Flow and heat transfer performance of the channel with different shaped ribs cooled by mist/steam two-phase flow

Abstract

The flow and heat transfer performance of mist/steam coolant in a straight channel with 45°/60°/75°V-shaped ribs, 45°/60°/75°/90°paralleled ribs and a smooth channel under different working conditions are studied. Based on vortex analysis, for mist/steam coolant, the regions where the Mainstream Secondary Flow Vortexes and the Longitudinal Secondary Flow Vortexes exist simultaneously can achieve better cooling performance. Among all mentioned rib structures, the 45°V-shaped ribbed passage achieves the best cooling enhancement, its sidewall average Nu number ratio is 33.8%–74.0% higher than the 90°paralleled ribbed channel. Although the heat transfer non-uniformity of the channel with 45°V-shaped ribs is not the lowest, it has lower heat transfer non-uniformity than the highest 45°paralleled ribbed channel. For mist/steam coolant, increasing inlet Re number, the sidewalls average Nu number ratio gradually decreases, but their heat transfer non-uniformity increases. As wall heat flux increases, the secondary flow vortexes in the channel does not change but both average Nu number ratio and the heat transfer non-uniformity clearly decreases. Raising mist/steam will not change the secondary flow vortexes structure. Instead, it will obviously increase the average Nu number ratio and heat transfer unevenness. Enlarging the mist diameter decreases the heat transfer performance of the sidewall, but also makes the sidewall heat transfer become less even.