[Stoves] Side holes in TLUD reactor (was Re: Bangladesh TLUD

[Jorund Buen]

Dear Crispin,

Prof Nurhuda is testing different stoves, in coordination with Prime, which Prime then may decide to commercialise. 

 

Kind regards,

 

Jorund Buen

CEO

Prime Cookstoves

Skype ID: jorundb1

Mobile: +47 932 83 350

 <http://www.primestoves.com/> www.primestoves.com

 

 

 

Fra: Crispin Pemberton-Pigott [mailto:crispinpigott at outlook.com] 
Sendt: lørdag 9. desember 2017 16:57
Til: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Kopi: Julien Winter <winter.julien at gmail.com>; Mahbubul Islam - Bangladesh with Julien W <mailccdb at gmail.com>; Jorund Buen - Norway - Prime stoves <jorund.buen at primestoves.com>; Kirk Harris <kgharris at sonic.net>
Emne: Re: Side holes in TLUD reactor (was Re: [Stoves] Bangladesh TLUD

 

Dear Paul

 

While some stove models of Dr Nurhuda's were licensed to Prime, he has other models that are not, more recent ones, also submitted to various projects for evaluation. We're you aware of that?

 

One of the great drawbacks of TLUD's is flame stability. An approach to control the unwanted extinction of a smoke burning flame is to ensure there is a pilot flame below the main one set in a way they burns some of the char. The number of them is not important, the presence is. 

 

The great TLUD's burn to extinction leaving no smoke at flame-out. That is not to say there is no pulse of CO, but I have seen at YDD some that achieve a high degree of volatile burnout before the flame extinguishes. 

 

The best way to achieve this enviable result is to preheat the flame's air and to give it very effective protection from cross drafts. The Vesto uses a triple shell.  

 

We have discussed the toroidal flow of air in the zone above the char. That is a viable alternative way to keep the flame going. Generally speaking it means the vertical gas velocity is low so power is not high per sq cm of reactor space. Even when the torus is working well, it is safer to have one 'lick' of flame hugging a secondary air jet. Continuous re-ignition. 

 

Regards 

Crispin 

 

‎

Crispin,

Subject line changed because this topic merit further, on goind discussion (and is about holes, not about Bangladesh).

Your comments below are totally correct and raise important questions.   I focus here on the second one, about the side holes.

You point out the multitude of side holes in the Prime stoves (designed by Prof. Nurhuda and sold by Prime, led by Jorund Buen).   And that the Vest has three.  Paal Wendelbo's Peko Pe has several.  Anderson's Champion TLUD (and derivatives in Uganda by Awamu) has none.  Paul Wever's large tall TLUDs (Chip Energy, Stove-pipe stoves) have a few.   And Kirk Harris also deals with the "pilot light" topic to sustain the flame.   And we can add more to this list, even to note those that do not have any side holes. 

My few trials years ago with some holes was inconclusive, but I now think to seriosly consider them again.   

Many, 9, 3, zero is certainly a wide range.   

So, let's try to collectively become better informed about this.   So far, the "theory" (shown to work) is that a small entry of secondary air just above the slowly decending level of the top of the charcoal inside a TLUD stove, produces as small flame (usually light blue because ti is burning CO and maybe H.)

Okay, how many holes?  positions?   diameters?    And what factors (including diameter and height of the fuel chamber, fuel, ND vs FA) are to be considered.

In the end, the practical, funcitonal results are what matter.   So experiments are important to do and to be reported.

Comments, please.   [This topic could be an example of why and how the Stoves Listserv is really valuable.]

Paul   





Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu <mailto:psanders at ilstu.edu> 
Skype:   paultlud    Phone: +1-309-452-7072
Website:  www.drtlud.com <https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.drtlud.com&data=02%7C01%7C%7Ca52b825c8e214783d4dd08d53f16ca16%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636484289464687418&sdata=PtDBspGbA9q%2FKqKtWxRSdldnbWbB5LaEnW6b2dRnTJQ%3D&reserved=0> 

On 12/9/2017 7:47 AM, Crispin Pemberton-Pigott wrote:

Dear Paul and Julien

 

I am responding to Paul’s comments on Julien’s earlier message.

 

On Dec 7, 2017, at 6:51 AM, Paul Anderson <psanders at ilstu.edu <mailto:psanders at ilstu.edu> > wrote:

 

> 1.  The thermal mass is estracting heat, meaning cooler gases inside the chamber, with risk of insufficient temperature for ignition at the top, especially when nearing the end of pyrolysis.

 

Before anyone worries about heat going into the stove body, please perform the trivial calculation about how much heat we are talking about. Just because heat goes into a stove body does not mean a) it is significant, b) that it happens at a time that affects performance of the cooking experience, c) that it is not returned later in the session (which is cooking behaviour-dependent.) Yes, there is heat invested in the stove and usually it is a loss, but the other features of the stove may not only recover that heat through other energy paths, it may make the stove far more accessible by being cheap and easy to make from local materials.


2.  The concrete (or ceramic) inner cylinder does not have any of the side holes (24 in the metal version).  Such holes allow for some "pilot light" effect after the char level is below a hole.    

 

Dr Nurhuda’s very successful TLUD stove had such pilots sprinkled around the fuel chamber. The Vesto uses three holes only, and the purpose is to maintain pilot lights to ensure the flame never goes out. They are placed in a way that guarantees a small portion of char is burned and there is never a need to relight because of a gust of wind.

Regards

Crispin

 

 

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