Numerical investigation of counter flow microchannel heat exchanger with slip flow heat transfer

摘要

The rectangular microchannel heat exchanger performance is numerically investigated in this paper. Hydrodynamic and heat transfer characteristics in a laminar, 3-D, incompressible, slip flow, steady state and counter flow are proposed. The Navier-Stokes equations and energy equation for the hot and cold fluids are solved with the slip velocity and temperature jump conditions. The governing equations are discretized using finite-volume method-upwind differencing scheme, and then these are solved using SIMPLE algorithm method on staggered grid with FORTRAN code. From the obtained results it was found that the factors affecting the effectiveness are: Reynolds number Re, thermal conductivity ratio K_r, Knudsen number Kn and aspect ratio α. Increasing of Re, Kn and α separately lead to decrease the effectiveness. While the effectiveness increases with increasing K_r until it reach a certain optimal value which gives the maximum effectiveness at K_r = 90. Also, it is found that Nusselt number decrease with increases Knudsen number. Increasing of Re and Kn separately lead to increase pressure drop.