A thermodynamic investigation and optimization of an ejector refrigeration system using R1233zd(E) as a working fluid

Abstract

The increasing contribution of heating, ventilation, air conditioning and refrigeration systems to energy consumption and global warming is driving the search for technologies that are energy efficient, clean and renewable. The ejector refrigeration system is one such system with the potential to reduce energy consumption and CO2 emissions. It is simple, low cost, has no moving parts, and can use low grade heat sources such as solar or waste heat. However, the coefficients of performance (COP) of these systems are still low. Moreover, most studies on ejector refrigeration systems have used refrigerants that are not environmentally benign. In this paper, the performance of an ejector refrigeration system working with R1233zd(E) is numerically investigated. R1233zd(E) is a newly introduced Hydroflouroolefin refrigerant with no ozone depletion potential and very low global warming potential. No studies on the performance of this refrigerant in ejector systems have been conducted. A novel mathematical model that uses ejector coefficients which are dependent on the evaporator and generator pressures to accurately determine performance was used in the present study. In the analysis, area ratios between 6.44 and 10.94, evaporator temperatures between 0 and 16°C, and generator temperatures between 70 and 110°C were considered. Results show that system performance in the critical mode of operation increases as the generator temperature reduces and as the evaporator temperature increases. Furthermore, there is an optimal generator temperature at each condensing and evaporator temperature with the highest COP. Correlations for the optimal generator temperature and optimal COP have been derived and presented.