Numerical study of conjugate heat transfer of cryogenic methane in rectangular engine cooling channels at supercritical pressures

Three-dimensional conjugate heat transfer of cryogenic methane in rectangular engine cooling channels at supercritical pressures with asymmetric heating imposed on the top channel surface is numerically investigated, focusing mainly on effects of the thermal conductivity of the solid channel material and the geometric aspect ratio of the channel on fluid flow and heat transfer. Results indicate that variations of the thermal conductivity in the solid fin produce significant impact on conjugate heat transfer owing to heat flux redistribution in solid region and convective heat transfer variation in fluid phase. The latter factor is dictated by strong variations of fluid thermophysical properties at a supercritical pressure. At a constant inlet mass flow rate, variations of the geometric aspect ratio of the channel exert strong influence on both heat transfer and pressure loss due mainly to fluid velocity variations. Results indicate that convective heat transfer plays a more dominating role than thermal conduction in the solid fin. A thermal performance factor can be used for the combined evaluation of heat transfer and pressure loss. The modified Jackson & Hall empirical heat transfer expression is tested to be applicable for heat transfer prediction of cryogenic methane at supercritical pressures. (c) 2013 Elsevier Ltd. All rights reserved.