Subcooled water critical pressure and critical flow rate in a safety valve

Subcooled water critical flow phenomena in a safety valve are investigated experimentally at various subcoolings between 10 and 125 K, and about 1 MPa of the inlet pressure with three different disk lifts, 1, 2, and 3 mm. The purpose of this experiment is to find the effects of subcooling and disk l ift and to visualize flow patterns in a safety valve when the critical cond ition is established. All of the experiments show the critical characterist ics such as constant throat pressure and constant flow rate when the back p ressure is sufficiently decreased. Two correlations, critical pressure rati o and non-equilibrium factor, are developed by using the present experiment al data represented in the form of non-dimensional disk lift, subcooling, a nd pressure. Critical pressure ratios and non-equilibrium factors are consi derably affected by different subcoolings while the effect of disk lifts on them is relatively small. A non-equilibrium critical mass flow correlation for the safety valve is also developed based on Fauske's non-equilibrium m odel and the presented experimental data. The predictions of the correlatio n are within +/-11% of the experimental data. (C) 2001 Published by Elsevie r Science Ltd.