Review of Research Progress on Auto-cascade Refrigeration Systems and Component Separation, Migration, and Regulation

Auto-cascade refrigeration technology has broad application prospects in refrigeration and cryogenic refrigeration owing to its wide operating temperature range, simplicity, and reliability. The construction of new refrigeration cycles and the diversification of mixtures have been extensively studied. The active regulation of mixture mass fraction in auto-cascade refrigeration systems to improve performance has been a technical bottleneck and research challenge. This study first reviews the state-of-the-art of auto-cascade refrigeration systems and describes the history of refrigeration cycles. Research on the component separation and migration characteristics of zeotropic mixtures, which affect system efficiency, is also summarized. Research on component separation is discussed in terms of refrigeration cycle improvement and the separation performance of the key component-the gas-liquid separator. The causes of component migration, the current status of research on component migration characteristics, and theoretical models of phase accumulation are summarized. Based on this, existing research methods for the regulation of zeotropic mixture components in auto-cascade refrigeration systems are presented. This study summarizes the current status and research directions of component optimization and control as a reference for further performance improvement of auto-cascade refrigeration systems.