What exactly do fluorinated gases do in AC units or refrigerators? Is there any alternatives?
In: Chemistry
There are many alternatives.
https://en.wikipedia.org/wiki/List_of_refrigerants
In particular, towards the bottom of the list are a number of non-fluorinated gases. CO2 is one, butane, even air (R729) are possibilities.
However, they mostly have properties that make them less attractive than fluorinated chemicals – either that very high pressures are required to make them work (CO2) which are difficult to achieve with cheaply mass-produced compressors, or that they are flammable (butane is, after all, what we refill cigarette lighters with) or that phase-change doesn’t happen in their use (aircraft PACK air conditioners which use high-pressure air which is bled from the engine compressors) and hence very large quantities of refrigerant are needed to be used (compressed and then de-compressed) with an attendant high cost in terms of energy usage.
In computer cooling, heat-pipe coolers used on some CPUs utilise distilled water as the cooling mechanism. It’s held in the closed system at reduced pressure, and consequently boils at temperatures far below 100’C. It will re-condense back into liquid at the ‘cool’ side of the heatpipe (the main heatsink) to cycle back through the system. No compressor is used.
It’s also possible to cool via other means – Peltier (thermoelectric) coolers are solid (no liquids, gases or moving parts) slabs of ceramic with PN junctions typically made of Bismuth Telluride which pump heat from one side of the device to the other when electricity is applied to them. They’re the cooling device in the mini-fridges which are cheaply available. They’re in some respects a very good solution – silent, no moving parts to wear out, compact, reliable etc. However their energy efficiency is significantly lower than compressor based phase-change refrigeration – I think about a third of the efficiency.
https://en.wikipedia.org/wiki/Thermoelectric_cooling
The fluorinated-type of common refrigerants are used because of their desireable properties – cheapness, practicalities of construction of the refrigeration units, lack of flammability and toxicity etc.
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