proportional to Log10 X. As calculated in the calculation part, we then found out

that the gradient is -0.64.

As we look at table3, it is shown that when the power is set to the minimum, the

temperature shown on the temperature reading is 30 oC. The reading on the radiometer

shows that the radiometer is 160 Wm-2 .The temperature is 39 oC when the power is set to

the medium level. The radiometer then show a reading of 575 Wm-2 . The radiometer

shows a reading of 1999 Wm-2 while the power is set to the maximum level which has a

temperature of 77 oC. Ambient temperature is constant throughout the whole experiment

which is 27 oC same as the room temperature. By observing the pattern of the results, we

know that when the power increases which makes the temperature to increase, the

intensity of the radiometer also increases. With the help of Stefan-Boltzmann Law, we

can calculate the α which is 0.117, 0.136 and 0.196 respectively. Calculated average for

α is 0.15. The different value of α is due to some error occur in the experiment. But still

we can prove that the Stefan-Boltzmann Law is credible.

4.0 Error Analysis

From the graph above, we can see that the values are a bit different from the

theoretical value. This can be explained as error occurs during the process of conducting

11

the experiment. The error that may occur in this experiment might be random and

systematic error.

One of the random error is caused by human errors. When conducting the

experiment, by looking at the apparatus to measure the distance may cause some error as

the eyes is not parallel to the measuring tape. This will lead to the inaccuracy of the result

for the experiment. Besides that, the apparatus which is rusty may also cause error to

occur.

While the systematic error is caused by the gadgets we have around us which may

effect the reading of the radiometer because our gadgets emits out radiation as well. The

other systematic error which occurs is due to the apparatus which can only go up to 1999

Wm-2 . This means that the reading of the radiometer might go higher but due to the limit

of the reading of the radiometer.

By having all these errors occur, we can minimize it by repeating the experiment a

few times to get the average result to increase the accuracy of the experiment. Besides

that, the university should be generous enough to change the apparatus or upgrade it so

that we can get a more accurate result while conducting the experiment.

5.0 Conclusion

After conducting this experiment, we can see that the intensity of the radiometer

depends on the distance of the radiometer and the heat source. We then can conclude that

12

the intensity of the radiation is inversely proportional to the distance between the heat

source and the radiometer. Log10 R is inversely proportional to Log10 X which has a

gradient of -0.64. The value ofα is almost the same regardless of the changing of the

temperature. In conclusion, we can prove that Stefan-Boltzmann Law is true.

6.0 References

1. unknown. (2014). Introduction to the principle of heat transfer. Available:

http://www.efunda.com/formulae/heat_transfer/home/overview.cfm. Last

accessed 30th Sep 2014.

2. Unknown. (2014). Stefan-Boltzmann Law. Available: http://hyperphysics.phy-

astr.gsu.edu/hbase/thermo/stefan.html. Last accessed 30th Sep 2014.

13