OBJECTIVES

To examine the temperature profile and determine the rate of heat transfer resulting from

radial heat conduction through the wall of cylinder.

To investigate the influence of thermal insulation upon the conduction of heat between

adjacent metals.

SUMMARY

The main purposes of this experiment is to examine the temperature profile and at the

same time to determine the rate of heat transfer resulting from radial heat conduction through

the wall of a cylinder and also to investigate the influence of thermal insulation upon the

conduction of heat between adjacent metals. The variables involved in this experiment are

power (Watts), temperature (oC), and types of insulation materials. Based on the results

acquired in experiment 1 (Radial Module), it was observed that as the power (Watts)

increases from 10 Watts (Test A) through 15 Watts (Test B) to 20 Watts (Test C), the

temperature recorded fairly increases for each thermocouple temperature (TToC) by which

shows a directly proportional relationship. However, the power (Watts) and the difference in

temperature (dT) increases when the distance of the thermocouples is closer to the heat

supply, and vice versa. As for experiment 2 (Linear Module), the results were observed in

which directly creates a hypothesis. The temperature varies when different insulation

materials were used. It was also observed when the power is at a constant value of 20 W, and

the thermocouple temperature is consistently increasing, the temperature recorded decreases

which shows and proves the best insulator between all the three insulation. In addition to that,

for experiment 1 (Radial Module), the average thermal conductivity for Test A (10 W) is

7.376 W/mK, for Test B (15 W) is 6.526 W/mK, and the average thermal conductivity for C

(20 W) is 7.376 W/mK. As for the insulators in experiment 2 (Linear Module), the average

thermal conductivity for paper is 0.02808 W/mK, the average thermal conductivity for cork is

0.06331 W/mK, and the average thermal conductivity for the blank is 0.3231 W/mK. A trend

graph/temperature profile was generated to demonstrate the relationship between the

difference in temperature (dT) and difference in distance/displacement (dx). From that, based

on the results recorded and the theory stated, the objectives were achieved.

INTRODUCTION

This experiment is about the principles of heat transfer in conduction. In this

experiment, there are two ways to practice heat conduction; Radial Module and Linear

Module. The principles involved in this experiment is Fourier’s Law in which states that heat

flow rate (Q) is proportional to the temperature differences (dT) and cross-sectional area (A)

per unit length (dx) where the thermal conductivity (K) is a constant. In conjunction to that

statement, thermal energy (heat) will always maneuver from warmer objects to cooler

objects.

For Radial Module (Experiment 1), the process will first begin by starting the flow of

the coolant and connecting the heater supply lead to the control panel. Next, connect the six

sensors (TT1,2,3,7,8,9) to the Radial Module. Then, set the power supply to 10 W, 15 W, and

20 W respectively and wait for the readings to stabilize before selecting the numbered sensor

to take its temperature readings. The set-up is as shown in Figure 1.

Figure 1 – Radial Module

For Linear Module (Experiment 2) on the other hand, similar steps as for the Radial

Module will be taken but with constant power supply of 20 W. The power supply will be in

the OFF position first and the six sensors (TT1,2,3,7,8,9) will be connected to the Linear

Module. Next, connect the heater supply lead for the Linear Module to the control panel.

Then, place the insulating material (Paper/ Cork/ Blank) in the specimen section and switch

on the power supply. Wait for the readings to stabilize for about 5 minutes before selecting

the numbered sensor to take its temperature readings. Also, wait for similar time after

changing between insulating material. The set-up is as shown in Figure 2.

Figure 2 – Linear Module

THEORY

The Fourier’s Law states that the rate of heat transfer through a material is proportional to

the negative gradient in the temperature and to the area, at right angles to that gradient,

through which the heat is flowing [Anonymous A, 2013]. The relationship is as shown

below :

Where :

Q = Heat flow rate, [W] dT = Changes in temperature, [K]

A = Cross-sectional area of the conduction, [m2] dx = Changes in displacement, [m]

k = Thermal conductivity of the material, [W/mK]

Heat always conducts from warmer objects to cooler objects. The composition of a

material affects its conduction rate. For cylinders, Fourier’s Law states that the heat flux (Q)

is proportional to the temperature differences per unit length. The proportionality constant is

the thermal conductivity (k) [J. C. Diaz, 2013]. The relationship is shown below :

Where :

Ri = Inner radius, [m] Ti = Inner section temperature, [K]

Ro = Outer radius, [m] To = Outer section temperature, [K]

Q = Heat flow rate, [W] L = Thickness of the material, [m]

k = thermal conductivity of the material, [W/mK]

The higher the value of k (Thermal conductivity of material), the better insulator the

material is, and vice versa.

Q = - 2 πkL(T 1−T 0)

lnRo

Ri

Q = kAdTdx

DISCUSSION

An experiment on determining the rate of heat transfer resulting from heat conduction

through both radial and linear pattern of a cylinder, as well as to observe the influence of

thermal insulation towards heat conduction was conducted by operating on the Heat

Conduction Apparatus.

Two experiments were conducted; the first experiment, which is to determine the

radial heat transfer at the Radial Module of the apparatus. The control panel was connected to

the Radial Module and the system was switched on. The wattmeter was then set to 10 Watts,

followed by 15 Watts and 20 Watts. Each numbered thermocouple/sensor was selected with a

5 minutes wait before each setting to obtain a steady state condition, and the displayed

temperature was recorded. For the second experiment, it is about the linear heat transfer with

the influence of several types of insulators (Paper, cork, and blank) at the Linear Module of

the apparatus. Similar steps were conducted as the Radial Module but with uniform power

supply of 20 Watts. Data obtained from both experiments were recorded and was then used to

calculate the thermal conductivity (k), of each material.

For experiment 1, Ti of 39.3 C and To of 32.4 C were obtained for given power

supply of 10 Watts. Ti of 43.5 C and To of 31.8 C were obtained for power supply of 15

Watts, and for power supply of 20 Watts, Ti of 47.6 C and To of 33.8 C were obtained. For

experiment 2 (Constant power supply of 20 Watts), Ti of 112.3 C and To of 32.6 C were

attained for the paper insulator. Ti of 122.6 C and To of 32.2 C were attained for cork

insulator, and for blank insulator, Ti of 72.3 C and To of 31.2 C were attained. For the Radial

Module, the calculated values for the average thermal conductivity (k) acquired for power

(Q) of 10 W, 15 W, and 20 W were 7.376 W/mK, 6.526 W/mK, and 7.376 W/mK. Whereas

for Linear Module (Constant Q = 20 W), thermal conductivity (k) of 0.02808 W/mK was

obtained for paper insulator, 0.06331 W/mK for cork insulator, and 0.3231 W/mK for blank

insulator. The higher the value of k, the better insulator it becomes and vice versa. The best

insulator among the three materials is cork, followed by paper, and blank.

Theoretically, Fourier’s Law of Heat Conductivity states that the heat flux (Q), is

directly proportional to the temperature difference (dT) per unit length (dx) [J.C. Diaz, 2013],

which means the lowest dx has the highest Q and dT. It was observed that when power was

supplied to both modules, the thermocouple with the least distance to the power supply has

the highest rate of heat transfer and temperature, while the thermocouple with the most

distance has the lowest rate of heat transfer and temperature. It can be observed that the

results agreed with the theory stated. Trend graphs/Temperature profiles were plotted to

support the statement. Hence, it can be deduced that the objectives of this experiment were

achieved.

There are several possibilities that might have contributed to the errors that occurred

during the experiment. Among those errors is physical errors (caused by experimenters). The

experimenters might not have waited for the readings to stabilize first and have recorded

down the wrong readings, which could lead to an abnormal trend of results. Not just that, the

experimenter may not have focused well during the experiment and may have recorded down

the readings of the parameter in the field of another parameter. By doing so, it will disrupt the

results, and the trend graphs will not result as expected. Other than that, the experimenter

may be careless and accidentally set a higher/lower power supply than it was supposed to

thus, resulting in different temperature values.

TEMPERATURE PROFILE – RADIAL MODULE

Constant distance between sensors = 1 cm

Sensor 1 Sensor 2 Sensor 3 Sensor 4 Sensor 5 Sensor 605

101520253035404550

Radial Module

Test A (10 W)Test B (15 W)Test C (20 W)

Difference in displacement, dx (m)

Diffe

renc

e in

tem

pera

ture

, dT

(C)

Sensor 1 Sensor 60

2

4

6

8

10

12

14

Radial Module

Test ATest BTest C

Difference in displacement, dx (m)

Ther

mal

cond

uctiv

ity, k

(W/m

K)

TEMPERATURE PROFILE – LINEAR MODULE

Constant distance between sensors = 1 cm

Constant power supply = 20 W

Sensor 1

Sensor 2

Sensor 3

Sensor 7

Sensor 8

Sensor 9

0

20

40

60

80

100

120

140

Linear Module

Paper InsulatorCork InsulatorBlank Insulator

Difference in displacement, dx (m)

Diffe

renc

e in

tem

pera

ture

, dT

(C)

Sensor 1 Sensor 90

0.050.1

0.150.2

0.250.3

0.350.4

0.450.5

Linear Module

Paper InsulatorCork InsulatorBlank Insulator

Difference in displacement, dx (m)

Ther

mal

cond

uctiv

ity, k

(W/m

K)

CONCLUSION

In conclusion, the length (m), power (Watts), the inner radius (m), the outer radius

(m), inlet temperature (K) and the outlet temperature (K) are essential in determining the

thermal conductivity (W/mK) of the insulation material. The thermal conductivity for

experiment 1 (Radial Module) and experiment 2 (Linear Module) were calculated using a

specific formula. The thermal conductivity was acquired to show how good of an insulator

the insulation material is. By the end of the experiment, the objectives were achieved which

are to examine the temperature profile and to determine the rate of heat transfer resulting

from radial heat conduction through the wall of a cylinder and also to investigate the

influence of thermal insulation upon the conduction of heat between adjacent metals. Overall,

this experiment has been a success as the results obtained were supported much with the

theory.

RECOMMENDATIONS

There are steps that can be taken to prevent these types of errors from occurring. To

prevent physical errors (caused by experiments) from occurring, experimenters have to focus

and be patient for the readings to stabilize before recording any data. Also, work together to

record data, and not just be dependent on just a team member. Next, in order to prevent

recording the wrong data, team members should reconfirm with each other on the results to

acquire the readings which best fit. Besides that, to prevent conducting a slow process, those

who conduct the experiment should read the lab manual prior to conducting the experiment.

Furthermore, even before conducting the experiment, each team should request assistance

from available technicians to check whether the experiment is faulty or not, to avoid

unwanted results.

TUTORIAL

EXPERIMENT 1

1. Plot of the temperature, T versus distance, r. Calculate the thermal conductivity, k.

Sensor 1 Sensor 2 Sensor 3 Sensor 4 Sensor 5 Sensor 605

101520253035404550

Radial Module

Test A (10 W)Test B (15 W)Test C (20 W)

Difference in displacement, dx (m)

Diffe

renc

e in

tem

pera

ture

, dT

(C)

Sensor 1

Sensor 2

Sensor 3

Sensor 7

Sensor 8

Sensor 9

0

20

40

60

80

100

120

140

Linear Module

Paper InsulatorCork InsulatorBlank Insulator

Difference in displacement, dx (m)

Diffe

renc

e in

tem

pera

ture

, dT

(C)

EXPERIMENT 2

1. Plot the temperature profile in the heater and cooler to determine the temperature

gradient across the insulating disc. Determine the thermal conductivity of paper and

cork.

Sensor 1

Sensor 2

Sensor 3

Sensor 7

Sensor 8

Sensor 9

0

20

40

60

80

100

120

140

Temperature gradient across the insulating disc

Paper InsulatorCork InsulatorBlank Insulator

Difference in displacement, dx (m)

Diffe

renc

e in

tem

pera

ture

, dT

(C)

2. Comment the influence of insulators upon the conduction of heat transfer between

the heater and the cooler.

Conduction is the transfer of heat from one molecule to another through a substance.

When something hot gain contact with something cold, heat transfer will occur through

the touching of the surface of the particular cold substance. Thus, making the particular

substance burn which spreads the heat around which then makes it warm [R walder,

2013]. Moreover, the influence of insulators upon the conduction of heat transfer between

the heater and the cooler is to reduce the rate of heat transfer in which in this experiment

shows the difference in heat transfer between insulators which are the paper, the cork, and

the blank because not all substances conduct heat at the same speed [Anonymous B, 2003

- 2013].

3. How this material can inhibit conduction?

Less dense materials are better insulators. The denser the material, the closer its atoms are

together. That means the transfer of energy of one atom to the next is more effective. Poor

conductors of electricity are also poor heat conductors/good insulators. Metals that

conduct electricity allow free electrons to roam through the material. This enhances the

transfer of energy from one area to another in the metal. Without this ability, the materials

used like ‘the paper, the cork, and the blank ’ insulators do not conduct heat well

[Anonymous C, 2013].

.

4. Suggest practical uses for insulating materials.

a) Reduced noise levels:

The use of thermal insulation can reduce disturbing noise from neighbouring spaces or

from outside. This will enhance the acoustical comfort of insulated buildings [Dr.

Mohammad S. Al-Homoud, 2013].

b) Fire protection:

If the suitable insulation material is selected and properly installed, it can help in

retarding heat and preventing flame immigration into building in case of fire [Dr.

Mohammad S. Al-Homoud, 2013].

c) Environmental benefits:

The use of thermal insulation not only saves energy operating cost, but also results in

environmental benefits as reliance upon mechanical means with the associated emitted

pollutants are reduced [Dr. Mohammad S. Al-Homoud, 2013].

d) Vapor condensation prevention:

Proper design and installation of thermal insulation helps in preventing vapor

condensation on building surfaces. However, care must be given to avoid adverse effects

of damaging building structure, which can result from improper insulation material

installation and/or poor design. Vapor barriers are usually used to prevent moisture

penetration into low-temperature insulation [Dr. Mohammad S. Al-Homoud, 2013].

e) Customer satisfaction and national good:

Increased use of thermal insulation in buildings will result in energy savings which will

lead to [Dr. Mohammad S. Al-Homoud, 2013]:

Making energy available to others.

Decreased customer costs.

Fewer interruptions of energy services (better service).

Reduction in the cost of installing new power generating plants required in meeting

increased demands of electricity.

An extension of the life of finite energy resources.

Conservation of resources for future generations.

REFERENCES

1. [Anonymous A, 2013],

Thermal Conduction,

http://en.wikipedia.org/wiki/Thermal_conduction,

[26th September 2013]

2. [J.C. Diaz, 2013],

Fourier’s Law,

http://www.ens.utulsa.edu/~diaz/cs4533/flowheat/node4.html,

[28th September 2013]

3. [R walder, 2013],

http://wiki.answers.com/Q/

How_heat_is_transferred_between_a_hot_and_a_cold_object_by_conduction,

[29th September 2013]

4. [Anonymous B, 2003 - 2013],

http://www.wisegeek.org/what-is-conduction.htm,

[29th September 2013]

5. [Dr. Mohammad S. Al-Homoud, 2013],

http://www.sciencedirect.com/science/article/pii/S0360132304001878,

[29th September 2013]

6. [Anonymous C, 2013],

http://www.school-for-champions.com/science/thermal_insulation.htm,

[29th September 2013]