[2O01-06] Accident Behavior, Emergency Exercise

[2O02] Role of Bubble Coalescence in Causing OSV in Subcooled Flow Boiling

*Binh Thanh Nguyen¹, Okawa Tomio, Ryoma Tsujimura (1. The University of Electro-Communication)

Keywords:subcooled flow boiling, onset of significant void, bubble coalescence

Although available correlations can calculate the critical subcooling at POSV with reasonable accuracy, the mechanism to cause OSV is still not understood sufficiently. The bubble coalescence-based mechanistic model proposed by Okawa (2021) yields a good agreement with the empirical correlations on the prediction of subcooling conditions at OSV. Therefore, in the present study, an experiment was carried out to investigate the possible role of bubble coalescence in the onset of significant void (OSV) in subcooled flow boiling. The high-speed camera (HSC) was used for observation of the bubble dynamics before and during the OSV occurrence, whereas a gamma densitometer and a void probe are used to measure the global and local void fraction of the channel at the OSV.