HMT Heat conduction Experiments

8/10/2019 HMT Heat conduction Experiments

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Lab Session 1

Statement:

Investigation of Fourierslaw of heat conduction by using same material.

Apparatus:

Heat conduction apparatus, Brass sample.

Theory:

Conduction:

Heat movement due to small molecules e.g. at microscopic level heat movement.

When we place one end of iron rod on lighted candle and other end is on our hand

then this end will be soon hotter as metal is good conductor of heat and electricity.

By vibrating molecules will transfer heat to other molecules. A conduction

phenomenon is in following order:

Solid>Liquid>Gases

Convection:

Heat movement due to bulk molecules e.g. at macroscopic level of heat transfer e.g. heat transfer

from bike engine to the environment. Drop the red color in water after some time whole water

will get red color.

Natural convection: When fluid coincides with cooler body then it will transfer its energy to

cooler body its density decreases.

Forced convection: Fan is used to increase the rate of cooling.

Radiation:

Inphysics,radiation is a process in whichelectromagnetic waves (EMR) travel through

avacuum or through matter-containing media; the existence of a medium to propagate the waves

is not required. Everybody emits radiation but radiation is from higher temperature to lower

temperature.

E.g. Solar radiation reaches to earth. Earth is also emitting radiation but radiation travels is from

higher to lower temperature.
http://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Electromagnetic_radiationhttp://en.wikipedia.org/wiki/Physics


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Fourier Law of Heat Conduction

The law of heat conduction, also known asFourier's law, states that the time rate ofheat

transfer through a material isproportional to the negativegradient in the temperature and to the

area, at right angles to that gradient, through which the heat flows.

For many simple applications, Fourier's law is used in its one-dimensional form. In the x-

direction,

Is the amount of heat transferred per unit time (in W), and

is an oriented surface area element (in m2)

The abovedifferential equation,whenintegrated for a homogeneous material of 1-D geometry

between two endpoints at constant temperature, gives the heat flow rate as:

Ais the cross-sectional surface area,

is the temperature difference between the ends,

is the distance between the ends.

where Uis the conductance, in W/(m2K).

Fourier's law can also be stated as:

The reciprocal of conductance is resistance, R, given by:
http://en.wikipedia.org/wiki/Joseph_Fourierhttp://en.wikipedia.org/wiki/Heat_transferhttp://en.wikipedia.org/wiki/Heat_transferhttp://en.wikipedia.org/wiki/Proportionality_(mathematics)http://en.wikipedia.org/wiki/Gradienthttp://en.wikipedia.org/wiki/Differential_equationhttp://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Integralhttp://en.wikipedia.org/wiki/Differential_equationhttp://en.wikipedia.org/wiki/Gradienthttp://en.wikipedia.org/wiki/Proportionality_(mathematics)http://en.wikipedia.org/wiki/Heat_transferhttp://en.wikipedia.org/wiki/Heat_transferhttp://en.wikipedia.org/wiki/Joseph_Fourier


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Resistance is additive when several conducting layers lie between the hot and cool regions,

because Aand Q are the same for all layers. In a multilayer partition, the total conductance is

related to the conductance of its layers by:

So, when dealing with a multilayer partition, the following formula is usually used:

Calculation:

P=5 watt

No. Distance Temperature1 5 39.3

2 15 39.0

3 25 36.8

4 35 37.5

5 45 35.4

6 55 34

7 65 33

8 75 32.6

9 85 30.5

30

31

32

33

34

35

36

37

38

39

40

5 25 45 65 85 105

Temperature

Distance


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Comments

1) In this experiment axial heat flow would be studied.

2) Temperature is decreasing along the length as heat transfer from the hotter body to cooler

body.

3) As apparatus heats up it gives error in the reading. So by increasing Power it would give

more error.

4) Power dont remain 5 watt throughout the experiment it varies from 5 to 5.1 watt

5) 4th

reading varies from the trend it may be due to power fluctuation to 5.1 watt.


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Lab Session 2

Statement:

Draw the temperature profile of a composite materials and find the overall heat transfer co-

efficient.

Apparatus:

Heat conduction apparatus, 6 thermisters, Different samples of materials

Theory:

Composite Material:

Composite materials are materials made from two or more constituent materials with

significantly differentphysical orchemical properties, that when combined, produce a material

with characteristics different from the individual components. The individual components remain

separate and distinct within the finished structure. The new material may be preferred for many

reasons: common examples include materials which are stronger, lighter or less expensive when

compared to traditional materials.

Typicalengineered composite materials include:

Composite building materials such ascements,concrete

Reinforced plastics such asfiber-reinforced polymer

Metal Composites

Ceramic Composites (composite ceramic and metal matrices)

Heat transfer Co-efficient:

The heat transfer coefficient or film coefficient is theproportionality coefficient between theheat

flux and the thermodynamic driving force for the flow of heat (i.e., the temperature difference,

T):

q : heat flux, W/m2i.e.,thermal powerper unitarea,q= d /dA

h: heat transfer coefficient, W/(m2K)

T: difference in temperature between the solid surface and surrounding fluid area, K
http://en.wikipedia.org/wiki/Physical_propertyhttp://en.wikipedia.org/wiki/Chemical_propertyhttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Cementhttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Fiber-reinforced_polymerhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Composite_armorhttp://en.wikipedia.org/wiki/Proportional_(mathematics)http://en.wikipedia.org/wiki/Heat_fluxhttp://en.wikipedia.org/wiki/Heat_fluxhttp://en.wikipedia.org/wiki/Thermal_powerhttp://en.wikipedia.org/wiki/Areahttp://en.wikipedia.org/wiki/Areahttp://en.wikipedia.org/wiki/Thermal_powerhttp://en.wikipedia.org/wiki/Heat_fluxhttp://en.wikipedia.org/wiki/Heat_fluxhttp://en.wikipedia.org/wiki/Proportional_(mathematics)http://en.wikipedia.org/wiki/Composite_armorhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Fiber-reinforced_polymerhttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Cementhttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Chemical_propertyhttp://en.wikipedia.org/wiki/Physical_property


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The heat transfer coefficient hasSI units in watts per square meter kelvin: W/(m2K). Heat

transfer coefficient is the inverse ofthermal insulance.This is used for building materials (R-

value)and forclothing insulation.

Q=U*A*( T)

1/U=Resistance

Q=A*k*( T)/( x)

=A* T/( x/k)

=A* T/Resistence

1/U= ( xh/kh)+( xs/ks)+( xc/kc)

Length Temperature Group1 Group 2 Group 3 Group 4

P=5W P=6W P=7W P=8W

5 T1 34 40.2 43.4 45.4

15 T2 33.5 38.8 41.6 43.5

25 T3 33 37.7 39.6 41.5

65 T7 32.3 32.6 32.8 32.8

75 T8 31.7 32.5 32.4 32.6

85 T9 31.5 32.4 32.2 32.

31.5

32

32.5

33

33.5

34

34.5

5 25 45 65 85 105

Temperature

length

Group1 P=5W
http://en.wikipedia.org/wiki/International_System_of_Unitshttp://en.wikipedia.org/wiki/Thermal_insulancehttp://en.wikipedia.org/wiki/R-value_(insulation)http://en.wikipedia.org/wiki/R-value_(insulation)http://en.wikipedia.org/wiki/Clothing_insulationhttp://en.wikipedia.org/wiki/Clothing_insulationhttp://en.wikipedia.org/wiki/R-value_(insulation)http://en.wikipedia.org/wiki/R-value_(insulation)http://en.wikipedia.org/wiki/Thermal_insulancehttp://en.wikipedia.org/wiki/International_System_of_Units


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32.2

33.2

34.2

35.2

36.2

37.2

38.2

39.2

40.2

41.2

5 25 45 65 85 105

Temperature

Length

Group 2 P=6W

32.2

34.2

36.2

38.2

40.2

42.2

44.2

5 25 45 65 85 105

Temperature

Length

Group 3 P=7W


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Length Temperature P=5W P=6W P=7W P=8W

5 T1 46.8 48.6 50.6 51.3

15 T2 46 47.4 49 50.4

25 T3 43.5 45.3 46.6 48.5

35 T4 43 44 45.5 46.8

45 T5 40.7 42.1 43.4 44.6

55 T6 39.3 41.4 42.7 43.7

65 T7 32.9 41.4 33.6 33.9

75 T8 32.2 33.4 38 33.1

85 T9 32 32.6 32.6 32.6

32

34

36

38

40

42

44

46

48

5 25 45 65 85 105

Temperatu

re

Length

Group 4 P=8W


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Lab Session 3

Statement

When area would change then investigate the heat transfer.

Length Temperature P=5W P=6W P=7w P=8W

5 T1 45.8 51 52.2 52.4

15 T2 45.8 49.2 49.9 52.3

25 T3 42.2 45.4 47.3 47.9

65 T7 32.7 33.3 33.6 33.8

75 T8 32.5 33 33.1 33.1

85 T9 31.9 32.6 32.9 32.8


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Lab Session 3

Statement:

Draw the temperature profile for steady state heat conduction along the radial direction for a

cylindrical object and find k.

Calculation:

Ri=4mm

Ro=55mm

L=3mm

No. Radii(mm) T (P=15W) T(P=17W) T(P=19W)) T(P=21W)

1 0 38.7 40.2 40.9 41.22 4 38.7 40.2 40.9 41.2

3 10 37 38.6 39.3 39.6

4 20 36.4 37.2 38 38.2

5 30 35 35.4 36.1 36.3

6 40 33.7 33.9 34.3 34.5

7 50 32.4 32.4 32.7 32.8

8 55 31.75 31.5 31.8 32

qr =

q=15W

L=310-3

m

Ri=410-3

m

Ro=5510-3

m

Ti=38.7

To=31.75

15

=2k310-3[38.7-31.75]

K=300.100W/m.k (for P=15W)

K=328.31W/m.K (for P=17W)

K=382.89W/m.K (for P=19W)


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K=435.829W/m.K (for P=21W)

30

31

32

33

34

35

36

37

3839

40

0 10 20 30 40 50 60

Temperature

Radii

30

32

34

36

38

40

42

-5 5 15 25 35 45 55

Temp(atP=

17W)

Radii


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qr =

q=2W

L=310-3

m

Ri=410-3

m

Ro=5510-3

m

Ti=38.7

To=31.75

30

32

34

36

38

40

42

-5 5 15 25 35 45 55

Temp(p=19W)

Radii

30

32

34

36

38

40

42

44

-5 5 15 25 35 45 55

Temp(P=21W)

Radii


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2

=2k310-3[38.7-31.75]

K=39.72W/m.k (standard Aluminum oxide k=39W/m.k at 293K)

Comments:

1) This experiment give knowledge of heat transfer through cylindrical objects.

2) As power is increased then temperature would rises as Temperature is directly propotional to

energy dessipiation.

3) As from 0-4 mm convection phenomena takes place we assume that temperature during the

process remain constant further 4 mm is very small distance.

4) We have thermister up to 50 mm while cylindrical object is up to 55 mm . So we draw the

graph up to 50 mm and by line trend we take temperature corresponding to 55 mm. This is

To.

5) Thermal conductivity comes out to be 300-435W/m.K in experiments with applying different

powers which is Copper(pure) at 385-386-390-401 at 293 K. Also Silver is from 401-439W/m.K at 293 K. But more chance of having that it is Copper Pure.


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Lab Session 5

Statement:

Investigation of thermal contact for study heat conduction (k,A same0

Apparatus

Conduction apparatus, Thermister apply axially, Conducting Paste

Theory:

Conducting Paste

Thermal paste is a very high heat conductive paste that is used between two objects (usually a

heat sink and a CPU/GPU) to get better heat conduction. It fills in all those microscopicimperfections on the heat sink and CPU/GPU that can trap air in them and cause a loss in the

heat sinks performance. Air is a very poor conductor of heat. Thermal Interface Materials (TIM)can be up to a 100 times greater conductor of heat than air.

However, thermal paste is not near as good of a conductor as copper. Thus, too much thermal

paste will hinder a heat sinks ability to cool properly.

This is an exaggerated view of what these microscopic imperfections would look like. All the

white area would represent the air pockets, and this is what the TIM would fill in. It wouldn't be

such a gap like this, but this just an example to give you a rough idea of what it would look like.

If you could have a perfectly flat heatsink base, and CPU, you would not need thermal paste. But

it is impossible to do so, and thats why we need thermal paste.

Types of thermal paste

There are essentially three types of thermal pastes:

Metal based

Ceramic based

Silicon based


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Metal-based

These pastes have lots of little metal particles in the grease that have a high thermal

conductivity. One disadvantage of this type of paste is that it is also electrically conductive as

well, which can cause a problem, more on this later.

Ceramic-based

TIMs are -based pastes, but the difference is minimal (1-3C). These consist of some form of

thermally conductive material with lots of little ceramic particles. The advantage of ceramic-

based pastes is that they do not conduct electricity.

Silicon-basedTIMs are usually what thermal pads that come on stock heat sinks are made of.

These work well, but nowhere near to what other pastes will. Usually they come with coolingkits.
http://www.techpowerup.com/articles/134/images/thermalpaste4.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste2.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste4.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste2.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste4.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste2.jpghttp://www.techpowerup.com/articles/134/images/thermalpaste.jpg


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Calculation

No. Length(mm) Temperature(P=6W) Temperature(P=7W)

1 5 41.1 41.3

2 15 40.5 40.2

3 25 39.4 39.54 35 38.1 37.9

5 45 38 38.1

6 55 34.4 35

7 65 33.8 34.3

8 75 32.9 33.6

9 85 33 33.1

32

33

34

35

36

37

38

39

40

41

42

5 25 45 65 85 105

Temp(P=6W)

Length(mm)

32

33

34

35

36

37

38

39

40

41

42

0 20 40 60 80 100

Temp

(7W)

Length(mm)


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Comments:

1. Conducting paste is used to conduct heat between space in between two metal.

2. In space air is entrapped as air is a bad conductor of heat and electricity.

3. So, by applying conducting paste we remove the vacuum in between two metal.

Lab Session 6

Statement:

Investigation of thermal heat resistance on the temperature profile for steady state heat

conduction (k, A same)

Apparatus

Insulation Paper, Consucting apparatus, 9 thermister attach axially

Calculation

No. Length(mm) Temperature(P=5W)

1 5 40.4

2 15 39.5

3 25 39.2

4 36 35.2

5 46 34.7

6 56 34.2

7 66 33.4

8 76 33.39 86 32.8


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Comments:

1. Experiment helps us to study the affect of resistance in the flow of heat.

2. We take the resistance as 1mm . When we see temperature after resistance then temperature

drops from 39.2 to 34.7. This sudden decrease in temperature is represented by slope.

3. This shows that paper is a bad conductor of heat and electricity.

4.

32

33

34

35

36

37

38

39

40

41

0 20 40 60 80

Temperature

Length

HMT Heat conduction Experiments

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