Flow and Heat Transfer Characteristics of the Mist/Steam Two-Phase Flow Cooling the Rectangular Channel with Column-Row-Ribs

Abstract

Using mist/steam two-phase flow by mixing a small amount of fine water droplets into steam as the working fluid for the internal cooling passages of blades and vanes is a promising cooling technology for future gas turbines. We proposed a new cooling channel roughed with the column-row-ribs to achieve higher cooling efficiency and better heat transfer uniformity. The heat transfer experiment was conducted to validate the effectiveness of our numerical method. Flow and heat transfer performance of mist/steam two-phase flow was investigated in channels of different gap ratios and in a column-row-ribbed channel with gap ratios of ε=0.177 under different working conditions. Comparing to the solid ribbed channel, the column-row-ribbed channels sacrifice the heat transfer performance to achieve better heat transfer uniformity. As ε larger than 0.264, the column-row-ribs have better thermal enhancement performance than the solid ribs. For the column-row-ribbed channel with gap ratio ε=0.177, the heat transfer effect increases with the Re number. But the thermal uniformity and the thermal enhancement of the channel decreases obviously. As the wall heat flux q rises from 3000W/m2 to 40000W/m2, the thermal enhancement factor F gradually increases. But the wall heat transfer becomes less even. Continuously increasing the mist/steam mass ratio will help to increase the heat transfer effect of the heated walls, so does the heat-transfer non-uniformity. Simply increasing the droplets diameter will decrease the thermal enhancement factor and increase the heat transfer non-uniformity at the same time.