2743: Hand Dryers

2023-02-27T21:34:45Z

Cser: Corrected date reference to sound barrier being broken. Y'all were making Chuck Yeager cry big manly tears.

{{comic
| number = 2743
| date = February 27, 2023
| title = Hand Dryers
| image = hand_dryers_2x.png
| imagesize = 618x309px
| noexpand = true
| titletext = I know hand dryers have their problems, but I think for fun we should keep egging Dyson on and see if we can get them to make one where the airflow breaks the speed of sound.
}}

==Explanation==
{{incomplete|Created by a DYSON ENGINEER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
A {{w|hand dryer}} is an electrical device which usually uses hot air to dry the user's hands after they have just washed them. In the 30 or so seconds it takes for user's hands to be dried, the user may feel as though the air coming from the hand dryer isn't actually warm, hence seeming like they "take forever to heat up," while in reality the water evaporating from the user's wet hands absorbs heat energy from them (as {{w|evaporation}} is an endothermic process). Thus, the user only ''feels'' that the air from the dryer is not warm, even though it is. Interestingly, this absorption of heat through evaporation is how human {{w|sweat}} has its cooling effect.

Randall has apparently procured a small airplane, accompanied by a banner with a message explaining this phenomenon. He elaborates in the caption that he's spent dozens of years feeling angered with the engineers of these hand dryers, as he was under the comic's erroneous impression that the air from the dryers was not actually warm. In a presumable act of justice for hand dryer engineers everywhere, he now considers it his personal mission to explain to the public why this is actually a misconception. And indeed, it seems to be working - a person on the ground has already been enlightened by Randall.

In the title text, the {{w|speed of sound}} is (obviously) the speed of a sound wave in a given medium, usually air. Breaking the {{w|sound barrier}} is often touted as a significant achievement for powered aircraft (though this was first achieved many decades ago, in the 1940s). Here, Randall thinks it would be a good idea to try and get the {{w|Dyson (company)|Dyson company}} (a technology company known for its hand dryers) to design a hand dryer whose airflow would break this sound barrier. This would probably not be possible to achieve with such a relatively small device as a hand dryer, nor would such a hand dryer really be practically useful, given that air currents faster than the speed of sound would probably injure the hands of the dryer's users, among other things{{citation needed}}.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[An airplane tows a banner. In the distance, there are three small clouds and three birds]

:[On the banner is written:] It seems like hand dryers take forever to heat up, but that's because the evaporation cools your skin, so the hot air feels cold until the water is gone.

:Voice coming from the bottom of the panel: Ohhh!

:[Caption below the panel:] I spent decades mistakenly annoyed at hand dryer engineers, so now I'm on a mission to save others from the same fate.

{{comic discussion}}

Talk:2743: Hand Dryers

2023-02-27T21:29:41Z

Cser: Please correct date of sound barrier reference

The mouseover text is trolling, since that would be impossible. [[Special:Contributions/172.70.200.140|172.70.200.140]] 16:23, 27 February 2023 (UTC)

The Pratt & Whitney J58 is capable of producing exhaust velocities exceeding that of Mach 2 at ground level. It would be possible (though extremely inadvisable) to dry one's hands in the exhaust, at least for the brief period where one still has hands. [[Special:Contributions/172.70.115.72|172.70.115.72]] 16:44, 27 February 2023 (UTC) J. Kupec

With a low enough vacuum in the surrounding area, a supersonic hand dryer should be able to apply drying without enough energy dissipation to damage the skin. [[Special:Contributions/172.69.65.184|172.69.65.184]] 17:27, 27 February 2023 (UTC)

As far as I understand it, the low velocity dryers heat the air, the high velocity ones don't, but rely on the air being compressed and air speed is of the essence. The other problem with the idea of very high speed is that 'stuff' could penetrate the skin (there is a type of needle-less vaccination gun on that principle).[[User:RIIW - Ponder it|RIIW - Ponder it]] ([[User talk:RIIW - Ponder it|talk]]) 19:31, 27 February 2023 (UTC)

That matches my memory, the first ones I remember were fairly low airspeed and had a data tag "1500 watts" for the heating element. Has anyone tried one of these with *dry* hands, to see how long the element takes to get hot? I don't think they heat up instantly. They certainly get hot--motorcycling on cold days I've pointed the nozzle inside my clothing to warm up at a rest stop.[[Special:Contributions/172.70.111.76|172.70.111.76]] 19:40, 27 February 2023 (UTC)

I don't think this effect fully explains observations. For example, the airflow feels warmer sooner when someone has used the dryer just before you. [[User:P1h3r1e3d13|P1h3r1e3d13]] ([[User talk:P1h3r1e3d13|talk]]) 21:10, 27 February 2023 (UTC)

"though this was first achieved many decades ago, in the 1950s" Yeager broke the sound barrier in level flight on Oct. 14, 1947, and planes had been doing it in dives for years. [[User:Cser|Cser]] ([[User talk:Cser|talk]]) 21:29, 27 February 2023 (UTC)

explain xkcd - User contributions [en]

2743: Hand Dryers

Talk:2743: Hand Dryers