Investigation of combination of a rotary vane expander and an expansion valve in a refrigeration system.

Throttling loss is a major source of inefficiencies in a typical refrigeration system. Expanders have been proposed and studied to recover the expansion work previously. In this study, a four-vane rotary expander is developed and will be tested in an R22 refrigeration system. The expander will be installed in combination with an expansion valve to allow for refrigerant flow adjustments. Preliminary experiments were carried out using compressed air as the working fluid to study the expander. The experiments show that the maximum isentropic efficiency was 19% at 561 rpm, the maximum volumetric efficiency was 30% at 1264 rpm and the maximum mechanical efficiency was 7% at 561 rpm. A simulation model was also developed to observe the COP improvements in the modified R22 refrigeration system. The simulation results show that the COP improvements were 2.5-6% and 3.58.5% on the heating and cooling sides, in comparison with the benchmark system without an expander.