Dangerous pressure excursion incidents in industrial refrigeration systems have been attributed to condensation-induced shock and vapor-propelled liquid slugging. Because of industry trends towards the use of alternate refrigerants and centralized systems and the resulting higher localized volumes of potentially dangerous refrigerants, the occurrence of hydraulic shocks in refrigeration systems has become a critical issue. Although the initiating mechanisms of condensation-induced shock and vapor-propelled liquid slugging are not well understood, these transients have important implications on system maintenance, repair costs, system downtime, and public safety. The purpose of this research was to provide system designers and operators with methods for avoiding these transients. This objective was accomplished through the review of two-phase flow regimes, the analysis of the generic causes and resulting pressure surges of condensation-induced shock and vapor-propelled liquid slugging, and by the study of the critical flow regimes that occur in industrial refrigeration systems.

The purpose of mis work is to provide system designers and operators with methods for avoiding these transients. The main objectives are accomplished by reviewing two-phase flow regimes, by analyzing the generic causes and resulting pressure surges of condensation-induced shock and vapor-propelled liquid slugging, and by studying the critical flow regimes that occur in industrial refrigeration systems. In Chapter 2, an overview of two-phase flow regimes is presented. This review includes the variations in flow patterns due to flow configurations, alternate fluids, and refrigerant-oil mixtures. The ability of flow maps to predict flow regimes under these various situations is also discussed.