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Trichlorofluoromethane was first widely used as a refrigerant.Because of its high boiling point compared to most refrigerants, it can be used in systems with a low operating pressure, making the mechanical design of such systems less demanding than that of higher-pressure refrigerants R-12 or R-22.
According to ASHRAE standard 34, the R-number of a chemical refrigerant is assigned systematically according to its molecular structure and has between two and four digits. If there are carbon -carbon multiple bonds , there are four digits in all: the number of these bonds is the first digit and the number of carbon atoms minus one (C-1) is next.
Being phased out: A widely used hydrochlorofluorocarbon (HCFC) and powerful greenhouse gas with a GWP equal to 1810. Worldwide production of R-22 in 2008 was about 800 Gg per year, up from about 450 Gg per year in 1998. R-438A (MO-99) is a R-22 replacement. [71] R-123 HCFC-123 CHCl 2 CF 3: 2,2-Dichloro-1,1,1-trifluoroethane: 292 79 US phase-out
As a result of CFCs contributing to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) [1] including R-410A, R-134a and R-1234yf. [2] [3] [4]
Researchers have focused on using new mixtures that have the same properties as past refrigerants to phase out harmful halogenated substances, in accordance to the Montreal Protocol and Kyoto Protocol. [3] For example, researchers found that zeotropic mixture R-404A can replace R-12, a CFC, in household refrigerators. [19]
HCFC-123 is used in large tonnage centrifugal chiller applications, and is the most efficient refrigerant currently in use in the marketplace for HVAC applications. HCFC-123 is also used as a testing agent for bypass leakage of carbon adsorbers in gas filtration systems, and as the primary chemical in Halotron I fire-extinguishing agent. [2]
The use of R-134a is being phased out because of its high global warming potential (GWP). HFO-1234ze(E) itself has zero ozone-depletion potential (ODP=0), a very low global warming potential (GWP < 1 ), even lower than CO 2, and it is classified by ANSI/ASHRAE [4] as class A2L refrigerant (lower flammability (see below) and lower toxicity). [5]
R11 Highly flammable R12 Extremely flammable R14 Reacts violently with water R15 Contact with water liberates extremely flammable gases R16 Explosive when mixed with oxidising substances R17 Spontaneously flammable in air R18 In use, may form flammable/explosive vapour-air mixture R19 May form explosive peroxides R20 Harmful by inhalation R21