Temperature recovery factor for gaseous nitrogen flow in a microtube.

Abstract

For gas flow over a flat plate, the temperature recovery factor is defined as a fraction of free-stream total temperature rise recovered at the wall or is the ratio of the actual temperature rise at the wall to the maximum possible temperature rise in the free-stream. Its value depends on Prandtl number and is independent of Mach number. The gas velocity and temperature are determined by the temperature recovery factor using the adiabatic wall temperature. It is an important parameter to be used to evaluate the gas velocity and temperature indirectly. In the present study, for internal flow, a methodology was introduced to estimate the temperature recovery factor numerically based on the total and bulk temperature for both laminar and turbulent flow regions in a microtube. The numerical simulations are based on the arbitrary Lagrangian-Eulerian method. The compressible momentum and energy equations for an ideal gas were solved to obtain the temperature recovery factor. To further validate the temperature recovery factor from numerical results, experiments were conducted using stainless steel microtubes. Although it is not a direct comparison, the gas bulk temperature and Mach number that were determined by the temperature recovery factor were compared with the experimental results and they were in good agreement.