TITLE: Why are cooling towers at nuclear power plants shaped the way they are?
QUESTION [28 upvotes]: The iconic cooling towers at most nuclear power plants are shaped like hyperboloids. Wikipedia mentions that this is because the wide base promotes thin film evaporation and the narrow point accelerates the laminar flow. Out of all the shapes with a wide base and narrow middle, why are hyperboloids the preferred structure for a cooling tower?
Also, most cooling towers I've seen have the hyperboloid shape extend past the narrowest point by what appears to be roughly the same amount. Is there a reason for this?

REPLY [0 votes]: The hyperboloid form is an economic compromise. This shape is made entirely of straight lines. Imagine a cylinder with maybe 40 I-beams vertical and parallel to one another. Now pick it up, (I forgot to say imagine a small one, just control minus it a few times. Perfect.) and now give the top and bottom circle a 15 degree twist in opposite directions, like you do with your aluminum plant grinder. You have your hyperboloid structure. If you don't like to imagine geometric objects, a handful of pencils or straws on a tabletop will do nicely. Once you see it, you can conclude that it is in fact a very easy shape to build, even on the massive scale of your typical Homer Simpson workplace. anything else is far more expensive to design, validate, and build. "We" built those things to save money, right?
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