Heat loss to the ground 1

[jabonet]

We are building an oven, 34 meters x 5.5 meters x 10 meters.
the temperature inside will be 80 C, outside 20 C.

The footprint of the oven is a rectangle 34 by 10 meters, I know how to calculate the heat loss on the walls, but have no idea on how much heat will go to the ground.

The floor is a concrete slab some 10 inches thick over dirt.

Thanks in advance for any help.

 

[PremP]

Dear Jabonet,
To answer fully to your question it is necesary to know the thermal conductivity of the material using for the construction of the furnace. if it is known then the following formulla can be used to calculate the heat transfer through the wall.

(T2-T1)
Q = K*A* -------
L
where
Q - heat transfer
K - Thermal cond of the material
T1&T2 - inside / outside temp.
L - thickness of the wall
A - area of the wall.

Hope this will solve your problem.

Prem Patil.

 

[jabonet]

I already know how much heat is lost thru the walls and roof. but the floor is bare concrete, and I need to quantify the amount of heat that is lost here.

 

[Yeldud]

IF you assume the ground temperature is approx 15C and the oven air temperature at the floor is 80C, then if you have little or no air motion at the floor, heat loss will be approx 210 W per square meter. If you have any significant air motion on the floor, then the heat loss will increase to approx 350-375 W per square meter, because your air film coefficient drops toward nil. This assumes no insulation in the floor, just 10" thick standard weight concrete exposed to the oven temperature of 80C. 1 inch of polystyrene insulation would reduce the heat loss to approx 75 W per square meter.
Hope this helps,
Cheers