Assessment of COBRA-SFS cycle4 with various single phase flow tests

COBRA-SFS (Coolant Boiling in Rod Arrays - Spent Fuel Storage) code has widely been used to analyze flow field and temperature profile in spent fuel storage canisters. The flow mechanism within spent fuel storage system is natural circulation driven by temperature difference. It is hard to find a validation work about COBRA-SFS's ability to predict flow field rather than temperature profile under natural circulation. The test cases used in this study are flow mixing test at CNEN 4x4 rod bundle, flow redistribution test at Westinghouse two 14x14 rod bundles, and low flow transient test at PNL 2x6 rod bundle. In the flow mixing test at CNEN 4x4 rod bundle, the flow velocity at the corner channel was under-predicted. In the low flow transient test at PNL 2x6 rod bundle, flow velocity at the cold channel became negative earlier than the measured and the temperature rise was over-predicted at that subchannel