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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.

A new automatic interior temperature control algorithm has been developed that comprehends the thermodynamic constraints for the interactions of the interior temperature and air flow with the outlet temperature. Thus, the heat flux is controlled directly. By contrast, conventional algorithms utilize a proportional outlet temperature response to the interior temperature, ambient temperature and radiant load. This lack of attention to the air flow quantity has added unneeded complexity (and inaccuracy) to the task of control system calibration.

Simple thermodynamic and heat transfer mathematical models have been developed to aid in the study of HVAC system designs in field testing. The refrigeration system, heating system and vehicle cabin have been examined. Test data are used to determine parameter values in governing equations. These parameter values may be used for performance simulation and competitor comparison. A benefit of this approach is that individual component performance can be extracted from system performance. Another benefit is that performance data can be adjusted, for comparison purposes, to identical test conditions.