An efficient equivalent porous media model designed to simulate the heat and fluid flow in a gasgas micro heat exchanger is presented. Although similar models are common in macroscale environment, the present implementation takes into account several issues typical of microscale applications. In particular, three coupled solutions provide the hot fluid temperature, cold fluid temperature, and solid temperature, thus including conjugate heat transfer effects. Proper source terms incorporate the pressure loss effects and provide the coupling among the domains via the mutual heat transfer computation. Furthermore, since for gaseous, compressible flows no fully developed flow is attained, specific local based microscale correlations are used for the determination of heat transfer coefficients and friction factors, using only local values and properly taking into account both rarefaction and compressibility effects.
