Convective Heat Transfer Analysis of Supercritical-Pressure Methane in a Regenerative Cooling Channel

Comprehensive analysis of coolant thermal behavior in regenerative cooling channels is one of the main steps in optimum design of launch vehicles. In methane-based propulsion systems, thermal analysis of methane coolant is important to predict the thermodynamic properties which depend on local temperature and pressure. Methane may experience a state change from subcritical to supercritical and heat transfer deterioration due to the high temperature gradients in the proximity of the walls, high Reynolds numbers, and three-dimensional flow structures in cooling channels. In the present study, a computational fluid dynamics solver was developed, which is able to simulate the convective heat transfer of supercritical methane coolant flow inside rectangular cooling channels. The solver was validated using reliable experimental data. The coefficients of current Nusselt number correlations were improved using minimization of relative root mean square error. Additionally, the entrance-region effects on heat transfer coefficient were simulated. The accuracy of the proposed relations was studied at different operating conditions. The proposed modified Nusselt correlations have errors less than 10% at outlet pressures higher than 8 MPa and heat transfer rates lower than 13 kW.