[Stoves] central secondary air

[Ronal W. Larson]

Crispin,  cc list

	1.  Yesterday you said this:
	Personally I don’t think a ratio is a good design approach. You need a certain vertical space to burn the gases before you attempt heat transfer. A total of 125-150mm is normally OK assuming you have the fuel deck covered with secondary air and it is burning hot near the fuel bed. If you bleed in secondary air through a lot of small holes, there will be no secondary air in the middle. Some try to compensate for this by putting in a vertical tube. That tube is a sign that he secondary air entrance has not been handled correctly. It is a common ‘solution’ to a problem that should not be there in the first place. Try to avoid it.

	2.  Re the “vertical tube”:   I have been involved in several off-list discussions where central secondary air seemed to be providing turbulence benefits  (benefits that including reducing the height and therefore lowering costs.   A central pipe can also prevent gases from rising in the center, which can be a benefit if one has swirl.   Can you give a cite on where a central secondary pipe was shown to not be of value?

Ron
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