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1 – Introduction Since the HFCs are foreign to nature, widespread use of these fluids will always include a potential risk of unexpected negative global environ- mental effects, as already experienced with the CFCs and the HCFCs. An alternative to the HFCs is to apply naturally occurring and ecologi- cally safe substances, so-called natural working fluids. The most impor- tant substances in this category are ammonia, hydrocarbons, carbon dioxide, water and air. From an environmental point of view, carbon dioxide (CO2, R-744) can be regarded as an almost ideal working fluid since it is non-toxic, non-flammable and neither contributes to ozone depletion nor global warming2. In former days, CO2 was used as a working fluid in many refrigerating and air conditioning applications. With the introduction of the CFCs in the 1930s and the HCFCs in the 1950s, the application of CO2 was gradually reduced until it ceased completely during the 1960s. However, after several decades of ignorance, CO2 was “rediscovered” as a working fluid by Lorentzen and Pettersen (1993), who initiated several projects regarding CO2 heat pump and air conditioning systems. Due to considerable international research and development activities in recent years, CO2 now appears as a viable long-term alternative to the HFCs in a number of residential, commercial and industrial applications. 1.1.2 ResidentialCO2HeatPumpSystems Since virtually all residential heat pump units are charged with HFCs, it is relevant to examine whether CO2 heat pumps can be successfully applied in the residential sector. 1.1.2.1 Research Projects on Residential CO2 Heat Pump Systems In recent years a number of universities, research institutions and com- panies have been evaluating and testing various types of residential CO2 heat pump systems. The applications include CO2 heat pump water heaters (Saikawa and Hashimoto, 2000), CO2 heat pumps for the retrofitting of boilers in high-temperature radiator systems (Brandes and Kruse, 2000), CO2 heat pumps in combination with low-temperature heat distribution systems (Kerherve and Clodic, 2002), air-to-air heat pump systems for the heating of ventilation air (Rieberer and Halozan, 1998), and reversible split-type air-to-air CO2 heat pumps (Richter et al., 2002; Aarlien, 2002). 2 The CO2 which is used as a working fluid is a by-product from industrial processes. 2PDF 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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