Refrigerant

Properties

In theory, air or nitrogen (of the current fluids on our planet…) could be used as cooling agent. All in all, any fluid has a potential in term of refrigeration. But, in practice, it is differently. These fluids must answer the following criteria:

the cooling fluids are selected mainly for their great property of absorption of Calorie S when they pass from their phase liquid to their gas phase (the heat absorptive by the fluid during the change of state is called: latent heat of Vaporization). The cooling agents are used pure or mixes some in the trades of the cold and the Climatisation.

These fluids must respect the environment because of the possible hazard of escape in the atmosphere.

They must as be inoffensive for the man for the same reason as above…

They are also selected according to the operating temperatures of the two exchangers of the refrigerating circuit concerned (the condenser and the evaporator). Indeed, the fluids used to obtain low temperatures are different from the fluids of air-conditioning for example.

Lastly, their pressures (which are function of the temperatures of service of the exchangers quoted above) must allow their use in a refrigerating circuit with a reasonable dimensioning of pipings and compressor. Indeed, it would not be profitable to use nitrogen to make air-conditioning, the pressures being too important would require very thick pipings and a gigantic compressor.

In air-conditionings, their capacity to absorb a certain quantity of heat per cooling unit is still expressed in BTU.

The Fréon is the trade name of several of cooling gases manufactured by the company Dupont de Nemours.

Role of the refrigerant

In a refrigerating circuit, the refrigerant conveys two elements:

calories. Those Ci are collected with the evaporator and the level of the compressor. They are then evacuated on the level of the condenser.
the oil of the compressor. This is rather a disadvantage. Indeed, the oil of the compressor is completely useless for the other bodies of the refrigerating circuit.

(For more precision, to see: Cold industrialist)

Various categories of refrigerant

One distinguishes among cooling gases various categories of Molécule S:

the Chlorofluorocarbon S (CFC),
the Hydrochlorofluorocarbone S (HCFC),
the Hydrofluorocarbure S (HFC),
the Hydrocarbon perfluoré or perfluorocarbures (PFC),
the Hydrocarbon S or made up organics not making part of the categories previously quoted,
the compounds Inorganic like the Ammonia.

Refrigerants used before 1929

The principal gases used before 1929 for the first period of mechanic refrigeration, were:

the Sulfur dioxide (S O ₂),
the Chloride methyl (C H ₃ Cl),
the Carbon dioxide (C O ₂),
the Chloride ethyl (C ₂ H ₅ Cl),
the Ammonia (NR H ₃)

All these fluids had interesting thermodynamic properties but they presented a whole a danger to the man from their toxicity or owing to the fact that they were combustible.

Refrigerants used between 1929 and the Protocol of Montreal

In 1929, an American scientist, Thomas Migdley, and its team produce the first molecules of Dichlorodifluorométhane (C Cl ₂ F ₂) or R12. The R12 and the refrigerants of the same family have the property to be relatively inoffensive for the man and to be interesting from the point of view thermodynamic.

They were industrially manufactured by the company Dupont de Nemours as from 1932 (Dichlorodifluorométhane - R12 and Trichlorofluorométhane - R11) under the name of Fréon. These refrigerants are derivatives of oil.

Restriction of use since the Protocol of Montreal

Since the September 16th 1987, the Protocol of Montreal signed by 24 countries and the European Economic community and which counts 190 countries signatories today, is an international agreement aiming to reduce and, in the long term, to completely eliminate the substances which impoverish the Couche of ozone. the EEC thus since voted laws in this direction.

This protocol imposes the suppression of the use of CFC (except for qualified of criticisms or essential uses), halons, bromide of methyl and other substances impoverishing the layer of ozone (HCFC, carbon tetrachloride, bromochlorométhane, hydrobromofluorocarbone, méthylchloroforme), and that within a time allowing the installation of substitutes.

The protocol of Montreal invites the interested parties to take the necessary measures to reduce the emission of refrigerants in the atmosphere; it acts:

• not to use these products as propellent more (they were prohibited as of 1978 in the U.S.A. for this use)

• to improve the sealing of the refrigerating circuits

• to fight against the purgings and the rejections in the atmosphere

• to recover the refrigerants systematically

Moreover, it recommends to reduce then to stop the production of the most harmful gases to the layer of ozone and those having an significant impact on the greenhouse effect. These are the refrigerants whose molecule is rich in chlorine and of which the lifespan is large.

Among these gases, one finds:

Chlorofluorocarbons (CFC) *: Chlorine contained in their formulas, destroyed the layer of ozone. They also have an impact on the Greenhouse effect.

In the event of escape, it is interdict to reload with this fluid.

It is thus necessary to replace the totality of the fluid. Sometimes, according to the age of the equipment and its outdatedness, it is preferable to change equipment.

refrigerating equipment intended for the destruction must be imperatively cleansed of its refrigerants and lubricating; some will be destroyed (CFC) and others recycled (oil).

(* R 11, R 12, R 502, R 504…)

Hydrochlorofluorocarbones (HCFC) *: Chlorine contained in their formulas, destroyed the layer of ozone. They also have an impact on the Greenhouse effect

For the moment, the refill is authorized. But, as from 2010, it will be interdict to reload by new fluids and as from 2015, by recycled fluids.

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