Abstract: Numerical simulation on flows and heat transfer of water at supercritical pressures in inclined upward smooth tubes of Φ32 mm×3 mm at an angle of 20° respect to the horizon is made. Length of the tube is 8 000 mm. Influence of violent variation of water properties in the so-called "large specific heat region" on heat transfer characteristics was investigated. Numerical method was validated by comparing numerical results with experimental data. Variation of the inner surface temperature of tube wall with enthalpy of water, mass flow rate and heat flux were obtained at pressures of 26 MPa and 34 MPa, respectively. It was found that distributions of wall temperature, as well as heat flux, along tube wall's circumference were non-uniform. Difference between top generatrix wall temperatures and the bottom generatrix wall temperature was analyzed. Effect of water properties in the so-call "large specific heat region" on heat transfer of water was also discussed. Two parameters, namely cross-section transverse kinetic energy and cross-section relative transverse kinetic energy were introduced to quantitatively describe intensity of secondary flow. And density grads along a cross-section perpendicular bisector were used to analysis secondary flow. Abnormal mechanism of inner wall temperature distribution in a large specific region in inclined upward tubes at supercritical pressures was discussed.

Key words: supercritical pressure, large specific heat region, wall temperature distribution, ununiformity, secondary flow, transverse kinetic energy