Visual Experimental Study on Bubble Behavior on Inclined Downward Facing Surfaces

In this paper,in a setting of In Vessel Retention（IVR） strategy of molten core debris in AP1000 reactors,a visual experimental study of bubble behavior and two-phase flow in inclined confined spaces are performed for near-saturated demineralized water at atmospheric pressure with gap sizes of 3mm to 8mm,and inclination angles of 0o to 30o.Bubble sliding and deformation are observed and analyzed.It shows that geometry and downward facing heating surfaces may be two of the reasons leading to these important phenomena.Visual analyses of wavy phenomena between two-phase flow of vapor and liquid have also shown that lift-off of wavy interface between vapor and liquid phase may be the mechanism which triggers the occurrence of critical heat flux（CHF）.