Variable geometry ejectors and their applications in ejector refrigeration systems

Refrigeration and air-conditioning units powered by low-grade thermal energy have economic advantages. However, the current market is dominated by mechanical vapour-compression systems powered by electrical energy. Ejector-refrigeration cycles offer a low-cost and reliable option for harnessing low-grade thermal energy. Recent studies have shown that variable-geometry ejectors play an important role in achieving optimal performance. Unfortunately, detailed design information on these systems is not in the public domain. Here, we analyse the effect of ejector geometries on performance. Technical data including flow rates, entrainment ratio and ejector geometry are provided for a 5kW steam-jet refrigerator. These data may serve as guides in designing ejector-cycle refrigerators with other cooling capacities.