Abstract
Passive residual heat removal heat exchanger (PRHR HX) in AP1000 is important for the safety of reactor and core as the main heat transfer device for cooling the primary circuit coolant during the residual heat removal. This C-type heat exchanger is vital in ensuring the safety of the reactor in accident conditions. Theoretical calculation methods and research for the coupling heat transfer of the primary and secondary sides of a new C-type heat exchanger with double natural circulation are limited. In this paper, the heat transfer characteristics of the passive residual heat removal tubes are studied from three aspects: theoretical calculation, experiment and numerical simulation. Theoretical calculations used multiple heat transfer calculation models to obtain the heat transfer characteristics such as temperature distribution in the tube. Scaling experiments with primary and secondary side coupling of PRHR HX were carried out and experimental data was obtained. Numerical model of C-tubes was simplified and established based on the experimental device, and coupling heat transfer process inside and outside the C-tube was simulated by FLUENT. The comparisons mentioned above present the coupling heat transfer characteristics in double natural circulation on the primary and secondary sides of PRHR HX. Its outlet temperature decreases obviously compared with inlet temperature, with an average heat transfer coefficient of 1000–2000 W/m2·K. It indicates that the new C-type heat exchanger has a strong ability for heat transfer and most of the coolant heat can be taken away during the operation. This also further validates the accuracy of theoretical calculation.
