Comparison and performance analysis of single and double-stage in-series ejector refrigeration systems using various refrigerants
Bassil M. Anan, Mahmoud A. Kassem, Ahmed Hamed
Abstract
Ejector refrigeration systems (ERS) are promising refrigeration systems that can replace conventional vapor compression systems, because of their ability to operate by thermal energies of low grades and their capability to be integrated with renewable energy sources. However, there are restrictions concerning its low system COP, limited range of operating conditions, and high sensitivity of the performance to the variation of operating conditions. Therefore, this present paper introduces a detailed mathematical model to design and investigate the performance of a novel double-stage in-series ERS, which is believed to overcome the abovementioned restrictions of the single-stage ERS. The present work investigates the critical operating points of the double-stage in-series ERS to reach the maximum COP. Four refrigerants are employed in the analysis, R600a and R134a are compared to each other as they are widely used; additionally, R1234yf and R290 are compared to each other, as they represent the future refrigerants. The comparison shows that double-stage in-series ERS improves the system performance and ability to withstand a high range of operating conditions with low COP variations. Double-stage in-series ERS can result in performance improvements ranging between 3 % to 160 % depending on the refrigerant and its operating condition. Moreover, the usage of double-stage in-series ERS gives the chance to operate at low evaporator temperatures below 0 °C and high condenser temperatures above 50 °C, which is not reachable by single-stage systems. Furthermore, the analysis shows that R600a and R290 have higher performance than R134a and R1234yf, respectively.