The heat transfer mechanism coupling pyrolysis and flow of hydrocarbon fuel in heated tube under supercritical pressure

The coupling mechanism between pyrolysis and fluid flow of endothermic hydrocarbon fuels plays a crucial role in the design of regenerative cooling systems for advanced aircraft. In this work, the convective heat transfer for HF-1 with pyrolysis including 18 species and 24 reactions is numerically investigated in a horizontal circle tube under supercritical pressure (5 MPa). The results show that the mechanism of small molecule products on different heat transfer phenomena varies. In the inlet heat transfer deterioration region, small molecule products exacerbate the non-uniform radial distribution of fluid density and dynamic viscosity. At the outlet position, it significantly enhances the physical heat sink of the mixture with its high thermal conductivity and specific heat capacity. Additionally, the aromatic hydrocarbons significantly contribute to non-uniformities in thermal conductivity and specific heat capacity due to the low specific heat capacity and thermal conductivity in inlet HTD region. When the radial non-uniformity coefficient of fuel conversion keeps between −0.1 and 0, the pyrolysis of the fuel enhances heat transfer, remarkably.