A novel methodology for designing a multi-ejector refrigeration system

Highlights: • Multi-ejector system can operate over wide range of ambient temperatures. • Multi-ejector refrigeration system can continuously operate at optimum efficiency. • Multi-ejector system can improve the seasonal COP of the system up to 85.0%. • Multi-ejector system with three or at least two ejectors is recommended. -- Abstract: Ejector refrigeration system has many advantages over traditional compressor-based systems, including: simplicity, low installation and operating costs and the ability to operate with low-grade thermal energy sources. However, its main drawbacks are low Coefficient of Performance (COP) and failure at high ambient temperatures. To overcome these problems, a novel methodology for designing a multi-ejector refrigeration system is proposed. This system utilizes a parallel array of ejectors instead of one ejector. Therefore, the system can continuously operate at its optimum efficiency. Each ejector works within a specific range of condensing pressures. The condenser pressure governs the selection of the operating ejector. The proposed methodology uses geometric shape optimization to maximize the entrainment ratio of the installed ejectors with different back-pressures. The efficacy of this methodology is demonstrated by designing a multi-ejector refrigeration system for cooling a house located in Tehran, with a maximum ambient temperature of 40 °C. The performance of the system is studied over a hot season. Obtained results indicated that applying the multi-ejector refrigeration system can improve the seasonal COP of the system up to 85.0% compared to a conventional ejector refrigeration system, and the system can meet the required cooling load.