Simulation of heat transfer in high speed microflows

Abstract

The dynamic flow behavior and heat transfer characteristics of high speed gas flows through two-dimensional microchannels are investigated by using direct simulation Monte Carlo (DSMC) method. In order to study the effects of the Knudsen number ( Kn) on fluid flow and heat transfer behaviors, flows in both slip flow regime and transition flow regime have been investigated. The collision process has been treated in a statistical way using the NTC (no-time-counter) scheme. The VHS (variable hard sphere) model was chosen to simulate the collision from the kinetic point of view. The different viscous effects produced from different Kn significantly influenced the development of the flow and also the development of the thermal boundary layers. The bulk flow has a high increase in temperature due to the wall friction and the deceleration of the supersonic flow as it enters the narrow channels, and this dominates the wall heat flux phenomenon. The effect of gas species on the flow properties was studied using helium and nitrogen. It has been found that the wall temperature jump, the wall heat flux, and the centerline temperature for helium are much higher compared to nitrogen. No significant effects of the variable wall temperature distribution were observed on the total amount of heat transferred between the bulk flow and the channel walls.