Thermal Conductivity


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This presentation is about the basics of thermal conductivity and its method, formula derivation and also its applications.
short but comprehensive

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  • Great introduction to thermal conductivity. More in-depth information on transient plane source can be found here:
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Thermal Conductivity

  1. 1.
  2. 2. Presentation topic: “Thermal conductivity”<br />Thermodynamics<br />
  3. 3. Contents <br />Definition.<br />Explanation. <br />Methods to measure the <br /> thermal conductivity.<br />Experiment.<br />Application (importance).<br /> ……Use in industry.<br /> ……Use in laboratory.<br />Latest researches in this field.<br />
  4. 4. Thermal:<br /> MEANS <br />“HEAT.”<br />Conductivity:<br /> Means <br /> “ability to convey”.<br />
  5. 5. Definition:<br /><ul><li>It is the property of a material that indicates its ability to conduct heat.
  6. 6. It is represented by k and is measured in watts per kelvin per metre (W·K−1·m−1).
  7. 7. The reciprocal of thermal conductivity is thermal resistivity.</li></li></ul><li>
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  9. 9. Thermal Conductivity<br />Assume that no heat is lost through the edges of the disc.<br />Thermodynamics<br />
  10. 10. Thermal Conductivity<br />For a uniform rod the rate of flow of heat through a conductor ( Q/ t) is proportional to<br /><ul><li>the cross sectional area (A) of the conductor
  11. 11. the temperature gradient (  q/  x)</li></ul>The constant of proportionality, k, is the thermal conductivity BUT note that heat flows down a temperature gradient so we also introduce a negative sign to account for this and obtain:<br />Thermodynamics<br />
  12. 12. Thermal Conductivity<br />k depends on the material and is called the thermal conductivity.<br />Rearranging in terms of k we can evaluate the units of k:<br />So k is defined as the rate of flow of heat through unit area of cross section of 1m of material when the temperature difference between the surfaces is 1K.<br />Thermodynamics<br />
  13. 13. Methods to measure thermal conductivity.<br />Main methods:<br />Steady state methods.<br />Transient state methods<br />
  14. 14. Steady state methods.<br />Definition:<br />These methods are used when the materials are in equilibrium state( means when temperature of the materials is constant).<br />Advantage :<br />Accurate readings can be taken.<br />It steady state implies constant signals.<br />Disadvantage:<br /> As material take to long time to reach equilibrium state so it is slow method.<br />
  15. 15. TRANSIENT STATE METHOD:<br />Definition:<br />These methods are used during the heating of material.<br />Advantage:<br />Non-steady-state methods to measure the thermal conductivity do not require the signal to obtain a constant value.<br />Readings can be taken during heating of material.<br />Disadvantage:<br />Readings are not accurate<br />Mathematical analysis of the data is in general more difficult.<br />
  16. 16. METHODS: <br />IEEE Standard 442-1981, "IEEE guide for soil thermal resistivity measurements", ISBN 0-7381-0794-8. See also soil thermal properties. [5][1]<br />IEEE Standard 98-2002, "Standard for the Preparation of Test Procedures for the Thermal Evaluation of Solid Electrical Insulating Materials", ISBN 0-7381-3277-2[6][2]<br />ASTM Standard D5334-08, "Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock by Thermal Needle Probe Procedure" [3]<br />ASTM Standard D5470-06, "Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials" [7]<br />ASTM Standard E1225-04, "Standard Test Method for Thermal Conductivity of Solids by Means of the Guarded-Comparative-Longitudinal Heat Flow Technique" [8]<br />ASTM Standard D5930-01, "Standard Test Method for Thermal Conductivity of Plastics by Means of a Transient Line-Source Technique" [9]<br />ASTM Standard D2717-95, "Standard Test Method for Thermal Conductivity of Liquids" [10]<br />ISO 22007-2:2008 "Plastics -- Determination of thermal conductivity and thermal diffusivity -- Part 2: Transient plane heat source (hot disc) method" [11]<br />
  18. 18. OBJECTIVES:<br />
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  20. 20. PROCEDUER:<br /> Take ice block ,find its weight and volume and place it on the material sheet.<br />Then place it on the plate which is under observation<br />Then provide steam for sometime then we the ice converted to water then measure the weight of the water (in beaker).<br />Then place this values in the formula and calculate the conductivity.<br />
  21. 21. Exp:<br />Formula:<br />K= Ro dx / A dT<br />dx = thickness of material.<br />dT =change in temperature.<br />
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  26. 26. Applications:As aluminums sheets are used in houses for blocking of heat to come in and remain in cool inside.<br />
  27. 27. Used in lab: Experiments are performed in lab for finding thermal conductivity of different materials.<br />
  28. 28. <ul><li>Now a days different materials are used such like graphene and diamonds for transferring heat which is also due to the techniques of finding thermal conductivities.</li></ul>Also because of this property of the material we can use desired elements in electric circuits like copper, steel etc according to their conductivity.<br />
  29. 29. Latest researches.CARBON NANOTUBES <br />
  30. 30. MAIN POINTS:<br />Before carbon nanotubes the best thermal conductor was diamond.<br />Carbon nanotubes have extraordinary thermal conductivity properties.<br />
  31. 31. STRUCTURAL IMAGE:<br />
  32. 32. RESEARCHES<br />The record-setting anisotropic thermal conductivity of carbon nanotubes is enabling applications where heat needs to move from one place to another.<br />carbon nanotubes have the intrinsic characteristics desired in material used as electrodes in batteries and capacitors.<br />
  33. 33. Graphene:<br />
  34. 34. Properties:<br /> has very high current capacity.<br />Used in high modified circuit in which current gain is required<br />
  35. 35. Group:<br /> “ IEFRIANS”<br />Talent participated:<br /> HASSAN ALI (50+8)<br /><ul><li> HASSAN SULTAN(50-21)</li></ul> TAUSEEF AWAN.(50-22) ANAS AMIN (50+6)<br /><ul><li> M. AWAIS SATTAR.(50+4)</li></ul>Special thanks to HASSAN ALI<br /> (YOUNG RUFFIANS)<br />