Viability of capacity control of high temperature heat pump water heaters operating non-azeotropic mixtures

Leon Liebenberg, Josua P. Meyer

Research output: Contribution to journalConference articlepeer-review


A high temperature electrically-operated heat pump water heater is evaluated in terms of the viability of employing capacity control using non-azeotropic refrigerant mixtures (NARMs). The system coefficient of performance (COP) is improved by introducing capacity control, which offers continuous modulation by varying heat pump capacity to match the load. This is accomplished by using a non-azeotropic refrigerant mixture (NARM) and changing the composition (x) of the circulating mixture. The NARM R-22/R-142b is selected due to the requirement for a high condensing temperature and a wide capacity range. The life-cycle cost effectiveness of this heat pump is compared with that of a conventional heat pump (operating a pure fluid). Computer simulations show that the capacity-controlled heat pump, operating between compositions of 100% R-22 and 70% R-22, shows a 29.6% improvement in energy conversion when compared with a conventional R-22 heat pump water heater. The payback periods of the capacity-controlled systems, are strongly dependent on electricity tariff, additional system cost, and period and duration of heat pump operation.

Original languageEnglish (US)
JournalAmerican Society of Mechanical Engineers (Paper)
StatePublished - 1997
Externally publishedYes
EventProceedings of the 1997 ASME ASIA Congress & Exhibition - Singapore, Singapore
Duration: Sep 30 1997Oct 2 1997

ASJC Scopus subject areas

  • Mechanical Engineering


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