DIRECT HEAT TRANSFER IN PRESSURE-SUPPRESSION SYSTEMS
The basic laws of heat transfer for direct condensation of vapour jets in subcooled water pool are investigated in small devices, with reference to the pressure-suppressure systems in B.W.R's. Heat transfer coefficients hdc are very high (of the order of 300 W/cm2 °C) and depends mainly on the pool subcooling ( ΔTsub) and on the vapour quality of the discharging jet (X):
hdc = (360X2 − 530X + 250) ΔTsub(X/10.5)+ . 26
To obtain stable vapour cones at the outlet section of the discharging channel it is necessary to reach critical flows at the outlet. Stability depends on both the specific mass flowrate and the pool subcooling.