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Re: [Phys-l] Heat transfer lab



Yes, I've even done better than that. I epoxied long thermal-chromic strips to half-inch diameter 18-inch long rods of aluminum, stainless steel, copper, and a heat-exchanger rod (hollow with a freon material inside). I hang them side by side with their bottom ends immersed about an inch deep in hot water, and the race is on. You can watch the race progress. Stainless has gone practically nowhere in the short time it takes the special heat-exchanger rod to change color along the full length of the rod.

Michael Edmiston, PhD
Professor of Physics & Chemistry
Bluffton University

On Nov 16, 2010, at 9:25 PM, "Bill" <wreitz@neo.rr.com> wrote:

Lay a piece of temperature sensitive liquid crystal film on the exposed
portion of the Al bar to "see" the temperature gradient.

Bill Reitz


On 11/16/2010 2:56 PM, Edmiston, Mike wrote:
We have the same thing. You've already expressed the basic idea. I have used it as a demonstration in general-education physics classes.

It's not quantitative. Too much thermal energy escapes into the room from the exposed portion of the aluminum bar. You can cut losses by putting some insulation around the exposed bar, but basically all you are going to do is demonstrate that thermal energy transfer occurs through the aluminum bar.

If one cup is water hotter than room temperature, and the other cup is room-temp water, and you don't have the aluminum bar in place, the hot cup slowly drops in temperature, and the RT cup stays the same.

If you repeat it with the bar in place, the hot water gets colder faster, and the RT cup gets warmer. This offers a believable demonstration of thermal-energy transfer through the aluminum bar.

Warning, this is not a fast demonstration. You need to let it sit for 15-20 minutes to see a substantial change. If you use thermometry that can be displayed on a computer screen or projected with an LCD projector, you can just let the reading change in view of the class while you continue to discuss other things.


Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Chair, Division of Natural and Applied Sciences
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu



-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Souder Dwight
Sent: Tuesday, November 16, 2010 11:44 AM
To: Forum for Physics Educators
Subject: [Phys-l] Heat transfer lab

While doing some cleaning, I came across an old box that was here long before I started teaching. The contents look like something for a heat transfer lab. There are several styrofoam cups with styrofoam lids. There are also "U" shaped pieces of Aluminum. The lids of the cups have a slot cut out so that half of the "U" shaped aluminum is able to fit through the lid and into the cup. I'm assuming it's used for the study of heat transfer - pour hot water in one cup, cold water in the other cup, and the aluminum allows for the heat transfer.

The problem is, I can't find any instructions with it and haven't found anything online. I was wondering if anyone had the lab and if they could email them to me?

Any help would be greatly appreciated.

Thanks,
Dwight Souder
souder.dwight@crestviewschools.net
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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l