The air circulation refrigeration system achieves refrigeration by adiabatic expansion of compressed air in the expander to obtain low-temperature airflow. Its ideal working process includes four processes: isentropic compression, isobaric cooling, isentropic expansion and isobaric heat absorption.

During the development of China's civil aviation, the A320 aircraft air-conditioning system frequently broke down, and the failures were repeated and complicated, which brought great inconvenience to the flight crew. In the survey results of China's major airlines, it was found that the number of aircraft air-conditioning system failures has almost reached half of the total number.

Breakpoint repair method of high-pressure inflatable sealing shroud in high-speed wind tunnel: the ventilation skeleton is inserted into the breakpoint, and both ends of the shroud are bundled on the ventilation skeleton, and then repaired by applying sealant.