Experimental studies on heat transfer and flow characteristics in micro-channels

Outflow of coolant from cracks generated in reactor structures due to long-term operation has attracted attention as a leak before break (LBB) phenomenon. In addition, a small flow path formed between the debris bed and the reactor vessel at severe accidents is considered helping the cooling of reactor lower plenum and debris bed. These small flow paths are characterized by a very small aspect ratio, and their flow and heat transfer characteristics affect the outflow of coolant, system pressure, and temperatures of debris bed and reactor vessel. In this study, experiments in single phase flow are carried out using microchannels (equivalent diameter D_e < 0.5 mm) with a very small aspect ratio, and their flow and heat transfer characteristics are investigated. (author)