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!
These work so long as the air around them is not humid already
Swamp cooler, they do work, but raise the humidity, which might cause increased mold growth
It’s been crazy hot and humid this past month where I live. This thing would kill me
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’s not really like that. As long as you have a limitless supply of dry air, and a limitless supply of water, it will work indefinitely. If you seal the room, you will eventually hit 100% humidity. If you run out of water, well that’s the end of that. But if you don’t, then you will get cooling that is the result of water phase changing from a liquid to a gas. With a small unit you won’t cool a room, but it will feel nice blowing on you, and it will be cooler than a fan. How much cooler I can’t say. I wouldn’t personally bother with a small unit like this.
OP, where do you live? What is the surrent relative humidity of your house? The lower it is the more likely this thing is to work. It is a legitimate technology but they only work well in dryer places. A dry heat is perfect for this.
These are often called swamp coolers.
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.
That may have been my intro video to him. Can’t go wrong with any topic, no matter how trivial it may sound. You will come back afterwards saying, wow, never knew that.
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
It’s cheaper to make a shitty time based solution.
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.
I have a swamp cooler going right now on my roof. It works just as good as AC but at a lower energy/money cost.
Technology Connections has a video on exactly these devices that dives into how they work and what they can and can’t do. TLDW; you’re not wrong about the physics of cooling a room, though in some cases this little thing might make you feel a bit cooler.
Here is an alternative Piped link(s): https://piped.video/watch?v=2horH-IeurA&pp=ygUddGVjaG5vbG9neSBjb25uZWN0aW9ucyBjb29sZXI
Piped is a privacy-respecting open-source alternative frontend to YouTube.
I’m open-source, check me out at GitHub.
I was about to share this! Always glad to see Alec get recognition!
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.
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.)
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.
You sound persnickety. You’ll probably like this persnickety video about swamp coolers
Simplest physics: it takes energy to evaporate water (phase change) and that drops temp and raises humidity.
But a desktop EVAP cooler is a joke, it’s too small (not enough water evaporated) to affect the temperature of even a small room.
Swamp coolers (evaporative coolers) work great under specific conditions, such as deserts where it’s hot AND dry (lots of ability to evaporate)
Whatever you do don’t read Wikipedia:
https://en.wikipedia.org/wiki/Evaporative_cooler?wprov=sfla1
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.
