Eisenhour, R., "A/C Cycle Power Recovery Method," SAE Int. J. Passeng. Cars - Mech. Syst. 5(2):1050-1058, 2012, doi:10.4271/2012-01-1202.
The conventional A/C cycle develops high pressure refrigerant that is throttled (via a small opening) to low pressure and temperature for cooling an evaporator's airflow. This paper explores the conceptual and practical development of deriving useful work from that pressure potential by replacing the throttling device with an expander/motor. One key technical challenge is to maintain a large pressure drop across the expander/motor. This translates into a strict control requirement of the location of the refrigerant flow's phase change within the motor. The cycle's COP benefits from recovered work and the evaporator's refrigerant energy content reduction while delivering conventional cooling performance.