Study on flow and heat transfer characteristics of the mist/steam two-phase flow in rectangular channels with 60 deg. ribs

Flow and heat transfer characteristics of mist/steam two-phase flow in a high temperature square channel with 60 degreed ribs are studied experimentally and numerically. First, a 3-D fluid-solid coupled numerical model was established for this channel cooled by mist/steam. The numerical results are in good agreement with the experimental results and the maximum temperature deviation of bottom wall centerline is less than 4.6%. Then, the effect of longitudinal vortex and the distribution of the “mainstream influenced zone” and the “vortex influenced zone” on the channel wall temperature distribution were analyzed qualitatively according to the simulation results. Finally, the influence of the key factors Re number, mist/steam mass ratio, water droplet diameter and heat flux on the flow and heat transfer characteristics were studied using this numerical method. The following conclusions can be reached: When Re increases from 74,000 to 170,000, the average centerline Nu number rises from 376.3 to 882.2, under the condition of q = 8000 W/m2 and mist/steam = 3%. As the mist/steam mass ratio increases from 0.5% to 9%, the average Nu number rises from 636.3 to 996.3 at the condition of inlet Re = 147,000, q = 8000 W/m2. The ratio f/f∞ is increased by nearly 22% when Re rises from 74,000 to 170,000 under the condition of q = 8000 W/m2. Mist/steam mass ratio has little influence on f/f∞, and the ratio f/f∞ is slowly increased with wall heat flux. When the heat flux and the mist/steam ratio are certain, the heat transfer enhancement increases with the increasing of the friction resistance.