Experimental investigation on convective heat transfer from a horizontal miniature tube to methane at supercritical pressures

• Heat transfer of supercritical cryogenic methane was investigated experimentally.
• A new PDF-based correlation for supercritical cryogenic methane was developed.
• The acceleration criterion was analyzed to predict heat transfer deterioration.

Heat transfer of supercritical cryogenic methane in miniature tube has been experimentally investigated. Experimental conditions included pressures of 5–15 MPa, mass velocities of 6000–150,000 kg m−2 s−1 and heat fluxes of 1–16 MW m−2. The mass flux, heat flux and pressure effect were analyzed. A physically reasonable property averaging technique, Probability Density Function (PDF)-based time-averaged properties, were proposed for accounting for the effect of highly nonlinear dependency of properties on instantaneous turbulent temperature. A semi-empirical new correlation evaluated by PDF-based time-averaged properties for convection heat transfer of supercritical cryogenic methane was developed. The experimental Nusselt numbers were compared with those calculated with empirical correlations. The Dittus–Boelter and Gnielinski correlations overestimate the measurements in the pseudo-critical region since they could not accurately reflect the properties variations.The newly developed PDF correlation works so well that more than 85% experimental data are captured within an accuracy of 25%. Jackson acceleration criterion is found valid in evaluating the acceleration effect and works well in predicting heat transfer deterioration occurring in present experiments.