CONVECTIVE HEAT TRANSFER OF TURBULENT GAS FLOW IN MICRO-TUBES WITH CONSTANT WALL TEMPERATURE (COOLED CASE)

Numerical computations were performed to obtain for heat transfer characteristics of turbulent gas flow in micro-tubes with constant wall temperature whose temperature is lower than the inlet temperature (cooled case). The numerical methodology was based on Arbitrary-Lagrangian-Eulerinan (ALE) method to solve compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was employed to evaluate eddy viscosity coefficient and turbulence energy. The tube diameter ranges from 100 mu m to 400 mu m and the aspect ratio of the tube diameter and the length is fixed at 200. The stagnation temperature was fixed at 300 K and the computations were done for wall temperature, which ranged from 250 K to 295 K. The stagnation pressure was chosen in such a way that the flow is in turbulent flow regime. The results in wide range of Reynolds number and Mach number were obtained. The bulk temperature based on the static temperature and the total temperature of the cooled case are compared with those of heated case and also with temperatures of the incompressible flow. The result shows that different heat transfer characteristics are obtained for each cooled and heated case. A correlation for the prediction of the heat transfer rate of the turbulent gas flow in a micro-tube is proposed.