격납용기 피동 냉각을 위한 수직관 외벽 증기 응축에 영향을 미치는 요인에 대한 실험연구

Abstract

This research is a study on the development of PCCS, a passive containment building cooling system, which is one of the passive safety systems to be applied to next generation nuclear power plants. PCCS is a system for removing the energy released into the containment buildings through condensation heat transfer without help from the operator or external power source in case of an accident such as a coolant loss accident or breakage of the main engine, and maintaining the integrity of the nuclear power plant. The PCCS, which has been developed to replace the role of spray of the containment sprinkler system, which previously required power, is installed in the form of a tube, condensing the steam of the mixed gas coming down the wall in case of an accident, It will serve to lower the temperature. The focus of this study is to derive the correction factor which can evaluate the effect of curvature and, to assess the effect of the velocity of the air-steam mixture on the wall during the accident on condensation heat transfer In this study, to investigate the condensation heat transfer coefficient in the presence of a non-condensable gas, an experimental studies was performed on the single vertical condenser tube with 10 mm, 21.5 mm, and 40 mm in outer diameter, and 1000 mm in the effective heat transfer length. In natural convection condition, experiments were conducted at the pressure ranging from 2 to 5 bar, and the air mass fraction ranging from 0.1 to 0.8. And in forced convection condition, the experiment was conducted with 40 mm in outer diameter tube in pressure ranging 2, 4 bar and the air mass fraction ranging from 0.29 to 0.63. This study focused on two topics, curvature effect with tube diameter under natural convection condition and velocity effect of air-steam mixture to heat transfer in forced convection condition. For the derivation of correction factor for curvature effect, rate of heat transfer coefficients among the experiments with 10, 21.5, and 40 mm in outer diameter tubes. When the diameter is changed, the change of heat transfer coefficient was also changed. These changes are independent of air mass fraction and pressure, and there is a curvature effect on diameter. For the effect of velocity, the conditions for experiment was fixed for example, conditions of pressure, air mass fraction, and wall subcooling was well controlled.