Thursday, January 25, 2007

Water in Zero Gravity

In my apartment the heating is in the ceiling. Not a joke. I've wondered where the guy grew up who had this ingenious idea, had he never heard that hot air rises? But NASA has provided me with a hint regarding this question.

This morning, I was staring at the tea water, waiting for it to boil. Did it ever occur to you that the rising heated water is necessary to get the temperature homogeneously distributed? But what if the hotter water with smaller density does not rise? Say, because there's no gravity?

Well, it stays where it is. And here's how boiling looks like in zero gravity: The heated water stays close to heater. Regions further away from the heater stay cooler, so the actually heated part boils earlier. Once it begins to boil, the vapor bubbles don't rise, but join each other due to surface tension. Eventually, one large bubble forms, that clings to the heater. Cool, eh? I mean, hot. It looks like this




Also: Don't miss a demonstration how to eat tea with chopsticks, a truly essential piece of research.

Now I'm convinced the guy who constructed my heating came somewhere from outer space. That's just how things are up there, why bother. All I have to do is sleep on the ceiling.


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20 comments:

Rae Ann said...

Actually, heat in the ceiling used to be pretty common in the US back in the forties and fifties and maybe later. Our first house was built in around 1949 and had "Ceil Heat" that had been disconnected by some previous owners. Most people soon realized how inefficient Ceil Heat was and had those systems replaced. Is your apartment old? I haven't seen a working Ceil Heat system since I was a child.

Bee said...

Hi Rae Ann,

I've never heard of ceil heat before I moved here. The apartment where I grew up had the heating in the floor, which was really nice for us kids. I'm not sure but the building I live in isn't really that old, I'd guess it was built some time in the late 70ies or so (judging on windows, doors, bathroom, ventilation, etc). Anyway, the landlord pays heating, water, electricity... so most of the people here just have the heating running for those who live above them... I'm also happy to report that the guy living below usually comes home earlier than I do. Best,

B.

Arun said...

Install a ceiling fan.

Bee said...

it's kinda hard to get something screwed to the ceiling, seems there's resistance close below the surface...

Cynthia said...

Without meaning to sound too morbid, this film clip demonstrating a puff of air being injected into a water sphere grossly reminds me of seeing a coup-contrecoup head injury.;( Needless to say, it ain't a pretty sight.

By the way, arun, very good advise!

Best,
Cynthia

stefan said...

Wow,

these movies are really amazing!

I especially like the youtube one with these three experiments inside the big water bubble. There are so many phenomena it makes you think of...

First order phase transitions are fascinating ;-)

Thank you, Bee :-)

stefan

Rae Ann said...

Hi Bee, yeah, heat in the floors is really nice. One of my college dorms had that. I meant to comment about how cool the zero gravity water is, but my computer froze up. Do you get any deep insights about how the water acts in zero gravity? Or is all of that pretty much basic knowledge (that I'm lacking)? I guess I'd like to imagine that the Universe as a whole might look like that if you could see it from the 'outside'. Well, it's just really cool anyway! :-)

Bee said...

Hi Rae Ann,

Do you get any deep insights about how the water acts in zero gravity?

Ah, well, I don't. But I guess zero gravity allows to make some studies more precisely by excluding additional gravitational contributions. E.g. the surface tension of the water bubbles is far more obvious. I'm not sure though if water is such an exciting thing to study, but I bet they had fun the experiments :-) Best,

B.

CarlBrannen said...

Radiant heating systems are traditionally installed in the ceilings. The heat gets to you by thermal radiation (photons). They are as efficient as any other electric heating system, and are considered quite comfortable. They are supposed to allow you to keep your air temperature lower than you other wise would. The feeling is said to be like being in the sun on a cold day.

stefan said...

Dear Rea Ann,


Do you get any deep insights about how the water acts in zero gravity?

Let me just expand on Bee's comment :-)

I would say its not so much about water as such that you can learn something in these experiments, but about the generic behaviour of fluids with a surface tension. And because gravity is switched off, you see just all kinds of funny effects caused by surface tension, which bounds the blobs of fluid in the nice spherical form, and is responsible for all the wonderful vibrations that you can see going on.

So, in my opinion, these movies have an enormous pedagogical value.

For example, take these surface waves running over the sphere following an impact which are focussed at the opposite, antipodal point: Such things have been discussed for large meteor impacts on Mercury and the Moon.

Or look at the free vibrations and the wobbeling of the sphere: I guess that's a nuclear physicist's dream, since the nucleus is, to a very good approximation, a drop of nuclear matter, and the first understanding of nuclear fission was that this drop is vibrating so strongly as to split...

Then, if you have surface tension, as in water, boiling always involves the formation of bubbles, which have to grow an coalesce. That's a completely generic feature of any so-called first-order phase transition. It is not even restricted to phase transitions between liquids and gas.

For example, the quark-gluon pahse transition in the early universe was for a long time thought to be of first odrder, which means that hadrons from in bubbles, which were thought of as candidates for the seeds of structure fornation in the universe. This is now known to be wrong (the transition is not first-order), but nevertheless, there are many other cases were you have to do with such transitions, and not only in condensed matter physics.

In all these examples, the vapor/water bubbles can help you to gain lots of intuition about what kinds of effects can happen...

That's why I am so excited about the movie ;-) But I have also to admit that I see Bessel functions on a cup of coffee ;-)

Best, stefan

Bee said...

Dear Stefan,

yeah, I thought vaguely along the same lines. A drawback I see is the location of the heater, and the fixed volume so you don't actually complete the phase transition. Wouldn't it be nicer to make some of these experiments we were shown in Thermodynamics were the phase transition is caused by volume expansion/compression or so? I mean, I'd think one would see the bubbles of vapor homogeneously appearing, joining each other, growing, until one has bubbles of water in vapor instead of vapor in water.

But yeah, the videos are cool, I esp. like the Alka Seltzer :-)
Best,

B.

QUASAR9 said...

Hi Bee, Awesome video
Did I miss how they keep the bubble of water that large - and prevent it dividing into smaller bubbles

PS - We do have bubbles of water in vapour - clouds
When the droplets grow, it rains!

QUASAR9 said...

PPS - What do you think of the US Military Active Denial System

Supposed to fire a pulse that boils the water under your skin - thus encouraging crowds (or was it clouds) to disperse - lol!

Bee said...

Dear Quasar,

Did I miss how they keep the bubble of water that large - and prevent it dividing into smaller bubbles

One large bubble is the configuration with the smallest surface. If you'd divide it into smaller bubbles the surface grows, and it's no longer energetically optimal. That is why the bubbles join to form a large one. I would think in the movie they haven't turned off the heater, so the bubble just stays how it is (I assume the volume is fixed, i.e. it's a closed pot or something). Best,

B.

Bee said...

PPS - What do you think of the US Military Active Denial System Supposed to fire a pulse that boils the water under your skin - thus encouraging crowds (or was it clouds) to disperse - lol!

I like the word 'active denial system' (AdS?) Is that somewhere encoded in the DNA?

Plato said...

I like the idea working with no gravity.

I created a link to "this post" as well as point toward this one here

What Stefan said "about intuiting" is like "setting the stage" for what works in the "gravity free environment." Yes "condense matter physics", but as to the "geometric inclinations of bubbles" is a very nice way to study cosmological events unfolding?

That has always been my contention in terms of sonoluminence and studing "this effect" in relation to blackholes. I do not know if that is right or not? But "bubble technologies" in terms of geometrodynamics seem appealing do they not?

AS to the type of heat. My son install a "radiant heat in concrete" which is a very pleasing heat compared to "forced air heating systems."

Plato said...

And if I may, one might call it "Stretching the Brain?":)

Yes, under a "guiding hand" this thinking can be most defintiely be wrong, so of course I rely on the experts "to criticize" so as not to lead anyone astray.

Thanks

Bee said...

Hi Plato,

regarding brain stretching, see also :-) Best,

B.

Rae Ann said...

Stephan and Bee, thanks for answering my question! That's funny about the waves in the coffee cup because I see them too, but just didn't know what they were called. ;-) And, yeah, the surface tension of water always kind of amazes me and seeing it in no gravity is so cool.

iamvisheshur said...

nice video!
and i have had a similar experience too(well i think) when i on the window AC and the celing fan together the room kinda reamins at same temperature ....The cool air stays down but when it becomes warm it moves towards the fan which kinda beats it up...(or maybe im entirely wrong)