HEAT-TRANSFER CORRELATIONS FOR SUPERCRITICAL-WATER AND CARBON DIOXIDE FLOWING UPWARD IN VERTICAL BARE TUBES

This paper presents an analysis of new heat-transfer correlations developed for SuperCrifical Water (SCW) and Super Critical Carbon Dioxide (SCCO2) flowing upward in vertical bare tubes. Previous studies have shown that existing correlations deviate significantly from experimental Heat-Transfer-Coefficient (HTC) values, especially, within the pseudocritical range for both fluids. Therefore, new empirical correlations based on the following approaches in terms of characteristic temperature were developed: 1) bulk-fluid-temperature approach (SCW); 2) wall-temperature approach (SCW and SCCO2); and 3) film-temperature approach (SCW). Analysis showed that for SCW the best correlations, i.e., the most accurate ones, are based on the bulk-fluid- and wall-temperature approaches. Calculated wall temperatures according to these new correlations were within +/- 15% and HTC values were within +/- 25% for analysed datasets. For SCCO2, the new correlation was within +/- 20% for wall temperatures and within +/- 30% for HTC values. The proposed correlations can be used for (1) calculations of SCW and SCCO2 heat-transfer in Super Critical (SC) steam generators / heat exchangers; (2) preliminary heat-transfer calculations in reactors fuel channels as a conservative approach; (3) future comparisons with other independent datasets and with bundle data; (4) verification of computer codes for thermalhydraulics; and (5) verification of scaling parameters between SCW, SCCO2 and other SC fluids.