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what is the relationship between cavitation of pumps and pressure of liquid and temperature of liquid? Answered

I want to know the relation of cavitation and liquid pressure and temperature? 

6 Replies

Toga_Dan (author)2017-05-28

"vapor pressure" is a good search term to help understand cavitation.

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Downunder35m (author)2017-05-16

You guys really like answering homework questions it seems ;)

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iceng (author)Downunder35m2017-05-16

Fun to respond with each other when the OP is hopelessly under-educated about a subject.. Throwing high enough detail facts makes the the student either give up or learn something new.. Both are reasonable results in my way of thinking..

BTW I did learn cavitation is reduced as pressure increases..

And it does feel good to take a jab at stupid US politicians and Jap spies..

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Jack A Lopez (author)2017-05-14

Intuitively, I would expect cavitation, like near a propeller blade in water, to become more active, as the temperature of the water is increased, or as the pressure of the water is decreased.

I mean, if I look at the phase diagram for water,


and assuming I start in a point, in P-T space, somewhere the area that represents liquid water, from there a increase in temperature or a decrease in pressure will move the point closer to the line that separates liquid from vapor.

I guess what I am saying is, the distance from that line is sort of like a measure of how much energy is needed to go from liquid to vapor.

Based on that logic, I would guess that in water at 0 C, and 1000 atm, cold and at really high pressure, it would be difficult to make cavitation happen. In contrast, for water at 90 C and 1 atm, water that is almost boiling anyway, I would expect it would be easy to make cavitation happen.

Also I asked Google(r) to search for, "cavitation submarine screws temperature pressure", and one of the links I found, a Google Books look into a book titled, Military Technologies of the World [2 volumes], by T.W. Lee, has some words that seem to confirm this guess. Here's the quote, from the bottom of page 343:

"However, one way to suppress the cavitation noise is to operate at deeper depths, and therefore higher pressure, in which case the cavitation (boiling) temperature would be higher than the seawater temperature."

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iceng (author)2017-05-14

Cavitation is lost mechanical energy in impeller style pumps...

Tell your teacher that pressurizing a liquid will raise the liquid temperature and the lost cavitation energy does also heat the liquid..

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iceng (author)iceng2017-05-14

BTW cavitation is a very extensive https://en.wikipedia.org/wiki/Cavitation Science especially in Military submarines called the Silent Service. Propeller cavitation makes an underwater noise that enemy subs can detect and send a torpedo after you.

I have unpublished knowledge, about long ago the USA developing a very special propeller shape that did not cavitate.. But more then that, American engineers developed a one-of-a-kind of lathe that could machine the very special non-cavitating propellers.

Now, for some bizarre political reason, they the US turned this one-of-a-kind lathe over to a Japanese unamed company to manufacture the propellers for the US military submarines.

This unamed company reverse engineered the lathe and sold it to the Russians during the cold war times !

And that's a cavitation story about fleeting military secrets..

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