Water boils at a lower temperature high on a mountain or when subjected to a vacuum pressure. Water exists in ice, liquid, or steam. Water isn't suitable as a refrigerant gas as it's too inefficient. Other substances are required.
Some substances change temperature according to how much pressure (or vacuum) they're subjected to. These are classified as refrigerant gases. Different substances have different pressure / temperature correlations. Different cooling systems are designed to run with different substances - there is no one size fits all. Some substances occur naturally, other substances are engineered by chemists in a lab. When released into the atmosphere (for various reasons), some substances deplete the ozone layer, others contribute to global warming, others are flammable, and all of them displace oxygen. It is possible to mix most substances to obtain custom operating properties and / or improve energy efficiency.
Gas is pumped into the condenser coil and is restricted by the metering device. This restriction banks up the gas in the condenser coil, causing it to heat up, and the gas that does make its way through to the evaporator coil cools down as it discharges. Different gases perform differently, and mixing gases also affects performance. Lower pressure gases (especially hydrocarbon gases) take less energy to compress - resulting in energy savings.
Generated from an Excel Spreadsheet of Pressure Temperature charts.
What I'm about to describe is oversimplified. The rabbit hole goes deep with this one.
A technician will know what I'm talking about.
• R32 is one of the coldest evaporating refrigerant gases.
• Ethane (R170) is a component of Hychill HC32, Minus 50, and Minus 60 - it is much colder than R32, but is unstable at or above 32°C. It is used sparingly.
• Propylene (R1270) is a component of Hychill HC32 and Engas M20. It isn't as cold as R32, but compresses more easily.
• Propane (R290) could be used instead of HC32 or M20, but still needs some R32 to function.
• You can mix these gases to get the best of both worlds.
• A small amount of R600A may be beneficial. It would be subjected to the same condensing pressure as R32, and it would flash at tremendous heat, moving the higher pressure gases along in the refrigeration cycle.
• When the compressor operates, most of the R32 and R170 is on the cold (evaporator) side. Most of the R1270 is subjected to the same compression as R32. Because of the different pressure temperature characteristics, the R1270 yields a higher temperature - propelling most of the gas on to the next part of the refrigeration cycle.
• Different gas blends work best in different climates. In hot parts of Australia, you're best off using a mixture of R32 and R290 (Propane). In cold parts of Australia, you're best off using Hychill Minus 60 (mediocre cooling performance, but awesome heating performance)
Refrigerants containing R170 slightly reduce the system cooling capacity or slightly increase power consumption when the condenser is at or above 32°C. If the proposed gas blend has 5% of R170, mix 10 - 15% of R600A to help restore energy efficiency. Where R32 is unavailable, use HC32. This chart does not account for all installation scenarios. For example: In a hotter climate, a poorly insulated downstairs room may require more heating performance in winter, than cooling in summer, and an upstairs room (as heat rises from downstairs) would likewise require a gas blend strictly optimised for hot conditions. R32 systems may need to be charged up to 105% of manufacturer specified gas charge in order to obtain optimal efficiency. Minus 50, HC32, and Minus 60 (In order from least to most) all contain R170.