Impact of primary nozzle area ratio on the performance of ejector refrigeration system

Abstract

This paper proposes an experimental investigation to demonstrate the impact of the primary nozzle area ratios on the ejector performance in an R141b ejector refrigeration system. The experimental refrigerator was tested based on the alternative testing method in which the generator temperature and condenser pressure were held constant for particular test cases. Three primary nozzles were studied which had identical throat diameter but different nozzle area ratios which produced different exit Mach numbers. Three primary nozzles were equipped with one mixing chamber with throat diameter of 9 mm. With the alternative testing method, two critical evaporator temperatures were found, the lower and upper critical evaporator temperatures. It was also found that the change in the nozzle exit Mach number and the primary fluid mass flow rate (using different generator temperatures) had significant impact on these two critical points which affected the entire ejector performance. The primary fluid expansion coefficient (Cprimary), which is key to indicate the limited range of the working condition, was introduced. It indicates the expansion wave formation which has significant impact on two critical points. Hence, the proper value of Cprimary under various primary nozzle area ratios was determined for this present work.