Numerical Analysis For Performance Comparison Between Hybrid Ejector And Conventional Refrigeration Systems

Recently, the utilization of low-grade thermal energy has gained increased attention as an attractive opportunity to save energy. Heat driven ejector refrigeration systems are among a number of promising solutions for utilizing thermal energy from waste heat. However, the main drawbacks of this system are low efficiency at off-design conditions and difficult controllability. Hybrid ejector refrigeration system is a promising solution for overcoming these drawbacks. In this system, a booster compressor is installed in order to improve the efficiency for a wide range of conditions and substantially improve controllability. In this study, a numerical efficiency analysis for hybrid refrigeration ejector system is performed and compared with conventional ejector system and vapor compression system. The investigations are focused on chilled water supply conditions (evaporation temperature is 5 °C) at various ambient temperature conditions ranging from 15 °C to 35°C. The seasonal performances in Tokyo and Los Angeles for each system are compared. R1234ze(E), which is a promising low-GWP refrigerant, is used in the system. The calculation results show that the hybrid system performance is 142 % higher than ejector system, 16 % higher than vapor compression system in Tokyo, and 86 % higher than ejector system, 21 % higher than vapor compression system in Los Angeles at summer conditions. Therefore, this study clearly demonstrates the potential of the hybrid ejector system

Numerical Analysis For Heat Driven Ejector Refrigeration Systems For Various Refrigerants

In this study, a numerical efficiency analysis for ejector refrigeration systems driven by low grade waste heat (65-85 °C) is performed. A 1-D numerical ejector model which was validated is applied to estimate the characteristics of the ejector. Investigation is focused on various refrigerants such as HFC (R134a, R245fa, R365mfc), HFO (R1234yf, R1234ze(E), R1233zd(E), R1336mzz(Z)), and natural refrigerants (NH3, R600, R600a), and their COPs (Coefficient of Performance) are compared. Main operating conditions (e.g. generation temperature, evaporation temperature, condensation temperature) are also considered to compare the system characteristics for each refrigerant. Simulations are performed for different operating conditions and their effects on system performance is analyzed. The results show that high NBP (Normal Boiling Point) refrigerants tend to show higher theoretical performance because of their high latent heat. In addition, it is found that sensitivity of generation temperature is less than evaporation temperature and condensation temperature