Luckily in my life, they just work but there’s gotta be way more to it than gas/electricity make air hot, refrigerant/coolant make air cold. Also what is refrigerant/coolant?
Also I’m sure it can vary in application so I’m mainly asking about buildings/residences.
In: Technology
Most heaters work by one of three principles:
* Push electricity really hard through a wire that resists current going through it. Resistance generates heat, and that heats the air around the coil. (You can see this at work on electric stove burners.)
* Burn something (coal, gas, wood, etc.), and make use of that heat to heat other stuff. This is your standard gas furnace.
* Heat up water, and then pump that hot water through pipes in the space you want to heat. Some “combined heat and power” systems use this, especially in geothermically-active areas like Iceland.
Refrigeration systems usually use one basic process, but particular variations exist. The TL;DR is that you can exploit thermodynamic processes to use something that evaporates at low temperature in order to extract heat. It works like this:
1. Send the refrigerant into an electrically-powered compressor. This raises the pressure and temperature of the refrigerant.
2. Pass the pressurized, hot refrigerant through coils at the back, which dissipate this heat, producing pressurized liquid at ambient temperature.
3. Pass the now-cooled refrigerant to coils inside the insulated refrigerator, where the refrigerant is then sprayed (still inside the closed system), causing it to drop in pressure and evaporate.
4. Doing this extracts heat from the refrigerant’s surroundings, causing the inside of the refrigerator to cool down.
5. Pump the resulting evaporated refrigerant back into the condenser. Repeat from step 1.
Both AC units and refrigerators use this same principle. Refrigerators just get things much colder.
You can experience the cooling effect yourself, by the way, simply by rubbing a few drops of rubbing alcohol on your skin. That’s a volatile compound that evaporates at temperatures below your body temperature, so it extracts heat from its surroundings (specifically, your skin) in the process of evaporating away. Freon (specifically Freon-12), aka dichlorodifluoromethane (CCl2F2), is one example of a refrigerant. Because it evaporates at around -30 C, freon works for getting most things we want to get cold. It can’t cool anything to lower than that temperature.
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