Chimney in the CENTER of a Wood-Fired Oven - BAD IDEA!
When you fire your oven, you place your firewood in the center of the oven and continuously add more firewood each time the fire starts to die down. Over a period of 1 hour, you will notice that your once black oven ceiling is now white (white hot). So - the two hottest parts of the oven are: The ceiling (center) and the firebrick cooking surface where the fire has been sitting (center). This is also the exact same spot where you will be doing the majority of your cooking.
If you had a chimney in the center of your oven - you would loose all the heat from the fire as it would LITERALLY go out the chimney. Not to mention, when you did eventually push the fire to the rear / back of the oven and place your food inside - what is supposed to cook your food from the top? There’s nothing there but a gaping chimney hole…
Chimney in the BACK of a Wood-Fired Oven - BAD IDEA!
Yeah, this is just as bad as putting your chimney in the middle of the oven…
After you build your fire in the center of a standard oven (one that has a chimney in the front of the oven), you use a brush to push the fire to the back of the oven, then insert your food into the center of the oven. The heat from the fire in the rear of the oven goes up - hits the ceiling of your oven, then moves forward until it reaches the chimney or exits the front of the oven / door opening.
That heat is around 900° - 1100°. That heat ALSO keeps the firebrick or castable refractory in your oven ceiling super-hot (which allows for fast-baking and longer bake times) as it rolls across your oven ceiling and eventually out of the oven (unless you have a damper - then you can keep the heat inside the oven).
If you had your chimney in the rear of the oven, what happens? 2 things:
The heat from the fire would go straight up and OUT of your oven via the chimney that you put back there.
The oven would never reach the crazy-high temps that it needs to achieve since there is no heat rolling across the oven ceiling. Thus - the oven ceiling will probably never get over 500° - 600°.
NEVER PUT A CHIMNEY IN THE CENTER OR BACK OF A WOOD-FIRED OVEN. NO MATTER WHAT YOU SEE ON YOUTUBE OR READ ONLINE - DO NOT DO IT! YOUR OVEN WILL NOT WORK!