Safety relief valve sizing: comparison of two-phase flow models to empirical data

Abstract

The proper sizing of safety relief valves is an important issue in chemical process safety. Many emergency relief scenarios require consideration of two-phase flow conditions. However, two-phase flow involves complex physics and is the subject of intensive on-going study. The objective of this research is to identify and verify simple yet accurate two-phase flow models which allow the design engineer to predict the mass flux of any given relief scenario. Two contemporary models were considered in this study: The Two-Phase-Homogenous-Equilibrium Model (TPHEM), proposed by the Center for Chemical Process Safety (CCPS), and the Homogenous-Nonequilibrium Model proposed by Fauske. These models were evaluated against steam/water data (both sub-cooled and two-phase entrance) from Sozzi and Sutherland. This research allowed the determination of what conditions were.