Asymmetric heating and buoyancy effects on heat transfer of hydrocarbon fuel in a horizontal square channel at supercritical pressures

Abstract

Heat transfer of the hydrocarbon fuel at a supercritical pressure is a key process in the aerospace engine cooling applications. A CFD model is applied in this paper to study flow dynamics and heat transfer of the aviation kerosene RP-3 in a horizontal square cooling channel under asymmetric heating and buoyancy effects at various supercritical pressures. The turbulent fluid flows are handled by the standard k–ε turbulence model with an enhanced wall treatment, and the strong thermophysical property variations are calculated using the extended corresponding state approaches and a four-component surrogate model of RP-3. The effects of secondary flows and heat flux redistribution induced by buoyancy on supercritical-pressure heat transfer are analyzed. Results indicate that drastic variations of the fuel density with temperature at a supercritical pressure of 3 MPa induce strong buoyancy effect on heat transfer. In the top heated case, secondary flows carry the relatively cold fluid to the side and opposite walls, thereby increasing their fin effectiveness in heat transfer. As the operating pressure increases from 3 to 5 MPa, the density variation of RP-3 is decreased, consequently leading to the weakened buoyancy effect. As the solid thermal conductivity increases from 20 to 100 W/(m-K), the surface heat flux redistribution is dictated by heat conduction in the channel walls, and therefore, the buoyancy effect is significantly reduced. Numerical results herein could help elucidate the heat transfer characteristics of RP-3 in practical engine cooling processes.