Experimental investigation of different ejector geometries for R-744 transcritical systems

This work describes measurement results of ejectors manufactured and experimentally investigated at SINTEF Energy Research / NTNU. The ejectors are experimentally investigated in an oil free R-744 test facility in order to focus on the ejector properties and behaviour. Five different ejectors were experimentally investigated at equal boundary conditions. The results are promising with pressure lifts close to 9 bars at low mass entrainment ratios of 0,22 and suction pressure ratios of 1,24. At an higher mass entrainment ratio of 0,56 and suction pressure ratio of 1,14 a pressure lift of 6,5 bar was achieved with the smallest mixing section. Best performances were measured with the smallest mixing section diameter (3 mm) and a short nozzle with an ID of 0.9 mm The results are very promising and show a very good COP improvement potential for R-744 transcritical process deploying an ejector, as the pressure ratio for a compressor could be reduced by close to 10 bars. Copyright © “2010” IIR/IIF.