Ejector and Vapor Injection Enhanced Novel Compression-Absorption Cascade Refrigeration Systems: A Thermodynamic Parametric and Refrigerant Analysis

Abstract

This study investigates the performance of two novel compression absorption cascade refrigeration systems, the Ejector Compression Absorption Cycle (ECAC) and Ejector Injection Compression Absorption Cycle (EICAC), in comparison to traditional system. In these cascaded systems, the absorption cycle (top cycle) is modified by adding a refrigerant hear exchanger (RHX) which provides higher mass flow of refrigerant to increase the COP. The simple vapor compression cycle (bottom cycle) performance is enhanced by incorporating the ejector and Vapor Injection technologies. A systematic analysis is accomplished to establish the optimal operating conditions for performance enhancement, taking into account of ejector parameters and the effect of different environmentally friendly refrigerants by the energy and exergy method. The findings demonstrate that both ECAC and EICAC systems can achieve near 15 % and 6 % higher COP, respectively, compared to conventional cascade system when using the R41-LiBr/H2O refrigerant pair under different working conditions. Maximum exergy efficiency is found to be achieved at around 73 °C, with ECAC and EICAC showing higher exergy efficiency of near 20 % and 10 %, respectively than the conventional system. The analysis also reveals that while the COP of all layouts augments linearly with increasing evaporator temperature, the exergy efficiency decreases at different rates, making the cascade systems more efficient for low-temperature applications. The LiBr/H2O refrigerant pair demonstrates superior COP and exergy efficiency as HTC refrigerant, while R161, R290, and R1270 perform better as low-temperature refrigerants for both ECAC and EICAC from both energetic and exergetic perspectives. The results of this detailed theoretical thermodynamic analysis provide a comprehensive understanding of the performance of ECAC and EICAC systems and offer valuable insights for further improvement and optimization.