Investigation of ejectors in refrigeration system: Optimum performance evaluation and ejector area ratios perspectives

Abstract

This paper presents an ejector model to determine the optimum performance as well as obtaining the design area ratio of an ejector in a refrigeration system. Working fluid properties and auxiliary dynamic equations are used to model the processes in the ejector. The normal compression shock in the mixing chamber is considered. Experimental data from literature are used to validate the model, and the agreement with the model at optimum operating conditions is very good. The deviation between the model and the experimental data at non-optimum conditions is slightly larger.A study of working conditions for refrigerants R123 and R141b indicates that the condenser temperature has more influence than the generator and evaporator temperatures on the area ratio and the entrainment ratio in the ejector. Furthermore, area ratios need to keep up the pace with the variation of entrainment ratio as operating conditions are changed. A variable-geometry ejector seems a very promising alternative to ensure that the ejector refrigeration system operates at its optimum conditions. Ejector efficiencies play a very important role in the present model, and the influence of the efficiencies on the ejector performance is investigated. This ejector model may be used for parametric analysis and optimum performance evaluation as well as ejector design.