Experimental Investigation on Heat Transfer and Frictional Characteristics of Vertical Upward Rifled Tube in the Advanced Ultra Supercritical Steam Generator

This paper experimentally studied the heat transfer and frictional characteristics of a single rifled tube with vertical upward flow under the parametric range of pressures P = 10.5–32 MPa, mass fluxes G = 300–1300 kg·m⁻²·s⁻¹, heat fluxes q = 275–845 kW·m⁻². The results show that in the subcritical pressure region, dryout is the predominant mode of heat transfer deterioration. In the near critical pressure region, departure from nuclear boiling (DNB) occurs when the q/G value increases. In the supercritical pressure region, heat transfer and frictional characteristics will be strongly influenced by the sharp changes of the thermophysical properties of supercritical water when the value of mass flux is approximately lower than 1000 kg · m⁻² · s⁻¹ in this experiment. The mass flux and the pressure are two crucial factors to the variations of total pressure drop and frictional pressure drop. An empirical correlation is selected to estimate the frictional pressure drop. The results indicate that in the low mass flux circumstances, the calculated value significantly underestimates the experimental data in the large specific heat region. Whereas, when the value of mass flux is larger than 1000 kg · m⁻² · s⁻¹, the calculated value agrees well with the experimental data. (CSPE)