A Thermal Experimental System with Freestanding Microchannels

Abstract

MEMS technology can significantly facilitate the study of two-phase flow in microchannels by providing instrumented chips with multiple control and measurement accesses. The importance of heat distribution control in the experimental system as well as the thermal isolation of the test channel has been addressed in the last chapter. The discussions lead to the idea of experimental devices with a single channel or a very small number of channels for accurate heat transfer measurement. With an instrumented MEMS device, the only possible problem lies in the excellent thermal conduction in the silicon substrate. Having a thermal conductivity of k=148 W/m−K, silicon is a better thermal conductor than most metals. This helps to distribute heat from a computer chip to its heat sink, but in thermal experiments, it threatens the accuracy of local wall temperature measurements, because the heat can easily diffuse from high temperature areas to low temperature areas. To minimize the heat diffusion problem, FEM (Finite Element Modeling) has been used to simulate the thermal conduction in a silicon substrate to design the geometry of the single-channel devices.