[Stoves] Improving Thermal Efficiency (TARP-VE)

[Crispin Pemberton-Pigott]

Howzit Ken?

 

It will induce a lot of draft and is a very good method of preheating. The
Vesto stove uses this as a balancing force to overcome the tendency of small
stoves to have too much excess air drawn in a bottom hole and a top outlet.

 

If you are drafting the air upwards, you can used the standard draft
calculation method. There is a draft calculator on the Bioenergy lists
website.

 

It will model down-drafting as the air preheats too, in the section on the
right. This is used in both the Vesto and the Lion Stove. The careful
placement of the air entry points can produce an auto-balancing draft that
will limit EA under a wide range of power conditions without operating a
draft control mechanism (damper or λ controller).

 

It is worth remembering that the heat exchanged off a vertical round pipe is
exactly double that of an open air horizontal round pipe. It might be
relevant to some portion of the stove.

 

Regards
Crispin

 

 

Here's a related question,

Suppose I have a vertical metal cylinder that is being heated by combustion
gases from the inside - for the sake of argument - like a 48" length of 12"
diameter 316 stainless steel flue pipe.

Let's assume that this pipe is getting hot - dull orange, even when the
outer surface is exposed to free air.

If I then enclose this pipe in an annular sleeve - again 48" long - open at
each end,  like a 14" diameter tube - so that there is a 1" annular gap for
air to freely be drawn into, will the effect of this sleeve create a
beneficial flue effect, and increase the velocity of the cooling air draught
around the flue pipe?

I'm considering this arrangement as a means of delivering preheated air, and
providing cooling to a large woodgas burner.

Any thoughts 



Ken 

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