Those in the know??? Question about stove mods?

[woodgeek]

While the fin system extracts heat from the stove using conduction, it releases it using both radiation and convection from hot fins exposed to air.

Defending my comment from 15 mos ago.....when the fins are closely spaced (as in #4), convection dominates.

 

[DevilsBrew]

I think I am catching on. Fins are a passive heat exchanger.

 

[Highbeam]

Dominates is a pretty loose word for a guy making "picky internet nerd" comments. It is fair to say that cooling fins lose plenty of heat from radiation says me with hot legs while riding air cooled motorcycles in shorts.

 

[savageactor7]

Don't you think fins would be hard to keep clean...or is it just our stove that produces daily amounts of noticeable dust?

ps ...still burning.

 

[Highbeam]

Don't you think fins would be hard to keep clean...or is it just our stove that produces daily amounts of noticeable dust?

ps ...still burning.

This is my first year with the black steel BK and I too notice that the stove seems to be a dust machine. Is the stove just a magnet for the stuff or is it making dust?

 

[downeast]

Inconvenient truth:
I hacked my Oslo.


From the Bungalow Syndrome ( thanks John G.) the non-cat stove controls primary air too much ( IMNSHO also ) to satisfy EPA "tests" .
So an extra 1/4" hole was drilled into the "doghouse" air box for extra primary air at WOT, yet it will do its bare shutdown when closed ( sic ).

Does it add more heat ? Perhaps, but it does make starting and burning larger splits or more dense wood more efficient.
Sorry, no devices to check the specific gravity or moisture of the wood, or exact temps of the stove. Hey, we only want to keep warm.

Now, please do not tell Jotul USA. Thankyou. Thankyou very much.

 

[begreen]

I hacked my Oslo.

Now, please do not tell Jotul USA. Thankyou. Thankyou very much.

No worry. You just did.

 

[DexterDay]

I made a convection deck for my 30-NC

Started life as .040 piece of 1055. Then I added a few bolts to level it.


Then cut a 4" piece of rigid dryer vent in half and screwed to the plate.

Then painted it all black. I only use it when I run the blower. It helps to run the air directly across the top of stove, rather than shoot it up on a 40* angle like the deflector on the back does...



I only did this a little while ago. But after 2 yrs of running the stove, it seems to make a huge difference. Mind you I am running from the basement

 

[Highbeam]

Funny that you took such great efforts to seal the outer shell of double wall pipe.

 

[downeast]

No worry. You just did.

A joke Msr. Green...a joke.

The " Thank you. Thank you very much" is from a worn Elvis line from the Vegas shows. Google. YouTube.

P.S. Forget those smokepipe heat exchanger fins, or attachments to stoves, etc.. Minor gain with much effort. Instead follow the concept of Mass similar to the manufacturers using soapstone, heavy cast iron, or firebrick for mass storage.
Surround the stove with granite, soapstone, brick, slate, cementboard, or other dense material for wall protection. We use surplus lab bench tops from schools ( the asbestos is safe if not cut ).

And, stand alone wood stoves in unfinished, unused basements are a poor use of mass and heat.
Most of that heat goes into cellar walls, cinderblock as shown, passing out to dirt unless seriously
insulated on the OUTSIDE of the foundation.

JMNSHO

 

[DevilsBrew]

I'm not sure about that, downeast . When I was first introduced to alternative stoves, I went along with the concept that mass was a necessity. The more research I do and the more projects I see, the more I doubt that philosophy.

 

[downeast]

I'm not sure about that, downeast . When I was first introduced to alternative stoves, I went along with the concept that mass was a necessity. The more research I do and the more projects I see, the more I doubt that philosophy.

Look over the efficiency of Russian/Masonry Stoves that use mass as the carrier of heat.
Or, study how different materials compare in density for both absorbing and distributing heat: cast, soapstone, steel, stones, concrete, etc...
For example: steel wood stoves throw heat fast, but don't hold heat as well as cast or soapstone. It's mass.

When we built our home in 2001 in northern Downeast Maine, a Masonry Stove/Fireplace was seriously in the cards. The necessary redesign and engineering of the
foundation and the cost of the units was prohibitive for us even if a DIY. So, we used a technology that was 1/4 the net cost of a Masonry Firepalce and that we were familiar with: stand alone wood stoves.

 

[Dakotas Dad]

The trick of a Russian stove or mass heater is that the heated mass is centered in the home/space so the radiated heat radiates into the space being warmed, not the flower garden, and the mass matches the bTu capabilities of the firebox and flue, so that it can be warmed enough to actually radiate said heat.

 

[DevilsBrew]

I came about this backwards. I was first introduced to RMHs back in Jan/Feb of 2012 followed by the traditional masonry stoves at the beginning of the 2012 summer. Now I am learning about the design and science behind metal stoves.

I have discovered during my current studies to not dismiss the capabilities of metal stoves and design options. To sum up a comment I read recently, why use mass when you don't need it? There seem to be many avenues to explore.

 

[woodgeek]

I contest that the effective heat storage capacity of a well insulated house is higher than that of a massive stove. If you get that heat spread around your whole living space, then 'storage' by the stove is a lot less of a concern. If your stove room is too hot, buy a fan, not a heavier stove----it'll be cheaper and you'll be more comfortable.

And none of this has anything to do with efficient burn.

 

[begreen]

Mass evens out the temperature swings between feedings. Having had both a radiant stove and more massive convective stove I prefer the latter. House temps are much more consistent and comfortable and that reserve warmth makes for nicer morning wakeups.

 

[ddahlgren]

I think there is one thing that can not be avoided. The flue has to be above 250F at the flue cap. Less than that and the rest does not matter so a capping on how much heat you can extract. this would make the larger stoves better as they would have a larger percentage of heat delivered vs. how much up the flue. That would infer that the long slow burn actually delivers less heat per pound of wood than a short fast one on a per pound of wood in the stove as the time to maintain 250F at the cap is less and a smaller percentage of btu input.

 

[Highbeam]

larger stoves better as they would have a larger percentage of heat delivered vs. how much up the flue.

It's not just temperature of the flue gas but volume as well that determine energy loss up the flue. My BK emits a very small amount of exhaust at a very low temperature. Compare that to my smaller hearthstone that blew out huge amounts of non-cat exhaust at double the temperature.

 

[ddahlgren]

It's not just temperature of the flue gas but volume as well that determine energy loss up the flue. My BK emits a very small amount of exhaust at a very low temperature. Compare that to my smaller hearthstone that blew out huge amounts of non-cat exhaust at double the temperature.

It has to take a certain number of BTU to keep the flue above 250 for the entire length. There are many ways to get it fro low volume high temperature or high volume lower temps. The heat loss of the flue system is what it is and no way to change that with the stove connected to it. The BTU requirement does go up as outside temps go down as well. In another post I mentioned when doing probe testing that I thought it would be useful to actually measure the temp at the chimney cap. Some discounted the value of the measurement but my thought is the number of BTU to keep the entire flue above 250 and enough draft for the stove to work right is all the heat you really need to send up the flue. Knowing the temp at one location does not mean you know it at some remote location. Consider just the difference between my short flue with only 5 feet outdoors vs. a 3 story brick chimney on the outside of the house. A safe and adequate flue temp for one would be wildly different for one vs. the other to maintain 250F in the flue. I know nothing about cat stoves but it would seem hard to believe any stove has zero emissions and cannot make creosote.

 

[Highbeam]

The cat stove has similar emissions as a non-cat and makes plenty of creosote when burned low. I suspect the low flue temps are a major factor for creo formation and those cat stoves unable to burn very low will not see as much creo formation.

I agree that the most important flue temperature with regards to creo formation is at or near the cap.

For any stove, it is not enough to simply know the flue temps in order to determine efficiency. One must also know the quantity of flue gas at the particular temperature in order to have a grasp on the energy (btu) sent up the stack. Unless you can measure flow, you know nothing other than whether creo formation is likely. Once you know flow and temp, then you can compare that to btu input to get an actual efficiency measure.

 

[ddahlgren]

The cat stove has similar emissions as a non-cat and makes plenty of creosote when burned low. I suspect the low flue temps are a major factor for creo formation and those cat stoves unable to burn very low will not see as much creo formation.

I agree that the most important flue temperature with regards to creo formation is at or near the cap.

For any stove, it is not enough to simply know the flue temps in order to determine efficiency. One must also know the quantity of flue gas at the particular temperature in order to have a grasp on the energy (btu) sent up the stack. Unless you can measure flow, you know nothing other than whether creo formation is likely. Once you know flow and temp, then you can compare that to btu input to get an actual efficiency measure.

I am not personally worried about the efficiency per se but staying hot enough to stay away from creosote and cool enough to within chimney ratings. That is the reason I mentioned a measurement at the cap. The efficiency is a moving target throughout the burn cycle and varies load to load and season to season. It is never a steady state device for a very long time at least at not for me. A fixed firing rate device like oil gas or coal is much easier to measure combustion efficiency. Not to get dismissed is the total system efficiency that combines combustion and heat delivered to the room. If trends in modern heating systems are extended to wood then a low mass quick heating stove would give the greatest amount of heat for a given load of wood. A comparison might be the cold start boiler in my house. It hold about 5 gallons of water and goes from room temp to 190 degrees in about 2 minutes and starts delivering heat to the house in under 1 minute. Combustion wise it is about 35 better than the one it replaced but system wise it burns 40% less fuel than the old one. A nice tip for anyone that does not have a large family home all day is to put the domestic hw heater on a timer. Mine runs an hour a day and feeds a 30 gallon storage tank. That is time enough for a shower do dishes and laundry all at the same time. The water in the tank is still quite warm at the end of the day to wash up or rinse a dish to be put in the dishwasher to run the next morning. That saved 40% of the now 40% less oil burning. Clock thermostats and zones laid out so you are not heating an area when not used a big help too. I have 5 zones in my house all on clocks other than the bathroom yes the bathroom has it's own zone for just 1 room. That stays warm 24/7 365 unless on a trip. I think following this mentality with wood or coal heat might help save a lot of wood and work cutting stacking etc. At least using a couple of stoves in a large house especially if it is not all used at the same time makes a lot of sense to me. My efforts this year resulted in a warm house using a combination of wood (2.5 cords and that is a lot with only 1.3 cu ft to burn in) fuel oil (under 125 gallons) solar by managing drapes open during the day to let in heat closed at nigh to help keep it in and a lot of common sense.

Sorry this is so long and yes digressed from the original post but got on a roll and a favorite subject of mine.
Dave