FURTHER STUDY ON COMPRESSIBILITY EFFECTS ON THE GAS-FLOW AND HEAT-TRANSFER IN A MICROTUBE

Both analytical results and numerical simulations for the compressible flow in a circular microtube show that the flow compressibility affec ts the velocity profile nor only in amount, but also in shape. The lat ter depends on the ratio of characteristic times of diffusion and acce leration, which is a function of local Mach number only. Consequently, the fully der eloped or locally fully developed approximation no long er holds even at very large value of l/(d Re) if the Mach number is su fficient large, and the local friction factor and Nusselt number incre ases with increasing local Mach number.