Stove BTU output based on temp and surface area?

Stove BTU output based on temp and surface area?

PostBy: pret On: Sat Feb 14, 2009 6:49 pm

Anybody know how to determine the btu output of a stove at a certain surface temp, based on exposed surface area??
pret
 

Re: Stove BTU output based on temp and surface area?

PostBy: DOUG On: Sat Feb 14, 2009 9:47 pm

A chart from "The Wooburner's Encyclopedia,1976" says: The amount of heat emmited per square foot is dependent on the temperature of the radiating body.

Temperature of Surface Fairenhiet -------------- Total Energy Transfered BTU's per hour per foot

80* ------------------------------------------------------ 15 Btu's / Sq.Ft.
100* ------------------------------------------------------ 51 Btu's / Sq.Ft.
150* ------------------------------------------------------ 168 Btu's / Sq.Ft.
200* ------------------------------------------------------ 315 Btu's / Sq.Ft.
400* ------------------------------------------------------ 1230 Btu's / Sq.Ft.
600* ------------------------------------------------------ 2850 Btu's / Sq.Ft.
800* ------------------------------------------------------ 5430 Btu's / Sq.Ft.
1200* ----------------------------------------------------- 9370 Btu's / Sq.Ft.
DOUG
 
Stove/Furnace Make: CHUBBY, D.S.MACHINE BOILER
Stove/Furnace Model: CLAYTON 1600

Re: Stove BTU output based on temp and surface area?

PostBy: pret On: Sat Feb 14, 2009 10:44 pm

Thank you... thank you... thank you DOUG! You are DA MAN! :D

What this means is that the AA-130 boiler with a rough (overestimated) 18.5 sq ft of radiant surface and water temp @ 200 degrees puts out just over 5800 btu's per hour... About as much as a little space heater on high.

Why am I interested you may ask??? Perspective. This goes back to my house drying out super quick as a result of this boiler operating in the basement... for those of you who have helped me rant or simply laughed at the ignorant lad ;)... seems kind of silly that a little space heater could do so much damage. :shock:
pret
 


Re: Stove BTU output based on temp and surface area?

PostBy: DOUG On: Sat Feb 14, 2009 11:19 pm

Thanks for the compliments. Glad to have helped. :idea: :) DOUG
DOUG
 
Stove/Furnace Make: CHUBBY, D.S.MACHINE BOILER
Stove/Furnace Model: CLAYTON 1600

Re: Stove BTU output based on temp and surface area?

PostBy: titleist1 On: Sun Feb 15, 2009 9:25 am

Just curious, when you figure out the BTU output, do you figure in the surface area of the baseboard or radiator in each room that the hot water is running through or just use the surface area of the coil in the stove?
titleist1
 
Hot Air Coal Stoker Stove: Harman Mag Stoker (old style) one in basement, one in workshop
Hand Fed Coal Stove: Harman Mark III on standby for long power outages
Coal Size/Type: Rice/Anthracite; Nut/Anthracite

Re: Stove BTU output based on temp and surface area?

PostBy: DOUG On: Sun Feb 15, 2009 9:38 am

From the chart, you can use these values to estimate the output of heat radiation of any or all of the heating surfaces. Now you have some figures to break down where you are heating and how much heat into each zone. :idea:
DOUG
 
Stove/Furnace Make: CHUBBY, D.S.MACHINE BOILER
Stove/Furnace Model: CLAYTON 1600

Re: Stove BTU output based on temp and surface area?

PostBy: Oakback On: Mon Feb 16, 2009 3:32 pm

DOUG wrote:A chart from "The Wooburner's Encyclopedia,1976" says: The amount of heat emmited per square foot is dependent on the temperature of the radiating body.

Temperature of Surface Fairenhiet -------------- Total Energy Transfered BTU's per hour per foot

80* ------------------------------------------------------ 15 Btu's / Sq.Ft.
100* ------------------------------------------------------ 51 Btu's / Sq.Ft.
150* ------------------------------------------------------ 168 Btu's / Sq.Ft.
200* ------------------------------------------------------ 315 Btu's / Sq.Ft.
400* ------------------------------------------------------ 1230 Btu's / Sq.Ft.
600* ------------------------------------------------------ 2850 Btu's / Sq.Ft.
800* ------------------------------------------------------ 5430 Btu's / Sq.Ft.
1200* ----------------------------------------------------- 9370 Btu's / Sq.Ft.



Wow! Now I can see why my home heats up so much better when I crank the stove up to 400 deg surface temp.
Huge btu output difference between 200 deg and 400 deg.
Thanks
Oakback
 

Re: Stove BTU output based on temp and surface area?

PostBy: pconn171 On: Tue Feb 17, 2009 1:59 pm

You should be a little careful with this calculation. The amount of heat emitted from an object can vary tremendously based on convection. If you're running a blower accross a surface, you will see enormous gains in heat transfer from the surface. Think about the radiator in your car. You're sitting idle and the car gets up to a limit temperature so the sensor kicks on the fan. This moving air drastically increases the amount of heat removed from the cooling system. Forced convection is a whole different ballgame as opposed to free convection.
pconn171
 
Stove/Furnace Make: Reading
Stove/Furnace Model: Susquehanna

Re: Stove BTU output based on temp and surface area?

PostBy: DOUG On: Tue Feb 17, 2009 2:10 pm

True, Maybe you can help us out with the rest of the equation variables regarding forced convection. This calculation was for steel plate radiating woodstoves, particularly the thin steel barrel stove variety. Any help would greatly be appreciated Pat. Thanks, DOUG
DOUG
 
Stove/Furnace Make: CHUBBY, D.S.MACHINE BOILER
Stove/Furnace Model: CLAYTON 1600

Re: Stove BTU output based on temp and surface area?

PostBy: pconn171 On: Tue Feb 17, 2009 6:15 pm

My wife and I are pulling everything out of the "drum room" tonight and are painting it. My college books are crammed away in the closet there so I'll be sure to set aside my Heat Transfer notebooks and review. If I remember correctly, the calculation is very complicated and conditional, but maybe there's a way to simplify it. I'm curious myself because I wanted to add the heatsinks to my stove body and that is something directly related to forced convection and surface area.
pconn171
 
Stove/Furnace Make: Reading
Stove/Furnace Model: Susquehanna

Re: Stove BTU output based on temp and surface area?

PostBy: rberq On: Tue Feb 17, 2009 7:38 pm

pconn171 wrote:If you're running a blower accross a surface, you will see enormous gains in heat transfer from the surface.

Hmmmm. I have a couple of those "super quiet" doorway fans and they don't do diddly for moving air from one room to another. Maybe I should make some little stands for them, and mount them to blow on the sides of the stove. Would they do better blowing directly at the sides, or blowing across the sides at an angle?
rberq
 
Hand Fed Coal Stove: DS Machine 1300
Coal Size/Type: Nut -- Kimmel/Blaschak/Reading
Other Heating: Oil hot water radiators, propane