Experimental demonstration of an air-source heat pump application using an integrated phase change material storage as a desuperheater for domestic hot water generation

Johann Emhofer, Klemens Marx, Andreas Sporr, Tilman Barz, Birgo Nitsch, Michael Wiesflecker and Werner Pink

Applied Energy, 2022, vol. 305, issue C, No S0306261921012034

Abstract: Heat pumps with a three-media refrigerant/phase change material (PCM) water heat exchanger (RPW-HEX), integrated in the hot superheated section after the compressor, have a promising potential for electric energy savings. The RPW-HEX operates as a desuperheater that stores the sensible energy provided by the hot gas during heating and cooling operation for later heat transfer to domestic hot water (DHW) storage devices. So far, such a system has not yet been implemented and analysed in an overall system suitable for heating, cooling and DHW generation. In the present work, the operation of a prototypical heat pump with integrated RPW-HEX connected to three artificial apartments, was demonstrated in the laboratory under controlled ambient conditions. For this purpose, two RPW-HEX modules with a total storage capacity of about 5kWh were integrated into an R32 air-source heat pump with a heating power of about 7.7kW at −10∘C ambient temperature and a feed water temperature of 45∘C. Technical feasibility and operation with rule-based control strategies have been successfully demonstrated for realistic use cases. Besides individual tests, the heat pump was operated over 48hours with and without RPW-HEX at an ambient temperature of −2∘C, a feed water temperature for the heating system of 40∘C. Both systems, achieved the same average COP, but the system with RPW-HEX was able to provide a 10K higher average feed water temperature for DHW generation compared to the system without RPW-HEX. For the same feed water temperatures for DHW generation, an enhancement of about 3.1% of the average COP can be expected with the current system. This is about 60% of the theoretically possible value. Furthermore, for a low feed water temperature for heating of about 32∘C at −2∘C, an enhancement of the average COP up to 9.4% can be expected for the analysed heating and DHW scenario with an improved design.

Keywords: Energy efficient DHW generation; Desuperheater; PCM; Air-source heat pump; R32; Storage (search for similar items in EconPapers)
Date: 2022
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Citations: View citations in EconPapers (8)

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DOI: 10.1016/j.apenergy.2021.117890

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