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heat transfer plates - Page 3

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Posted by <farview on December 13, 2003, 3:18 am

Bolts not required.  The longitudinal fin will be sandwiched between
subfloor and finished floor sort of like:

Require 19 Btuh/sf for 65F
[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]] 5/8" Bamboo R=0.7
=========       ================= Al fin 4" each side of U groove
||||| 1/2" Pex + 3/4" filler board (High R value)
XXXXXXXXXXXXXXXXXXXXXXXX 3/4" CDX plywood subfloor (in place)

I inspected a product called RTI board distributed under the Wirsbo name.
It uses aluminum foil (i.e. thin) bonded to MDF (medium density fiberboard).
It doesn't appear to run all the way down in the groove even.  They use the
MDF to help transfer the heat away from the pipe but this seems
counterproductive to me.  Seems a low density, higher R value material would
help reduce downward heat loss.

Posted by nicksanspam on December 13, 2003, 11:09 am

You might make 19 Btu/h-ft^2 with 95 F water and 19/(5(95-65)) = 0.127 feet
of 5 Btu/h-F-ft fin-tube pipe per square foot of floor, ie 1 $2 8' length
of fin-tube per 63 ft^2 of floor, vs about 2 sheets of filler board, 64 ft^2
of aluminum, 96 ft of Pex and more labor...


Posted by <farview on December 13, 2003, 3:44 pm
Hmmm...interesting.  I thought finned tube baseboard had to run at much
higher temperature in order to get the heat output, but then the fins do
create a large surface area for heat transfer.  So you suggest using fin
tube baseboard instead of radiant floor?  Certainly cheaper.

I picked up Yunus A. Cengel's "Intro to Thermodynamics and Heat Transfer" at
the college library so I can kick some numbers around myself.


Posted by Nick Pine on December 13, 2003, 5:30 pm

They move  more  heat with higher temp water, but the basic thermal
conductance in slow-moving air is about 5 Btu/h-F per linear foot.
Speed up the air with a fan or a "closet convector" and the thermal
conductance will increase.

Sure. You might put it under the floor for more of a radiant floor
feeling, and possibly add a few holes in the floor to let some warm
air flow up near the center of the house and let some cool air flow
down near the perimeter.

You might also look at the graphs on some fin-tube web sites.


Posted by <farview on December 10, 2003, 3:56 pm
Thanks for that info on roll forming.  I would make mandrels
sized to make a groove deep as the tupe o.d. so it lies fully down in the
groove for a flush top.  Prefab products are running $ - $/sf which
includes aluminum+filler board.  0.010" thick flashing runs $.50/sf and
0.032" sheet costs me $/sf.  I wonder if .010" flashing will conduct enough
energy 4" to 6" laterally to meet demand?  Warmboard uses .024" thick Al.
hmm...time for pencil and head scratchin.



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