Energy and economic analysis of a variable-geometry ejector in solar cooling systems for residential buildings

In the present, study two 1-D ejector mathematical models are used to predict the performance of a solar ejector cooling system with fixed and variable geometry ejectors. Thes models are implemented using MATLAB and EES Software. The effect of the mixing efficiencies on the performance of the system was investigated, and two empirical correlations were obtained using experimental data for an ejector cooling cycle with R141b as a refrigerant. The results obtained with varying efficiencies were found to be significantly more accurate than those obtained with previous models, which assumed a constant efficiency. The results showed that the ejector with fixed-geometry was very sensitive to the variations of the operational conditions and could practically be functional only under specific conditions. It was also found that the solar ejector cooling system with a variable area ejector has higher coefficient of performance under a vast range of operational conditions. The new system could be easily implemented in residential building air conditioning systems with solar energy as the driving source of heat. The refrigerant R134a was found to give the best performance considering operational, safety, and environmental factors. The economic analysis revealed that the new system is profoundly better than the conventional systems in terms of payback period and net present value.