Investigation of the Natural Convection Boundary Condition in Microfabricated Structures

Hu, X., Jain, A., and Goodson, K.E., 2008, "Investigation of the Natural Convection Boundary Condition in Microfabricated Structures," International Journal of Thermal Sciences, Vol. 47, pp. 820-824.

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Heat loss through surrounding air has an important thermal effect on microfabricated structures. This effect is generally modeled as a natural convection boundary condition. However, the correct procedure for the determination of the convective coefficient (h) at microscales continues to be debated. In this paper, a microheater is fabricated on a suspended thin film membrane. The natural convection on the microheater is investigated using 3-omega measurements and complex analytical modeling. It is found that the value of h that fits experimental data should have an apparently larger value than that at larger scales; however, it is also shown that the increased h is actually contributed by heat conduction instead of heat convection. A method of determining the correct h that can be used for microfabricated structures is proposed by using ththermomechanicale heat conduction shape factor.

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