Author Topic: Forno Napoletano  (Read 7639 times)

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Offline scpizza

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Re: Forno Napoletano
« Reply #40 on: February 17, 2007, 08:00:59 AM »
It might be useful to take a trip to your favorite wood-burning pizzeria and measure the air flow in their oven.  If you have no way of doing that, I can probably give you a decent estimate based on a few calculations.

Sure.  Am curious how big a fan would be needed to replicate convection from burning wood.


Offline November

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Re: Forno Napoletano
« Reply #41 on: February 17, 2007, 08:11:17 AM »
Am curious how big a fan would be needed to replicate convection from burning wood.

Large and slow if you want to replicate the airflow more precisely, but I will get back to you (probably today) on the numbers.  I might also post the numbers in the thread I just linked to since it's probably a more appropriate location for convection discussion.

- red.november

Offline pizzanapoletana

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Re: Forno Napoletano
« Reply #42 on: February 17, 2007, 08:18:12 AM »
How inconvenient.  Would you mind explaining to whom you are addressing and what theory needs a pictorial?

You among others...

I lost the rest of the post.....

So wood theories in a commercial pizzeria...
Electric or gas oven in a commercial environment...

And some thoughts on the fact that if this discussion was commercially viable, many corporations out there would have already developed such a product...

No offence, I love science when it explain thing happening in reality and not when is used for virtual discussions

Last post from me  so I leave you talking on the subject and will wait fro practical demonstrations

Offline Bill/SFNM

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Re: Forno Napoletano
« Reply #43 on: February 17, 2007, 08:18:58 AM »
Sure.  Am curious how big a fan would be needed to replicate convection from burning wood.

In my oven and in others I have observed, the size of the fire needed to maintain the temp during baking, is much smaller than that needed to heat it up. Sometimes wood shaving or chips are tossed in to stoke the flames which would create a brief, but dramatic, change in the conditions in the oven, but I always do that in between pies since I missed once and added wood shavings to the toppings.  :(

At any rate, we are talking here about pies that bake in 30-60 seconds. The vast majority of the exposed crust is on the bottom of the pie so the temp and moisture absorption characteristics of the oven floor are far more important than any other factor. The cooking of the rim and the toppings which must be perfectly timed with that of the crust, is going to be influenced mainly by the radiant heat from the walls, ceiling, and coals. In that short time, air flow through the oven with a relatively small fire isn't going to be much of a factor. I would also guess that moisture coming off the toppings in that intense heat will contribute more to the humidity of the chamber than that  from fuel combustion.

Bill/SFNM

 

Offline November

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Re: Forno Napoletano
« Reply #44 on: February 17, 2007, 08:44:09 AM »
And some thoughts on the fact that if this discussion was commercially viable, many corporations out there would have already developed such a product...

For many businesses, a wood-burning oven is not commercially viable, so viability is relative.  Air impingement ovens, combo-convection ovens, etc. have already been developed and have been in use for quite some time.  I don't know what has led you to believe this kind of product functionality doesn't already exist.  As I mentioned in another thread, even conveyor ovens have an element of convection.

Bill,

From footage I've seen in some very large wood and coal burning ovens, and from my own personal experience, the fires create significant airflow.  By the very laws of physics they have to.  The fire needs oxygen to burn and that's only going to come from air rushing into the oven.  It won't seem like hurricane force winds because it's a large volume of air moving very slowly, but the CFS remains significant.  I imagine that the reason you don't have a large fire going all the time is because it isn't a commercial wood-burning oven.  For commercial purposes, that fire needs to be large enough to deliver heat for pizza after pizza after pizza, all day long.  If you can describe what the mass of the wood is that's burning in the oven at the time the pizza is also in there, and the temperature of the flame at 1 cm or less from the wood, I can provide reliable numbers for airflow.

- red.november

EDIT: By the way, I agree that the two main forms of heat transfer are conduction and radiation, but convection is not just a form of heat transfer, it's also a method of moving moisture away from the surface.  If you were to construct an oven that heated radiantly and conductively, but kept the pizza in a vacuum, you wouldn't get a very crisp crust, you would get a boiled crust.
« Last Edit: February 17, 2007, 08:48:13 AM by November »

Offline November

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Re: Forno Napoletano
« Reply #45 on: February 17, 2007, 08:56:49 AM »
Bill,

If you have access to an anemometer, place it over your chimney/vent of your oven during baking and measure the air speed per square cm of the opening.  Either that or the mass of the burning wood would suffice.

- red.november

Offline scpizza

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Re: Forno Napoletano
« Reply #46 on: February 17, 2007, 09:17:57 AM »
I would also guess that moisture coming off the toppings in that intense heat will contribute more to the humidity of the chamber than that from fuel combustion.
That argument would contradict Shango and Marco's experience that gas does not cook as well as wood.  Certainly sticks of wood on a brick floor are heating that floor via conduction in a way a gas jet sitting above the floor will not.  But given the key role of humidity in baking it seems hard to ignore moisture produced from the fuel source.

I leave you talking on the subject and will wait fro practical demonstrations
Sorry, I have not the resources to acquire a neapolitan oven and convert it to electricity in order to test my theory, though you are right, that would be the only way to prove it is valid in the real world.  Until then it remains just a theory, though an interesting one in that the humidity-is-bad arguments that favor wood over gas would seem to favor fan-assisted electricity over wood.

I did a rough cost calculation comparing electricity to gas to wood:

$/Kwh   Kwh/MMBTU      $/MMBTU
in NY   radiant
 0.20      250            50

$/therm  therm/MMBTU   $/MMBTU
in NY
 1.00       10            10
 
$/cord  cord/MMBTU     $/MMBTU
in NY   for Beech
 200      .037             7

So electric heat is roughly 7 times more expensive than wood heat.  Ouch.

Offline November

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Re: Forno Napoletano
« Reply #47 on: February 17, 2007, 09:25:29 AM »
That argument would contradict Shango and Marco's experience that gas does not cook as well as wood.

It don't see it as a contradiction, it's just a fact about baking a pizza.  You can't escape the moisture that comes from a pizza, but you can escape the moisture that comes from the burning fuel.

I did a rough cost calculation comparing electricity to gas to wood:

I get my wood for free, and I pay about $0.20 per hour to keep my electric oven at 600 degrees F.

- red.november

Offline Bill/SFNM

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Re: Forno Napoletano
« Reply #48 on: February 17, 2007, 09:32:12 AM »
That argument would contradict Shango and Marco's experience that gas does not cook as well as wood.  Certainly sticks of wood on a brick floor are heating that floor via conduction in a way a gas jet sitting above the floor will not.  But given the key role of humidity in baking it seems hard to ignore moisture produced from the fuel source.

Are you taking into consideration the coals that result from the burning logs? I think in my oven these radiate a large amount of heat that plays a very key role in cooking the top of the pizza and also in keeping the entire oven up to temp. Once logs have been burned down to coals, very little new moisture will be released. Gas combustion would produce a very different environment than one with coals and burning logs.

Bill/SFNM

Offline pizzanapoletana

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Re: Forno Napoletano
« Reply #49 on: February 17, 2007, 10:36:22 AM »
A very last thought:

There are hundred of different ovens out there ( I know..) NONE of which can replicate the performance of a forno Napoletano (that is the key argument): e.g. Pizza cooked in 30-40 seconds for 5-6 continuos hours...


My arms are pending right now...


Ciao


Offline November

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Re: Forno Napoletano
« Reply #50 on: February 17, 2007, 12:03:39 PM »
Sure.  Am curious how big a fan would be needed to replicate convection from burning wood.


I'm still interested in what Bill's oven is pushing, but here are some general numbers from Wikipedia.  15-30 CFM for a metal oven and up to 600 CFM for a medium brick fireplace.

http://en.wikipedia.org/wiki/Stove#Wood_stoves_.28metal_stoves.2C_masonry_stoves.29

I also found several wood-burning oven sites that claim the maximum rating is 500 CFM.  Since that's the maximum some of these ovens can handle, I would guess that half that would be pretty common during normal use.  It all depends on the operator.  I did find a few larger commercial ovens that are rated for 1500 CFM, but that represents a minority.  I also believe the CFM could potentially be greater in brick ovens, as it is pointed out in the Wiki entry, metal ovens are typically designed to restrict air flow.  Brick surfaces also contribute to more turbulent flow causing the overall effect of convection to increase.  I can still calculate the more precise numbers if I know the precise conditions you're interested in, but I think these numbers give a pretty good idea of airflow.

To be conservative, I would start out with a fan that pushes 100 CFM at a very low speed, perhaps 40-50 RPM with the option to crank it much lower or higher, and direct the flow against the back wall of the oven where you could keep a super absorptive material.

- red.november

EDIT: By the way, good luck in finding an inexpensive fan that can withstand those temperatures.
EDIT2: I realize that the numbers given in the Wiki article are for wood-burning stoves.  It's just a matter of perspective.  Put the food inside with the fire rather than outside.
« Last Edit: February 17, 2007, 12:14:27 PM by November »