Experimental Investigation and Analysis of Convective Heat Transfer to Supercritical Pressure Aviation Kerosene RP-3 in Vertical Miniature Tubes Based on the Pseudo-Boiling Theory

The peculiar convective heat transfer characteristics of supercritical pressure hydrocarbon fuel in vertical tubes (inner diameter of 1 and 2 mm) were investigated experimentally. The purpose of this study is to analyze the heat transfer phenomena observed from experiments and correlate the Nusselt number based on the theoretical framework of supercritical pseudo-boiling. The operating parameters covered pressures of 3-5 MPa, Reynolds numbers of 3,000-141,500, and various wall heat fluxes. An enhanced heat transfer regime was found under large mass flux condition within the temperature range of 0.6 < Tb/Tpc < 1.05. Two types of deteriorated heat transfer phenomena were observed under small mass flux condition, which could be attributed to low values in cp for the entrance region and pseudo-film-boiling for the high enthalpy region, respectively. It was proposed to use Nu/Nuref,pb to identify the heat transfer regimes of supercritical pressure hydrocarbon fuels under various operating parameters, in which the reference Nusselt number was calculated based on an assumption of a ho-mogenous mixture of the liquid-like and gas-like fluid. In addition, a new correlation was developed by including a term characterizing the effect of pseudo-boiling on heat transfer, the K number. Promising findings on un-derstanding the complex heat transfer behaviors and improvement in the prediction of heat transfer charac-teristics have been obtained.