Abstract: Experiments are performed to investigate the effect of grid spacer on refloodingheat transfer. The test section is rod boundle with 21 rods. The wall temperature,collapsed liquid level and liquid carryover transient are measured. The effect ofwall temperature of channel tube on rewetting velocity are investigated. The experimental results show that wall temperature in downstream of thegrid spacer decreases. The heat transfer coefficient in downstream of the gridspacer is higher than in upstream of the grid spacer. But heat transfer coefficientdecreases with the distance from the grid spacer. The incidence of the grid spaceris about 100-150 mm. The test parameters ranged 15-80℃ for inlet subcooling, 400-610℃ for initialwall temperature, 1.5-6 cm/s for reflood flow rate, 0-0.25 kW/m for heatingpower and atmosphere for system pressure.