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Simple Method of Composition Shifting With a Distillation Column for a Heat Pump Employing a Zeotropic Refrigerant Mixture.


pdf icon Simple Method of Composition Shifting With a Distillation Column for a Heat Pump Employing a Zeotropic Refrigerant Mixture. (283 K)
Rothfleisch, P. I.

NISTIR 5689; 27 p. July 1995.

Sponsor:

Environmental Protection Agency, Research Triangle Park, NC

Available from:

National Technical Information Service
Order number: PB95-255821

Keywords:

heat pumps; air conditioning; distillation; refrigerant mixtures; refrigeration; zeotropic refrigerants

Abstract:

This work presents a simplified method of controlling heat pump capacity by shifting the composition of a zeotropic refrigerant mixture with a distillation column. Simplicity is achieved by incorporating the distillation column into the typical suction accumulator used by residential heat pumps. A U.S. patent has been applied for under the title "Accumulator Distillation Insert for Zeotropic Mixtures". An experimental system employing this distillation concept has been evaluated in the laboratory for zeotropic mixtures of R32/134a (30/70) and R32/125/134a (23/25/52). For the binary mixture the circulating refrigerant composition was shifted to R32/134a (54/46). For the ternary mixture the circulating refrigerant composition was shifted to R32/125/134a (36/36/28). Seasonal calculations have shown these composition shifts to reduce the seasonal resistance heat requirement by up to five percent compared to R22. Additionally, the instantaneous peak energy requirement of the dwelling has been reduced relative to R22 by six to nine percent depending on the climate region. The distillation insert should be capable of producing greater composition shifts after further optimization of the insert and improved integration with the heat pump system. For the ternary mixture, it is expected that the insert will be capable of producing a circulating refrigerant composition composed entirely of R32/125.