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 Fan Use With Rocket Stoves

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Hitchhiker



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PostSubject: Fan Use With Rocket Stoves   Fri Feb 21, 2014 1:42 am

Didn't find this topic in a search.  Are you using a fan with the stove?  How would a fan benefit or hurt the rocket stove and hybrids?
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gadily
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PostSubject: Re: Fan Use With Rocket Stoves   Fri Feb 21, 2014 2:36 am

fans create a higher burn and use more wood to do so

is the use of a fan cost effective enough and more so if off the grid however a fan could be created using heat and blowing the air into the burner off the grid

looking at the car turbo it compreses air into the chamber upon firing it gives much better performance it would be the same with stoves except its not an enclosed space so energy would be lost
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Tim Keith



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PostSubject: Re: Fan Use With Rocket Stoves   Tue Apr 22, 2014 5:04 pm

I will use an electric fan to reduce smoking in a wood chip heater. The fan will cycle on and off by use of a timer or Arduino. The goal is to blow off ash and induce air flow for cleaner combustion. I hope the fan is only needed intermittently. There aren't many small heater designs that use wood chips. I don't have the patience to experiment with natural air flow. Please let me know if someone knows of a small wood chip burning heater that doesn't smoke, and has been in use for several months.
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gadily
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PostSubject: Re: Fan Use With Rocket Stoves   Tue Apr 22, 2014 8:18 pm

tim

ive seen wood chip feeder for a gas system only problem its big in design ive seen wood chips burnt in a rocket barrel something like the sawdust burner

further more i suspect that you would need a hopper that is big enough for holding the wood chips in near to the system for feeding

roughly from what youve posted your needing a design that burns wood chip thats small enough like a smaller gas bottle rocket stove or a design like trying2hards portable one

a pellet/woodchip holder at front been fed from on top

however they all will smoke at first until warmed after that they wont smoke my tests have proven this to me that i dont need a long burn vortex for it to go smokeless and to me is exceptable for 1 min of smoke per lighting

its the long burn times that im after or within a timed system
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gadily
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PostSubject: Re: Fan Use With Rocket Stoves   Tue Apr 22, 2014 8:47 pm









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Tim Keith



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PostSubject: Re: Fan Use With Rocket Stoves   Wed Apr 23, 2014 7:54 am

I intend to include provisions for a fan but hope that it isn't needed. A fan "supercharges" the small wood chip heater to produce greater heat. There is an incentive to increase the refractory content of the heater to tolerate the higher temperature. Initially the heater would be mostly made of steel, as its easy for me to cut and weld scrap steel. There will be a grate in the bottom of the burn chamber that has air holes (and an ash pit below). Natural convection and the vortex effect from combustion will draw some cooler fresh air up through the holes in the grate. That is similar to how coal stoves work. I want the heater to burn so cleanly that neighbors aren't aware of its use. It would probably be used two hours a day, maybe twice a day during colder weather.

The heater will be mostly steel with a refractory liner in the burn chamber and maybe some ceramic tile, it is not a mass heater. The small wood chip heater would be a portable test system that I use for evaluation. Eventually I'd like to build a larger hydronic outside heater in its own shed.

The advantage of wood chips is the heat can be somewhat better regulated than chunked wood, but mechanical assistance is required. I think the steady heat is worth the design effort. The local regulations prohibit most outside burning which leads to mountains of wood chips free for the hauling. I also use wood chips for mulching landscape. The burn chamber of my heater would be about the diameter of a 1-gallon paint can, not as small as some rocket heaters. Winter temps can get down into the 25+ F at night in south Texas, but generally rise to at least 50 F in the day light. With wood chips I can operate for a longer daily time period and not have to manually tend to the fueling.

The videos are encouraging. I don't put much weight in videos that lack a follow up. It is encouraging that some of these are ongoing projects.
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T2H
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PostSubject: Re: Fan Use With Rocket Stoves   Sat Apr 26, 2014 1:54 pm

Gadily once again my friend you are quite the resource!
Great finds.
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Hitchhiker



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PostSubject: Re: Fan Use With Rocket Stoves   Sat Apr 26, 2014 9:51 pm

Tim Keith wrote:

The heater will be mostly steel with a refractory liner in the burn chamber and maybe some ceramic tile, it is not a mass heater.      

Many metal cookstoves are using the basic firebrick as liners.  I would like to see the alternative that you come up with.
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gadily
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PostSubject: Re: Fan Use With Rocket Stoves   Sat Apr 26, 2014 9:52 pm

seen as i mentioned this one

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Tim Keith



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PostSubject: Re: Fan Use With Rocket Stoves   Sun Apr 27, 2014 9:08 am

Hitchhiker wrote:

Many metal cookstoves are using the basic firebrick as liners.  I would like to see the alternative that you come up with.

I will likely use castable refractory for the liner.  The 2600 F degree insulating refractory is a bit expensive but I know that it will work and I only need to make a form from wood or even cardboard.   Some burn out the wood form.    There is a heat conducting and an insulating refractory, I think the insulating type is best.  

I also like soapstone.    Check around for leftovers scraps from local shops that make stone counter tops, soapstone is often used for those.  Traditionally soapstone was often used for laboratory bench tops, it resists chemicals and heat very well.  With castable refractory I won't need to use any high temperature mortar between bricks.
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Tim Keith



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PostSubject: Re: Fan Use With Rocket Stoves   Sun Apr 27, 2014 3:34 pm

In the video of producing dry steam, I wonder how long this rate of production could be sustained?  Its generally safer to produce a small amount of super heated dry steam in a flash boiler than a lot of wet steam - in a contained vessel.  This demonstration being vented its mostly a curiosity.  I am targeting  just hot water, about 130 F to 160 F.   The Steam Automobile Club of America is a good source of information on producing steam, which is highly risky(deadly) unless you follow best practices and have a peer reviewed design. Many of the Youtube steam videos show dangerous techniques.   Wood and steam has an especially dangerous history.   Steam is a topic where intuition and competence in other fields does not count for much.  http://www.steamautomobile.com/

I believe it would be *possible* to fire a flash steam generator with wood chips in a regulated feeding system - in a scenario where there is relatively little water being circulated, then condensed and reused.   Its not a DIY project.  A well designed low pressure boiler that has more than a few gallons of water would be dangerous unless constantly monitored by an operator standing by.    Many of the steam "inventors" on Youtube are doing crazy stuff.  The steam engineering and best practices is proven, no need to learn by trial and error, but a steam operator should have proper certification.  Now and then a competent steam builder blows themselves up because they take a chance that they should have known to avoid.    That being said, an atmospheric vented heat exchanger that does not boil the water can be safe

As a diversion check out Jay Leno's new video on the Doble steam car that was owned by Howard Hughes.
https://www.youtube.com/watch?v=rUg_ukBwsyo
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Hitchhiker



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PostSubject: Re: Fan Use With Rocket Stoves   Sun Apr 27, 2014 9:46 pm

Tim Keith wrote:
Hitchhiker wrote:

Many metal cookstoves are using the basic firebrick as liners.  I would like to see the alternative that you come up with.

I will likely use castable refractory for the liner.  The 2600 F degree insulating refractory is a bit expensive but I know that it will work and I only need to make a form from wood or even cardboard.   Some burn out the wood form.    There is a heat conducting and an insulating refractory, I think the insulating type is best.  

I also like soapstone.    Check around for leftovers scraps from local shops that make stone counter tops, soapstone is often used for those.  Traditionally soapstone was often used for laboratory bench tops, it resists chemicals and heat very well.  With castable refractory I won't need to use any high temperature mortar between bricks.


Good advice.  How much will the cast liner refractory weigh?  Can it be destroyed easily if needed?
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Tim Keith



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PostSubject: Re: Fan Use With Rocket Stoves   Mon Apr 28, 2014 10:26 am

Hitchhiker wrote:

Good advice.  How much will the cast liner refractory weigh?  Can it be destroyed easily if needed?

I don't know how much the castable weighs, but with the steel shell it would be heavy.   Does there need to be an air gap between the steel shell and the castable ?   I have read that an air gap is good to prevent the castable from cracking, some type of insulation that allows for expansion might be between the steel shell and the castable.   I think the castable liner should be at least 2-inch thick.  There are coatings that can be applied to prolong the life of the castable.

One issue with a fan is if it is not used all the time,  when the blower is not running some smoke might feed back into the room.  Depends upon the airflow.  The air feed to the fan might be ducted outside the building. In my scenario the heater would be outside in a shed, but I think the rocket effect would create plenty of draft without the blower.
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Hitchhiker



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PostSubject: Re: Fan Use With Rocket Stoves   Mon Apr 28, 2014 9:30 pm

Tim Keith wrote:
Hitchhiker wrote:

Good advice.  How much will the cast liner refractory weigh?  Can it be destroyed easily if needed?

I don't know how much the castable weighs, but with the steel shell it would be heavy.   Does there need to be an air gap between the steel shell and the castable ?   I have read that an air gap is good to prevent the castable from cracking, some type of insulation that allows for expansion might be between the steel shell and the castable.   I think the castable liner should be at least 2-inch thick.  There are coatings that can be applied to prolong the life of the castable.

One issue with a fan is if it is not used all the time,  when the blower is not running some smoke might feed back into the room.  Depends upon the airflow.  The air feed to the fan might be ducted outside the building.  In my scenario the heater would be outside in a shed,  but I think the rocket effect would create plenty of draft without the blower.  

Not sure if this is what you are looking for (double skinned) but there does seem to be expansion.  

http://donkey32.proboards.com/thread/1065/non-metal-barrel-downdraft-chambers
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