Abstract: Computational fluid dynamics（CFD） methodology is adopted to simulate the fluid flow and heat transfer characteristics of the passive residual heat removal heat exchanger（PRHRHX）. The C-type tube region is modeled by the porous media method. The coupled heat transfer rate from the primary side fluid to the secondary side fluid of the PRHRHX tube is calculated during the calculation. The secondary side temperature and velocity distribution in the in-containment refueling water storage tank（IRWST） at different times are analyzed. The primary side fluid temperature distribution inside the heat transfer tube is obtained.