Refrigerant, just as cooling agents transport, enthalpy (warmth is called), away from the cooling property and to Umgebung.Der difference it is that a refrigerant in a cooling cycle can do this against a temperature gradient, so that the ambient temperature may be even higher than the temperature of the article which can be cooled, while a cooling agent in a cooling cycle is only able to transport the enthalpy along the temperature gradient to a place of lower temperature.
According to DIN 8960 exp. 3,1 a refrigerant is defined as a "working medium, which takes up warmth in a refridgerator process at low temperature and low pressure and at higher temperature and higher pressure warmth delivers".
Accordingly refrigerant is generally produced begun, where it applies to manufacture in a constantly working system cold weather e.g. frame in a refrigerator, in a heat pump, air conditioning system or in with refrigerants strictly speaking for cold weather everywhere by evaporation, takes place this in a chemically by means of a mixture and/or a solution reaction. The regeneration takes place therefore with refrigerants via liquefaction (in a conventional compressor with following condensor), with via separation (in a "thermal" compressor of an absorption refrigeration system).
As first "professional" refrigerant first Diethylether, then also ammonia (R717) was used. A disadvantage of these refrigerants is however the physiological danger (lung damage; Diethylether also Narkosewirkung). Diethylether is besides very easily inflammable and forms explosive mixtures with air.
In contrast to this it has late used halogen hydrocarbons the advantage that by the variation of the chemical composition a broad spectrum at characteristics can be opened. So also non-combustible and/or innocuous refrigerants can be made available. Usual commercial names for these halogen hydrocarbons are followed the terms Freon (company DuPont) and/or freon (company most), of the contractions for the respective chemical compositions. Thus z stand. Ex. the names Freon 502 and freon 502 for the same refrigerant, for which today the abbreviation R 502 (R for Refrigerant) is used firmneutrally. A disadvantage, above all with chlorine, iodine and bromine halogenierten, halogen hydrocarbons are however that they strengthen the greenhouse effect and the Ozon-Abbau. Their employment in new equipment was strongly limited therefore. Thus nowadays above all nichthalogenierte hydrocarbons are used such as butane (R600/R600a) or propane (R290) beside teilhalogenierten hydrocarbons without chlorine, iodine or bromine, which are however inflammable. This limits the permissible places of assembly and/or amount of filling.
Therefore recently also strengthens the non-combustible carbon dioxide (R744) used, which besides is food-technically harmless.
Water (R718) is usable due to its freezing point only above 0"°C as refrigerants. On the other hand it is suitable due to its very high specific thermal capacity well as cooling agents. The admixture of anti-freezes such as z. Ex. alcohols or salts makes possible also the use as cooling agent below 0"°C.
Refrigerants should ideal-prove the following characteristics to possess:
The refrigerants are arranged according to combustibilities and Giftigkeit (EN 378-1 Anh. E) in the safety's groups of A1, a2, A3, B1, B2, B3. The letters stand thereby for
the numbers for
Into the simpler handling the safety's groups of A1, B1, a2 are combined" etc. in the so-called L-groups of L1, L2, L3 (EN 378-1 exp. 5.4.2):
The moreover one three list ranges A, B, C leave themselves differentiate with refrigerant plants according to the kind of the list (EN 378-1 Anh. C):
Dependent on the L-group and the list range requirements apply to the permissible refrigerant amount of filling (EN 378-1 Anh. C).
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