Early type of steel stove made in Germany in 17 centry

As an early stage steel casting stove was in lack of technology, made a square plate, assembled as if attaching with a box shape and then used.
There were 2 holes up & down on the wall rear face, and it was a system that smoke comes out from the upper hole once burn the fire at the lower hole. Upper hole was mostly passed to kitchen or hall through which smoke was flown away to the entrance exit or gap of the eaves.
As the steel stove was in general attached to the wall, it was called '5 pieces plate stove' for the 5 pieces of the steel plate were used, but later a case that hang up the stove on the wall and leave an uniform interval was also happened.

Since at that time it becomes a '6 pieces plate stove', it was a structure that gets heat even a little bit more because air is scudding to the rear face of the stove and then heat generation space is becoming wide.
Since the stove was far away from the wall, a stovepipe was needed. While stovepipe is attaching to the stove, people paid attention to a one phenomenon.
It was such a fact that can take heat much more if make the stovepipe as many as possible and bend zigzag then plait long.