Experimental Study On Coupling Characteristics Of Primary And Secondary Sides Of C-type Heat Exchanger

As a representative third-generation nuclear power technology,AP1000 mainly relies on passive safety systems to achieve the purpose of preventing and mitigating accidents.The Passive Residual Heat Removal Heat Exchanger(PRHR HX)and the In-containment Refueling Water Storage(IRWST)are the most important equipment of the Passive Residual Heat Removal System(PRHRs).The safe and efficient operation of both the IRWST and PRHR HX are of great significance for the residual heat removal of the core.In the present work,taking the design of PRHR in AP1000 plant as the prototype,the experimental apparatus is built to simulate the natural circulation heat transfer process of PRHR HX in IRWST.The primary and secondary fluids of the C-type heat exchanger are naturally circulating.The heat transfer experiments of C-type heat exchanger under different water level conditions are completed.The experimental study focuses on the temperature change of the primary side of the C-type heat exchanger,the overall temperature field distribution and thermal stratification in the IRWST.The experimental results indicate that the temperature variation of the primary side is similar under different pressures.During the heat exchange process,the thermal stratification phenomenon in the IRWST is gradually obvious,but in the horizontal direction,the fluid temperature at the same height is basically the same.In addition,the natural circulation characteristics of the primary side of the heat transfer tube bundle,the temperature distribution of the inner and outer wall surfaces,and the heat transfer characteristics of the secondary side in the single-phase natural convection phase and the two-phase boiling phase are also studied.The experimental data validate that the heat transfer coefficient in the heat exchange tube changes little with the advancement of the heat transfer process.The heat transfer form of the different tube bundle areas on the secondary side is not the same.The heat transfer form of the heat transfer tube bundle also occurs at different heat exchange stages.There are two types of heat transfer in the IRWST:natural convection heat transfer and subcooled boiling heat transfer.