The Pursuit of Efficiency and the Science of Steam

https://technicshistory.com/2023/11/30/the-pursuit-of-efficiency-and-the-science-of-steam/

by cfmcdonald • 3 years ago

43 6 3 years ago

leetrout• 3 years ago

Pasting a comment from yesterday. The linked video talks about how the double cylinder engine works and shows an up-close of the valves at around the 48 min mark.

If you enjoy videos, Proper People did a fantastic video about a 115 year old steam engine that still works that used to pump water for a city in Massachusetts. Great watch full of info and some beautiful shots. https://youtu.be/nBImv1mlcMg?si=XUyME3AmDB30sKaj

__MatrixMan__• 3 years ago

My grandfather was apparently known quite widely as "Mr. Horsepower". He would go around to people's farms with his 25 horsepower steam engine and win tug-of-war competitions against 100 horsepower combustion engines. He'd then give lectures on why this was possible.

The crux of the matter is that horsepower is an instantaneous measure. There's a sweet spot just after the combustion where a 100 hp engine is indeed producing 100 hp, but it doesn't last for very long. Steam engines generate power more evenly (more area under the curve) so ones that are rated for less power may in fact be capable of more work.

There wasn't much about him for an eight year old to appreciate, but every time I see an article on steam power I end up wishing he'd have lived longer so I could've known him as an adult.

jmatthews• 3 years ago

The creation of the steam turbine is also fascinating.

It's a testament to engineering that hot air engines are remotely competitive when so many of the physics line up for steam.(phase change, heat capacity, heat conductivity)

The limiting factor as always is heat transfer between the heat source and the medium. If we had better heat exchangers, the theoretical maximum of steam is still the best.

archgoon• 3 years ago

Woolf led himself astray with an entirely unsound theoretical model for the inner workings of his engine: he believed that steam at twenty pounds per square inch (psi) would expand to twenty times its volume before equaling the pressure of the atmosphere, steam at thirty psi would expand thirty times, and so on ad infinitum.

This seems to to exaggerate the incorrectness of Woolfs model. Assuming that the temperature is held constant (which apparently was stipulated in Woolf's patent) this is true according to the ideal gas law.

It is not clear where Woolf's model breaks down, but this part seems reasonable.

It is possible that the temperature was not held constant in his device, and, working off of the caloric theory of heat, assumed that the issue was leakage of either the original steam gas or of the caloric. In a sense, losing heat (caloric) would be to Woolf's model the same thing as having a leak.

cfmcdonald• 3 years ago

Well, the pressure of the atmosphere is not 1 psi, it's ~15psi.

So under the ideal gas law, a gas falling from 20 psi to 15 would expand about 20/15 = 1.33x its original volume, not 20 times. Likewise it would expand about 2x when falling from 30 to 15, not 30x.

imoverclocked• 3 years ago

A fantastic read and a solid reminder to listen for quiet voices that may be hinting at better ideas.

The Pursuit of Efficiency and the Science of Steam

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