Air is an environmentally friendly refrigerant that can be charged into the air cycle refrigeration (ACR) system from the ambient or discharged from the system to the ambient unrestrictedly. The ACR system is widely used in environmental control systems (ECSs) of airplanes

owing to its compact structure

low sealing requirements

high reliability

and easy maintenance. Herein

the configurations and basic characteristics of the ACR system are introduced. Research status concerning the performance analysis

experiments

and key components of the ACR system are summarized. Applications in the fields of air-conditioning

heat pumps

food freezing and refrigeration

airplane ECSs

and energy storage are reviewed. The development and application of key technologies for the ACR system are evaluated. ACR technology has developed rapidly corresponding to the significant progress in the design and manufacturing technology of turbomachinery

efficient heat exchangers

and high-speed motor technology in recent decades. The ACR system is compact and widely used in train air-conditioning and refrigeration systems. The coefficient of performance (COP) of the ACR system is higher than that of the conventional cascade refrigeration system in the refrigeration temperature ranging from -100 °C to -50 °C; therefore

the ACR system is advantageous for food freezing and cold storage. Moreover

the ACR system exhibits significant potential in heat pumps and energy storage applications.