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Originally posted by bigben2k
Interesting.
Since you brought up fittings, maybe you can answer something that's been bugging me for the longest time:
We all know that a 90 deg elbow is very restrictive. What we end up doing, as much as possible, is taking the 90 degree bend over a larger radius, by bending a tube.
My question: how much of a benefit is this, really?
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I can't find any numbers on that, despite checking three of my texts. Sorry. The best I can tell you is that Perry's Chemical Engineers Handbook says it is "significant."
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I mean, the mass of water will still be re-directed 90 degrees, so the same amount of work is applied. I do understand that because of the sharp bend, the flow will tend to "keep going straight", which is restrictive, but isn't the same being done over a much larger radius?
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I *think* the issue is that the fitting serves to convert some of the fluid's energy into creating a radial angular acceleration. The force required to change the fluid's direction would be equal to the velocity of the fluid squared over the radius of the bend. I *believe* that that would be integrated over the angle of 90 degrees, so the work would be less when the radius is larger.
Just a guess, though.
Alchemy