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While flammability is not an issue like it is with Hydrocarbons, with Carbon Dioxide, also known as R744, there are issues related to high pressures that can cause some concern among refrigeration manufacturers looking at changing to CO2. Most of these involve design specifications, but also include manufacturing feasibility. Specifically, the higher critical point of CO2 makes it more difficult to handle the gas as you would other refrigerants. In comparison, the critical point of R134a is 590 psia (or 210° F), while the critical pressure of CO2 is 1,067 psia (88°F).
Traditional volumetric metering devices aren’t rated for the pressure, so a mass flow meter with a suitable rating must be used instead. Other components such as the filling head, valves, etc. must also be of a suitable design. As far as the working environment is concerned, adequate ventilation is all that is required to prevent the increase of atmospheric concentration which could result in mild health concerns. CO2 need not be reclaimed and can simply be vented.
Applications include, in particular, vending machines, which are driven by the end-user's (e.g. Pepsi's) need for a "green" alternative as a way to reach and expand their customer base by displaying their attention to environmental concerns.
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Often, manufacturers will run a standard refrigerant line (e.g. R134a) alongside a CO2 line, as the demand numbers for CO2 systems are still low in comparison to traditional refrigerants. VTech can assist these manufacturers by providing "all-in-one" solutions for HFC's/HCFC's and CO2 in order to minimize tooling costs and equipment footprint. Please click here to learn more about our CO2 refrigerant charging systems. |
