Discussion of heat transfer phenomena in fluids at supercritical pressure with the aid of CFD models

The paper discusses heat transfer enhancement and deterioration phenomena observed in experimental data for fluids at supercritical pressure. The results obtained by the application of various CFD turbulence models in the prediction of experimental data for water and carbon dioxide flowing in circular tubes are firstly described. On this basis, the capabilities of the addressed models in predicting the observed phenomena are shortly discussed.Then, the analysis focuses on further results obtained by a low-Reynolds number k – ε model addressing one of the considered experimental apparatuses by changing the operating conditions. In particular, the usual imposed heat flux boundary condition is changed to assigned wall temperature, in order to highlight effects otherwise impossible to point out.The obtained results, supported by considerations drawn from experimental information, allow comparing the trends observed for heat transfer deterioration at supercritical pressure with those typical of the thermal crisis in boiling systems, clarifying old concepts of similarity among them.