With the recent rediscovery of CO_2 as a working fluid, there has been a great interest in optimizing the efficiency of the CO_2 cooling cycle. One possible means of improving the CO_2 cycle efficiency is to flood the compressor with oil in order to absorb the heat of compression of the vapor refrigerant. In order to gain significant benefit with compressor flooding it is critical to provide regeneration. The addition of oil flooding and regeneration for subcritical operation can increase the system COP by over 20% for source and sink temperatures of -30°C and 20°C respectively. For transcritical operation, the increase in COP from flooding and regeneration can be nearly 20% for source and sink temperatures of 5°C and 40°C respectively. In addition, results from a detailed model of a CO_2 oil-flooded scroll compressor are presented which suggest that a properly designed scroll compressor should be able to handle the large amount of oil necessary.
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