[Stoves] Mis-information

[Ronal W. Larson]

Gordon, list et al:

See inserts.


> On Mar 31, 2018, at 8:42 PM, Gordon <gordon.west at rtnewmexico.com> wrote:
> 
> Just a couple of comments about possible dynamics that aren’t being considered, or that are difficult to observe and document. First, I acknowledge that the diagram posted from the World Stoves website was probably not a completely accurate representation of all the features of the device, so we can disregard any assumptions about it.
> 
> In discussing pyrolysis in a TLUD with my colleague Bill Knauss, he believes that the airflow may not be a linear updraft through the feedstock and that there may be internal circular flows and eddies.
	[RWL:  Yes - same comment as from Alex English.  Norm Baker has some video made with a 55 gallon version in which this could be viewed through a glass plate (with a TLUD which for sure was overall updraft).  I take it that this paragraph is not on TLODs.

> One cause for this is that the gasification of volatiles is dramatically expanding the gas volume well beyond the combustion air input, creating a much higher gas pressure, which could cause localized “downdraft” at the mpf.
	[RWL:  Totally agree on the presence of a lot more up-flowing gas - starting only at the MPF - (downward) moving pyrolysis front.  (And the same sentence applies for a TLOD with down -flowing  hot gases the fuel bed.)  I hope someone can supply some equations to better understand this.  In my recent reading of the simple Venturi devices it doesn’t surprise me that a constriction speeds up the gas flow.  But I am amazed that this leads to lower, not higher pressure.  The argument is one of conservation of energy.  I can see this in the equations used to relate a pressure measurement to velocities - but the lowered pressure is counterintuitive to someone trained in electrical engineering.

> In any case, the expanded gas volume has to get out somehow, potentially even through holes assumed to be ventures.
	[RWL:  But TLUDs provide no such holes (in any I have seen).  The word “ventures”  looks like a typo for “vents” or “Venturis”?  The term Venturi implies air flow past a “vent”  not in or out of.  Or “through”.

> During experiments we did in capturing syngas from a large TLUD (made from a vertical 500 gallon propane tank), we calculated that there was a 4:1 expansion of syngas volume over the combustion air volume. That increase in volume and pressure has to go somewhere.
	[RWL:  Can you rephrase this?  The syngas creation is associated with low amounts of primary air - and we know the secondary air has to be 5-6 times larger to convert the CO and H2 to CO2 and water (which chemical reactions create a pressure drop as 3 particles convert to two).   My concern is over your phrase “combustion air volume”.  In any case,  we know that air flow is always from high pressure regions to lower (even with a Venturi effect - which low pressure is occurring in the faster flowing fluid).

> 
> Another possible effect to be considered is that the “flame cap” at the top of the pyrolysis cylinder would consume all of the O2 from any air being drawn down from the top, which means it would not be supporting a downdraft pyrolysis reaction.
	[RWL:  Agreed.  The Mulcahy patent is clearly stating that his downdraft is caused by a Venturi effect.  The downdraft has zero relation to oxygen content,  but the flame cap is helpful in not converting (desired) char to CO2 - as the flame cap consumes all/most of the O2..

>  I am not visualizing where the O2 would come from, except from the bottom as an updraft.
	[RWL:   We have to be careful with terms here.  The whole sentence is correct, but in the TLODs, that “updraft” is Not through the fuel bed.  The upward flowing oxygen in the outer annular region can certainly be called “updraft”, but the term “downdraft” in TLODs refers to the flow through the fuel bed.
> 
> I hope this is useful.

	RWL:  All dialog on this topic is useful.  Thanks for it.  (Say hello to Bill.)

Ron
> 
> Gordon
> 
> 
> 
> On Mar 31, 2018, at 7:17 PM, Ronal W. Larson <rongretlarson at comcast.net <mailto:rongretlarson at comcast.net>> wrote:
> 
>> List and Crispin and Gordon:  cc Paul, Kirk and Andrew  (in this thread)
>> 
>> 	See inserts below.
>> 
>> 
>>> On Mar 28, 2018, at 6:10 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
>>> 
>>> Dear Gordon
>>>  
>>> The World Stove works very well. When it was discussed here some years ago, I mentioned that it appeared to be a new type of stove. I agree that how it works is not obvious, however I can assure you it does and that many thousands of them have been sold. 
>> 	RWL1:  Thanks to Crispin for his additional support that World Stove is alive and well.  
>> 
>> 	I agree with Crispin that it is by no means obvious with how the TLOD works.  But I suggest that there is now not much reason to doubt what Nat has claimed in his successful patent.  The patent is at: 
>> 	https://patents.google.com/patent/US20110209698 <https://patents.google.com/patent/US20110209698>.   
>>  Look especially at patent figure item #50 in part #19 for what I consider the main new (Venturi) feature that is not a part of any TLUD.
>> 
>>> There are elements of the design missing from that drawing.
>> 	[RWL2:  Agreed.  The simple figure given by Gordon is only vaguely similar to the many figures in the patent.  I am intentionally not re-inserting the figure introduced by Gordon.
>> 
>>>  
>>> A significant aspect of the design is that it can be refueled cleanly while running, separating it from most TLUD’s,
>> 	[RWL3:  I agree on being able to add fuel with Nat’s TLODs. (Some Mulcahy videos show this.)  But so can any TLUD.  The doctoral thesis by Jessica Tryner covers this topic as expressed (with unhappiness) by Paul Anderson at:
>> http://www.drtlud.com/epost/re-stoves-new-handbook-for-biomass-cookstove-research-design-and-development/ <http://www.drtlud.com/epost/re-stoves-new-handbook-for-biomass-cookstove-research-design-and-development/>
>> which leads one to 
>> http://cleancookstoves.org/resources/517.html <http://cleancookstoves.org/resources/517.html>
>> where there are multiple cites to Dr.  Tryner’s work.  This (otherwise very nice) stove overview document has nothing on TLODs and World Stove.
>> 	
>> 
>>> at least until there is a significant accumulation of ash at the bottom.
>> 	[RWL4:   Disagree again.  Essentially no ash.   A main beauty of the TLOD is that it is virtually impossible to burn up the produced char (unlike all TLUDs).  This is mentioned briefly in the above patent.  Nat makes a major emphasis on using the produced char as biochar.
>> 
>> 
>> 	[RWL5:  New topic:  How much new and additional effort by this list should go into comparing TLUDs and TLODs?
>> 	a)  On the one hand, Nat has a patent - and this has presumably caused little work by others. I am not advocating anyone trying to duplicate Nat’s work and ignore the patent.
>> 	b)  I admire Nat’s work, and know he has invested a lot of time and money in its development.  I don’t want to cause him any new patent defense difficulties.  Actually I am impressed by the work of hundreds in improving and modifying TLUDs.  Is this perhaps because there are no patent issues (that I am aware of).
>> 	c) On the other hand,  his work is only poorly known and acknowledged.  It seems logical that because he has a 10 year head start on everyone else, any TLOD discussion should generally help World Stove.  And Nat has an existing manufacturing approach designed to minimize costs that will be hard to beat.  Besides the above two issues of adding fuel and avoiding char production, the stove is obviously very clean (but no detailed report I am aware of) and seems to have all the advantages of a TLUD (time saving, income generating, etc)
>> 	d)   (Getting agreement today to bring up this topic from Kirk Harris), I hereby apologize to Nat if I am making the wrong choice in encouraging others to see if they can (while necessarily acknowledging the above patent) strive for modifications that might convince the patent office that another TLOD type patent is justifiable.  I am pretty sure that one can’t patent use of the (several hundred year-old) Venturi principle.  (Nor do I see that Nat has made that claim).
>> 	e).  Maybe Nat can authorize (with royalties) other manufacture and use of what he is selling.
>> 
>> Ron
>> 
>> 
>> 
>>>  
>>> Regards
>>> Crispin
>>>  
>>>  
>>>  
>>> On 28 March 2018 at 15:51, Gordon West <gordon.west at rtnewmexico.com <mailto:gordon.west at rtnewmexico.com>> wrote:
>>> Is this the downdraft stove concept being discussed? (From the World Stove website)
>>>  
>>> <image001.jpg>
>>> In this depiction, I do not understand how the feedstock that is below the “gas” holes would ever pyrolyze, whether updraft of downdraft, since no air would be passing through it.
>>>  
>>>  
>>> Good find Gordon, I had heard Nat talking over the table about this but never seen a schematic, I'm tending toward being sceptical.
>>> 
>>> Andrew 
>>> _______________________________________________
>>> Stoves mailing list

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