This paper presents an analysis of new heat-transfer correlations developed for SuperCritical Water (SCW) and SuperCritical 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 SuperCritical (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.
