Abstract: Abstract Natural refrigerants are attractive candidates for replacing the high Global-Warming-Potential fluorinated refrigerants used in ground-source heat pumps (GSHPs). This paper presents a comprehensive survey on GSHPs using CO2, NH3, water, and hydrocarbons. We compared the refrigerants’ thermodynamic properties, analyzed their performance in brine-to-air and brine-to-water GSHPs, and discussed recent progress in their use in GSHPs. Studies of CO2 were the most common due to its favorable properties, covering advanced cycles, direct-expa...
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