A comprehensive investigation of heat transfer in a high aspect ratio cooling channel of a rocket engine using LNG coolant

Small quantities of hydrocarbon impurities in liquefied natural gas (LNG) play a significant role in regenerative engine cooling in propulsion systems. Conjugate heat transfer in a high aspect ratio cooling channel is numerically studied at a supercritical pressure of 10 MPa, for pure methane and two different LNG with a 97.5% and 88.5% methane mole fraction. The Reynolds-averaged Navier-Stokes equations are numerically solved. The thermophysical and transport properties of methane with varying quantities of impurities are calculated using the GERG-2008 equation of state and extended corresponding states. The results indicate that the hydrocarbon impurities significantly affect LNG cricondenbar pressure, coolant properties, cooling capabilities, and pressure drop, whereas the pressure drops and the heat transfer performance increase with purity. Finally, the overall thermal-hydraulic performance dropped by less than 1% and more than 10% for lean and rich LNGs, respectively. The acquired consequences can help design the cooling system in rocket engines under trans-critical operating conditions.