A NEW EJECTOR DESIGN METHOD DISCLOSES POTENTIAL IMPROVEMENTS TO THE PERFORMANCE OF JET-PUMP CYCLE REFRIGERATORS

So far the jet-pump refrigeration cycle has always been characterised by low COP values, due in the main to the low performance of the ejector in fulfilling its role as cycle’s compressor. The recently suggested Constant Rate of Momentum Change (CRMC) method seems to offer a real possibility to significantly increase the performances of the ejector and in so doing, open up new prospects for the jet-pump refrigeration cycle. Using a numerical simulation code, developed by the authors, this paper offers a comparison between jet-pump refrigerator cycles operating with ejectors designed using both conventional and CRMC methods. In both cases the ejectors are designed with supersonic primary nozzles. The numerical optimisation code devised by the authors covers the whole jet-pump refrigerator cycle. This is considered as a open system exchanging heat with three thermal sources. The optimisation function in each case is assumed to be the system COP and the work needed at the pumps to win the pressure losses incurred by the external water flows are included. This theoretical paper shows that the COP of the jet-pump refrigerator is improved when the ejector is designed with CRCM method. This opens up prospects for the commercial utilisation of the jet-pump refrigeration system, particularly when low-grade heat is available to produce cooling.