Experimental study of heat transfer characteristics on condensation in the presence of NCG through thermal resistance analysis

Abstract

As an efficient approach of heat transfer, condensation is applied to the passive containment cooling system in the nuclear power plant for a fast export of heat. However, the existence of noncondensable gases in the containment will inhibit condensation heat transfer then increase the risks to the nuclear power reactors. In order to search effective methods to improve the condensation heat transfer, this study investigated condensation in the presence of NCG experimentally focusing on two aspects: (i) to search heat transfer characteristics of filmwise condensation; (ii) to evaluate possible heat transfer enhancement taken by dropwise condensation. For the first one, a new numerical model was developed to quantitatively analyze the thermal resistance distribution in the condensation process. The result indicated that the effect of various parameters on condensation heat transfer depended on the variation of both the thermal resistances of the liquid film and NCG accumulation layer. It provided a reliable explanation for the divergence of early perspectives around the effects on condensation heat transfer of subcooling or system pressure. For the second one, dropwise mode was proved to significantly enhance the condensation heat transfer when the noncondensable gas existed. However, this heat transfer enhancement is limited by the NCG accumulation in the gaseous mixture.