Experimental study of steam and steam-air mixture condensation over vertical chrome-plated tube and polished tube exterior surface

摘要

In this article, a series of steam condensation experiments were performed on the outer surface of chrome-plated tube and polished tube under steam and steam-air mixed conditions to study their heat transfer characteristics and whether they could be used to optimize Passive Containment Cooling System in advanced nuclear reactors. The effects of total pressure, air mass fraction and subcooling on condensation heat transfer of the chrome-plated tube and polished tube were analyzed. Moreover, basing on the existing experiment, a smooth tube that has the same size as the polished tube and chrome-plated tube was tested under the same conditions. The experimental phenomena indicated that filmwise condensation and dropwise condensation co-exist on the tube exterior surface, and more droplets were observed on the exterior surface of the chrome-plated tube. Under the steam condition, with the fixed wall subcooling, condensation heat transfer coefficient of the polished tube and chrome-plated tube shows different change rules under different pressure: the condensation heat transfer coefficient of the polished tube increases with the increase of pressure, while the chrome-plated tube decreases with the increase of pressure. Compared with the smooth tube, the heat transfer performance can be improved by using the chrome-plated tube and polished tube. Under the steam-air condition, the existence of air deteriorates heat transfer performance seriously. The heat transfer performance of the chrome-plated tube and the polished tube are both improved compared with the smooth tube when the air mass fraction is below 60 degrees C. When the air mass fraction is over 60 degrees C, the heat transfer ability of these tubes are similar to the smooth tube. Besides, within the measurement parameters of our experiment, the increase in total pressure has a positive effect on steam condensation with air.