Refrigerant Types for Air Conditioners
|Our visit to refrigerant overview in air conditioner parts, has provided us with general characteristics required for any cooling media.|
What we are going to discover in this page, is something more detailed into its general properties and issues.
A brief explanation of its function:
It is a media, used to expel heat in a condenser, and absorb heat in an evaporator (same hyperlink).
Therefore, media that can boil and condense repeatedly, can be a termed as refrigerants.
However, we need media that boil at temperatures below our ambient temperature, around ambient pressure, in order to maintain the required heat transfer, be it during condensation stage, or evaporation stage.
We need something that evaporates and boils extremely quickly at ambient temperature and pressure.
A brief history:
Refrigerant types used during these times we of flammable and light hydrocarbons. Namely naphta and petrol ether.
These material, although with good thermodynamic properties for heating and cooling, are extremely flammable, and highly toxic for human being. Transportation, handling and maintenance were an issue during these times.
What was (and still is) required for a refrigerant?
These must have,
- lower boiling temperature than minimum air temperature at evaporator, and
- higher temperature than maximum air temperature after compression
- non flammable and non toxic properties
- good mixing properties with compressor’s lubrication oil
In summary, it has to maintain reliability of air conditioner compressors, safe, non-toxic, while maintaining its thermodynamic properties.
Mr Midgley was assigned to lead a team in 1926, to find out cooling media that have all those properties mentioned in the previous sub-heading.
And the team succeeded, in which they have found fluorine based substance as suitable, and safe refrigerant.
These were named using "R" as the beginning symbol, and numbering system subsequent to the symbol. Example: R-134a.
These were numbered based on the building block of the compound.
The first cooling medium found by the team was R-12 or di-chloro-di-fluoro-methane, also known as Freon.
R-12 contains chlorine, fluorine, and carbon. Thus, the first CFC or chloro-fluoro-carbon, was born. Now that sounds familiar, doesn’t it?
It can cool a space, but the discussion around it, is always heated:
|Indeed. Topic on refrigerants has been never ending and very dynamic ever since mankind needed ”artificial cooling”. Yes, the flammable and highly toxic part has been removed, but the stable properties of these refrigerants pose a threat to the ozone layer.|
In addition to that, high and prolonged exposure to these halon based (chlorine and fluorine based) material may cause long term degenerative diseases. Cancer.
Let me take you though most commonly used, general types of refrigerant:
- CFC. Banned in most countries nowadays, as the chlorine will react with O3 ozone molecules, and cause thinning. Hello sun’s radiation!
- HCFC (hydro-chloro-fluoro-carbon ) has lower toxic and ozone depleting properties compared to CFCs. It has the element of hydrogen in it. Even then, it is about to be banned by 2030 due to its global warming property. See what I meant by “dynamic”?
- not to worry though. HFC and PFC (hydro-fluoro-carbon, per-fluoro-carbon) are still around! These have got NO chlorine content in the molecules. The former contains hydrogen and fluorine, and the latter contains carbon and fluorine. At least the ozone (and yourself) is safe
- natural media are not used for residential, offices or normal buildings. These types if refrigerants are used in industries as industries requires high capacity cooling, and relatively clean service compared to the others. Additionally, industries are equipped with dedicated personnel to monitor the health of the refrigeration or cooling system, day in, day out.
Propane (C3H8), butane (C4H10) and ammonia (NH3) are the common ones.
BUT, these are dangerous and toxic. Propane and butane may cause BLEVE (boiling liquid, expanding vapour explosion), if leakage and ignition are present.
Ammonia may cause cold burn (if the condensed liquid comes in direct contact with the skin), respiratory difficulties, vomiting and irritation.
There is always a “but” isn’t it?
- secondary cooling media, is not really a refrigerant. This type of heat transfer media is used for delivering cool temperature from air conditioner evaporator, to cooling coils. These are used in very large air conditioning system, or “district cooling”. The reasons are, to keep the maintenance cost, safety risk, and compressor breakdown, low.
Brine, and propylene-glycol are the famous examples
Personal safety and regulations must be followed when handling these refrigerants.
We will not go into details of industrial, secondary, and,
Currently banned cooling media:
The most famous ones are,
|R-11||CCl3F||CFC based compound|
|R-12||CCl2F2||CFC based compound|
|R-114||CClF2CClF2||CFC based compound|
|R-500, R-502, and R-503, R-505, R-506||Blend of series “1” and series “2” refrigerants||CFC based compound for the first set. Cancer causing agent for the second set|
Nevertheless, manufacturers are trying to appeal for the lifting of the ban for CFC based refrigerant types. No news on the ban being lifted so far.
Widely used, and currently approved refrigerant types:
|Name||Compound||Base||Boiling temperature at 1.013 bar (oC)|
|R-404A||R-125 44%, R-143a 52%, R-134a 4%||HFC blend||-46.2|
|R-407C||R-32 23%, R-125 25%, R-134a 52%||HCFC blend||-44|
|R-410A||R-32 50%, R-125 50%||HFC blend||-51.6|
|R-507||R-125 50%, R-143a 50%||HFC blend||-46.7|
The data presented is just a simple one. We will have to use a chart called p-h chart, or the pressure and enthalpy chart, to determine various states of a refrigerant, at different pressures and temperatures.
We have to use these charts, to design and select air conditioner parts, for the desired cooling.
Safe as it may be, these refrigerants still pose threat to the health of human being, and the environment, at excessive exposures. We have to be safe with these refrigerants. It’s better that these media, stays within an enclosed loop.
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