피동격납건물냉각계통 수직 전열관에서의 응축 열전달계수 측정 및 MARS-KS 코드를 이용한 분석

Abstract

The importance of the passive safety systems has increased to assure the safety of the nuclear power plant after the Fukusima nuclear power plant accident. Especially, the Passive Containment Cooling System(PCCS) will protect and maintain the structural integrity of the containment by condensing phenomena of the released steam mixed with air. In this study, to investigate the condensation heat transfer in the presence of a noncondensable gas, an experimental study was performed on the single vertical condensing tube with 40 mm in outer diameter, 5 mm is thickness, and 1000 mm in the effective heat transfer legth. Experiment were carried out at the pressure ranging from 2 to 5 bar and the noncondensable gas mass fraction ranging from 0.1 to 0.8. Almost isothermal wall conditions are maintained and uniform concentration of gaseous mixture is also kept during the experiments to reduce the effect of noncondensable concentration along the height. The heat transfer coefficients from experiments were compared with existing correlations by Uchida, Tagami and Dehbi's correlations. The comparison results show the considerable derivations of the geometrical effect of the test tank and the lack of the physical grounds in the existing models. The experimental results were applied to assess the condensation model of the Korean thermal-hydraulic system code, MARS-KS. The comparison results reveals that the MARS-KS condensation model needs to be improved for more accurate thermal-hydraulic analysis of the PCCS.