Experimental study of heat transfer characteristics under supercritical pressure of upwards inclined rifled tubes

The heat transfer characteristics of water under supercritical pressure, together with the wall temperature distribution of upwards inclined (α = 19.5°) φ28.6 × 5.8 (mm) rifled tubes concerned, have been experimentally investigated. The test range was: p = 23.28 MPa, specific mass flow G = 600~1200 kg/m2s, mean heat flux of the tubes' inner surface q = 300 - 600 kW/m2. Test results indicate that the circulating flow, initiated by the rifles, weakens the effect of natural circulation over the tubes' cross-sections. The nonuniformity of wall temperature distribution, and that of the heat transfer coefficient, along the tubes' circumference, is rather small. The wall temperature increases with increasing heat flux and reduces with increasing mass flow. In the high enthalpy region, heat transfer is intensified by rising pressure. A formula for calculating the heat transfer coefficient is moreover offered for design reference purposes.