why does the air conditioner cold feel so different from “normal” cold?


why does the air conditioner cold feel so different from “normal” cold?

In: Chemistry

Air conditioners also remove humidity from the air. That dry crisp air from the air conditioner feels very different than the more humid cold air outside.

Air conditioners work both to keep sensible heat (temperature) and latent heat (humidity) in check, ideally at the same time. Thermostats are typically controlled only by temperature, so if the humidity is high, a dehumidifier can help and if the humidity is low, a humidifier can help. Generally, the comfort range is a relative humidity between 40-60%. If your AC is maintaining the space within this range, as well as maintaining temperature, you are most likely comfortable.

There is also the factor of air movement that helps give a persecution of added cooling. If you are in an area of a space where you can feel air movement, you are more likely to be cold. This is due to a couple factors. First, the air coming from your AC is generally pretty cold, most likely between 50-60 degrees. It has to be cold to get the air below the dew point temperature to get the moisture out of the air (same concept as condensation on a glass or rain). Unless the air is reheated before being delivered to the space you are in, the air you feel coming out of a diffuser/grille will be approximately the same temperature as the air leaving the AC unit. Second, the act of air moving over your skin has a cooling effect (same way fans help make a space seem cooler). The moving air helps to dissipate heat and evaporate sweat, adding to the cooling effect.

You don’t mention what you consider “normal” cold, but assuming you mean the cold outdoors in the winter, this air is typically very dry and you can have effects from wind that would make it seem colder (wind chill factor)

because it is VERY DRY.

AC units also de-humidify (this is useful to know in your car, when you turn the heater on in the rainy winter, turn AC on at same time and it will dehumidify a bit as well.)


edit 2: there is another effect sometimes at play: Ozone. some modern AC units have intentionally added the effect of some modern air cleaning devices (often sold as “air purifiers”) which have a nasty side effect of creating OZONE in small amounts. this ozone actually has a TASTE to it (a kinda sweet chemical taste) which you can taste in the air in places with air purifiers running. that can effect the “feel” of the atmosphere as well. (i personally HATE it. i wont use purifiers) also that ozone is technically harmful. i honestly suggest not using those air purifiers. and it is also possible that older AC units unfortunately create ozone through similar processes. i suggest you google “how do air purifiers work” and “air purifier ozone” to learn more.



edit 1: getting a lot of questions so to explain how it works:

oil (called ‘refrigerant’) in a sealed system of tubes (the A/C system) is compressed mechanically by a pump. the act of compressing the oil (and passing it through a condenser core/radiator) pushes heat out of the oil, ~~making the oil very cold and compressed~~. (edit: its actually compressed to ambient temperature, not cold).

the oil is then passed through a radiator that is positioned inside your house / cabin of vehicle, where it also decompresses. (the interior volume of the tubes it is traveling through is increased / expanded, which allows the refrigerant to expand / de-compress)

the act of decompressing absorbs heat from the radiator (fins attached to the tubes) as it passes through. a small fan blows air from inside your room/cabin through that radiator, which absorbs heat from the air (cooling the air, heating the radiator, where the oil passing through takes the heat out of the radiator, into the oil).

the oil then passes to the outside of the building / vehicle cabin, where it is compressed and passed through a second radiator (condenser unit) that has a fan blowing outside air through it to remove the heat from the oil / condenser.

the heat is blown into the outside air, thus the outside half of the AC unit has to be outside of the room you want to cool, so that heat from the room can be released outside.

the fan on the outside of the unit is stronger and louder than the small fan on the inside of the unit. thats why ac units are loud outside, but not so loud on the inside, because the interior fan is pretty weak. (the mechanical pump is also situated on the outside, and also makes noise.)

the air that is already inside the room is the same air that comes out of the AC unit (the unit does not create NEW air, nor does it filter clean “outside” air to the inside as it is running except in some very rare large industrial applications (sometimes also in central air!))

the cold radiator that it passes through, being colder than the interior air passing through it, causes moisture from the warmer air to collect on the surface of the much colder radiator (that is called “condensation”. and it does not require the air to be at 100% humidity to happen. a cold beer sitting outside on a hot dry day will still get condensation on its surface. that moisture is coming from the outside air, not inside the can. even if the outside air is only 5% humidity, this still happens.)

the liquid condensation on an AC core then drips to a collector tray positioned outside where it evaporates over time. if the unit is run for a long time, it will drip on the outside because the liquid has no where else to go (the collector tray over-fills / overflows). this is normal and not a hazard. the water that drips is also clean, other than any mildew/mold/bacteria that might be in the tray.

dripping from an AC unit is NOT “FREON” (which is sometimes the oil used inside some AC units, though not that often anymore) though I would not suggest drinking it or allowing animals to drink it either. let it drip on the ground, dont collect it. (yes i have seen people keep bowls under their ac unit to collect the drips, and they let their dogs and cats drink from it. it MIGHT be safe, but i strongly advise against it JUST IN CASE. you would consider this water to be: “Distilled water” and if you google: “should i drink distilled water” you will understand more.)

in a vehicle, the interior cold ac core (radiator) under your glove box is SEPARATE from your Heater Core (another radiator under your glovebox) which itself gets coolant from your engine (very hot) passed through it IF you set your temperature high enough on your control unit.

most cars have a “A/C” button that is separate from the temperature control, and if you turn on the AC button while also turning the temperature dial to hot, BOTH the AC AND the heater core will be functioning and have air passing through them.

the heater core is a lot more effective at adding heat to the air than the AC core is at removing it. thus if you have both units on, the air WILL be hot.

however, since the AC core is so cold (the surface of it) the moisture in the air inside your cabin will condensate on the surface of the ac core even if the air is hot. just like a can of beer outside on a hot day still collects condensation even though the air is hot.

thus dehumidifying your hot air.

if your car doesnt have a separate AC button, MOST likely the manufacturer has already set up the system to automatically turn on the AC unit when the heater is on, though on many cars this may only happen when you use the DEFROSTER setting.

you may be able to verify when your ac unit turns on with the defroster by inspecting the pump from the engine compartment (its almost always driven by a belt on the front of the engine), you may also be able to tell the AC is on because the car will need to idle at a higher RPM to compensate from the increased power draw from the engine/alternator especially if you have electric cooling/radiator fans like basically all modern cars do now, since they will draw more power from the alternator.

in a lot of cases, your radiator fans may not even turn on when you are at idle and do not have the AC on, because the water pump alone is capable of controlling the temperature. but if you turn on the AC unit, the radiator fans may turn on as well, because many AC units dissipate the heat from the AC back into the engine block / engine oil / engine coolant, so the coolant temp will rise and the water pump wont be enough, so the fans will turn on.

did i miss anything?

edit 3: it is more accurate to say “Refrigerant” instead of “oil” in the system

(also i just learned, the modern refrigerant (replacement for Freon) is called PURON. an interesting article about it: [https://www.ac-heatingconnect.com/homeowners/whats-the-difference-between-r-22-and-r-410a/](https://www.ac-heatingconnect.com/homeowners/whats-the-difference-between-r-22-and-r-410a/) )

edit 4: some people have pointed out that actually the refrigerant at its most compressed state is in fact at ambient temperature (not very cold itself). the cooling effect (absorbing heat from the radiator as it expands) is only occurring from the expansion process itself. there is no transfer of heat from just the latent temperature of the refrigerant before expansion.

also, the refrigerant compression is taking place on the gaseous portion of the refrigerant mixture specifically

thank you for helping me explain this fellow nerds 😀


Also in an air conditioning environment you are inside, away from the sun’s infrared rays, which even on a cloudy day, will warm you