Review on research status and prospect of frost suppression methods for air source heat pump system in last decade

Frost formation in air source heat pumps (ASHPs) can cause blockage of the outdoor heat exchangers, reduce system performance, and even result in malfunctions. Therefore, suppressing frost formation in ASHPs has become one of the effective ways to solve these problems. This paper classifies frost suppression methods into four categories: regulating the outdoor environment, modifying evaporator parameters, applying external driving forces, and adjusting component configuration and operation strategy. Spraying an anti-icing solution and exchanging heat with the ambient air can improve the operating conditions, enabling the ASHP to operate under frost-free conditions. Meanwhile, the thermal drive separation and freeze regeneration methods can effectively regenerate the anti-icing solution. Changing the fin parameters, structure, and surface properties of the evaporator can improve the heat transfer performance and suppress frost formation. Superhydrophobic heat exchangers can significantly suppress the formation and growth of the frost layer, which warrants further investigation and application. In addition, applying external driving forces to suppress frost formation is not mature, and the application in large and medium-sized finned tube heat exchangers is limited. Adjusting component configuration and operation strategy can increase the evaporator surface temperature and suppress frost formation. This review analyzes the evolution of frost suppression technologies, provides a comprehensive comparison of existing methods, identifies promising solutions, and outlines future research directions in this field.