[en] Simulative experiment focused on transient temperature is performed on a 5:1 model of surge line nozzle, with sealed sleeve or unsealed sleeve, of pressurizer in PWR, under inlet and outlet flow condition. The range of Re is 4500-750000. The conclusion is as follows: sealed sleeve can effectively protect surge line nozzle from thermal shock and thermal fatigue; Sealed sleeve has better protection than unsealed sleeve; at low flow rate unsealed sleeve has some protection from temperature, but it loses its protection at high flow rate