Heating and cooling systems contribute to approximately 50% of the world’s final energy consumption, highlighting their crucial role in the global energy transition. Ejector refrigeration cycles have the potential to convert heat into cooling, thereby improving refrigeration sustainability. This study aims to provide a thermodynamic performance analysis of solar ejector refrigeration cycles, specifically focusing on their applicability for residential air conditioning. To provide a framework for ejector refrigeration, all components of a solar ejector refrigeration system are analyzed, detailing their fundamental principles, working mechanisms and relevant nomenclature. The emphasis of this part of the study lies on the ejector itself, including an analysis of key factors determining ejector performance such as entrainment ratios, and the definition of ejector e!ciency along with typical values. 

Next, conventional and ejector refrigeration cycles are explained, highlighting the function of the ejector inside a refrigeration cycle. An overview of refrigerants, emphasizing R744 (CO2) is also included. Following this, a short review on thermodynamic ejector modeling is presented, highlighting differences and similarities across existing models in literature. Based on this literature review, two thermodynamic ejector models are developed and presented. The first model can predict the outlet saturation temperature with a maximum error of 1.54°C for known entrainment ratios. The second thermodynamic ejector is able to predict entrainment ratios and outlet pressures with an average error of 5.86% and is used for the subsequent simulations. 

Three ejector refrigeration cycles are presented in terms of configuration and COP calculation. One of the presented cycles uses ejector refrigeration for mechanical sub-cooling of a R744 vapor compression cycle. A thermodynamic model is developed for both the mechanical sub-cooling cycle and a hybrid ejector refrigeration cycle to evaluate their seasonal performance. The results of this evaluation are presented through a comparative study, comparing the performance of the proposed ejector refrigeration cycles to reference vapor compression refrigeration cycles. This comparison is carried out in four distinct Koppen climate types: tropical, arid, temperate and continental. The proposed hybrid ejector refrigeration system shows a seasonal coefficient of performance (SCOP) increase between 4.74% and 18.7% across the four climate types through the use of the refrigerant R290 (propane) and a solar thermal collector area of 25 m². The mechanical sub-cooling cycle that combines R290 and R744 displays a SCOP increase between 11.3% and 25.1% through the use of a solar thermal area of 20 m². A multi-ejector design is presented to enhance performance under varying refrigerant mass flow, as well as a short economic analysis of the proposed refrigeration cycles. This research aims to form a starting point for assessing the feasibility and potential of solar ejector refrigeration cycles in residential space cooling.   ... Read more