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Re: Heating Cables

>Date: Fri, 25 Sep 1998 05:43:27 -0700 (PDT)
>From: Jim Spencer <jimsp at yahoo_com>

>If the DIY cables are heating the substrate they have to be causing
>some convection currents.  

Not necessarily. Heat can flow via conduction, convection or turbulent
flow. Which one depends on the heat density and the viscosity of the medium. 

An obvious example is a piece of metal heated from below. It is unlikely
that there are any convection currents going from the bottom to the top of
the metal. On the other hand, heating a body of air even a little will most
likely create convection currents. A water and gravel mixture falls
somewhere in between. 

I assume that Dupla did enough research into this area so that their cables
are designed to create an appropriate heat density. Measurements in our
tanks indicate that Dupla cables, installed per Dupla's recommendations,
create a temperature differential between the cable and the surface of the
gravel of about 8 degrees F. I further assume that a differential much less
than this may not procduce the desired results.    

George Booth, Ft. Collins, Colorado (booth at frii_com)
  Back on-line! New URL! Slightly new look! Same good data! More to come!