can't believe my eyes

norfitz

I'm trying to size a boiler to fire a 96' long 2" steel pipe underneath an 8,200 gallon steel tank (a random design by the end user), and the Hoffman Data Book's "Heat Losses From Horizontal Bare Steel Pipe" says I can only expect 190 btu/hr. per foot from 2" pipe if using 200 F water, or 270 btu/hr. per foot if 240 F steam. Am I missing something here, or can this assembly absorb no more than the output of a doodly little resi boiler? Any advice would be greatly appreciated.

Bruce Tompkins, Power Boiler Sales

Unknown

Horizontal pipe in 65° F air?

What are the conditions around the outside of the pipe?

Is it all convection, or is the pipe in contact and conducting?

Noel

Einsiedler_2

end result

what is the application?
heatload calculated?

what is the end result you are looking for...??

norfitz

\"design\" conditions

The pipes are suspended below the tank in 65-70 F air, and heat the tank by convection & radiation, not conduction, so the load and the application aren't really relevant other than the end user should have engineered this thing rather than leaving it to voodoo. I am trying to quantify the load now, and I'm led to believe it is nothing more than the heat losses of the bare 2" steel pipe. Any feedback would be welcome.

Bruce Tompkins, Power Boiler Sales

Unknown

here it is

http://www.heatinghelp.com/newsletter.cfm?Id=84

Noel

norfitz

new in town

Thanks, Noel. I'm new to this site and didn't find a newsletter section nor would the link open for me. Can you assist, please?

Thanks much,

Bruce Tompkins, Power Boiler Sales

Einsiedler_2

Bare Pipe HL

Here is the chart noel referred you to (see below).

what is the design criteria for the 8200 gallons?
start temp, proposed end temp, time cycle to get there..?

Unknown

Bruce,

On the menu bar at the top left, within the pipe picture, is a page called Hot Tech Topics.

Click on that, and enjoy the articles.

The library is very interesting, as well.

Noel

norfitz

That's the chart I have, and since the pipes are suspended below, the tank's load does nothing but change the ambient air temp. I'm going to size the boiler @ 300 MBH output @ 10 PSIG steam and hope the thing drains. Thanks so much for your input, guys.

Bruce Tompkins, Power Boiler Sales

Mike T., Swampeast MO

Do my eyes deceive me

Or have you added an extra zero to that 300 mbh output?

Christian Egli

Not much heat

A quick back of the envelope calculation makes me see this:

A 2 in pipe with no fins has about 0.5 ft2 radiation surface. 96 ft of that yields a total of about 50 ft2 of radiation (EDR).

Considering some old rule of thumb that 1 ft2 of waterside boiler surface will produce enough steam for 10 ft2 of radiation (in ambiant air) means that for the 50 ft2 that we have, we will need a boiler with 5 ft2 of heating surface.

A 5 ft2 boiler is about the value of 1/2 BHP, or about 5 kW, or about 17,000 BTU/h. Not much indeed.

If there is need for more heat in the tank, a finned tube will be necessary.

An electric heater core could be good enough if the installation is for occasional use only.