对某大型核反应堆非能动安全壳冷却系统（PCS）中安全壳外部的热环境进行了研究。建立了安全壳外部狭长空间的自然对流换热计算模型，基于Navier-Stokes（N-S）方程进行了求解，同时研究了安全壳出口高度对非能动安全壳冷却系统冷却性能的影响规律。结果表明：在标准大气压下、进口空气温度308.15 K时，基准型安全壳按面积加权的出口平均温度为330.33 K，引射的冷却空气质量流量为275.85 kg/s，冷却空气带走的热量为6160 kW；随着安全壳出口高度的增加，安全壳出口质量流量、换热量不断增加，但变化曲线斜率不断降低，最后趋于平缓，同时,衡量冷却空气有效冷却能力的温度效率线性降低，流动损失线性增大，兼顾换热量与流动损失存在一个最优解。

The containment external heat environment of a large nuclear reactor passive containment cooling system (PCS) was studied. Established a natural convection heat transfer model of the containment narrow space, the flow field was simulated which based on Navier-Stokes (N-S) equations, also the influence of the outlet height to passive containment cooling system cooling performance was studied. The results show that: when the inlet air is under 308.15 K, 1atm conditions, the area weighted average temperature of criterion type containment outlet is 330.33 K, the cooling air mass flow is 275.85 kg/s, the took away heat is 6160 kW; with the increase of outlet height, the mass flow and heat transfer of containment outlet are increasing, but the slope of the curve changes is decreasing, and finally leveled off, while the cooling air temperature efficiency which is a measure of cooling capacity linear decreases, air resistance linearly increases, so there is an optimal design.