An Experimental Study on Flow Boiling Critical Heat Flux Characteristics of Suddenly Expanded Region

In this experiment, test section has been designed to simulate sudden flow path change due to deformation of cladding. It was tended to simulate cladding deformation that has discontinuous diameter change so coolant flow path changes suddenly. Experiments are in progress. Experiments on test section that simulate deformed flow path which contains sudden contraction and sudden expansion part have been done. Location of CHF has been varied by different condition of experiment. CHF at the outlet of test section fits well into the Macbeth's correlation and data of reference experiment, which was held on plain test section that had same diameter with inlet diameter of deformed test section. CHF at sudden expansion part was in churn flow regime and CHF was very low compared to expectation. It is discussed that liquid film separation from wall or bubble accumulation by backflow might be the reason of this result. For future work, experiments for two additional blockage ratio conditions will be carried out. Also, discussion and model development for deformed channel with sudden expand flow path will be held on