An experiment that covered a wide range of parameters was conducted to investigate the flow and heat
transfer characteristics of water flowing in a vertical upward smooth tube. The effects of the operating
parameters on flow and heat transfer were analyzed, and the corresponding empirical correlations were
presented. Results show that at subcritical pressures, dryout dominates heat transfer deterioration. This
phenomenon can be delayed by reducing pressure and heat flux; however, the effect of mass flux on
dryout occurrence is nonmonotonic. At near-critical pressures, departure from nucleate boiling (DNB)
occurs at low vapor qualities under high heat fluxes and low mass fluxes. When heat flux increases,
DNB occurs early, and peak wall temperature increases significantly. At supercritical pressures, heat
transfer is enhanced within the pseudo-critical region, and the heat transfer coefficient peaks
correspondingly. When pressure approaches the critical value, heat transfer deterioration occurs at high
heat fluxes when the bulk fluid temperature is below and the wall temperature is above the
pseudo-critical temperature. Three hydraulic resistance correlations were evaluated using the
experimental data, and all three correlations underestimated the frictional pressure drop.