I have to disagree Max!
The return gases are cold, wet and mixed with a bit of exhaust gases. They first need to heat untill they can rise back up the wood bed, and suffocateing the hearth while goeing down.
If they are disposed, the volume of them gets replaced with strongly preheated air that keeps the hearth hot eaven at wery low engines gas demand, while produceing exess heat riseing up the bed, drying the wood. In a way, turbocharged hearth.
But, at the expense of higher fuel consumption.
Bob, yes, you show and describe the original plan. But two problems have occured that lead me to the slimer, monorator way.
Lack of space and the use of a fan. Althugh the fan seems wery quiet by its self, once its runing in the trunk, the story is different. Its anoying and above all, a potential cop magnet at regulat police patrools.
I have to come up with something that is both simple, foulproof, safe and quiet.