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Posted by HeatPro on November 30, 2007 at 10:18:01:

In Reply to: CURIOUS QUESTIONS posted by pete on November 30, 2007 at 09:10:19:

Why would you need the baffles in there for?
++ The baffles make the hot gases reach the heat exchanger surfaces instead of 'tunneling' through the hole in the center more than the outsides. There are fancy words to describe that in engineering, but that's the idea.

If you raise water pressure you have to heat it hotter to boil. Does that go the other way to?
++ Yes there is the idea of boiling temperature according to pressure. That is a way factories send 500 degree steam out to processes to break fats apart. It is also why there is a pressure relief valve on a residential boiler to keep pressure up to a limit so water won't boil away until the high limit of 240 degrees if there is 15 pounds pressure inside.

If you raise the water pressure would it have to be colder to freeze, or have to be left longer in 30 degree temp to freeze? No, the freezing of water will happen close to 32 degrees so pressure doesn't change its freezing or thawing temperature enough to be considered a factor; the atoms don't change distances due to energy excitement state as much as when turning to steam. To state it simpler, you can't prevent water from freezing any temperature far from 32F by raising its pressure. That's why an outside boiler or tubing will still freeze around 32F although the pressure is 15 psig inside, so people put kinds of alcohol or salts in to change its total structure as antifreeze. Pressure does affect boiling or condensing temperatures much more. Seems the theory of distance of atoms from each other is the main factor, machines can't bother to reach high enough pressures below 1400 psig to squeeze water enough to change that.

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