Numerical analysis of effects on gaseous flow and heat transfer characteristics in microchannels

A flow and heat transfer numerical simulation was performed for a 2D gaseous flow through microchannels to investigate the effects of roughness and compressibility. These effects were simulated by various relative roughness, inlet Mach numbers, and so on. The numerical results demonstrate that recirculation zones and barriers lead to the pressure drop and average Poiseuille number(po number) increasing. For incompressible gases, The relative roughness´ existence could undermine the export effect Compared with the relative roughness effects on the Po numbers, there are relatively less effects on the Nusselt numbers(nu number). The roughness elements peak density(pd)effects are obvious when the relative roughness is large. Relative to the pd value on the Po number, pd values´ influence has little effects on average Nu number. Turned the roughness elements rectangular shape into random shape, Po number is decreasing slightly. The roughness elements shape has no significant influence on fluid heat transfer characteristics. In addition to the roughness elements peak density, flow field may be more sensitive to the roughness element shape. Considering compressibility, the greater the Mach number is, the greater the exit speed deviation degree of parabola becomes, and the Po number is higher. Since the inlet boundary conditions´ influence, compressible cases have greater Nu number than incompressible conditions. There are sudden shrinkages along the flow path, result in the mainstream temperature´s decrease, the mainstream speed´s increase, and the thermal energy´s turning into the fluid kinetic energy.