Heat transfer comparison investigation of mist/steam two-phase flow and steam in a square smooth channel

A small amount of fine water droplets is injected into steam to form mist/steam two-phase flow as the working fluid of internal cooling passages of blades and vanes, which is a promising cooling technology to replace compressed air cooling for next generation gas turbine. To simulate mist/steam flow in the internal cooling passage of gas turbine blade/vane, a smooth square channel was made by welding four stainless steel plates. The test channel employs a hydraulic diameter of 40 mm and a length of 420 mm. The thickness of the channel plate is 3 mm. The wall temperature distribution and averaged Nusselt number ratio of mist/steam and steam-only in this channel were numerically and experimentally investigated under the same test conditions for comparison. The effects of Reynolds number, wall heat flux and mass flow rate on the heat transfer performance have been analyzed. The results show that within the scope of allowable error the calculated results were acceptable to simulate the experiment subject with the numerical model in this work. Compared with steam-only, the variation trend of wall temperature distribution cooled by the mist/steam is different at the middle region of the test section. The heat transfer coefficient of mist/steam two-phase flow is significantly improved.