>>11388176>It shouldn't matter that it doesn't change phaseWhat? Yes it does lol. Look at a T-S diagram. The area inside the cycle is the total amount of heat that can be removed.
Refrigerants like R134a are better than air because they can exist in a saturated state at normal atmospheric pressure at temperatures between the freezing and boiling points of water (as opposed to very high pressures/very low temperatures, like for air). You want your fluid to be saturated because most efficient refrigerator is a reversed Carnot cycle. In this cycle, the working fluid is evaporated isothermally, compressed isentropically, condensed isothermally, and then expanded in a turbine isentropically. This cycle is ONLY possible if the fluid is saturated (i.e., is on the verge of boiling). However, the Carnot cycle is very impractical in real life because 1) you need to first separate the liquid and vapor parts of the working fluid before compression, and usually have a separate pump, which is expensive and adds a lot of mechanical complexity, and 2) because you need a fucking turbine to expand the fluid.
The solution is to use a vapor-compression cycle. Here, fluid is totally evaporated (it has a quality X=1) by the time it reaches the compressor. When the fluid leaves the compressor, it is a superheated gas. Superheated gasses are very easy to condense, they are practically begging for it. The, we ditch the turbine for a simple expansion value, sacrificing isentropic efficiency for something that is very easy and cheap to manufacture.
tl;dr moving energy around in the form of latent heat is very efficient and a strictly air-based refrigeration cycle either sucks or is very expensive
