heat transmission of copper pipe

zac_2

i'm planning on building a towel warmer/radiator for my bathroom and just need to know the btu output of 3/4" and 1/2" copper pipe per foot.

i'm sure i have it in a book somewhere but i thought it'd be easier to ask here. ;)

Brad White_28

Depends on water and air temperature

Zac-
If you like your bathroom warmer and/or run lower water temperatures (scalding protection for young and old) you will have less output. I am sure you understand this.

Personally I would use 1-inch copper for your application. 1/2" may not be strong enough should someone, a child even, use it as a pull-up bar. 3/4 inch, similar but certainly better. Also wider means there is more air space between the towel halves folded over. Use type L or if you can get it, K. Not M which is too think IMHO.

Pre-fabricated headers may be your friend if you are making a "ladder" type. Just a thought, but you may be limited to 3/4 inch rungs off of 1.25" risers.

Here is the heat output BTU's per hour per foot of 1/2" in a 75 degree room at respective water temperatures of 100, 120, 140, 160 and 180 (1.0 GPM flow rate):

6, 12, 20, 27, 36


Here is the heat output BTU's per hour per foot of 3/4" in a 75 degree room at respective water temperatures of 100, 120, 140, 160 and 180 (1.0 GPM flow rate):

8, 17, 27, 38, 49

Here is the heat output BTU's per hour per foot of 1" in a 75 degree room at respective water temperatures of 100, 120, 140, 160 and 180 (1.0 GPM flow rate):

10, 22, 34, 47, 61

I should also add that any bright metal will emit far less radiant heat when left bare. Painting increases emissivity. Conduction to towels should be fine. Just do not think of this as a radiator for the space too much.

Hope this helps.

Brad

zac_2

i was planning on running max 140 water through it.

perfect! thats just what i was after, thanks!

i was actually conidering 1" as well but thought it was overkill, maybe i'll give it another look.

Mike T., Swampeast MO

If you plan on running it year-round, I'd suggest keeping it as shiny as possible. The towels will warm just fine, but you won't be putting out much heat in the summer.

hr

A suggestion if I may

Watts Radiant sells these nice brass base branch manifolds. Available with 1 or 1-1/4" trunk 48" long.

They are perfectly spaced and aligned. Merely buy some 5/8" brass tube for the rungs.

hot rod

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zac_2

good idea

i have a few chunks of that stuff lying around somewhere, never even thought about it, thanks! ^_^

Brad White_29

Uh, zac...

Oh, never mind