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!
I think that the evaporation in theory is able to cool the room, the heat energy is transferred into launching a bunch of water molecules airborne so to speak. Hanging some wet towels around would also do that.
However, the performance of such small devices is probably not sufficient to significantly cool a room, and it has a lot of drawbacks (filter gets mouldy easily, …)
Here’s an excellent video about these swamp coolers: https://youtu.be/2horH-IeurA (he has many videos on heat pumps and stuff)
Aw. I was going to post the link to his video, but you beat me to it.
But yeah, Technology Connections makes some excellent and informative videos. To anyone else who sees this: If heat pumps, refrigeration, or climate control technology aren’t your cup of tea, he also covers older technology based around electromechanical designs (as in, pre-dating microcontrollers and programmable logic) and analog media recording devices.
I mean even if they aren’t your thing you should check out his videos.
I remember watching a 20 or so min video on an antique toaster and since then I’m also pissed at the inferior toasters of today.
His videos are gold.
Can someone please explain why toasters aren’t made like that anymore?? I would happily forgo the led and the obnoxious ding they make to have them make the toast perfectly every time
, and it has a lot of drawbacks (filter gets mouldy easily, …)
The more immediate drawback is after running it for a little bit, you’ll lose the ability to sweat.
Well, you’ll still sweat, it just won’t evaporate due to high humidity.
It’s at best a very short term solution before it starts making it worse
Plus if you have AC then the AC has to dehumidify the air first before it can cool it.
That isn’t how AC’s work. They work by using the fact that a phase change between a liquid and a gas is endothermic. It turns a refrigerant into a gas and that sucks heat from the air in your house and then pumps that gas outside to cool off with your compressor, moving heat outside. (Someone correct me please if I got details wrong). The act of pulling that heat from the air into the phase change cools down air and water condenses out of the air, dehumidifying it. Fun fact AC’s weren’t designed for our comfort, some facrory needed less humid air for their product, us lazy workers cooling down a little is a side effect.
Swamp coolers are a thing. I don’t know about the physics, but they can actually cool a space if the ambient humidity is low.
Using ice water in the gadget you have will improve its performance, obviously.
swamp coolers work through evaporation cooling. the water absorbs some energy from the air as it evaporates. (essentially the water gets hotter, the air gets cooler.)
Too add to that, slot of that energy goes into vaporizing the water, so the average temperature is lower.
it’s not technically a net loss- some of that energy is lost as it escapes the system, but conservation of energy generally means that as the air cools down, the water gets warmer. it’s just that the water has extremely excellent thermal mass, meaning that the air appears to cool much more than the water gains heat. This is especially true if the water itself is cold to begin with. (ie, blowing it over ice cubes.)
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’s not AC, it’s called a “Swamp Cooler”, and yeah, it will work for a limited time, to a small degree, especially in dry conditions.
It’s like setting up a fan to blow across a block of ice, yeah, it works until the ice melts.
https://www.nytimes.com/wirecutter/blog/do-swamp-coolers-work/
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.
