朝下沟槽结构表面池沸腾换热

核电站熔融物堆内滞留技术是一项关键的严重事故应对策略，该策略已被核电站广泛采用。为增强核电站压力容器下封头外表面的沸腾换热能力，实验研究了常压下朝下沟槽结构表面的池沸腾换热，测量了倾角5°、30°、45°、60°和90°下热通量随壁面过热度的变化，获得了相应倾角下的临界热通量（CHF）。与光表面相比，朝下沟槽结构表面的CHF可提高65%～90%。实验观察发现，在高热通量下朝下沟槽结构表面气泡运动形态存在蒸汽膜和波浪蒸汽层两种结构。分析表明，沸腾换热显著增强、临界热通量大幅提高的原因是沟槽结构大幅增加了换热面积同时还明显改善了表面的润湿性。

Saturated pool boiling from downward facing structured surfaces with grooves

In-vessel retention is a key severe accident management strategy now widely adopted by some nuclear power plants. The saturated pool boiling heat transfer coefficients and critical heat flux (CHF) were measured from downward facing structured surface with grooves in deionized water to enhance the CHF. The orientations were 5°, 30°, 45°, 60° and 90° (vertical). The results showed that the nucleate boiling heat transfer coefficients and the local CHF for structured surface with grooves were consistently higher than those for plain surface. Compared with plain surface, the CHF increase could reach 65%-90% for structured surface. The vapor blanket and wavy vapor layer bubble structures with different CHF trigger mechanisms on the downward facing surface at high heat fluxes were observed on structured surface. The enhancement of the local CHF and the nucleate boiling heat transfer coefficients was mainly due to the significantly increase of heat transfer area and the grooves that effectively improve surface wettability.