Evaluating ejector efficiency working under intermediate pressure of flash tank–absorption cooling cycle: Parametric study

Abstract

Combining the ejector–flash tank with the single stage absorption cycle using NH3/H2O as the working fluid has shown potential improvement in the COP. In our previous work, ejector efficiency faced some limitation due to the presence of booster at refrigerant streamline side. Removing the booster from the refrigerant streamline side and allowing the secondary flow of the ejector to work only under the intermediate pressure of the flash tank could optimize the ejector efficiency. This study examines the effect of system parameters, such as an entrainment ratio (ω), pressure ratio (PR), circulation ratio (CR), and the effectiveness of heat exchangers on the thermal loads, the coefficients of performance (COPc, COP), and the efficiency ratio (η) at various operating temperatures of the components. The study also discussed the effect of the operating conditions of the proposed cycle components on the performance parameters and the CR value in details. Comparing the results between the proposed cycle and our previous work showed that the new arrangement of the refrigerant streamline side increases the energetic secondary flow and consequently improved ejector efficiency. Moreover, the results showed that the thermal loads decrement of the generator and the absorber with SHE effectiveness increment is about 38% for each; while the thermal loads increment of evaporator and absorber with RHE effectiveness increment is found 14.86%, and 8% respectively. The performance increase ratio at maximum heat exchanger effectiveness is found 60.7% for SHE and 14.86% for RHE. Overall, the proposed cycle is considered beneficial from the viewpoint of the first law of thermodynamics.