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Author
Marques, M. E. | Domanski, P. A.
Title
Potential Coefficient of Performance Improvements Due to Glide Matching With R-470C.
Coporate
National Institute of Standards and Technology, Gaithersburg, MD
Book or Conf
International Refrigeration Conference at Purdue, 7th. Proceedings. July 14-17, 1998, West Lafayette, IN, 1998
Keywords
alternative refrigerants | air conditioner | coefficient of performance | glide matching | heat pumps | refrigerants | thermodynamics | zeotropic mixtures
Abstract
Potential improvements of the Coefficient of Performance (COP) were investigated for R-407C at cooling and heating conditions of a residential heat pump. The study used CYCLE-11, a semi-theoretical vapor-compression cycle model, which was upgraded to simulate cross-flow, counter-flow, and parallel-flow evaporator and condenser with no restructions on specifying superheated vapor and subcooled liquid regions. The COP benefit of using counter-flow heat exchangers in a low-life air-conditioning application was found to be 7.1% when compared to a system with a cross-flow evaporator and condenser. For heating conditions (high-life application), the predicted benefit was 3.6%. These results are representative of a water-to-water system, where counter-flow heat exchangers are suitable for implementing glide matching. Since air-to-refrigerant heat exchangers are not counter flow but rather cross-counter flow (in the best case), the potential to improve COP in a practical air conditioner is lower. The COP penalty caused by glide mismatch (parallel flow) is approximately twice as severe as the benefit that can be realized from glide matching.