How do heat pumps work and why are the energy efficient?
Edit: the question is sufficiently answered. Thanks guys!
In: 50
This is super high level, so there are more details to explain why, but i’ll skip those to make it easier to understand
gases get hot when you compress them. gases get cold when they expand. let’s say the different from compressed to uncompressed is 60 degrees for our silly high level example
air in your house is 70. the refrigerant is compressed, and it gains 60 degrees, so it’s now 130 degrees. it goes through a radiator, like the one on the front of your car. (also the same as liquid coolers in a computer) this is the loud box outside your house that blows hot air out of the top
now after the radiator, let’s say we get the temperature down from 130 to 90. now it goes j to the condenser. it lets the gas expand. remember the 60 degree difference between compressed and expanded? well now that we expanded the gas, it drops 60 degrees. now it’s 30 degrees. the condenser is basically like a radiator, but for cold. the air that blows through this is where the cold air comes from in your air conditioner. i completely pulled numbers out of my butt for the purpose of explaining this very simply
heat pump does the same thing. it just reverses the process. AC is just a heat pump. pumps heat from inside the house to outside. heat pump mode for heating is just reversed direction of AC.
let’s say outside is 30 degrees, so below freezing. sounds crazy to pump heat from outside to inside, right? but let’s look at the numbers. outside, the refrigerant starts at 30 degrees. it then gets compressed. it gains 60 degrees. now it’s 90 degrees. it goes through the radiator and a fan blows air through it and it heats the air (which pulls heat out of the refrigerant). this is the hot air you feel when your heat pump is heating your house. let’s say it drops 40 degrees after the radiator so it’s 50 now
it then goes back outside, is expanded, and that causes the 60 degree change, so it’s -10 degrees now. heat goes from hot to cold. despite outside being colder than freezing, the 30 degree air is much warmer than the -10 degree refrigerant, so it absorbs the heat. just repeat this cycle and that’s how heat pump works. it’s just air conditioning, but reversed to pump the heat in the other direction. heat pump capable systems just have a valve system that allows for this reversal.
now a big downside to heat pump: the temperature differences are limited by physics. for this reason, it it’s too cold outside; it won’t be able to get too hot. the heat from most heat pump systems on a really cold sub-freezing days won’t give you super hot air. it will usually feel slightly warm. that’s the only major problem. otherwise they’re very efficient
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