Liquid and solid carbon dioxide are important refrigerants, especially in the food industry, where they are employed during the transportation and storage of ice cream and other frozen foods. Solid carbon dioxide is called "dry ice" and is used for small shipments where refrigeration equipment is not practical. Solid carbon dioxide is always below 78.5 ° C at regular atmospheric pressure, regardless of the air temperature.
Liquid carbon dioxide (industry nomenclature R744 or R-744) was used as a refrigerant prior to the discovery of R-12 and may enjoy a renaissance due to the fact that R134a contributes to climate change. Its physical properties are highly favorable for cooling, refrigeration, and heating purposes, having a high volumetric cooling capacity. Due to its operation at pressures of up to 130 bar (1880 psi), CO2 systems require highly resistant components that have already been developed for mass production in many sectors. In automobile air conditioning, in more than 90% of all driving conditions for latitudes higher than 50° , R744 operates more efficiently than systems using R134a. Its environmental advantages (GWP of 1, non-ozone depleting, non-toxic, non-flammable) could make it the future working fluid to replace current HFCs in cars, supermarkets, hot water heat pumps, among others.
PROPERTIES CO2 CAS Number: 124-38-9 Colour: Colourless Odor: Odorless Appearance: Colourless and not turbid
Chemical name: Carbon dioxide Chemical formula: CO2 Molecular weight: 44 Melting point, ° C: 56.6 Density: 770 kg/m3 (liquid at 56 atm and 20 ° C) Vapor pressure: 5.73 MPa (20 ° C) Solubility in water 1.45 g/L at 25 ° C, 100 kPa Acidity (pKa) 6.35, 10.33 Viscosity 0.07 cP at 78.5 ° C Specific heat capacity C 37.135 J/K mol