Multi‐dimensional modelling and analysis of heat transfer of pyrolytic hydrocarbon fuel at supercritical pressures

Abstract

Endothermic hydrocarbon fuel cooling in hypersonic vehicles has recently drawn significant attention. There exists significant 3-D phenomenon of the supercritical reaction flow which exerts great influences on heat transfer process. In this paper, an efficient multi-dimensional numerical model is established based on OpenFOAM to investigate the steady heat transfer of supercritical hydrocarbon fuel with pyrolysis in mini-channels. Numerical tests indicate that the present numerical model is able to reach better convergence and offer a higher computational efficiency than transient models for its simplicity. The numerical results reveal that there exists an unbalanced heat flux distribution and a conspicuous difference of heat transfer coefficients among interior walls in the square channel. Violent near-wall pyrolysis and resulting strong thermophysical property variations, reduced turbulent intensity in the lower part of the core flow, and bulk fluid reaction play important roles in the heat transfer performance. The 3-D phenomena of the reacting flow also make also significant impact on heat transfer. Based on the analyses above, two methods are proposed to mitigate heat concentration by enhancing fin effects of solid walls: one is to increase solid thermal conductivity, and the other is to change the square shape of cross-section to inverted trapezoid. This work helps raise awareness of the flow behavior inside asymmetrically heated channels and provides useful information for the engineering design of active regenerative cooling systems.