Performance of a four-intersecting-vane expander in a R134a refrigeration cycle

Abstract

• Experiments with expanders installed at different locations were performed. • Expander located after the condenser produces the highest power and efficiency. • The effects of expander speed, cooling and heating loads are analyzed. • Cycle behaviors with a throttle valve and an expander were compared. • The expander was able to improve the COP by up to 6.2%. • The expander exhibited an expander efficiency of 34.9%. The use of an expander is a promising technique to improve the performance of vapor compression refrigeration systems, but its use in a system with HFC refrigerants has not been extensively explored. This paper studies the performance of a four-intersecting-vane expander prototype and the effect of different expander location arrangements to the overall system performance. A customized R134a vapor compression test rig was constructed for the experiments. The rig’s coefficient of performance was determined when using either a throttling valve or an expander for the same operating conditions. The relationships between expander placement arrangements, expander rotational speed, evaporating load and condensing load on the performance of the expander and the thermodynamic behaviors of the system were also investigated. Transient behaviours of the system are discussed too. The experimental results show that the expander could improve the performance of the system by 6.4% in comparison with a system with a throttling valve. The maximum expansion power efficiency was 34.9% at 500 rpm. Of the four expander arrangements, that in which the expander is located right after the condenser exhibited the highest performance. The results show the potential benefits of using a four-intersecting-vane rotary expander for energy recovery of a vapor compression refrigeration system, and the importance of the correct placement of the expander in the system.