Even after searching it up I still don’t understand how it cools down air.
And what exactly does Freon do?
In: 9
Long story short, refrigerant (such as Freon) is pressurized and used to cool warmer air that is sucked in by the air conditioner. Warm air sucked in by the fans runs through the cooling element, and comes back out colder and less humid
The key takeaway is that *boiling cools stuff down*. This is counterintuitive because we associate boiling water with being hot, but if you were to boil water with a vacuum instead of with heat, you’d find that the water actually gets colder the more it boils.
And that’s what an air conditioner does. It takes a liquid, freon specifically, boils it with a change of pressure, the boiling cools it down, and then you have a fan to spread the cold to the rest of the room. Then you take that boiled gas, bring it to a compressor, compress it back into a liquid and throw away the extra heat to get it back to the starting point.
Using Freon as gas airconditioning gas is being phased out as it isn’t environmentaly friendly if it leaks. Other gasses are used today, including CO2.
Although the exact details, such as temperatures and pressures are different with these different gasses, the working principle is exactly the same.
The gas in an air conditioning is enclosed in a loop and is recirculated by a pump (compressor). There is a deliberate restriction built in this loop, creating a high pressure zone (before restriction) and a low pressure zone (after the restriction).
Although not required, but it greatly improves performance, the gas and pressure is chosen so there is a phase change taking place. The gas becomes a liquid in the high pressure zone and becomes a gas again in the low pressure zone.
The compression and expansion created by this restriction creates a temperature difference between these 2 zones. The phase change increases this difference a lot as phase transitions require a lot of energy to take place (energy = heat).
By cooling the hot side (high pressure), the cool side (low pressure) will become even cooler. This is an air conditioner.
Similarly, by heating the cold side, the hot side becomes even hotter and then it is called a heat pump.
The cooling/heating is often done by ambient air, and the effect it induces is used to cool/heat a car/room/house/aquarium.
I don’t completely understand it myself, but I’ll give you what I do know.
The concept is that a liquid flows in a loop from the front of the ac to back. When the liquid is in the back of the ac it gets cooled. When it’s in the front, fans blow across the pipes containing the liquid, and since the liquid is cold, that blows cold air into your living space.
When the liquid is in the front of the ac with the fans blowing across it, it “looses cool”. It gets warmer. When the warm liquid gets back to the back of the ac, it gets cooled again and round and round it goes.
This principle could work if you ran plastic tubing through a bowl of ice, filled the tubing with water, pumped the water through the loop so it cooled in the ice, and then run the tubing across a fan blowing into your living space. The water would cool in the ice, warm as it passed across the fan and then cool again in the ice.
The problem is that it wouldn’t be cold enough to cool well. Therefore scientific principles are used to increase the temperature range of the water. The compressor in an air conditioner literally compressed the water, which allows it to reach colder temperatures, plus there’s no ice to melt and need to be replaced.
(The chemistry used to increase the water’s temperature range is complicated. But that process is at the heart of the air conditioner. Without it there would be no ac.)
However water has a narrow range of temperatures and it takes a lot of energy to cool it, so water is not used in a ac. Instead they use substances that react more. They get cooler than water, faster than water. Freon is that substance. It cools much better than any other safe liquid available.
(However now Freon has been found to be destructive to nature so it’s being replaced with something else – which is safe, but doesn’t cool as well as Freon, but still better than water.)
When you compress gas, it gets hotter. When you expand its volume, it gets colder. Both these processes preserve the same amount of energy stored in the gas. Air conditioner is basically a loop exploiting this phenomena:
1. Compress the gas (it gets hotter)
2. Pump it through a radiator and remove excess heat with a fan
3. Expand the gas to its previous volume (it gets colder than before, because you have removed some energy on previous step)
4. Pump it through another radiator to heat it back to room temperature (draw energy from the room into the gas)
5. Rinse and repeat
So aircon works as a heat pump moving energy from one radiator to another. The circulating gas is called freon. It is engineered to be the most efficient in this process.
Compressing a gas into a liquid (increasing pressure) means heat is released from the gas as the pressure increases and especially as it changes to liquid form.
Having a gas expand means it will absorb heat as it expands.
Put a substance in pipes with a compressor and an expansion valve in the circuit and you have yourself a basic refrigeration cycle.
An A/C unit is just that.
You have a pipe coil with aluminium fins that is at the outlet of an expansion valve called the evaporator. A fan blows air through the fins and as the gas expands, the heat from the air is absorbed leading which cools the air.
Outside, you have a similar heat exchanger, but there is also a compressor. The gas gets compressed and the heat absorbed from the inside air gets released to the outside air.
Run the cycle in reverse and you have a heat pump.
Freon is a trademark owned by Dupont. People call it Freon, but the technical term is refrigerant. The refrigerant is a mixture of chemicals that has been tuned to have properties that work for the temperatures and pressures encountered in a typical AC. When the refrigerant is past the expansion valve, it is in gas form or at least partial gas form and turns back to liquid after going thorugh the compressor.
Commercial systems may use higher pressures and use different refrigerants. You even have systems that use CO2 as the refrigerant. It requires pretty crazy pressures, as in thousands of psi, but it can make a pretty good refrigerant.
ETA: A refrigerator uses the same principle. It cools what’s inside and dumps the heat at the back into your home.
ETA2: AC was first invented to help a printing business prevent humidity in the summer from making paper warp and jam in the printing presses. AC due to its effect of cooling air also decreases humidity. There was also obviously demand to keep indoors cooler than outdoors, so using it for the purpose of cooling was only a matter of time.
Air conditioners, fridges, freezers and all similar devices work on the same principle called pressure-temperature law (AKA gay-lussac’s law).
The pressure-temperature law states that when the pressure of a gas increases, it’s temperature increases too (and vice versa).
The basic idea is that you have a loop with gas inside of it. The other side of the loop is inside a barrier (like inside a fridge) and the other side of the loop is outside the barrier. In the part of the loop which is outside the barrier the gas is compressed making it release heat energy. Therefore you have moved energy from inside to fridge to outside the fridge.
Squeeze gas -> gas gets hotter
Unsqueeze gas -> gas gets colder
Air conditioners squeeze a gas, freon, outside your house. The freon gets hot, but the surrounding air cools it down. Then the A/C pumps the freon inside your house and unsqueezes it. Now the freon is cold, and it cools down the air inside your house. Then the freon is pumped back outside and the whole thing starts over.
If you squeeze air into a tiny little space, a tiny tank, the air heats up. You’re probably thinking that’s the opposite of what you want to do. But let’s take that tank of very hot gas outside. The tank of air is hotter than the air outside, so the tank cools down to be the same temperature as the outside air.
Now we bring the tank back inside. It’s still warmer than we want it. In fact it is still as warm as the outside air. But it’s cooler than it was when we took it outside.
Now we do the opposite of squeezing it. We let it expand. This causes the air in the tank to cool down. The air in the tank is now cooler than the air in the house.
The air in the house causes the tank to warm up some. In doing so, heat energy is transferred from the house to the tank, which causes the house to cool down.
Now we squeeze the tank again and the process starts over.
An air conditioner is a kind of heat pump, which makes heat flow from one place to another just like a water pump. The place you pump heat away from gets colder and the place you pump it to gets hotter.
The most common kind of heat pump uses a refrigerant in a vapor cycle, meaning it pumps a fluid around in a loop between the side where you want to dump heat and the side you want to pull out heat or make cold. To make the fluid flow in the loop you need a fluid pump, so this heat pump has a fluid pump as part of it.
Let’s go around the loop starting at the pump. The pump uses electricity to spin a motor to push the fluid forward through the loop. So at the outlet of the pump the fluid is at higher pressure. The fluid is chosen such that when you increase its pressure with a pump it will also have higher temperature. Some fluids such as water would not increase in temperature much, but a refrigerant like freon does.
So now you have hot high pressure fluid leaving the pump. The pipes it flows through will also be hot, and so if you blow a bunch of air across those pipes some of the gets will go into the air, and you can blow that hot air outside or something. That is heat being pushed out of your heat pump.
Now you have high pressure fluid that is not so hot, maybe medium temperature. Then you put a blockage in the pipe with a little hole in it to restrict the fluid flow and then let the pipe get bigger, which will lower the pressure and temperature of the fluid. Now you blow air over these low pressure low temperature pipes, and the heat will go out of the air into the fluid and make the air colder, and then you blow that out a different place from your gets pump, now that’s the cold side taking in heat.
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