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-   -   How Heat Works (http://www.fornobravo.com/forum/f17/how-heat-works-1172.html)

james 11-05-2006 07:21 AM

How Heat Works
 
1 Attachment(s)
I've been meaning to build this graphic for some time, and got around to it this weekend. The graphic below is a visual representation of how heat moves, and is stored in both a Forno Bravo pizza oven, and in a high mass bread oven. It's is based on my personal experience with a range of ovens, and reports from many owners of various types of ovens.

There are a number of things that the graphic tries to capture, including:

1. Why higher mass ovens require longer firing periods.
2. Why insulation is so important to the traditional pizza oven -- as it comes in constant contact with high-heat on the outer edge of the oven chamber and floor.
3. Why a pizza can maintain high heat while cooking a large number of pizzas.
4. Why all wood-fired ovens, and most noteably bread ovens need time for the termperature to regulate before you bake bread.
5. Why a high mass oven actually starts to cool down inside the oven chamber when you start cooking pizzas -- those BTUs are still filling up the rest of the oven chamber mass.

Let me know if the graphic helps make this more clear.
James

james 11-06-2006 04:05 AM

Isn't anyone going to comment on my nifty graphic? :) Does it seem right to you?
James

maver 11-06-2006 06:29 AM

This is a nice graphical illustration of the theories of brick ovens we've talked about here. The question - for James or other bread oven owners with thermocouples - is what the oven is like at 3 hours - is it getting to suitable pizza temps then?

reid 07-17-2009 05:14 AM

Re: How Heat Works
 
I just finished three hours at our local farmers market baking 90 pizzas and the oven was still doing great.

This is a refractory barrel style oven with 3" of refractory. outside of the dome was 160 degrees F.

meranteboys@comcast.net 07-21-2009 09:10 AM

Re: How Heat Works
 
Do you know of anyone who can help me with calculating flue size when it comes to my indoor pizza oven that is in the process of being built!!!! HELP!!!!!!!!!

meranteboys@comcast.net 07-21-2009 09:12 AM

Re: How Heat Works
 
I'm having trouble with my indoor basement oven installation. I have a chimney top that is 30 feet from the basement where the oven is. What diameter flue do i need to feed through there to get the right flow for the oven to work properly. Anyone out there please help!!!!!!

wlively 07-22-2009 11:52 AM

Re: How Heat Works
 
To help, we need all of the details.
What kind, round/barrel?
What size?
How tall will the chimney be (from top of oven to end cap)?
Are we talking a straight up run or will you need curves?
Every detail you can include.

Also, being indoors you are going to have to follow local building codes, so that would be a good place to start.

meranteboys@comcast.net 07-23-2009 07:21 AM

Re: How Heat Works
 
Thanks for getting back to me. To give you all of the information that I have it is a rounded oven, with a 40 inch floor space and it is a 30' straight run from the top of the oven to the chimney cap. If you can help in any way I would appreciate it. :confused:

wlively 07-23-2009 06:31 PM

Re: How Heat Works
 
Also need to know the area of your oven opening, as proper sizing of the chimney is related to oven opeing size. The rule of thumb is a max of 1/10 ratio, meaning that the fireplace opening can be 10 times as large as the flue cross section. This ratio applies to the diameter of the flue, so if you use a square flue you will calculate the dia of the circle inside, as the corners will not flow much due the dynamics of circular airflow.

The good news is taller is better, so you should have a good draw. You want the vent opening in your arch to be as wide as possible to scavenge as much flow as possible. You want the area of the vent opening larger (at least 30%) than the area of the flue. Make the vent to flue transition as smooth as you can, a smooth and easy airflow path leads to more volume of flow and higher speed. You definietely want insulated chimney, at 30' I am sure Duravent is out of the question, but it may make good sense to use it for the first section. Just by going on oven size since opening is unkown, you might be able to use 6" (113 sq in), but 8" (201 sq in) is probably a better choice. Just remember as you go up any transitions need to be the same area or smaller, do not go larger.

Again, make sure you know what the code requirements are, as they may make a lot of the decisions for you.

Hope that helps.

meranteboys@comcast.net 07-23-2009 07:51 PM

Re: How Heat Works
 
Quote:

Originally Posted by wlively (Post 60205)
To help, we need all of the details.
What kind, round/barrel?
What size?
How tall will the chimney be (from top of oven to end cap)?
Are we talking a straight up run or will you need curves?
Every detail you can include.

Also, being indoors you are going to have to follow local building codes, so that would be a good place to start.


please help, can you give us your number so that we can contact you on this. I am only relaying info from my husband and I think he needs to personally talk to someone over the phone to get a better understanding of this job. My personal email is meranteboys@comcast.net Thanks, Domenica


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