[Stoves] Chimney Project in Madagascar

Sat Mar 23 20:57:17 CDT 2013

Hi all this is Gustavo I´m getting into chimneys, as I was working with Dr. Larry Winiarski I learn that the diameter of combustion chamber has to be equal the diameter of the chimney, but allwas depend on the size of the diameter of the cooking area and if you are not loosing heat in the cooking proces for that reazon what do and work for me is that if a rocket stove has a 4 inches diameter in the area wher you install the chimney I all ways reduce to 1/4 of an inch this will help to hold more heat under the cooking area surface, long time ago I wanto experiment with a Rocket Stove with diferent chimneys to calculate the optimal diameter and height of the chimney, I think not from a scientist point of view a big diameter loses heat and if is the chimney is too high the acelacion would affect the gases, therefore we would be causing a deficiency in the use of the energy produced by the combustion, I would like that someone with the right
 equipment put hands on the issue and get some controlled tests to pass the information to stovers. another thing thatI observe is that if the diameter of the chimney is smaller than the diameter of the combustion chamber, the heat go to the opposite direction of the combustion not folowing to the chimney or whether there is a heat exes not going to the right derection, it's like a water container that is overflowing by which while we add water at a higher speed to the output speed.
I said trying to increase the diameter gradually until the correct flow encontral
check this link is one of my stove, in this case the chimner was a bit to small, until Dr. Winiarki give the idea and keep trying to encrease the diameter gradually until I found the proper flow of gases, this a challange in every new desing.

http://www.youtube.com/watch?v=MQzHBU1CI80

ps:  this is not a scientific commentary, my work is based on common sense but on some occasions when the problem is more difficult I tried to get profecional advise otherwise I could not get ahead wiht my ideas.

Thank you

Gustavo

________________________________
From: Paul Anderson <psanders at ilstu.edu>
To: Michal Usowicz <usowicz at mail.usf.edu>; Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org> 
Sent: Saturday, March 23, 2013 5:34 PM
Subject: Re: [Stoves] Chimney Project in Madagascar

Dear Michal,    (and Stovers)

I am sending this reply and your message (below) to the 500+ readers of the Stoves Listserv.  Any replies from them need to be sent to you also at     Michal Usowicz mailto:usowicz at mail.usf.edu     because you are not subscribed to the Stoves Listserv.

About chimneys, I am not qualified to respond.  My only comment is to question the size (and probable expense) of what you are discussing.  

Dr TLUD

Paul S. Anderson, PhD  aka "Dr TLUD"
Email: psanders at ilstu.edu Skype: paultlud  Phone: +1-309-452-7072
Website: http://www.drtlud.com/On 3/23/2013 7:23 AM, Michal Usowicz wrote:

Dr Anderson,
>I hope that everything is going wonderfully with you and that your TLUDs are still burning!  I recently got to Madagascar for Peace Corps service and things have been progressing well.  My host family for pre-service training here cooks with wood inside but they are planning to build a chimney and I would like to help them construct a good one.  Large diameter (about 3-4 ft) brick chimneys similar to what you may expect to see in US homes are common in the community that my host family is in and I think a brick chimney will be the best solution to ventilating the home in this context.  
> 
>A large diameter, natural draft, brick chimney seems like a straight forward problem but I wanted to make sure that I was not making any mistakes.  I thought you may be a good person to ask even though I know this isn’t your exact specialty.  I expect the chimney will be about 15-20 ft tall and at least the hearth will have a rectangular cross-sectional area of 3.5x4 ft^2 since that it the current size of my host mother’s fireplace (although I am unsure if my host family will construct the chimney with a taper).  It will primarily be made out of clay bricks and mortar.   Could you please give me some guidance on the following questions?
> 
>1.        Is there a good rule of thumb for the minimum chimney height to have good draw from the hearth?  The only way that I have to estimate this is using the chimney effect equation (ie flow is proportional to Area, height^0.5) and I found that for practical chimney heights for my situation (ie 15-20 ft) there was not a significant change in the flow rate of the chimney.  However, for the equation to apply the chimney needs to be adiabatic, which I think is a bad assumption in this case.  Do you think 15 ft will be tall enough or does it need to be taller?
>2.      I do not understand the effects of geometry on chimney draw and was curious if there is a problem with necking down the chimney significantly after the hearth?  I suspect that my host family may copy the design of a neighbor’s chimney (since they are hiring the same mason to build theirs) which tapers down asymmetrically (ie the left wall is slanted and the right is straight) after the hearth from about 2x3.5 ft^2 at the base to about 2x1 ft^2 over about 6 ft.    
>3.      Along the lines of the previous question, I am concerned that the rain cap for the chimneys may choke the flow.  The rain caps of the chimneys here is a thin slab of concrete set at the top of the chimney with 1-3 bricks at each corner.  Do I need to pay attention to the size of the gaps under the rain cap?
>4.      I know if you build the chimney shorter than the apex of the house the chimney effect of the house may overwhelm the effect of the chimney.  Do you have any intuition or advice about the height difference between the chimney and the roof apex that is needed to avoid this?  
>5.      I feel intuitively that it would be a good idea to minimize the height of the hearth entrance to capture the smoke plume before it spreads but I am not sure if this matters if there is good draw in the chimney.  Do you have an opinion on this?
>6.      Have you ever heard of Rumsford chimneys?  I had a construction engineer friend of mine build one in his house and he said that the draw from the chimney was excellent.  I was just curious if you had heard of it and if you had an opinion of it.    
>Again I hope that everything is going well with you.  I would really appreciate any advice you may be able to give.
> 
>Sincerely,
>Michal Usowicz
>

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