Personal "air conditioners" - a borderline scam

I had actual HVAC classes that didn't explain phase change cooling as well as you did!

Leo

All that just to explain a body of still water! Nice job Alec! PS: read the message I sent you, earth shattering revelation for you.

Joe Kudrna

Why do Americans always assume all their viewers are Americans? "Degrees Fahrenheit", "PSI". I can't understand shit.

BoostCookie

Because California, most can air dusters contain a bitterant. One of the latest ones being used seems to be oil based and extremely potent. When the propellant is expelled in the liquid form, that appears to bring more of the bitterant with it and it gets on surfaces readily. If you keep getting an extremely foul taste at random, wash the desk with dish soap, ipa might also work.

Kadah

Great video. I had sort of “worried” that once I already knew a lot of the things that could be covered in brief YouTube videos that I wouldn’t enjoy the channel anymore. But while this essentially was a review of thermo and heat transfer, I still thoroughly enjoyed it due to your presentation and was reminded that it’s not necessarily about learning new stuff, but celebrating technology and engineering and being reminded of all the cool stuff that makes our world the way it is. Glad to be a patron!

This video was pretty great but I think it undersold (though technically covered) one detail about why a "central" swamp cooler works better than these units all other things being equal. A central swamp cooler on a house works better because it sucks the dry air from outside, humidifies it and pushes that cooler air inside the house and out the windows. There's so much air outside that the air going back into the cooler still has roughly the same humidity as before - constantly replacing the air in the house with the air that was dry then humidified. These devices that sit inside the room don't have that cycle so after a while the entire room saturates in humidity and they stop working with no mechanism to fix that. There are big portable swamp coolers the size of half a fridge that have the same problem (though it can help a little if you place it next to a window) - as a kid I once shut the door on our lounge with one running and there was water dripping off the walls ;) Having said that, I wonder how long it would take for this unit to actually saturate a room, maybe that's basically not easily possible? Would have to run the calcs I guess. (Central swamp coolers are somewhat popular in Australia although less so over time)

Trent Lloyd

They make your wallet more aerodynamic.

nobody

Awesome segment! As a bonus, I now finally understand the reasoning behind those misting fans. I always thought it was just to wet your skin and have the cooling evaporation happen there. Would love to hear your thoughts on stand alone dehumidifiers. The kind you empty a container of water out of after running it all day. Worth it?

Buckaroo Bunny Slippers

First off, what a great video explaining and demonstrating the refrigieration process. I bought one of these swamp coolers, similar to what you have pictured. It proved itself, but in specific conditions. It cost me AUD$15, I was an outdoor worker, this part of Melbourne had very clean tap water, 40+ degree heat and 20-30% humidity. My unit had two 18650's (tested at a paltry 1100mAh, replaced with two LG 3500mAh cells for about 5 hours runtime (it had a built-in boost converter). I also replaced the horrible included fan with one from. . . a dead portable air compressor based fridge ironically. I'm from NZ, a typically very humid (but usually comfortably cool) place. In Melbourne and Perth, these "evap" coolers are common (as Eric mentioned) on peoples roofs and also on factories.

Anton

We have a large pillar fan with a misting function. Seems to work fairly well. Obviously still not an AC and never will be.

Chris Crowther

I have a large floor-standing air cooler (not one of those "personal" desktop models) that works on the same principle, but it cycles water through the evaporative membranes with a pump rather than just soaking it like the model in the video. It also has a proper fan inside so if I turn off the pump it doubles as a regular floor fan. It doesn't do much to lower the room temperature, but the air that comes out is fairly cold due to the evaporating ice water, so when pointed directly at me it helps keep cool during heatwaves. So when you know the limitations of your device, and you get a proper one from a reputable brand (not those shiny toys from internet marketers), they can be useful. But the point you make is exactly right: they're not air conditioners. And if you go in expecting an air conditioning unit that runs on water and magic, like the marketing materials of these gimmicky "personal air conditioners" would have you believe, you're bound to be disappointed.

Love the video! I personally found spraying mist directly on my skin (arms/neck/face) to be extremely effective for cooling me down outdoors in hot weather. I'm surprised that people don't use it all the time in summer.

Have you ever looked into a Dry-o-Tron or Dectron? They are large dehumidifiers used for indoor pools. They can dehumidify the air and cool it or they can dehumidify the air and return warm water to the pool as auxiliary heating. https://www.youtube.com/watch?v=rdsafl7cRh0

Jackson Moyer

I took a course in heating and AC repair at our local trade school in 1981-82. On the first day of AC repair lab, the instructor dumped some R12 into a styrofoam cup so we could see the "magic" of a clear liquid boiling at room temperature. He also told us that he thought that all this business of chlorofluorocarbons harming the ozone was a lot of nonsense.

Mark Hesse

Great video man. As for your sense of humor (at 20:25) I find your humor wonderful--on the other hand, almost nobody ever gets my jokes. Take what you will out of that. heheh

Don Eitner

I was raised in a house with evaporative cooling. With a swamp cooler, you actually have to have the windows open in order for the heat exchange to take place. Made the whole house feel fresher. The cooler, on top of the house, had three pads filled with some type of shredded wood. The water pump would pump water to drizzle over the pads to evaporate the water and carry the vapors into the house. We had very hard water and had to completely replace the unit about every three years due to corrosion.

Eric Kalenak

"Terrible refrigerants we used to use" (Coughs in sulphur dioxide)

Avid Stan

Thanks for doing this video - I've always been annoyed by the existence of those personal ac things.

Professor Kroog

I thought of the idea *right before* I shot the talking head otherwise I would have planned to do that very thing! Maybe I'll do it for Connextras

Technology Connections

Would have loved to see you attempt to build your own and compare it with the commercial one!

More air conditioning Content in the middle of July? Yes please.

Steve Streza

I think the problem with silica gel is that it will quickly get saturated with the volume of air passing through. However, I have seen an article about a gas-fired air conditioner that uses liquid desiccant in a similar way, not that I've seen an actual product yet and would still involve installation and an outdoor unit. As air passes through the indoor unit, it first sprays desiccant to dry air, then through a wet membrane to cool the air (evaprative cooling) and another spray of desiccant to dry the cooled air. The saturated desiccant is piped to an outdoor unit where a gas-fired heater heats the desiccant to evaporate the water from the desiccant, which then goes back to the indoor unit to repeat the cycle.

Seán Byrne

This landed within a minute of an ad mail out I received for the device in question... Never heard of them before! Serendipitous coincidence

Paul Sharp

RE the evaporative cooling towers I mentioned earlier. Here's a description before the computer was installed of the physical hardware. This was when the machine was going to be built by IBM. The contract changed (long story) and the machine that was installed was NOT direct liquid-cooled, but the outside cooling towers have indeed been used since 2012 and are still being used. http://www.baltimoreaircoil.com/english/resource-library/file/1469 This wikipedia article has a reasonable summary of the contract change (and also mentions the cooling towers): https://en.wikipedia.org/wiki/Blue_Waters

Craig P Steffen

I agree with you that the teeny tiny desktop swamp coolers are probably little to no use except for places where you'd want humidification anyway. However, I did want to toss a quick chunk of information that might expand evaporative cooler's uses in the real world. The Cray supercomputer called Blue Waters at the University of Illinois at Urbana/Champaign has an evaporative cooling system that runs for the winter months of the year. When the weather is warmer/more humid they use the main chiller plant, but when it's dry/cold, they use the evaporative cooling. The system it's cooling is about 12 MW when running jobs. I'm trying to dig up a good article about it, but I haven't found a good one yet. I'll let you know, if that's something you'd like to add a link to or something.

Craig P Steffen

I saw swamp coolers all the time in hot dry central California. They worked okay turning hot dry air into moist cool air. Now I live in Iowa with its hot moist air, swamp coolers don't work around here

Would it be unfeasible to place a pack of heat-dried silica gel at the inlet of the fan (maybe in a sealable container when not in use) to dry the air and drop the dew point? This of course necessitates periodic disassembly and oven drying of the silica, but I could be talked into it.

That's a pretty good analogy!

Technology Connections

Here's how I think about refrigeration. The refrigerant acts like a sponge that soaks up heat. The compressor squeezes the heat out of it in the condenser coil. When it gets to the evaporator coil it expands and soaks up more heat.

B3

I was interested once when I saw these things, then I thought: I can make that myself with a bowl of water, some rags and a fan...

MrHammond

Fascinating! Where I work we a similar concept of perspiration to cool an entire datacentre without the need for air conditioning. It's possible because the building is right on the shores of a large inlet, but it works extremely well with less energy consumption.

Ian Spence

Can you go into too much detail? Can you go on too many tangents? That would be too ask if a detailed explanation of the multitude of spring washers and their applications is boring. No.

Simon Mikkelsen

Some names came into my mind like Vapour Pressure and Dew Point...

Mauricio Mariano

Ah, I have one of these. I direct selectmen meetings in a small hot room, especially the summer. I got one out of desperation. Does it work? Technically. Especially if I put the filter in the freezer. Do I recommend it? Not at all.

Tim Labonte