Numerical investigation of thermal creeping effect on a microsensor gas temperature and velocity distribution

摘要

The study of fluid flow and heat transfer inside micromechanical systems is the focus of many researchers due to their importance in microchannels as small-scale devices. Reducing the size of channel has lead the scientist to concentrate on microsensor. Metal oxide gas microsensors, as a micromechanical device, are used to detect gases such as O-3, SO2, CO2, NO, NH3, CH4, etc. The purpose of the current study is to numerically investigate the influence of three-dimensional diverging/converging microchannel on its gas inlet temperature while the flow of gas is due to thermal creeping. The coupled governing nonlinear differential equations, mass, momentum, energy, and species, are solved using an in-house code that is based on finite element. Maxwell equation for the slip boundary condition where the Knudsen number is between 0.01 and 0.1 is utilized. The result shows as channel width increases from 500 to 1300 mu m the maximum increase in velocity is about 19% and the maximum decrease in temperature is about 1%, and the velocity and temperature stay constant after l = 1300 mu m for all converging channels. From 500to 50 mu m, the maximum decrease in velocity is about 30%, and the maximum decrease in temperature is about 1% that the maximum velocity changes take place at y = 1000 mu m.