Prove me wrong, please?
edit: thanks for all the great comments, this is really helpful. My main take-away is that it does work, but requires dry air. In humid conditions it doesn’t really do anything.
Spouse bought this thing that claims to cool the air by blowing across some moist pads. It’s about as large as a toaster, and it has a small water tank on the side. The water drips onto the bottom of the device, where it is soaked up by a sort of filter. A fan blows air through the filter.
- Spouse insists that the AIR gets cooled by evaporation.
- I say the FILTER gets cooled by evaporation.
- Spouse says the cooled filter then cools the air, so it works.
- I say the evaporation pulls heat (and water) from the filter, so the output is actually air that is both warmer and wetter than the input air. That’s not A/C, that’s a sauna. (Let’s ignore the microscopic amount of heat generated by the cheap Chinese fan.)
By my reckoning, the only way to cool a ROOM is to transport the heat outside. This does not do that.
We can cool OURSELVES by letting a regular fan blow on us = WE are the moist filter, and the evaporation of our sweat cools us. One could argue that the slightly more humid air from this device has a better heat transfer capacity than drier air, but still, it is easier to sweat away heat in dry air than in humid air.
Am I crazy? I welcome your judgment!
That’s a swamp cooler and is very commonly used in dry environments. It will help a lot in Arizona (well, maybe not that tiny thing, but a properly sized one) and not at all in Miami, due to the difference in ambient humidity.
It is a swamp cooler. It works, and works better in drier air, but it is not a heat exchanger. Most of the cooling is gonna be from the moving air.
It’s evaporative cooling. Grew up with them. They’re great. They aren’t A/C. They don’t worm when it too humid.
Great for dry desert geography.
Well, what this thing doe is moisten the air and thereby cooling it. So temperature down, humidity up.
If you live in dry areas, this is good, but if you live in more humid areas, this will only worsen the problem.
Don’t forget to air the rooms regularly (at night, if it is too hot during the day) to get the humidity out again - you don’t want to get over 60% relative humidity for a longer period.
deleted by creator
Why not just try it for a day or two and see if it makes any difference?
Large versions of these are often used in greenhouses for temperature control, so they do in fact work as advertised.
Water is very good at absorbing thermal energy, far better than air. The moist pads are drawing thermal energy out of the air and storing it in the water, reducing the air temperature. Some water eventually evaporates, but in a gaseous state this water still retains the thermal energy it absorbed from the air, causing a noticeable decrease in air temperature, as well as a slight increase in humidity.
Put a very dry cloth in front of the cooler to trap water vapor, every now and again relocate the now damp cloth outside of the room being cooled, and replace it with a fresh dry cloth.
Like others said, this is an evaporative cooler aka swamp cooler. It takes energy to convert liquid water to water vapor. https://en.m.wikipedia.org/wiki/Evaporative_cooler
The issue here is that your wife bought this thinking it’s an ac when it’s an evaporative cooler aka swamp cooler. They do work if you have low humidity. If you are in a humid area this definitely won’t work. Since the unit is small it won’t cool the entire room but she should feel nice and cool about 3 to 5 feet in front of it. She will need to make sure the wicking action is working to get the pads nice and wet, otherwise she will have to manually remove them to wet them.
Edit: I wanted to add that I have had a similar small unit before which is why I know that she needs to be 3 to 5 feet in front of it to hit the little target cool zone.
On point 4, the key part that you are missing is that evaporation /takes/ energy. The standard central air works closer to how you are thinking by the evaporator above your furnace taking heat to then be dumped out by the condenser outside. This is necessary because it is a closed system that must continually reuse the refrigerant.
Sweat, and the swamp cooler you have here, are not closed systems and therefore don’t have to “dump” heat. Energy was transferred to the water molecules to cause them to evaporate. As latent heat exists (Google this if you are still confused) the heat energy has been transferred to “evaporation” energy and so the heat can be reduced without breaking any thermal laws.
Basically the water on your skin or in the swamp cooler is like a wall that heat has to break down. The heat can do this, and does get through but has been reduced by the work and is therefore less strong (lower temperature.
There was no subtraction or addition to total energy when you look at the whole process. Heat energy was transferred to kinetic energy to cause the state change of the water.
Central AC has to dump heat to reuse the refrigerant. The swamp cooler doesn’t have to dump heat but needs to be refilled often as the evaporation of water takes matter away from the system.
My partner and I started hanging up our clothes to dry on a dirt cheap clothes rack. Think we spent like $10~$15 on the whole setup. Anyway, we have it stood up on the hot side of the apartment and have a fan blowing on the wet clothes toward the coach / desk area in the living room. The thermostat says the room is about 5 degrees cooler, but the room feels more like 8 or 10 degrees cooler. Not sure how the physics works on all of this, but those dumb desk coolers sound like the same principle
That is not an air conditioner. An air conditioner needs a compressor, evaporator and condenser, this has none of them. What you have is a desktop evaporative cooler. Your theory of how it works is correct, the energy to evaporate the water is pulled from the air, that cools the air. But yes, the heat and moist air still stays in the room. Note, this only works in places with DRY air. If you are in a tropical location with humidity, this will not work because the air is already close to saturation with water.
There are large rooftop versions of this called swamp coolers, installed in places that have short hot dry summers, they work because the heat is still transported outside the building.
Some massive computer data centers have a giant version of this as a backup system in case the main cooling system goes down.
The one place that i know can use more power than 6000 homes and all of that power turns into heat. Cooling is critical and they need lots of it. They have a giant water tower that they can dump through the chillers if they need to.
I have one similar and it does work, granted the ambient humidity is less than around 50% I live in the desert in northern nevada and we cool our house with a huge one and I have a small desk size one I use in my room. Most of the time our ambient humidity is in the mid teens here so they work rather well.
