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  #121  
Old 12-21-2009, 05:45 AM
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Default Re: Pizza Bob's 42" Build

Grrrrrrrrrr.........
Thanks Rodney - that makes us feel much warmer now!

I wouldn't let this snow stop me from firing-up the oven but building it - that's another story. The snow doesn't stop us from cooking outdoors - the neighbors think my wife and are crazy. We fire-up the grill all winter long.
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  #122  
Old 12-21-2009, 12:06 PM
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Default Re: Pizza Bob's 42" Build

Bob, your oven looks great! So does your rock wall, but you can take pride in knowing you built the oven. Looking forward to seeing your finished project.

Merry Christmas,
Tom
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  #123  
Old 12-21-2009, 10:36 PM
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Default Re: Pizza Bob's 42" Build

Bob, the only thing about the heat here is when it gets into the high 30's you just don't feel like standing in frony of an open fire. Having said that, I will be there on Christmas eve firing it up ready for the roast turkey the next day. It will be my first turkey WFO style so It will be either a great success or a legendary failure. You can be sure either way I will have fun doing it.
Merry Christmas WFO builders.
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  #124  
Old 12-22-2009, 08:33 AM
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Default Re: Pizza Bob's 42" Build

Okay, I was inspired to take a photo or two. This was several days ( of thawing) after the storm, so...
Attached Thumbnails
Pizza Bob's 42" Build-cold_oven1.jpg   Pizza Bob's 42" Build-cold_firepit.jpg   Pizza Bob's 42" Build-cold_bench1.jpg  
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  #125  
Old 12-22-2009, 11:00 AM
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Default Re: Pizza Bob's 42" Build

Hey Lars, it all sure looks "cold"

Tom from sunny northern Calif.
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  #126  
Old 12-22-2009, 10:34 PM
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Default Re: Pizza Bob's 42" Build

Lars I don't think I could live with the inconveience of having that stuff all over the place. I love it when I go skiing, but as for living in it, I think I would just go crazy.
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  #127  
Old 01-14-2010, 06:41 PM
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Default Re: Pizza Bob's 42" Build

Not working on the oven due to this FRIGID weather is killing me! So I had to finally do something that involved the oven - well an electronic version of it...

I have been wanting to perform a heat transfer study of a Pompeii style oven. I hear everyone talk about how their ovens draw so well and others talk about how they wish their flue was larger after the smoke coming out of the front of the oven discolored their bricks. I'm an engineer and driven to things like this for some unknown reason...

I created this electronic CAD model of a 42" oven and applied some boundary conditions to it. The boundary conditions were:
1) A 30" diameter region in the center of the floor that represents a 900 degrees F heat source (a.k.a - fire).
2) An ambient temperature of 72 degrees at the oven entrance
3) An ambient temperature of 72 degrees at the top of the flue
4) The flue is rectangular - 14" x 8"

I didn't include radiation in the study because it is so unpredictable and creates long computer run times. The conduction and convection effects are not manipulated in any way! The vector arrows in the diagram display direction of flow and their color displays the temperature based on the legend on the side of the images. It's so cool to see the cooler air flow in from the front of the oven and follow along the floor because of it's lower temperature than the rair above it. This flow then continues into the hot zone, gets heated and flows to the back of the oven and then up to the top of the dome. Then the hot flow comes along the top of the dome and with the colder flow below it goes up the flue! Notice some flow or smoke trickles out the front and this analysis can be utilized to optimize the oven geometries to minimize the flow out the front.

I can build off of this analysis to include insulation around and under the dome. This would allow me to input different R-values for insulation to determine an optimal thickness to minimize losses. There are so many things that can be done with this tool. It can also measure pressures and flow rate of the heated/cooled air. I kinda wish I did this before I got so far into my build but it's still really interesting to visually see the behaviors of the oven that everyone explains.

I uploaded a four page PDF that shows the oven, the spot where the fire/heat is applied and then two more pictures that show the flow. Check out how the flow is layered coming in and out of the oven and going up the flue - too cool!
Attached Files
File Type: pdf Pompeii Heat Flow.pdf (325.4 KB, 555 views)
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  #128  
Old 01-15-2010, 07:11 AM
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Default Re: Pizza Bob's 42" Build

That is cool. When our oven is first fired up you can see a layer of smoke with relatively little movement hovering in the center just as in your model, as well as the smoke going up the chimney and a lesser amount out the front.
If I build another oven I will have a deeper transition to the chimney pipe. It looks like your model would suggest the same modification.
dave
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  #129  
Old 01-15-2010, 07:47 AM
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Default Re: Pizza Bob's 42" Build

Bob, A stagnating (or freezing) Pompeii oven builders mind is a terrible thing to waste . Glad to see you keeping yours so busy with interesting stuff.

I'm going to print out your pdf drawing to put in my wfo scrap-book to show others the heat flow principle. (Especially the bone-headed Greeks in my family who think the Italians were stupid enough to put the flu outside the dome opening )

You say you modeled an 8"x14" flu pipe and you can see some leakage of heat out the front. Is it not too difficult to taper the top of the flu to something like 8x8 to see if it can capture the Bernoulli Effect? Can your computer model factor in the acceleration of gases up the constricting flu pipe?

Interesting study, thanks for sharing it Bob,
Cheers, Dino
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  #130  
Old 01-15-2010, 08:14 AM
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Default Re: Pizza Bob's 42" Build

Wow Bob, that is cool. By radiation do you mean this analysis doesn't include just radiant heat affects, or also the combustion effects of the fire itself? I assume here you can also varry the size of the fire, or Btu output? I wonder if you can model the optimun size fire by doing that? Cool program, that would be fun to play with on a cold winters day.
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