Experimental investigation of bottom reflooding and modeling of quench velocity in a narrow rectangular channel

For the purpose of figuring out the thermal-hydraulic behaviors during bottom reflooding in the narrow rectangular channel of plate-type fuel reactor, experimental apparatus 'THERMAL' was established to simulate the bottom reflooding process, with different inlet velocities and initial surface temperatures. The narrow channel was formed between a heating plate made of stainless steel and a heat-proof glass. Thermocouples (TCs) were fixed to measure the solid temperature in vertical and horizontal directions, and a high-speed camera was used to record flow regime near the quench front. Based on experimental results, conclusions can be drawn that quench velocity increases with increasing inlet velocity and decreasing initial solid temperature. The quench temperature, which is strongly affected by the initial wall temperature, is almost independent of the inlet velocity. A new method is utilized to determine rewetting front and quench front from 'temperature variation speed' curve. Moreover, an analytical model of quench velocity in narrow rectangular channel is discussed and proposed, which can predict quench velocity more precisely in 'THERMAL' facility.