BTW, while wondering about the hyperboloid shape of cooling towers

[eub]

(and not running across any strong explanation for why that shape) I happened on the Adziogol lighthouse. "is a graceful vertical lattice hyperboloid structure of steel bars, 70 meters high."



(Now if what you have available is straight steel bar stock, then a ruled surface form must be a great temptation, but surely that's not what motivates nuclear cooling tower builders?)

Comments

[beamjockey.livejournal.com]

I have no insight to offer, but wish to mention Tractricious. It's by Manhattan Project cowboy sculptor Bob Wilson.

[eub.livejournal.com]

It is pretty and hyperboloidal. But I was expecting a tractrix!

hyperboloid cool

[brokengoose.livejournal.com]

I was under the impression that in cooling towers, hot water was pumped up the cooling tower somewhat and then allowed to fall through the air. By surrounding the water drops with air, you maximize the surface area for evaporation and heat exchange.

I could imagine that combining the heat exchanger and chimney makes condensation collection an integral part of the system (kind of like a tagine or doufeu) rather than something separate that has to be dealt with. From there, it's a question of engineering: which "cone with a hole on top" shapes are strongest/cheapest/lowest maintenance?

Re: hyperboloid cool

[eub.livejournal.com]

I'm imagining that you want your sprayed water to fall in free air, instead of hitting the side and trickling down (less heat exchange that way). If that's true, a hyperboloid has "dead space" above and below the slanty wings, and a cylinder of "working space" down the middle. And then I'd wonder wouldn't it take less material to build the cylindrical shell, and hold it up with guy wires if those are needed.

I'm sure there's some compelling reason beyond love of conic sections.

[hattifattener]

Cooling towers are venturis. I think it helps them maintain a draft or something.

[hattifattener]

Though Wikipedia and other sources seem to say that the reason that particular shape is used is for structural reasons— it's a compound curve, so it's strong; it's close to a minimal surface; and being made out of straight beams is probably a win too. The precise profile of a venturi doesn't seem to be terribly important.

[eub.livejournal.com]

Wikipedia mutters about "aids in accelerating the upward convective air flow" but I don't get it.

Oh, their venturi article does mention an hourglass shape to reduce drag (impedance-matching at the ends?), which would make sense.

[georgejas.livejournal.com]

DUDE, this actually came up in architecture lecture today - we had a structural engineer guest lecturing. sounds like the only reason they're hyperboloid is that it's really easy to make a form for the concrete (since you can make it from straight beams), and as hattifattener was saying, it's also a minimal surface, and strong because it's saddle-shaped.

[eub.livejournal.com]

Now I'm curious how the concrete forming goes on a cooling tower -- one ring at a time, from the bottom upwards? Can you arrange it to re-use forms? jinian's dad might know.

(By the bristly rebar edge, the incomplete reactor containment vessel had been mostly built upwards, but had a rectangular window still in the side too.)

[dgr.livejournal.com]

I was also under the impression that nuclear cooling towers in particular were that shape in case of a containment breach, the idea being that the heat would soften the supporting steel and cause the concrete to topple inward (since the center of mass is inside the base) and crush the reactor.

[eub.livejournal.com]

In this setup the reactor is in a containment vessel a few hundred meters away; I guess the water to be cooled is run over in pipes. (I don't know where the electrical-generator part of things is.)