Theoretical Evaluation of Energy, Exergy, and Minimum Superheat in a High-Temperature Heat Pump with Low GWP Refrigerants

Adam Sulaiman, Donal Cotter, Cordin Arpagaus, Neil Hewitt

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3 Citations (Scopus)
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Abstract

Suitable low global warming potential (GWP) refrigerants that conform to F-gas regulations are fundamental to the operation and future development of high-temperature heat pumps (HTHPs) used for industrial processes and waste heat recovery. This paper presents the results of a theoretical simulation to investigate a range of low-GWP refrigerants and their suitability to supersede refrigerants HFC-245fa and HFC-365mfc. A steady-state thermodynamic model of a single-stage HTHP with an internal heat exchanger (IHX) was developed to assess system cycle characteristics and performance at temperature setpoints at 60 and 70°C heat source, 90 and 140°C heat sink, at 30 and 70 K lift. This study focuses on energetic and exergetic efficiencies within the system and the impact of regulating superheat to optimise performance. Based on energetic and exergetic theoretical results, a trade-off between COP, VHC, and exergetic efficiency indicates HCFO-1233zd(E) and HFO-1336mzz(Z) as the most likely replacements for HFC-245fa and HFC-365mfc respectively. The refrigerant HC-601, followed by HFO-1336mzz(Z) and HCFO-1233zd(E), exhibited the lowest exergetic destruction within test conditions. Mapping the minimum superheat indicated optimum performance for HCFO-1233zd(E) between 5 to 8 K and HFO-1336mzz(Z) between 17 to 22 K, depending on temperature lift. Validation of the theoretical results with experimental data indicates that simulated COP closely matches empirical values. This work provides a method to optimise refrigerant selection in HTHPs based on operational indicators to maximise overall system performance.
Original languageEnglish
Pages (from-to)99-109
Number of pages11
JournalInternational Journal of Refrigeration
Volume153
Early online date2 Jun 2023
DOIs
Publication statusPublished (in print/issue) - 25 Sept 2023

Bibliographical note

Funding Information:
The authors gratefully acknowledge the support from the Department for the Economy (Northern Ireland, EP/T022981/1 ) DEcarbonisation of Low TemperAture Process Heat Industry, DELTA PHI and EP/R045496/1 Low Temperature Heat Recovery and Distribution Network Technologies (LoT-NET).

Funding Information:
In addition, the financial support of the Swiss Federal Office of Energy SFOE as part of the SWEET ( SWiss Energy research for the Energy Transition ) project DeCarbCH ( www.sweet-decarb.ch ) and the project Annex 58 HTHP-CH (Contract number SI/502336-01) are gratefully acknowledged.

Publisher Copyright:
© 2023

Keywords

  • High-temperature heat pump
  • minimum superheat
  • Energy & exergy efficiency
  • Low GWP refrigerants

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