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Appendix A – CO2 as a Working Fluid in Heat Pumps Appendix A CO2 as a Working Fluid in Heat Pumps The physical and thermophysical properties of the working fluid are of vital importance when designing the next generation of energy efficient and environmentally friendly residential heat pump systems. The proper- ties affect the selection of the thermodynamic process, component and system design, control strategies as well as issues related to the local safety of the installation. This appendix provides a presentation on the use of carbon dioxide (CO2, R-744) as a working fluid in heat pumps. Important physical and thermo- physical properties of CO2 are discussed, focusing on the main design parameters, operational characteristics as well as compressor and heat exchanger performance for residential systems. The last part of the appendix elaborates on the supercritical heat rejection process in the gas cooler, where the high-side pressure plays a key role regarding the heating capacity and the coefficient of performance (COP) of the heat pump. All calculations in the appendix have been performed by means of Microsoft Excel. The Span and Wagner (1996) equation of state was used for the thermodynamic properties of CO2, whereas the thermal conduc- tivity and dynamic viscosity were calculated from Vesovic et al. (1990) and Fenghour et al. (1998), respectively. A1 Physical and Thermophysical Properties CO2 is an environmentally friendly1 working fluid with unique physical and thermophysical properties, which has been identified as an interesting long-term alternative to conventional working fluids (Lorentzen and Pettersen, 1993). Table A1 shows some important physical and thermo- physical properties of CO2, propane (R-290) and HFCs that are commonly used in residential heat pumps. 1 CO2 is a non-flammable and non-toxic substance. CO2 does not deplete the ozone layer (i.e ODP = 0), and the Global Warming Potential (GWP) is zero since it is surplus CO2 from industry that is being used as a working fluid (i.e. no generation of CO2). A1PDF Image | Residential CO2 Heat Pump System for Combined
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CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
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