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Heat Transfer Handbook part 16

Heat Transfer Handbook part 16. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | 140 THERMOPHYSICAL PROPERTIES OF FLUIDS AND MATERIALS Cahill 1990 is being applied widely to measure the thermal conductivity of thin films especially for microelectronic applications. A single metal strip is fabricated on the film to be tested which is in turn mounted on a substrate of another material e.g. silicon . The metal film acts as both heater and temperature sensor. Analysis of the oscillation of electrical resistance at a frequnncy ff 3rn in response to oscillations of power and temperatore cf 2rn provides the in-plane thermal conductivity. Specific Heat Differential scanning calorimetry DSC has become widely used because modern commercial instrumentation allows simple use although the construction and control system of dee devtee may lee compeex R ci h doan 1992 . In DSC a small test sample and a reference sample of similar size are placed in adjacent separate holders. The samples are heated simultaneously at a specified rate often 1 to 10 C min. Thermocouples are typically used to monitor the temperature of each sample. The change in enthalpy ofthe sample is then determined by measurement of how much energy must be added to hee test sample to make tts temperaiute mack that of the reference. By keeping the sample and the reference the same size and temperature and making the two holders of toe aarne material toe fffects of parasitic convective and radiative losses are automatically canceled in the comparison of the two samples. Modulating the temperature rise of a DSC ee.g. by addmg an ac component to the steady rise in temperature provides additional insight into phase transitions in polymers. Thermal Diffusivity Measurements of thermal idiffus i M are populaf because they typically reeuire only measurement ofa temperature history due to a thermal perturbation of toe mpte whcd ss caiter i.haii meaiuring heat flux as tleiuited m many steady-state methods. Formerly hampered by complex error analysis microprocessors have made commercial devices relatively