Characterization of thermal and mechanical properties of porous material for electronic cooling applications
Metal foams are considered beneficial for several applications because of its significantly large surface area for a given volume. Foams form a high thermal conductive network in a thermal interface for electro cooling applications. The porous structures are relatively compliant and can provide for a better contact and thereby have a lower thermal resistance. Porous heat sinks made of aluminum foam have been well studied in the past. It is not only cost effective due to the unique production process, but also attractive for the theoretical modeling study to determine the performance. A study on the thermal and mechanical characterization of metal foams is presented. Metal foams are analyzed as viable thermal interfaces and heat sinks focusing on the electronics cooling applications. Generalized analytic models are developed to predict intrinsic thermal resistance as well as the contact thermal resistance defined by micro-deformation at the contact surfaces. Properties of porous structure as an effect of the characteristic geometric parameters are evaluated. Effective Young's modulus, effective thermal conductivity, Coefficient of thermal expansion, and surface contact, area for deformation are evaluated through analytic models and simulations. Experiments are also carried out in accordance to the ASTM D5470 standard for determining the total thermal resistance. The results verify the calculation from the model in intrinsic thermal conductivity of the foam as well as the constriction resistance to the actual area of contact. The bulk thermal resistance -contact resistance trade-off for thermal interface applications and pressure drop- heat transfer trade-off for heat sink applications are studied. An optimum value of porosity and pore size is found out for thermal interface and heat sink applications individually..
Nauman, Purdue University.
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