Studying of heat transfer on vertical nonuniform cosine heating in pressurized water reactor

The determination of the point of onset of significant void (OSV) has been completed by the experiment and by computing the temperature field of vertical tube wall in the up-flow boiling of water at nonuniform heat of cosine distribution, low pressure (< 4 bar) and middle velocities (< 2.5 m/s). The results show that the point of OSV firstly emerges from the top of cosine curve and goes to the tube inlet as the heating power increases and flow rate decreases. The blowdown test with simulated nonuniform heating of the reactor core element in the inlet break condition was carried out in the middle pressure water loop. An electromagnetic valve was used as a break. The time from the start of blowdown to the onset of critical heat flux (CHF), and the pressure, flow rate, fluid temperature in the blowdown process were measured. The analysis of these parameters is also given