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-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of Bennett
Sent: Wednesday, November 17, 2010 9:38 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Heat transfer lab
I seem to recall that the heat pipes included some sort of wick to
return
the liquid to the hot end.
On Wed, Nov 17, 2010 at 8:54 AM, Michael Edmiston
<edmiston@bluffton.edu>wrote:
I don't differ greatly with what Brian wrote except for some pointsthat
need clarification in my view.used
(1) He used slightly different words from what I usually hear. He
"fluid displacement" and "fan aided convection" and said "convectionto
depends
on buoyancy effects." I think most people use the word "convection"
cover all three processes of diffusion, natural convection, andforced
convection. So I would point out that... (1b) The wordingsconvection").
"displacement"
and "fan-aided convection" are not needed (nor is "pump-aided
We can just used the wording "forced convection." (1a) Buoyancy canbe
involved in natural convection, but not always, and forced convectiondoes
not depend on buoyancy. Incidentally, the Wiki article found undertransfers a
"convection" strikes me as reasonably good.
(2) Heat pipes are more than simple gas-phase displacement. The
evaporation
at the hot end absorbs the "heat of vaporization," and this energy is
released at the cold end as the "heat of condensation." That
lot more energy than simply moving a gas that heats at one end andcools at
the other end (always remaining in the gas phase). Also, theexpansion
fromliquid
liquid to gas at the hot end, and the contraction from gas back to
atcold
the cold end acts as the "pump" that moves the vapor from the hot to
end. I think this would be classified as "natural convection" but itis
much more than buoyancy and diffusion dependent.bucket
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Chair, Division of Natural and Applied Sciences
Bluffton University
1 University Drive
Bluffton, OH 45817
419.358.3270 (office)
edmiston@bluffton.edu
--------------------------------------------------
From: "brian whatcott" <betwys1@sbcglobal.net>
Sent: Wednesday, November 17, 2010 7:54 AM
To: <phys-l@carnot.physics.buffalo.edu>
Subject: Re: [Phys-l] Heat transfer lab
On 11/16/2010 10:00 PM, Bernard Cleyet wrote:
Sci.Am. long time ago discussed these w/ the comment, carrying a
whichof hot water was much faster than any conduction.
Reviewing heat transfer, conduction, convection, and radiation come
immediately to mind,
then recalling the topic of current interest, heat pipes, one adds
displacement.
As convection depends on buoyancy effects fan aided convection,
c.amounts to fluid displacement, is faster.
Heat pipes use gas phase transport. Radiation runs at the speed of
_______________________________________________
Brian W
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Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
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--
Clarence Bennett
Oakland University
Dept. of Physics, (retired)
111 Hannah
Rochester MI 48309
248 370 3418
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l