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Ultraphage 06-17-2012 09:58 PM

Place chimney in back of oven?
 
Is there any reason one could not place the chimney in the back of a pizza oven? I have seen some plans where the pizza oven entrance door seems like it is in front and some behind the chimney, so I wasnt sure how that would affect the oven since if it's vented in the rear, it will in all likelihood not be able to be closed (if needed).

I want to build a fireplace/pizza oven/grill combo.

It seems that a front facing fireplace with a side facing pizza oven that's vented in the back (instead of near the oven entrance) could work. I figure with some mild angling of the pizza oven chimney, I could get both chimneys to run parallel to one another and possibly bridge the two with a removable slide plate so the fireplace & pizza oven could function together as a slow smoker. I was also thinking of adding a small ash/coal dump slot that was also able to be opened/closed with a sliding sheet of stainless that would dump the coals down into the fireplace to be collected to use in the grill shelf on the other side of the fireplace.

Hopefully that description makes sense. What problems/issues/suggestions do any of you more knowledgeable than I have? All responses are appreciated.

Thanks
Jason

cleverdick 06-18-2012 01:00 AM

Re: Place chimney in back of oven?
 
I don't think the roof of your dome would ever get hot enough because the heat would not circulate. The cold air would enter through the mouth and just carry the heat straight up the chimney. The fire needs to roll back round on itself.

brickie in oz 06-18-2012 01:51 AM

Re: Place chimney in back of oven?
 
Quote:

Originally Posted by cleverdick (Post 133343)
I don't think the roof of your dome would ever get hot enough because the heat would not circulate. The cold air would enter through the mouth and just carry the heat straight up the chimney. The fire needs to roll back round on itself.

What he said. :)

Ultraphage 06-18-2012 05:49 PM

Re: Place chimney in back of oven?
 
Ok,

So the oven only works if the oven door closes the dome off completely (ie. the flue would be on the outside if the door were closed?), how does the fire get oxygen to burn?

It seems like I've seen plans with the flue/chimney that would be on either side of a closed door, I assumed that if the chimney was not on the "inside" of the dome, that the door was vented, or the oven had some means of supplying air.

I know this is noob stuff, I'm still trying to wrap my head around it.

Laurentius 06-18-2012 05:54 PM

Re: Place chimney in back of oven?
 
The chimney is in a space between the entrance of the oven itself and the outside arch if you have two. I think this area is called the vent. Most people close the door if they bake or to maintain the heat for saturation.

deejayoh 06-18-2012 05:57 PM

Re: Place chimney in back of oven?
 
1 Attachment(s)
This might help

Tscarborough 06-18-2012 06:24 PM

Re: Place chimney in back of oven?
 
5000 thousand years of global empirical experimentation says the flue should be A) outside the oven chamber, B) at the front of the oven and C) that the inner door to the oven should be around 63 percent of the height of the oven chamber.

It ain't rocket science, it is domestic science.

azatty 06-18-2012 09:44 PM

Re: Place chimney in back of oven?
 
Quote:

Originally Posted by Ultraphage (Post 133412)
Ok,

So the oven only works if the oven door closes the dome off completely (ie. the flue would be on the outside if the door were closed?), how does the fire get oxygen to burn?

It seems like I've seen plans with the flue/chimney that would be on either side of a closed door, I assumed that if the chimney was not on the "inside" of the dome, that the door was vented, or the oven had some means of supplying air.

I know this is noob stuff, I'm still trying to wrap my head around it.

What you may have seen is a coal-fired design. Some of the old coal ovens have offset fireboxes and will draft through the door.

clg763 06-19-2012 08:22 AM

Re: Place chimney in back of oven?
 
Several things...

When people have their doors on, it is because the fire has died and they are trying to preserve heat or...

They have put holes in the oven door making it into "blast door" which causes the fire to burn very fast and efficient so the oven will rise to temp quickly. However, heating an oven this rapidly strains the refractory material.

I have seen people place their door outside the chimney before as a secondary position, perhaps this is where some put their blast doors, I don't know.

Neil2 06-19-2012 12:28 PM

Re: Place chimney in back of oven?
 
The basic thermodynamic principal is that the hot gasses from the fire gives up its heat to the dome before cooling and exiting from the oven opening. The 63% ratio of the door height to inside oven height is critical for this to happen efficiently.

The vent is actually optional, and an oven without a vent will work just as well. The main purpose of the vent is to direct hot gasses/smoke upward and away from the operators face.

Some say the vent also increases the burn rate through some sort of "draughting" effect but I'm not convinced that this is significant (or you would not see so many oven is Italy and Croatia without a vent).


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