Effect of heat and mass flux on heat transfer characteristics of water forced convection inside vertical and inclined rifled tubes

In this paper the subcritical and supercritical water flow inside a rifled tube has been investigated experimentally. A comparison between vertical upward flow and a 20° inclined upward flow inside a specifically designed rifled tube for various heat and mass flux values has been conducted. The operating pressures for the tests were 15, 21.5, 22.5, 25 and 28 MPa, heat fluxes were 300, 400 and 500 kW/m2 and mass fluxes were 600, 800 and 1000 kg/m2 s. The low mass flux condition has been considered due to its important applications in boiler industries for once-through vertical and spirally wound tubes boilers. The results were shown as inner wall temperature versus fluid bulk enthalpies and convection heat transfer coefficient distribution for various fluid bulk enthalpies for various flow conditions inside the both vertical and inclined tubes. The results showed that the effect of inclination on heat transfer enhancement is incentive for subcritical pressure flows. Also the results showed the higher effect of mass flux on heat transfer in near-critical and supercritical pressures in comparison with the subcritical pressure conditions.