On Sun, 8 Oct 2006 11:02:12 -0500 David Gersic wrote:
> Ok, so high school chemistry class was a long time ago, but from
> what I remember it works like this:
>
> Solids, especially metals, expand and contract slightly with
> changes in temperature. Not very much, but enough that you can
<snip>
> Liquids boil, but otherwise don't change much.
Liquids do expand and contract, and from what i have found, more
so than solids. I don't have my books here (they are at work), so
after some googling i found this pdf:
http://www.google.com/url?sa=t&ct=res&cd=82&url=http%3A%2F%2Fsaxonhomeschool.harcourtachieve.com%2FHA%2Fcorrelations%2Fpdf%2Fp%2Fph_lesson_060.pdf&ei=r3gqRdLfEoH6hAOn4ejVCg&sig=__UhuVBXscwpI4PKTAs9tCO4vT5GU=&sig2=pOHzwGUdHbdgF1Nb4WvI2g#search=%22water%20coefficient%20of%20thermal%20expansion%22
or
>From the table (for example) aluminum has a volume expansion
coefficient of 7.2e-5 and glycerin has 4.85e-4.
> If they did, then
> we'd have trouble with hydraulic systems like brakes applying
> themselves as the fluid warmed up.
The brake fluid problem doesn't happen for the same reason that the
brakes let off when you take your foot off: the fluid flows back
into the reservoir.
> The cooling system shows this. You have a pressure cap set for
> 15psi or so. This raises the pressure on the system as the
> coolent heats up and tries to boil. With the higher pressure, the
> boiling point is increased, allowing the temperature to rise even
> higher before the solution can boil. Eventually the rise in
> temperature generates enough pressure to overcome the cap and
> does allow the solution to boil, which pushes some of the mixture
> out in to the puke tank and relieves the rise in pressure.
It's not (primarily) boiling that causes this, it's just the
expansion of the coolant.
Eric
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