Energy and Exergy Analysis of the Air Source Transcritical CO 2 Heat Pump Water Heater Using CO 2 -Based Mixture as Working Fluid

Yikai Wang, Yifan He, Yulong Song, Xiang Yin, Feng Cao and Xiaolin Wang
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Yikai Wang: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Yifan He: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Yulong Song: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Xiang Yin: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Feng Cao: School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Xiaolin Wang: School of Engineering, University of Tasmania, Hobart, TAS 7001, Australia

Energies, 2021, vol. 14, issue 15, 1-18

Abstract: Given the large demand nowadays for domestic hot water, and its impact on modern building energy consumption, air source transcritical CO 2 heat pumps have been extensively adopted for hot water production. Since their system efficiency is limited by significant irreversibility, a CO 2 -based mixture could offer a promising drop-in technology to overcome this deficiency without increasing system complexity. Although many CO 2 blends have been studied in previously published literature, little has been presented about the CO 2 /R32 mixture. Therefore, a proposed mixture for use in transcritical CO 2 heat pumps was analyzed using energy and exergy analysis. Results showed that the coefficient of performance and exergy efficiency variation displayed an “M” shape trend, and the optimal CO 2 /R32 mixture concentration was determined as 0.9/0.1 with regard to flammability and efficiency. The irreversibility of the throttling valve was reduced from 0.031 to 0.009 kW?kW ?1 and the total irreversibility reduction was more notable with ambient temperature variation. A case study was also conducted to examine domestic hot water demand during the year. Pure CO 2 and the proposed CO 2 blend were compared with regard to annual performance factor and annual exergy efficiency, and the findings could provide guidance for practical applications in the future.

Keywords: transcritical CO 2 heat pump; energy analysis; exergy analysis; CO 2 -based mixture; ambient temperature; case study (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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