[Stoves] A low-cost hood possibility

[David Meed]

On Fri, Jan 29, 2021 at 11:02 PM biocharFIRST <wmknauss at gmail.com> wrote:

> Computer fans are a good way to move air. I have had good luck using them
> for primary and secondary air and forced air heat exchangers. Something
> between a 2 to 10 watts, 120mm ,12v, 50 to 100 CFM fan should work for a
> vent hood. You can find these new for around $5.  You will most likely have
> a power supply laying around the house that will work and you can add a
> step down speed controller for under $5.
>

It is worth a try, but I suspect that life expectancy in a hot exhaust
stream might not be quite the same as with cool room air being blown into a
heat zone.  Some of the guys doing woodgas engines discovered that they had
problems with fans on the back end of the retort.  Mind you, they did not
have any cool room air added to the stream as would be the case for a vent
hood.  Does anyone have any idea the CFM of exhaust a TLUD produces?

David Meed
<-relurk->





>
> On Fri, Jan 29, 2021, 11:42 AM dan weinshenker <danweinshenker at gmail.com>
> wrote:
>
>> Make exterior chimney with 1/2 barrel, vertical, top end cut off.  Once
>> draft established, complete unit should draw.
>>
>> Sent from my iPhone
>>
>> On Jan 29, 2021, at 10:18 AM, ajheggie at gmail.com wrote:
>>
>> 
>> Ronal
>>
>> One would still need to have a pressure difference from the area above
>> the stove to the outlet from the hood. Much of the temperature gradient
>> from the fire to the chimney top has been lost in the mixing of flue gases
>> and ambient air in the cooking area. In the absence of a fan what would
>> determine what path the gases chose to take, if the hood presented an
>> obstruction the gases would simply go round and up? In a windy area
>> something like the cowl  used in oast houses might produce enough
>> depression but that also adds to cost and complication
>>
>> On Thu, 28 Jan 2021 at 11:17, Ronal Larson <rongretlarson at comcast.net>
>> wrote:
>>
>>> Stove list:
>>>
>>> I’ve been talking with several list members about one drawback of TLUDs
>>> being the complexity and cost of adding a chimney.  As clean as TLUDs are,
>>> they would certainly receive more favorable notice if the exhaust could be
>>> easily vented.
>>>
>>> A quarter of a converted waste 200 liter (55. gallon) barrel might do it
>>> cheaply enough. .Can come in different colors - and 4 can be totally made
>>> locally from one drum - dimensions  about 28 x 28 x 82 cm  (11 x 11 x 33
>>> inches).
>>>
>>> Is using a locally made quarter-barrel a new or old idea?  Dimensions
>>> close enough to  ideal?   I presume there are dozens of ways to mount and
>>> allow different amounts of closure for winter  and rainy conditions.. or if
>>> electricity is possible - a fan and light.
>>>
>>> Height above TLUD could be up to stove owner.  This width looks like it
>>> could handle 3-4 stoves in a row.  US hoods seem to be standard at 30
>>> inches width.
>>>
>>>
>>> Ron
>>>
>>>
>>> <PastedGraphic-1.png>
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