[Stoves] Heat transfer through holes in a metal plate

Crispin Pemberton-Pigott crispinpigott at outlook.com
Sat Sep 20 23:10:20 CDT 2014


Dear Stove designers

 

I am forwarding a short paper on the subject of heat transfer between air
flow and metal plates. When thinking of how to heat a perforated skirt the
formulas can be used directly. Some recent discussion on preheating air for
stoves shows the contents may be relevant but the heat transfer direction
will be reversed.

 

There are various approaches taken to determining the effectiveness of
heating air with hot metal where that metal is heated by convective and
radiated heat from the fire within. Bejan's Convective Heat Transfer (2005)
also has a section on the subject.

 

The flow velocity range discussed here is from 17-60mm per second but the
pressure starts at 4 Pa which is a little high for some short stoves (Jiko
and many charcoal stoves, for example) which have pressure gradients of 1-2
Pa. So, this is not an all-encompassing set of formulas because of these
limitations. It may however by useful for TLUD design and counter-draft
preheaters (downward heating) applications where the velocity is low and
there is an intention to heat the air or to capture heat from a hot gas
stream (check the Reynolds numbers against the gas composition).

 

Regards

Crispin

 

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