Heat transfer aspects of regenerative-cooling in methane-based propulsion systems

In the present article, thermal behavior and heat transfer deterioration (HTD) of transcritical methane as well as the fluid state change in regenerative cooling with straight/curved rectangular channels are studied numerically. Simulations are conducted with a finite-volume based CFD solver utilizing reliable turbulence models and thermo-fluidic relations in transcritical conditions. The experimental and numerical results of hydrogen inside a heated tube in the literature are used for validation. The effects of mass flow rate, outlet pressure, wall temperature, surface roughness, and the channel geometry on the thermal behavior of the coolant fluid are studied in detail. According to the results, variations in the slope of the transport property curves and the inflection point in the density distribution of the coolant flow are proposed as criteria for the recognition of the HTD and transcritical regions, respectively. In addition, the outlet pressure and surface roughness have negligible effects on both methane HTD and transcritical regions in contrast to the channel curvature, mass flow rate, and wall temperature. (C) 2018 Elsevier Masson SAS. All rights reserved.