How air conditioners take hot and humid air, and make it drier and cold.
In: 36
**How does an AC make air drier?**
Before the AC blows cold air into your room from vents, ambient air gets blown through a cold *evaporator coil.* Water molecules “stick” to the evap coil through condensation and drips away. Fewer water molecules in the vent air = drier air blown into your house. This effect is the same as condensation forming around a cold glass of water.
**How does an AC make air colder?**
When a liquid boils, it absorbs energy from its environment. This is *evaporative cooling*.
If we exploit this phenomenon, how can we invent a cooling machine?
First, we find a chemical that has the right properties, such as a low boiling point. This is the *refrigerant*.
Then we cycle this refrigerant through a system composed of two parts: the *condenser* and the *evaporator.*
Long story short, the condenser is the outside part of your home split AC system: it’s the loud thing with a huge fan. The boiled refrigerant is cooled (and usually compressed, but let’s keep it simple), turning into a liquid.
The liquid state refrigerant is sent to the evaporator coil (usually in your garage or attic), and the liquid refrigerant boils off, absorbing heat in the air. Refrigerant absorbing heat = colder air, which then gets blown into your room.
Finally, the refrigerant, now in a gaseous state, is sent back to the condenser to repeat the cycle.
—
A few things to note:
1) Think of your AC not as an air cooler, but as a heat mover. The hot air in your house is simply moved outside by exploiting a physical phenomenon.
2) This evaporative cooling effect can be observed in many places. If you have ever used an air compressor, notice how the compressed air usually blows out cooler than ambient. The swamp cooler uses the same principle: cooling by evaporating water via a fan.
1. Compress air
2. Air heats up when you compress it
3. Cool this compressed air back to normal outside temperature
4. Uncompress the air
5. Air now cold
Pump up a bike tire. The valve will get hot. (Feel it). Let the air out. The valve will get cold. Put two valves on the tire, on opposite sides. Pump air in one valve, and let it out the other. The cool side is one part of your air conditioner, the hot side is the other. Yeah, there are a few more details, but that is the basics.
There are two parts to this. How does refrigeration work, and what does refrigeration do.
The refrigeration system moves heat away from the “evaporator” and moves it to the “condenser” using “The Refrigeration Cycle”. I’ll tell you about that some other time buddy.
The evaporator gets cold and water condenses on the outside of it, then the water drains wherever your HVAC system was cleverly designed to send it. The HVAC system pushes air across the evaporator.
There is a clue as to how the mysterious Refrigeration Cycle works. The evaporator causes water to condense on the outside because something else is doing the opposite on the inside of the evaporator.
You know if you hold spary can (like canned air) upside down, the spray is super cold? If you sprayed that inside a tube and blew air over it, it would get so cold frost would form on it and the air would get colder.
Your ac does this. It turns a gas into a liquid , and that gas gets sprayed through a coil that air blows over. The coil shouldn’t freeze but should get so cold that water forms on it like in the outside of a cold glass of water. Water drips away and down a drain, making the air dryer. The air blowing over the coil gets cooler. So you end up with cool and dry air.
Outside your house the ac is basically making the gas back into a liquid again. The box outside is doing 2 big things. It is has a compressor to turn the gas back into liquid, and a fan and coil to remove the heat that compressing the gas to liquid creates. (it’s not a liquid until after the compressor, and after being cooled, but that may be beyond eli5).
Its a closed loop that happens over and over. Compressor makes the liquid by compressing then cooling the gas. Liquid gets sprayed through a small hole turning into gas in a coil inside, gets cold and cools and drys the air, then it goes back outside to get compressed and cooled into a gas all over again.
The compressor makes a gas pretty much at room temperature have much higher pressure. The gas gets hotter because pV = nRT. As p(ressure) goes up, T(emperature) goes up.
Because “=” .
You cool the pressurized gas a bit with a fan.
Then you release the pressurized gas into an unpressurized space. This greatly reduces the temperature because pV = nRT ( see above ) . You capture the cold and use a fan to send it somewhere.
For “drier” , when air with water in it gets colder, the water in it condenses – changes from gas state to a liquid state. It becomes water and gets drained off by gravity. You can experience condensation by putting ice water out in a humid place. Water forms on the outside of the glass, condensed from the air at the edge of the glass.
a series of tubes that squeezes and stretches a special liquid called “refrigerant”
when things get squeezed things get hotter and when stretched things get colder, so a machine (compressor) connected to the tubes constantly squeezes the refrigerant in one section of the tubes (condenser) and stretches the refrigerant in the other section of the tube (evaporator) making one side hot and the other cold
blow hot and humid air over the cold side, water condenses out of the air onto the cold side and the air cools down
Latest Answers