Experimental Study On Steam Condensation Heat Transfer With Noncondensable Gas

In consideration of the serious accidents such as the loss of coolant accident and the main steam line rupture,the third generation advanced reactors have designed passive containment cooling system to ensure the integrity of the containment.However,due to the presence of a large amount of air and other noncondensable gases,the heat transfer capability of the condenser will be limited seriously.Based on the application ground,this paper carries out experimental study on the steam condensation with noncondensable gases over vertical smooth tubes and enhanced tubes.For the vertical smooth tube,experiment has been conducted over a larger range of parameters.Especially,to measure data under different wall subcooling,two different cooling systems,forced circulation and natural circulation,have been used.According to the experimental results,the influence of the parameters such as the wall subcooling,pressure and the air mass fraction have been analyzed.It can be found that the heat transfer coefficient decreases with the wall subcooling to a negative exponent.But the value of the exponent changes with the pressure and wall subcooling,and this is different from the previous studies.Besides,the condensation heat transfer coefficient increases with the increase of pressure,and decreases with the increase of air mass fraction.Based on the analysis of the impact factors,a new empirical correlation has been developed.The predicted value of the correlation is in good agreement with the experimental value,and the error is within 20%.In addition,the correlation is compared with the existing correlations.The result shows that the accuracy of this correlation is the highest.Furthermore,this correlation has been verified with the experimental data of other researchers.In the experimental study of the enhanced tubes,the three kinds of tube,wave tube,longitudinal finned tube and pin-fin tube,have been studied.For pure steam condensation,the wave tube and the longitudinal finned tube show good enhancement,while the enhancement of pin-fin tube is influenced by wall subcooling.Pin-fin tube only can enhance steam condensation when the wall subcooling is exceed 13 ?.For steam-air condensation,the heat transfer capability of the three kinds of enhanced tubes decreases in different degrees.Among them,the wave tube can still exhibit an enhancement,but the condensation heat transfer coefficient is only about 1.1 times of that of the smooth tube.However,longitudinal finned tube and pin-fin tube only show the effect of heat transfer enhancement in high air fraction region.For low air fraction region,the heat transfer coefficient is even smaller than that of the smooth tube.This is mainly due to that the fins restrict gas flow near the wall.