Investigation of mixed convection of supercritical pressure RP-3 in vertical round tube

The mixed convection research of supercritical pressure hydrocarbon aviation fuel RP-3 in vertical tube was conducted and the effects of buoyancy and thermophysical properties on convection was investigated. The wall heat fluxes (200-500 kW/m²), inlet pressure (3-5 MPa) and inlet Reynolds number (5 000-10 500) were maintained in the experiments. The study shows that heat transfer impairment occurrs in inlet region for all upward flow conditions due to buoyancy effects, which is not observed in the downward flow. The heat transfer coefficient increases as the fluid bulk temperature increased as a result of comprehensive effects of thermophysical properties. At lower inlet Reynolds number (5 700), the radial velocity profile changes in downward flow conditions leading to heat transfer enhancement due to buoyancy effects. The buoyancy effects are also significant for higher inlet Reynolds number (10 500). The criterion equation (Bo^*<5.6×10^-7) failed to evaluate buoyancy effects on hydrocarbon fuel heat transfer.