The Rocket Woodstove Forum

Woodstove development using rocketstove technology
 
HomeHome  PortalPortal  GalleryGallery  FAQFAQ  SearchSearch  MemberlistMemberlist  RegisterRegister  Log in  

Share | 
 

 Cold Air vs. Warm Air.

View previous topic View next topic Go down 
AuthorMessage
sae140



Posts : 11
Join date : 2015-11-25
Location : Nr. Boston, Lincolnshire

PostSubject: Cold Air vs. Warm Air.   Thu Nov 26, 2015 3:29 am

I've never understood the thinking behind pre-heating an air feed to a rocket heater. On my old Peugeot I can supply the carburettor with cold air during summer, and air warmed via the exhaust pipe during winter - but the latter setting is only to prevent the carb from icing up. Cold air is ALWAYS to be preferred for such combustion.

Because - cold air is denser than warm air, and so contains more oxygen per unit volume than warm air. With solid fuel stoves, cold air will also expand to a much greater volume than warm air when heated to the same temperature - and so a rocket heater riser updraught would be enhanced with a supply of cold air, rather than warm.

Against these positive aspects there is the obvious disadvantage that cold air has a cooling effect upon the fire itself and the housing - and so the 'acid test' I suppose would be to run two otherwise identical stoves: one fitted with a cold air intake, the other with air intake pre-heating - and see which provides the greater heat output.

There are plenty of references on the Web to the advantages of supplying cold air to internal combustion engines, but few related to solid fuel stoves. However, here is one I found: ://mtbest.net/cold-air-intake.pdf

You'll need to preface that link with 'http' to make it valid, of course - as I'm not allowed to post links for seven days. A restriction that perhaps the Admin here might consider lifting on request ?

Colin
Back to top Go down
gadily
Moderator
Moderator


Posts : 1415
Join date : 2013-12-08

PostSubject: Re: Cold Air vs. Warm Air.   Thu Nov 26, 2015 6:53 am

Back to top Go down
caotropheus
Subscribers
Subscribers


Posts : 333
Join date : 2013-10-07

PostSubject: Re: Cold Air vs. Warm Air.   Thu Nov 26, 2015 3:41 pm

From empirical tests made by several people, stoves are more efficient when you supply hot air. An efficient engine runs at 70 C to 90 C lets say, an efficient combustion works best from 800 C upwards...

Take a look at these videos, the guy made the right experiments with nice results with very simple and crude set-ups.



Back to top Go down
tritowns



Posts : 267
Join date : 2013-12-03

PostSubject: Re: Cold Air vs. Warm Air.   Sat Nov 28, 2015 5:02 am

in a gasifier you use some of the fuel to drive it's thermal conversion of feed stock to wood gas. you do this in a very limited oxygen enviroment. the hotter the air coming in the less oxygen it takes to do the conversion. a rocket stove is doing some of this as well... the hotter the air the better it's internal efficiencies will be.
Back to top Go down
sae140



Posts : 11
Join date : 2015-11-25
Location : Nr. Boston, Lincolnshire

PostSubject: Re: Cold Air vs. Warm Air.   Sat Nov 28, 2015 9:08 pm

caotropheus wrote:
From empirical tests made by several people, stoves are more efficient when you supply hot air. An efficient engine runs at 70 C to 90 C lets say, an efficient combustion works best from 800 C upwards...

A good try, but it isn't really legitimate to compare the external temperature of a vehicle engine against the internal temperature of a rocket stove, is it ?

Various university sites on the Web state that the temperature generated inside vehicle combustion chambers is around 700°C on average, with the peak burned-gas temperature being in the order of 2500°C - which is why, of course, such engines require highly efficient cooling systems.

Those videos - very entertaining demonstrations of how to create a high burn temperature. Thank you for the links. But they do not show any increase in efficiency - although high temperatures and efficiency are related, they are NOT the same thing.
One of the problems is that draught is a two-edged sword - if you pre-heat air, then that air becomes less dense and so you need a greater volume of it to supply the same amount of oxygen. If you also burn fuel such as leaves (with a high ratio of surface area to mass) to create a short but intense burn, then the volume of air required during that burn will be even greater - which results in a vastly increased draught being generated.
But - only 20% or so of that air is taking part in combustion, so that 80% of a greatly enlarged volume of air will be sweeping the heat clean out of the heater and into the atmosphere - unless some means of recovering that heat is provided. In those video demonstrations, heat was vented directly into the atmosphere.


Perhaps it might be useful to quote here a reply from Graham Thornhill (a Chartered Engineer, and MD of the Burley stove company) to a customer enquiry about comparative efficiency of heating appliances:

Quote :
“Unfortunately the advertiser’s and companies have been deliberately using bad English and have been muddling people up. Efficiency is the ratio of what you get out compared to what you put in, how many Kw’s the appliance uses to how many Kw’s you can use. Example; an open coal or gas fire is about 20% efficient, in other words, 80% of the energy released goes up the chimney not into the room for you to use. Electric cookers are 100% ‘efficient’ as they have no chimney/flue, but electricity is not a fuel, but a means of transmitting energy, so it is generated from oil, gas, coal etc. This is inefficient so electricity cost around 12p/Kw. An oil fired ECO Range is about 90% efficient, so you lose 10% through the flue, but using oil directly (instead of paying to have it changed to electricity via a power station) the oil cost around 5.5p/Kw, so the cost to you is 5.5/.9 = 6.1p/Kw. About half that of an electric cooker. So if you want to heat your kitchen with 2 Kw’s per hour energy, an Everhot, Redfyre or Total control AGA will cost you 24p/hour, but an oil ECO will cost 12.2p/hour. It’s as simple as that, but of course they don’t want you to know that. [ ... ] Hope this helps, Regards Graham "


I've removed the 'sales pitch' for Burley heaters, but otherwise, that's his reply - which I think is fully valid. Efficiency needs to take into account ALL aspects of the heating process, from the true cost of fuel right through to the generation of warm toes. It's not just about creating a high burn temperature.

My own "cobbled-together-from-existing-materials" workshop rocket heater probably has an internal thermal efficiency of around 85%, due to lower temperatures from a 4" riser, uninsulated firebox, and so on ... but the 'system efficiency' is higher than anything else on the market - because my building costs (materials and labour) were next to nothing, and - most importantly - the true cost of the fuel I use (discarded pallets) is zero. Less than zero in fact, as some 50% of the wood is recycled, providing an income.

Ludicrous, I know - like many others I've struggled with the costs of winter heating for decades - and now I'm effectively 'being paid' to keep my toes warm during winter. Crazy. Wish I'd discovered rocket heaters (and a free supply of wood) years ago.


But - returning to this issue of pre-heating intake air - even if I am wrong on this - it is really something worth going to a lot of trouble over ?

I've visited a couple of commercial boiler sites in which claims are being made that pre-heating intake air by 20° (i.e. from 20 to 40°C) results in a rise in efficiency (undefined) of 1%. As they're using this figure to help sell their systems, my guess is that 1% - if true - will actually be an upper figure.

But, let's accept that figure with good grace, and without getting too hung up on what those firms mean by 'efficiency' ... is 1% really worth going to a lot of trouble to capture ?

To put this in context - here are a few figures given for 'efficiency' - the problem with these being that they are invariably quoted (without sources) by those with vested interests, such as heater manufacturers making a favourable case for their own products. But again, let's accept these with good grace - and perhaps a large pinch of salt ...

Open fires - an efficiency of 10 to 18%
Conventional woodburners - typically 65%
Commercial boiler systems - 65 to 75%

Now rocket stoves can probably attain somewhere around 95% or so - it's impossible to obtain reliable figures - but compared with the above, is 1% really worth getting obsessional about ?

Colin
Back to top Go down
hermetic



Posts : 19
Join date : 2014-02-18
Age : 65
Location : Driffield, East Yorkshire.

PostSubject: Re: Cold Air vs. Warm Air.   Mon Nov 30, 2015 2:56 am

Hi Colin, You are trying to compare apples and oranges, the air fed into an internal combustion engine needs to be cool for a completely different reason to the one that makes a rocket stove run better with hot air injected into it. This is all down to the faulty but very common misunderstanding of how an internal combustion engine works!! The explosion in the internal combustion engine creates heat, which expands the charge of AIR that the engine has ingested, and the expanding air drives the piston down, not the force of the explosion. If the air that the engine draws in is warm, then it is already partly expanded, and contains less potential energy than cold air. A super/turbocharger force more air into the cylinder, and the intercooler makes sure the air is as cool as possible, so that it contains the most possible potential energy. Read up on "volumetric efficiency in internal combustion engines"
In the rocket stove, the air is injected into the "flue" part of the rocket in order to promote secondary combustion of the remaining hydrocarbons in the already hot gasses. If you inject cold air into them, you will cause a condensation effect, exactly what you don't want! If however you can inject hot or VERY hot air into the gas stream you promote secondary combustion and more of the fuel is turned into heat instead of throwing it away up the flue.
A rocket stove is designed to turn fuel into heat, an internal combustion engine is designed to turn fuel into motion, the heat that the cooling system in the I/C engine has to deal with is wasted heat, which is wasted energy and is the reason for the still great fuel inefficiency of the internal combustion engine.
Phil
Back to top Go down
sae140



Posts : 11
Join date : 2015-11-25
Location : Nr. Boston, Lincolnshire

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 3:33 am

hermetic wrote:
A rocket stove is designed to turn fuel into heat, an internal combustion engine is designed to turn fuel into motion ...

Both create heat - and both create motion. The reason why a rocket stove is called a 'rocket' stove is not simply because of the sound it makes, but because the principle of operation is exactly the same as that of a rocket: that the gases leaving the system have a greater volume than any gases entering the system. Only the magnitude of increase is different.

The increase in volume of gas following combustion is utilised by the internal combustion engine in driving down a piston, whereas the increase in volume of gas following combustion in the rocker stove is employed in forcing those same exhaust gases out of the flue - which is why a horizontal flue may be used. Of course the differential pressure between intake and outlet is small, and not worthy of being harnessed - but it certainly exists. A comparison between the Internal Combustion Engine and the Rocket Stove thus remains valid.

Back to top Go down
sae140



Posts : 11
Join date : 2015-11-25
Location : Nr. Boston, Lincolnshire

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 4:15 am

In defence of my suggestion that cold air may have benefits over pre-warmed air, certainly within the context of rocket heater technology, I'll now introduce the Orbitec cool-wall co-axial vortex combustion chamber concept.

It appears to be 'a given' within rocket stove thinking, that it is a pre-requisite for the riser to become very hot in order for efficient combustion to occur - indeed, one often talks in terms of the stove "needing to warm-up" from a cold start in order to become smokeless.

In the world of real rockets, a significant amount of unwanted heat is produced in a combustion chamber as the by-product of propulsion. Now although the aim of the rocket heater is heat production rather than propulsion - heat within the combustion chamber presents a similar two-edged sword. On the one hand it provides a more complete combustion of fuel and thus maximum expansion of gas, but on the other hand, excessive heat often becomes destructive. What is required are high temperatures, certainly, but occurring in the right place.

What Orbitec has achieved is a combustion chamber design employing two co-axial vortices, the inner containing(sic) very high temperatures, with the outer vortex (which is where my suggestion of using cold air comes into the picture) cooling the combustion chamber wall in order that it remains barely warm. That Orbitec were able to produce temperatures of 3,000°C inside an ACRYLIC combustion chamber, where the walls reached only 60°C is clear evidence that this is indeed possible, although the complexities of producing a twin co-axial vortex are currently unknown to me.

What follows is a proposal for initial research funding by Orbitec:

Quote :

ORBITEC proposes to develop an innovative, cool-wall rocket engine combustion chamber that confines propellant mixing and burning to the inner region of a coaxial vortex flow field. The outer region of the flow field prevents the hot combustion products from contacting the wall. Though the chamber walls are subject to radiant heat transfer, one of the propellants provides effective wall cooling to prevent thermal degradation of the chamber. The Cool-Wall Vortex Combustion Chamber (CWVCC) offers several advantages over conventional liquid rocket engine designs. Avoiding severe thermal cycling of the chamber will extend chamber lifetime and allow for simple, lightweight, low-cost chamber designs. The vortex acts as an effective flame holder and may prevent combustion instability. The spinning vortices also provide an extended flow path much longer than the geometric length of the chamber. The chamber length may thus be reduced for a significant weight saving.


And here is a graphic of a report following successful trials:




So - what this all adds up to is that the best place for high temperatures are within a centralised combustion zone created by an inner vortex. If the outer vortex is fed with a cooling component of combustion (cold air ?), then degradation of the chamber wall can be avoided.

I'm left wondering if one of the most basic tenets of rocket heater design - that of the need for a hot riser - may not be flawed ... ? Well, it's a thought.

Hope someone finds this of interest - and can find out exactly how Orbitec creates those vortices ...

C
Back to top Go down
hermetic



Posts : 19
Join date : 2014-02-18
Age : 65
Location : Driffield, East Yorkshire.

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 6:55 am

"Both create heat - and both create motion". That connection is tenuous in the extreme! The Orbitec stuff is an interesting, but hugely expensive research project and completely different to what is required in a rocket STOVE. I burn wood, wood with an average moisture content of 20%. A rocket engine burning hydrogen and oxygen produces water (or at least steam!), which immediately leaves the engine via the rocket nozzle. If there are any cold surfaces in a rocket stove, the moisture and the creosotes from the wood will condense on those surfaces and run back into the stove. This is absolutely the worst thing that can happen to a wood burning stove of any kind. If you inject cold air into the stove rocket tube this will have the same effect . the primary air for the rocket stove does not need to be heated. The idea of heating the secondary air is to get the secondary burn going in the rocket tube and by keeping the flue gasses hot, and also providing extra oxygen, burn up the creosotes and any remaining flammable gas, and eject the water vapour as efficiently as possible UP the flue, not downwards as in a rocket.. Vortex creation in the secondary burn creates good gas mixing and better combustion, and better flue gas flow if it can be continued up the flue. Despite the fact that Orbitec have spent a fortune on research, the creation of counter flowing vortices to protect the outer wall whilst keeping something isolated by an inner contra rotating vortex was demonstrated by Viktor Scauberger (qv), in the early part of the last century, in the construction of log flumes which guided huge logs around bends without them smashing into the timber siding of the flume. Schauberger was persuaded to go to America late in life and unwittingly signed away most of his research, I wonder of there is any connection?
To sum up, if it is possible to keep the inner core area of the rocket tube hot, and inject heated air into it to burn all the remaining hydrocarbons, whilst keeping the tube itself cool with a buffer layer of cold air so that it increases the longevity of the tube, this is all to the good. My feeling is that what is a simple concept, and a simple, reliable way of getting heating and a clean burn/clean exhaust is beginning to get difficult to construct, and maintain in working order. Creating vortices is not difficult, maintaining them at different rates of flow may be, and if you need auxiliary air pumping equipment to create them in the first place, you are making something which will no longer work "off grid" and is becoming complex to build and difficult to maintain. KISS!
Back to top Go down
sae140



Posts : 11
Join date : 2015-11-25
Location : Nr. Boston, Lincolnshire

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 7:57 am

The difference between a stove and a rocket stove IS the rocket principle.

Tenuous ? Are you seriously suggesting that a rocket does not generate motion and heat - just as an ICE also generates motion and heat ?

There is a difference between underlying principles and design objectives: Internal Combustion Engines, Steam Engines, Jet Engines, Rockets - all employ exactly the same principle: that of oxidising a fuel source into a hot, voluminous gas. What use is made of that gas afterwards is the province of the system designer.


Ok - I've managed to find out a little more about this twin vortex stuff - incredibly high tech, as one might reasonably expect - but again, it is the underlying principle which might be of interest to designers of novel rocket heaters, where the burn chamber/ riser etc could then be of 100% steel construction:

http://enu.kz/repository/2011/AIAA-2011-5835.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a452364.pdf

To whet your appetite - here's a key graphic showing the underlying principle:



In their case liquid oxygen (in our case secondary air ?) is introduced into the 'base' of a twin-walled cone-shaped tube. As the gas (air) is forced along inside this cavity, it forms a vortex which increases it's formation as the diameter tightens. Finally it escapes out of a slot and continues to swirl, but now in the opposite direction to that of the existing vortex within the burn chamber. The outer vortex then constrains the inner vortex within the central area of the chamber and on into the propulsion tube (riser).

Anyone brave enough to take this idea on ? It could well become the future of rocket stoves ...

KISS is one approach - but it isn't compulsory.

C
Back to top Go down
hermetic



Posts : 19
Join date : 2014-02-18
Age : 65
Location : Driffield, East Yorkshire.

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 8:57 am

Dammit sae140, you got me thinking, another sleepless night!!
Phil
Back to top Go down
gadily
Moderator
Moderator


Posts : 1415
Join date : 2013-12-08

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 11:29 am

that can be created quite easily within a rocket burner but i wouldnt use cold air id be using heated secondary air

its the point where you would have the problem or better know as the top plate
Back to top Go down
Bluff



Posts : 5
Join date : 2015-08-15
Age : 75
Location : New Zealand

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 6:58 pm

Gentlemen,
Your discussion is fascinating, somewhat above this old engineers head. However When I was in charge of a boiler house I spent a lot of effort in capturing as much waste heat from the boiler shell and using it to preheat the primary and secondary air which was supplied by the same I.D. fan. The temperature rise was about 25 deg C. I can't prove it helped but I convinced myself it did at the time. I have applied the same principle to the wood burners I have built following advice from a scientist, working in the New Zealand D.S.I.R. (now disestablished). He demonstrated to me that the  heated secondary air mixed better with the burning gas from the primary combustion.
Back to top Go down
gadily
Moderator
Moderator


Posts : 1415
Join date : 2013-12-08

PostSubject: Re: Cold Air vs. Warm Air.   Sun Dec 13, 2015 9:38 pm

the item could be used to create an insulated vortex by using another vortex on the outside spinning the same way

the heated air on the outside could spin into the inner vortex therefore keeping away from the outer wall

spinning the opposite way for our purposed isnt feasable due to revoulutions needed to keep it spinning within a vortex
Back to top Go down
hermetic



Posts : 19
Join date : 2014-02-18
Age : 65
Location : Driffield, East Yorkshire.

PostSubject: Re: Cold Air vs. Warm Air.   Mon Dec 14, 2015 1:04 am

Don't knock it Bluff, an ounce of experience is worth a ton of theory!
Phil
Back to top Go down
T2H
Admin
avatar

Posts : 906
Join date : 2013-10-07

PostSubject: Re: Cold Air vs. Warm Air.   Mon Dec 21, 2015 10:09 am

sae140 wrote:
The difference between a stove and a rocket stove IS the rocket principle.  

Tenuous ? Are you seriously suggesting that a rocket does not generate motion and heat - just as an ICE also generates motion and heat ?

There is a difference between underlying principles and design objectives: Internal Combustion Engines, Steam Engines, Jet Engines, Rockets - all employ exactly the same principle: that of oxidising a fuel source into a hot, voluminous gas. What use is made of that gas afterwards is the province of the system designer.


Ok - I've managed to find out a little more about this twin vortex stuff - incredibly high tech, as one might reasonably expect - but again, it is the underlying principle which might be of interest to designers of novel rocket heaters, where the burn chamber/ riser etc could then be of 100% steel construction:

http://enu.kz/repository/2011/AIAA-2011-5835.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a452364.pdf

To whet your appetite - here's a key graphic showing the underlying principle:



In their case liquid oxygen (in our case secondary air ?) is introduced into the 'base' of a twin-walled cone-shaped tube. As the gas (air) is forced along inside this cavity, it forms a vortex which increases it's formation as the diameter tightens. Finally it escapes out of a slot and continues to swirl, but now in the opposite direction to that of the existing vortex within the burn chamber. The outer vortex then constrains the inner vortex within the central area of the chamber and on into the propulsion tube (riser).

Anyone brave enough to take this idea on ? It could well become the future of rocket stoves ...

KISS is one approach - but it isn't compulsory.

C
To be honest at first I got the impression you were bringing up the argument for arguments sake.
Now you have my attention.
I am definitely interested in this idea.

I will have to admit when I made some major changes to my outdoor rocket cook stove I placed secondary air inlet holes right at the base of the riser tube.
No pre-heating and the stove went smokeless pretty much instantly on start up.

It actually took me back wondering about why it was able to perform so well.
Now mind you this was with a double vortex creation.
Nothing like this.

So yes to your question is anyone up to the challenge.
I am.

It will be a few months out before I can get to trying these principles out.
Have quite a few irons in the fire I have to clear up first.
We have seen a couple other individuals come in questioning the results many of us are achieving and arguing why we are not getting what we claim or arguing it is really a waist of time to add secondary air.

Offering only their opinion with flimsy documentation of their counter claim.

Thanks for pushing on with this idea it is very easy to fall into our own rut here on the forum and not consider a radical opposing theory.

When you have good diagrams and explanations that changes everything.
If we are not wiling to look at what you provide we do so to our own disadvantage.

I think you have something here.

Back to top Go down
CVI04



Posts : 49
Join date : 2015-04-06

PostSubject: Re: Cold Air vs. Warm Air.   Sat Dec 26, 2015 2:06 am

Ok, reading this from the beginning the contex of the discussion has changed from preheating the intake air (primary or secondary) to the protection of inner components of the stove. In looking at the diagram sae140 provided, the rocket is set up in a linear design. Because we are using the "J" design this could be difficult to overcome. The other point to our stoves are to create heat. This design is aimed at reducing heat. Could be counterproductive.

With all that said, thank you sae140 for starting this discussion. I will look forward to hearing how the testing goes!!
Back to top Go down
ROACH

avatar

Posts : 127
Join date : 2014-12-27
Age : 57
Location : salem oregon

PostSubject: cold air vs warm air   Wed Apr 13, 2016 6:06 am

in a gas engine you want cooler air to create more horsepower in a rocket stove you want warmer air to become more efficient for more btu output
Back to top Go down
Gary B.



Posts : 47
Join date : 2014-03-18

PostSubject: Preheated combustion air. In my opinion the only way to burn.   Sat Apr 23, 2016 4:24 am

Gary B here from Minnesota. If you read my report on my end of the burning season report you will see my findings on this subject. My batch rocket stove heater has dual air controls(preheated combustion air and regular old school room temp air into the lower front of the batch box). I can not express enough the difference of how my batch rocket heater performs!! With preheated combustion air everything about the burn is better. Way way better! Please go to my report posted a few months back.
Back to top Go down
T2H
Admin
avatar

Posts : 906
Join date : 2013-10-07

PostSubject: Re: Cold Air vs. Warm Air.   Mon Apr 25, 2016 1:37 pm

How much wood did you use this winter Gary?
Back to top Go down
Gary B.



Posts : 47
Join date : 2014-03-18

PostSubject: Re: Cold Air vs. Warm Air.   Tue Apr 26, 2016 3:47 am

Ok Dale I just went out and did a real accurate measure of my fire wood used. In the fall I carefully measured out exactly two logger's cords in my wood shed. (one loggers cord=48"x48"x96" or 128 cubic feet.). I can't tell you how many people have asked me how much wood I burn over a winter.here in Central Minnesota. The burn season here starts November 1 and goes through the first week in April. I am heating  my shop a well insulated 2000 square foot building with 10 foot ceiling. I burn my fire every day never letting the temperature go below 60 degrees F. at night and 68-70 F. during the day. So I burnt 194 cubic feet of wood. In logger's cords I burnt exactly 1 1/2 cords of wood. (red and white oak).  Now I am building another stove and I think I can cut this by another 25%. There is a guy on youtube I have been in touch with Kirk. He has done some things that really impressed me and after going over it with him I have completely redesigned a good share of my stove. I am going to incorporate about half of his design and half of my own and I think we may have solved the main rocket heater problem of not being able to have controlled heat out put with long burn times. My current batch rocket heater works perfect but my burn times are 4 hours. Not really a big deal but 8-10 hour burn times would be nice. My stove in last years configuration had long burn times but the heat out put was way to much so the windows were open every afternoon. I will keep everyone posted how this works out this coming heating season.
Back to top Go down
T2H
Admin
avatar

Posts : 906
Join date : 2013-10-07

PostSubject: Re: Cold Air vs. Warm Air.   Wed May 04, 2016 2:54 am

Thanks for the update Gary.
Back to top Go down
Hybridizer



Posts : 9
Join date : 2014-12-31
Age : 70
Location : Richmond VA

PostSubject: Re: Cold Air vs. Warm Air.   Wed Oct 12, 2016 6:34 am

I create biochar now using what is called the KonTiki Biochar Kiln. Its original designers were unable to get adequate pyrolysis with a naked cone. When they added a skirt to preheat air coming to the top of the kiln, their temps jumped significantly. The skirt has the added benefit of keeping workers cool and safe while achieving high quality char at 1200+/-F. The force of the updraft between cone and skirt additionally reduced the effect of wind currents on the burn.
I was so impressed that I made one, and having no welder, used stainless pop rivets to hold it. It produces a full 55 gallon drum of pulverized char from a burn taking 4-6 hours. It pyrolyzes rough sawn Oak 4x4 ends with no problem. I think if I had a helper the burn would be reduced to 3 to 4 hours since this old man's chain saw/chop saw work limps along.
I have forgotten how to add photos/videos here. Google Kontiki biochar kiln to see examples. I studied the ones in Switzerland and Australia. Mine may be the only one in my state of Virginia. I always wanted to be a pioneer!!
Back to top Go down
Sponsored content




PostSubject: Re: Cold Air vs. Warm Air.   

Back to top Go down
 
Cold Air vs. Warm Air.
View previous topic View next topic Back to top 
Page 1 of 1
 Similar topics
-
» Cold Air vs. Warm Air.
» Hot taps but cold shower
» I cant get warm!
» hot water running cold/warm/hot?
» Prolonged Cold Snap (UK)

Permissions in this forum:You cannot reply to topics in this forum
The Rocket Woodstove Forum :: Main :: Explaining the Rocket stove-
Jump to: