A study of selected forced-convection supercritical-water heat-transfer correlations for vertical bare tubes based on a wide-range dataset

This paper presents an extensive study of heat-transfer correlations applicable to supercritical-water flow in vertical bare tubes. A comprehensive dataset was collected from 33 papers by 27 authors, including more than 125 graphs and wide range of parameters. The parameters range was as follows: pressures 22.5 - 34.5 MPa, inlet temperatures 85 - 350oC, mass fluxes 250 - 3400 kg/m2s, heat fluxes 75 - 5,400 kW/m2, tube heated lengths 0.6 - 27.4 m, and tube inside diameters 2 - 36 mm. This combined dataset was then investigated and analyzed by calculating Heat Transfer Coefficients (HTCs) and wall temperatures using various correlations and comparing them with the corresponding experimental results. Three correlations were used in this comparison: original Bishop et al., Mokry et al. (modified Bishop et al.) and Gupta et al. (modified Swenson et al). The main objectives of this study were a selection of the best supercritical-water bare-tube correlation for HTC calculations in: 1) fuel bundles of SuperCritical Water-cooled Reactors (SCWRs) as a preliminary and conservative approach; 2) heat exchangers in case of indirect-cycle SCW Nuclear Power Plants (NPPs); and 3) heat exchangers in case of hydrogen co-generation at SCW NPPs from SCW side. The comparison showed that in most cases, the Bishop et al. correlation deviates significantly from the experimental data within the pseudocritical region and actually, underestimates the temperature in the most cases. On the other hand, the Mokry et al. and Gupta et al. correlations showed a relatively better fit within the most operating conditions. In general, the Gupta et al. correlation showed slightly better fit with the experimental data than the Mokry et al. correlation. (author)