Heat transfer of supercritical carbon dioxide flowing in a rectangular circulation loop

Experiments were conducted to investigate the heat transfer of supercritical carbon dioxide flowing in a rectangular circulation loop. The effects of heat flux, pressure, buoyancy force on heat transfer of supercritical carbon dioxide were carefully discussed. A heat transfer correlation for supercritical fluid was developed based on experimental data. Distinct heat transfer enhancement and heat transfer deterioration were observed in the present experiments. The maximum of heat transfer coefficient decreased with the increase of heat flux and pressure. Noticeable heat transfer deterioration was only observed in conditions of buoyancy parameter higher than 2.2 x 10(-5), T-wint/T-pc higher than 1.4, T-b/T-pc less than 0.95. The mechanisms of the effects of heat flux, pressure and buoyancy force on heat transfer of supercritical carbon dioxide were discussed in detail. Results indicated that the steep gradient of physical property over the tube cross-section is the key reason for heat transfer deterioration. The new heat transfer correlation showed reasonably satisfactory prediction performance. (C) 2015 Elsevier Ltd. All rights reserved.