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Ramiro 06-29-2007 05:00 AM

How many BTU or Kcal/hr for my brick oven?
 
Hi, I'm installing gas for my brick oven that is still under construction and I'd like to know how many BTU or Kcal/hr do I need for my oven to heat up and reach 400șC. My oven internal size is: 90cm diameter and 45cm hight.

Thank you!

enz 06-29-2007 09:14 AM

Re: How many BTU or Kcal/hr for my brick oven?
 
I'll give it a shot.

90 cm is close to 35", which I'll use since all my data is in Btu. Assuming 3" walls, you have about 10780 cubic inches of brick, which weighs about 884 lbs @ 0.082lb/cuft. Brick has a specific heat of .200 Btu/lb*DegF. Average temperature of the brick is tricky, but previous threads have put the outside of the brick at 100F at the beginning of "operating" temp. I'll assume 800F inside temp, for an average of 450F. Assume a cool day 50F to start and you have a delta T of 400F. So, 884 lbs*400 DegF *0.200 Btu/lb*DegF =70720Btu.

Enz

Balty Knowles 06-29-2007 09:32 AM

Re: How many BTU or Kcal/hr for my brick oven?
 
GOOD FOR YOU ENZ. 70,000 btu is surprisingly light but theres no way I'm going to try to figure it out. My thermo dynamics class was right after lunch & several beers, I used it to recover from my partying the night before.

Ramiro 06-29-2007 10:49 AM

Re: How many BTU or Kcal/hr for my brick oven?
 
Thanks Enz. An italian builder recommended me 200.000BTU. Sounds too much, don't you guys think?:confused: :confused:

Balty Knowles 06-29-2007 11:10 AM

Re: How many BTU or Kcal/hr for my brick oven?
 
Would have guessed that 200k btu was more like it but check out the attached site. Smaller ovens approx. 60,000 btu. commercial around 140,000 btu. looks like ENZ was right on the money.

Foodservice Equipment Reports: Evaluations

Rgds

Balty

jengineer 06-29-2007 01:34 PM

Re: How many BTU or Kcal/hr for my brick oven?
 
Instead of re inventing the wheel although we often do that I will point you to a link form one of our resident, north american experts.

http://www.fornobravo.com/forum/f2/h...ural#post11454

followed up by your needing to get in touch with the moderator of the board, James, who will get you in touch with Alf who probably has may be able to provide pointer for you.

Safety with gas in a non-vented dome (which is what these ovens are when a fire is not present) is paramount. Gas accumulation, before the gas is burned can be catastrophic. I once received 2nd degree burns when a furnace did not light off properly, my removal of the access panel created enough draft for the gas to waft over the pilot light and whompf a 3 feet flame engulfed me. No eyebrows, eylashes, hair on arms for a few months and crisped skin was my reward.

enz 07-04-2007 05:59 PM

Re: How many BTU or Kcal/hr for my brick oven?
 
Hi all,
Sorry I haven't followed up. I was casting an oven. See my thread under tools, tips and techniques "Casting Refractory....". Phew!

So just to clarify, 70,000 Btu is what the brick needs to receive, not the burner spec. You will need to allow for a lot of heat to go up the chimney during your burn. I think 200k Btu is pretty reasonable.

Good luck,

Enz

v12spirit 03-07-2014 01:10 AM

Re: How many BTU or Kcal/hr for my brick oven?
 
Hi ENZ
You mean that the heat absorbed by the bricks should be 70,000 BTU so a higher heat supply say 3 times more is needed which is about 200,000 BTU. Is that what you mean?
If so, I'll suppose that 200,000 BTU heat source inside the oven will bring it to pizza temp. Cooking gas has a fuel efficiency of 11.8 Kcal/g which is 46.8 BTU/g. This implies that the 200,000 BTU inside the oven will require 4.274 Kg cooking gas. Is not that very much? It is the third of the medium size cooking gas bottle!! I would like someone to correct these calculations if they were wrong.
Cheers.

david s 03-07-2014 04:09 AM

Re: How many BTU or Kcal/hr for my brick oven?
 
I doubt whether you'll get any response as the last previous post on this thread was over six years ago.

v12spirit 03-07-2014 06:15 AM

Re: How many BTU or Kcal/hr for my brick oven?
 
Ah! :D I was not aware that this post is 7 years old. I hope Wiley will reply. He has a good background in thermodynamics, and his daughter is pursuing a master's degree in thermodynamics and is currently teaching in the university of Washington. He must have the answer.


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