Effect of inclination on frictional pressure drop of supercritical water flows in internally ribbed tubes: An experimental study

Internally ribbed tubes are highly advantageous for heat transfer enhancement in high pressure water flows. But these tubes increase the frictional pressure drop in comparison with smooth tubes. In this paper the frictional pressure drop characteristics of subcritical, near critical and supercritical water upward flows inside the inclined rifled tube with inclinations angles of 5, 20, 30, 45 and 90 with respect to the horizontal plane are studied experimentally. The test pressures were 15, 21.5, 22.5, 25 and 28 MPa, the heat and mass fluxes were kept at 400 kW/m(2) kW/m(2) and 800 kg/m(2)s. The effect of heat and mass fluxes on frictional pressure drop in inclined tubes was also investigated. The results showed the least frictional pressure drop for both subcritical and supercritical flows occurs at 5 degrees. The effect of mass flux on frictional pressure drop in all water flow conditions was more considerable than the heat flux. (C) 2017 Elsevier B.V. All rights reserved.