Mechanism research of two-phase flow regimes during bottom reflooding in narrow rectangular channel

Abstract

Visualization experiments and mechanism analysis were performed to fully investigate the thermal hydraulic behaviors during bottom reflooding within narrow rectangular channel. Qualitative and quantitative analysis of the two-phase flow regimes were conducted by means of high-speed camera. Conclusions can be obtained that five flow regimes were observed, including dispersed flow, inverse annular flow, rewetting front, coalesced bubble flow and isolated bubble flow; when the narrow rectangular channel thickness decreases from 5.0 to 2.0 mm, the rewetting velocity and corresponding critical heat flux decrease severely due to the space limitation, whereas the heat transfer capacity increases in the low superheat region; the locations of rewetting front can be determined both by image processing and ‘temperature variation speed curve’ method, and the mutual authentication results reveal that the visible three-phase contact line and highest point of the temperature variation curve can be regarded as the rewetting front during bottom reflooding.