This report describes the work carried out in the third year of a three-year project aimed at developing an innovative ejector-equipped heat pump architecture, with the goal of contributing to the penetration of electric technologies for residential air conditioning, in accordance with the NECP growth estimates required to meet the national decarbonization targets to 2030. During the first year, an extensive literature review of ejector refrigeration systems was carried out, highlighting their peculiar characteristics and the dependence of performance on the ejector’s internal fluid dynamics and the characteristics of the refrigerants, among which propane seems to be one of the best performing.
The second year’s activity focused on defining a modeling approach for the simulation of supersonic ejectors. Two modeling methods (namely concentrating-parameter – LPM – and thermo-fluid-computational – CFD) were developed and compared, both of which were validated through matching with literature data collected in the first year, determining the superiority of the CFD approach in predicting ejector performance parameters with satisfactory accuracy. A prototype moving-pin ejector was also designed for the purposes of subsequent experiments.
The third-year activity first involved experimental verification of the CFD model’s ability to describe and analyze the operation of a variable-geometry ejector in a propane cycle. The experimentation involved building the ejector, constructing a test circuit, and performing a series of tests aimed at verifying the operation of the ejector in a variable regime and the ability of the CFD model to replicate the experimental results. Subsequently, a useful modeling tool was developed to evaluate possible energy-saving effects in the residential air conditioning sector. The model based on a heat pump scheme involving the addition of an ejector in a standard refrigeration cycle was validated with literature data and used to make a comparison with the performance of a standard propane cycle under the conditions required by traditional radiator heating systems.