I am in the middle of designing/ building a brick built BBQ and am struggling to understand the dynamics of chimney design. The overall design looks like this...
The red areas are all brick/ block/ concrete. The silver areas are stainless steel and the yellow area is the gap in the chimney where the smoke comes out.
What I am trying to do is to optimize the draw to minimize the amount of smoke hitting the cook (i.e. me!) and also to provide good flow of air across the coals. I guess the variables I have with this design are... 1. Changing cross sectional area of the chimney section 2. Varying the width v's depth of the chimney 3. Varying the height of the chimney (although I have a max height based on the surrounding bushes etc.) 4. Changing the angle of the various slopes Any others?
Does anyone have any idea how these factors (or others) impact the draw? E.g. if I reduce the cross sectional area of the chimney and keep everything else the same will this increase or decrease (or even have no effect!) the draw?
Any help gratefully appreciated.
thanks in advance