Todd, I find that a TLUD with a well tuned air/fuel mix, that also has good turbulence in the mix, will produce little soot on pot bottoms. Proper carburation of a turbulent fuel air mix makes for a cleaner burning TLUD.
Excessive soot build up is a good indication that the carburation and turbulence of the mix are sub optimal. Regards, Jock On Jul 28, 2013, at 11:42 PM, Todd Albi <[email protected]> wrote: > Subject: Cajun Rocket Pot / TLUD Soot > > Soot is an end product on all pots used on biomass stoves with or without > fins or skirts. Heat transfer is increased by adding more surface area to > cooking pots with dowels, finned ribs, corrugated ribs, rows of fins or full > skirted pots as discussed. Steel woks with lamented cast iron bases with > fins have been available in China for quite sometime. We have both in our > SilverFire showroom. They are designed specifically for biomass. Finned > pots specific for LPG have also been available for a number of years. > > The Chinese Enron turbo pots have been marketed in the USA for several years > (www.turbopot.com). Rebates for Enron finned pots are available from > utility companies in the USA for LPG savings. The LPG fin design on Turbo > pots differ significantly from the biomass design. Narrow LPG finned pot > channels clog with soot and the end result is that the soot negates heat > transfer, if used with biomass. Fin designs for biomass cooking are > significantly wider and work well. Time to boil is significantly reduced. > > > The ease of cleaning and product acceptance is also important, as Dale > touched upon. We had early prototypes of both fin pot & skirted pots > fabricated in 2008. I was not a proponent of the Aprovecho fin pot. It made > no sense for the end user. The early design had fins that extended from the > base and up the sidewalls of the pot. We would have had to provide tetanus > shots for end users, had that design ever reached the market. The exterior > design was unacceptable. Cleaning or handling the pot was a handling hazard. > > > Our production pot we introduced to the introduced to the market was the > skirted pot. It cut approximately 5 minutes to time to boil in our early WBT > work. I brought the skirted pot to market though, for the important fact > that we designed the skirt to protrude below the cast iron cook top. This > important design feature reduced the chance of the pot sliding off the stove > to prevent burning the cook or children. Since soot did not accumulate on > the exterior skirt, it also meant less cleaning for the cook, compared to the > finned pot. The skirted pot was more acceptable than our fin pot design. > Combining a skirt and fins would provide even greater heat transfer. A > well-designed pot must be easy to clean. > > > Todd Albi, SilverFire > > > > > On Sun, Jul 28, 2013 at 11:26 AM, Tom Miles <[email protected]> wrote: > Is a TLUD likely to have less soot buildup on fins? > > > > Tom > > > > From: Stoves [mailto:[email protected]] On Behalf Of > Andreatta, Dale A. > Sent: Sunday, July 28, 2013 11:12 AM > > > To: Discussion of biomass cooking stoves > Subject: Re: [Stoves] Cajun Rocket Pot > > > > I like it!!! > > > > As some of you know, I spent a lot of time around 2007-2008 working on finned > pots, and never really got them to work well. I didn’t try this type of “pin > fin” design because I couldn’t figure out how to make a prototype. > > > > With this pin fin design (that’s what mechanical engineers call this shape of > fin) you increase the heat transfer area, but unlike the fins I worked with, > you don’t significantly change the flow of the gas. You get high convective > heat transfer coefficients. Hot gases impinging on a surface (hitting the > surface from a perpendicular direction) usually gives better heat transfer > than hot gases flowing parallel to a surface. The basic tests that have been > done prove this, at least with industrial fuel flames. > > > > I expect that with a sooty flame, you could use a brush to scrape off most of > the soot, and what you don’t get this time you can get next time. Thin > layers of soot wouldn’t have much effect. Perhaps arranging the fins in rows > rather than circular arrays would make them easier to clean quickly. > > > > I expect that emissions per unit of time will increase, since you are > quenching the flame more quickly at the bottom of the pot and stopping the > reactions that would otherwise burn up some of particles and CO. The effect > might be small or large. On the other hand, if the time to boil is greatly > reduced, the total emissions might be a lot less. > > > > I expect that you could make a pot out of cast aluminum with the fins cast in > place. You could use tapered pins to save material and improve castability. > You could probably also use sophisticated welding techniques, as has been > described, or possibly furnace brazing techniques. > > > > The material of the pot doesn’t make much difference. Since all metals are > much better conductors of heat than gases, it doesn’t matter whether the > metal is much better at conducting (stainless steel) or much much better at > conducting (aluminum). It would mostly then be a cost and manufacturing > issue. > > > > The fins must be bonded (welded, brazed, soldered, cast in place) to the pot > itself, otherwise there is too much resistance to heat transfer across the > interface. > > > > What to do next? Where does one get one? If I can get a sample I could test > it out on a variety of stoves, rocket, charcoal, open fire, gasifier, LPG, > fire-in-a-bucket, etc. I could prepare a quick report by the next ETHOS > time. Or, someone who does experimental work full time, such as Apro or many > other labs, could do a better job in less time. What I’m saying is that this > is a very exciting development, that could make a huge difference in what we > do. We should pursue this quickly. > > > > Dale Andreatta, Ph.D., P.E. > > > > > > > > From: Stoves [mailto:[email protected]] On Behalf Of > Dean Still > Sent: Sunday, July 28, 2013 11:36 AM > To: Discussion of biomass cooking stoves > Subject: Re: [Stoves] Cajun Rocket Pot/ capacitive discharge stud weldie > > > > Hi Lanny, > > > > We tested a couple of pots with fins but the space between the fins clogged > up quickly with soot, a good insulator. > > > > Best, > > > > Dean > > On Sun, Jul 28, 2013 at 5:21 AM, Lanny Henson <[email protected]> wrote: > > > > Lanny have you seen capacitive discharge stud welding? > > > Yes I have a stud welder but I did not realize it would weld dissimilar > metals especially aluminum to anything else. > > Stud welding is very finicky and will leave a blemish on the opposite side of > thin metal. > > When a stud weld fails you have to grind the surface to clean it up before > rewelding.. How are you going to do that if it is between the other studs? > > Attaching studs, fins or anything to a pot is going to be problematic, but > attaching something to the pot holder may be practical. The heat transfer may > not be as good as having something attached to the pot but it could possibly > improve the heat transfer. > > Lanny Henson > > ----- Original Message ----- From: <[email protected]> > To: "Discussion of biomass cooking stoves" <[email protected]> > Sent: Sunday, July 28, 2013 5:23 AM > Subject: Re: [Stoves] Cajun Rocket Pot > > [Default] On Sat, 27 Jul 2013 20:48:02 -0400,"Lanny Henson" > <[email protected]> wrote: > > I like creative people and take no pleasure criticizing their work but it is > going to be too expensive and difficult to make with all the pegs. > > > Lanny have you seen capacitive discharge stud welding? This would > allow welding of dissimilar metals to the pot in any pattern. I have > no idea of costs. > > Have you done heat transfer tests with your 4mm aluminium pot compared > with the thinner stainless one? Stainless is a notoriously poor > conductor of heat and theoretically would need to be just under a > tenth of the thickness of aluminium for the same conductivity, but I > do use stainless pots at home. > > Finally can you explain the difference between a vat and a pot? > > Paul I do consider this to be important because biomass stoves have an > inherent problem with heat transfer compared with natural gas or LPG > so improvements in heat exchange will have high benefits. > > AJH > > > > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://stoves.bioenergylists.org/ > > > > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://stoves.bioenergylists.org/ > > > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://stoves.bioenergylists.org/ >
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