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pex vs copper - Page 3

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Posted by Dick LeCompte on September 16, 2005, 12:43 am
 
I was under the impression that once you reached equilibrium steady state
heat transfer the amount of heat transfered was equal regardless of the heat
transfer coeficient but the  the  temperature difference across the wall may
be greater but the net transfer is the same once equilibrium is reached.

"Bert Menkveld" <bertATreentronicsDOTcom> wrote in message


Posted by Duane C. Johnson on September 16, 2005, 2:51 am
 
Hi Dick;


 > I was under the impression that once you reached
 > equilibrium steady state heat transfer the amount
 > of heat transfered was equal regardless of the
 > heat transfer coeficient but the  the  temperatur
 > difference across the wall may be greater but the
 > net transfer is the same once equilibrium is
 > reached.

You are technically correct.

However, when considering a solar collector the
higher temperatures promote higher losses to the
environment due to radiation and convection.
This higher loss necessarily causes less heat to
be available to transfer into the PEX tubing
than the copper one.

OK, the losses aren't a lot higher but not zero.

Duane

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Posted by Cosmopolite on September 10, 2005, 4:16 pm
 Gary wrote:


    Wonderfull test. Thank you for the info.

    What size and wall thickness was the cpvc ?  Looks like tubing spec,
rather than shed..

Posted by Gary on September 11, 2005, 10:01 pm
 

The CPVC I have is nominal half inch.  The OD is 0.625 inch, and the
wall thickness is 0.075 inch.  This is measured with my calipers, and
might be up to a couple thousands off.
Also have some PEX on hand that turns out to the be same.

--


Gary

www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects








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Posted by Cosmopolite on September 11, 2005, 10:15 pm
 Gary wrote:

   Thank you for the info. I am currently working on a plastic collector
using 3mm space fabric with thermosetting resin and any info on plastic
collectors is a help. The resin that I am using has the same
conductivity as cpvc. Wall will be .02" on solar side.

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