Experimental investigations were conducted into the heat transfer characteristics of supercritical water in a downward flowing cooling tube surrounded by pool boiling for the passive cooling system of the Generation-IV Supercritical-Water-Cooled Reactor (SCWR). The experimental parameters cover the extreme high ranges of pressure (23–27 MPa), mass flux (600–1000 kg·m⁻²·s⁻¹), bulk fluid temperature (150–500 °C), and inner heat flux (98–1143 kW·m⁻²). A new thermal amplification system was applied to measure the heat transfer coefficient near the pseudocritical region under various mass fluxes and pressures. A sharp jump in the wall temperature and maximum heat transfer coefficient was observed at the pseudocritical point, and the mass flux and pressure exhibited different influences below and above the pseudocritical point. Based on the experimental data, a new heat transfer correlation for predicting the Nu is proposed for the subject cooling scenario. The proposed heat transfer correlation includes the density ratio and requires only the fluid properties at the bulk temperature. The mean absolute and root-mean-square error of the proposed correlation were about 7.94% and 9.60%, respectively. The proposed correlation can serve as a reference in the design of the passive cooling system of the SCWR.

对第四代超临界水冷堆（SCWR）的被动冷却系统，在向下流动的冷却水管中进行了实验研究，该冷却水由池沸腾包围在向下流动的冷却管中。实验参数涵盖了极高的压力范围（23–27 MPa），质量通量（600–1000 kg·m ^-2 ·s ^-1），散装流体温度（150–500°C）和内部热通量（ 98–1143 kW·m ^-2）。一个新的热放大系统被用来测量在各种质量通量和压力下在伪临界区附近的传热系数。在伪临界点处观察到壁温和最大传热系数的急剧变化，并且在伪临界点的上方和下方，质量通量和压力表现出不同的影响。基于实验数据，针对目标冷却方案，提出了一种用于预测Nu的新的传热相关性。所提出的热传递相关性包括密度比，并且仅需要整体温度下的流体性质。所提出的相关性的平均绝对误差和均方根误差分别约为7.94％和9.60％。