Numerical investigation on convective heat transfer to aviation kerosene flowing in vertical tubes at supercritical pressures

Numerical simulations of convective heat transfer to aviation kerosene (China RP-3) flowing in vertical circular tubes at supercritical pressures are reported in this study. Firstly, performance of a variety of Reynolds-Averaged Navier-Stokes turbulence models in predicting the fluid-thermal behaviours under both forced and mixed convection conditions are evaluated. Under forced convection conditions, all models predict a gentler growth of wall temperature along the flow direction than experimental measurements. Under mixed convection conditions, the effect of buoyancy become significant and there are large discrepancies in the predicted wall temperature by different models. Only the low-Reynolds number k-ε models are found to be able to qualitatively predict the flow laminarization and heat transfer deterioration. Profiles of thermal, flow and turbulence fields obtained using various models are studied to explain the differences in predictions. For mixed convection conditions, an examination on the turbulence production due to shear and density fluctuation indicates that the direct effect of buoyancy on the turbulence production is negligible compared with the indirect effect. Furthermore, the effect of turbulent Prandtl number on the predicted heat transfer is studied. It is found that turbulent Prandtl number has a significant influence on the simulation results. Under the conditions considered in the present study, the value of 1.0 for turbulent Prandtl number leads to a closest agreement with the experimental data.