Department of Mechanical EngineeringAlabama A&M University

ME 312L Heat and Mass LabSpring 2013

Experiment #6Thermal Conductivity of a Different Specimen

Cameron Alexander

Instructor: Dr. S. ChowdhuryDate Submitted: April 1, 2013

AbstractThe process by which heat moves through a surface is called conduction. We measure this when we want to see the rate of transfer of heat. There is an equation that we can use to find conduction. In this lab, we will be putting this concept to the test and seeing how it is used in the real world. Our objective was to determine the thermal conductivity (k) of a brass and aluminum specimen. We are to calculate the thermal conductivity of the specimens using the Fourier Rate Equation and measuring the temperature difference across specimens resulting from a known steady flow of heat through the specimen.

IntroductionThermal conductivity(k) is thepropertyof a material toconductheat. It is measured mostly in terms ofFourier's Lawforheat conduction. Heat transfer occurs at a higher rate across materials of high thermal conductivity than across materials of low thermal conductivity. Therefore, materials of high thermal conductivity are widely used inheat sinkapplications and materials of low thermal conductivity are used asthermal insulation. Thermal conductivity of materials is temperature dependent. It is also classified as a physical property of materials. Unlike some physical properties, however, thermal conductivity cannot be directly measured. In order to determine a material's thermal conductivity, intermediate quantities must be determined from which the conductivity may be ultimately calculated.

ProcedureIdentify the different components of the HT10X Heat Transfer Service Unit and HT11 Linear Heat Conduction Accessory.1. Clamp the intermediate Aluminum section between the heated and cooled section of the HT11, having lightly coated the mating surfaces with thermal paste to reduce contact resistance.2. Take care of the shallow sections before clamping.3. Connect the thermocouples on the HT11 to the appropriate sockets on the front of the service unit. Ensure that the labels match the socket labels.4. Set the Voltage Control potentiometer to minimum and the selector switch to Manual, then connect the heater lead from the HT11 to the service unit.5. Switch on the front main switch.6. Turn on the cooling water and adjust the flow control valve to give approximately 1.5 liters/min.7. Set the heater voltage to 9 volts.8. Allow the HT11 to stabilize.9. When the temperatures are stable record the readings from the front panel display, using the selector switch to select each required value in turn.x10. Set the heater voltage to 12 volts and repeat the above procedure.11. Repeat the steps above with diameter of 0.013m.

CalculationsLength of the specimen, x=0.030mDiameter of bar, D=0.025m and 0.013m.

Heat flow (Power to heater), Q=V1 (Watts)Cross sectional area, A=D2/4Th=T3- CTc=T6- CThe thermal conductivity of a specimen,k= (W/m.C)

ResultsV=9.0 voltsI=0.92 ampsq=8.28 WattSpecimen Diameter=0.025mObs#TimeT1T2T3T6T7T8ThTck

12:4946.044.342.534.132.731.641.634.874.4

V=9.0 voltI=0.92 ampsq=8.28 WattSpecimen Diameter=0.013mObs#TimeT1T2T3T6T7T8ThTck

13:1156.655.153.634.032.931.952.8534.5120.01

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ConclusionThis lab was very effective. It thoroughly explains the concepts needed to be explained. I was able to see a real world application of the given concept so that I can use it later in my engineering life. However, a more simplistic breakdown during the class lecture would be greatly appreciate. With that, we will be able to better understand certain concepts once the lab starts instead on going in blind. Still, this lab was very effective and should continue to be used.

References Laboratory Notes