Radiant versus convective heat

[Woody Stover]

The chimney is inside the house except for the part that will be through the cathedral ceiling. It's centered so there won't be much above the roof. I'm using 12"x12" clay liners stacked. I put refractory mortar (sariset) between the clay liners and a hi-temp silicone to fill in the outer crack. I left 1/2" gap and bricked up around the clay liners.
I don't need to fill this 1/2" gap with perlite insulation do I? Just insulation around the clay flue once it is through the roof?

My post was tongue-in-cheek....you certainly wouldn't want to insulate the flue, you want that heat to migrate into the thermal mass, correct? I don't recall if, in your previous posts, you described the routing of the exhaust through the thermal mass. You based this heater on other designs, so I'm assuming it will work well for extracting heat from the exhaust. My BIL has a Russian fireplace but I've not seen it yet...not sure how the flue system is constructed. The 1/2" gap between the liner tiles sounds like it would make heat transfer more difficult but I just don't know enough about it...

 

[Woody Stover]

Anything between the heat source and the surface that will be radiating will act as an insulator....Its very conceivable the larger amounts of surface area combined with the hotter surface temps cause significantly more radiant heat transfer vs my King that has external shields on the side and internal steel shields/fire bricks.

That's why I don't think the sides of the BK will get as hot as some other stoves, because of the inner shields. The outer shields are creating a convection chamber to heat air; Not sure what the inner shields are doing, but I think they may help the low burn stay clean....

 

[tpenny67]

While we're talking about this, what about conduction and surface area? On a radiant stove, the metal side usually ends at the top of the stove (duh?), but on a convection stove like a Liberty, the stove sides extend beyond the top and bottom of the firebox to form the side of the convection chamber. The top of the convection chamber is connected to the sides and also the bottom step of the stove top. If you squint this all starts looking like a giant finned heat sink. This should be pulling heat away from any hot spots on the stove, producing the reduced side temperatures we've been talking about. So most of the metal is a lower temperature than a radiant stove, but you still get good heat transfer to the room because there's so much more of it.

Also, I imagine that super-heated fire inside is going to have spectacular heat transfer when it does find a bare piece of metal, thus explaining the 800 degree stove top.

 

[byQ]

My post was tongue-in-cheek....you certainly wouldn't want to insulate the flue, you want that heat to migrate into the thermal mass, correct? I don't recall if, in your previous posts, you described the routing of the exhaust through the thermal mass. You based this heater on other designs, so I'm assuming it will work well for extracting heat from the exhaust. My BIL has a Russian fireplace but I've not seen it yet...not sure how the flue system is constructed. The 1/2" gap between the liner tiles sounds like it would make heat transfer more difficult but I just don't know enough about it...

By the time the exhaust/gas gets to the flue there isn't that much heat to dump into the masonry - most of it has already been absorbed. The area above the firebox is where most of the energy goes. I had to use some angle iron with a heat shield of firebrick splits here or else it's crack city. I messed up when I put the door in - the firebrick splits are suppose to be below the top of the door frame but I put the door in to low. Now I need to bolt or weld another shield onto the first shield so I'll end up with 2 shields - oops.

 

[Woody Stover]

on a convection stove like a Liberty, the stove sides extend beyond the top and bottom of the firebox to form the side of the convection chamber. The top of the convection chamber is connected to the sides and also the bottom step of the stove top. If you squint this all starts looking like a giant finned heat sink. This should be pulling heat away from any hot spots on the stove, producing the reduced side temperatures we've been talking about.

Looks like the convection chamber extends down the outside of the firebox...more of a convective stove than I thought. Then, above the brick, it looks like the secondary air channels are grabbing radiant heat before it reaches the wall of the box.

 

[tpenny67]

Yep and yep. The convection chamber is a C-shape that starts on either side of the air intake at the bottom front of the stove, goes under the firebox, up the backside, and out the step. When the blower is on hot air comes out the step, and also out the bottom of the stove in front. Leave the blower on long enough with the air control closed and it will lose the flame.

 

[tpenny67]

They are a little generous calling it a 5-sided convection chamber though. There is a heat shield that wraps around the sides and back, which technically is also a convection chamber but it isn't fan-forced. This also means there are 3 layers of metal in the back of the stove. If the blower is running the rear shield barely reaches body temperature. Have I mentioned how much heat the blower can pull off the stove?

 

[Woody Stover]

Have I mentioned how much heat the blower can pull off the stove?

I'm not sure if you did, but I know that the Buck 91, with side, back and entire top shielded, pulled off a huge amount of hot air...couldn't hold your hand in front of the vents for more than a couple seconds.

 

[lsucet]

That's why I don't think the sides of the BK will get as hot as some other stoves, because of the inner shields. The outer shields are creating a convection chamber to heat air; Not sure what the inner shields are doing, but I think they may help the low burn stay clean....

Woody i will tell you something and is my wish that is not take in the wrong way. I dont see problem with the BK radiating heat from the sides because of the inner shields, they are just covering the upper part of the stove just in a partial way plus there is like 2" space between them and outer wall. I know you have that in mind. Any stove with outer side shields regardless the technology has no good radiation of the heat from the sides. After all that is why manufactures installed them or give you the option to have it or not. The main purpose like you already know is clearance to combustors

I don't burn every day like most of you here cause you know i told you i am there just on weekends, but that make me when i get there to burn the stove hard and hot to bring the house to temp. at that point i start the fire and i don't pack the stove too full cause i want air moving and a hot fire I can get 750 easy the stove top and if i point the laser between side shields and the side of the stove, the parts that i am able to point at it are in the high 500 df and i don't have to tell you what is the temp coming thru that glass.lol.

at this point i closed the tstat cause what is the point of leave it wide open and keep sending all that heat up the flue. I hear the tstat clicking closed about 3 o'clock at that point and i turn the fans, I keep that temp for at least 2 to 3 hrs with fan running on high

What you are not seeing here is the BK design is not based on that radiation most people are used to it and like to continue seeing from a wood stove. But it has the ability if that is the way you want to run it. You just need the model like the classic or the parlor without side shields and convention deck and you will have it. the good thing is that you will not overfire it because of the tstat.

In the past people had all that heat from old stoves but i take the liberty to says that most of them, were over fired most of the time.

 

[bholler]

In the past people had all that heat from old stoves but i take the liberty to says that most of them, were over fired most of the time.

And do you have anything to base that wild generalization on?

I was really hoping this would not turn into a blaze king bs thread like so many others do.

 

[lsucet]

well for what i can see the bs is just coming from you cause i said most of them. I never said all of them or everybody. I never had and don't have the need to heat with wood stove like main heating source like i am doing for the past 3 -4 winters, but i always had wood stove at the ranch. an old Sears & Roebuck in enamel that it is now in the back yard. I used to burn in it for years sometimes. Plus the whole family in that land are using wood stove all their life like main heating source. it just was easy to turn the in wall furnaces. I never care about pay for the propane and still not care if i have to.

I decide to do this because i want not because i need and if is to cold i can come back in town and stay warm on natural gas. don't get wrong what it is just a point of view and a reality. at least i have burn on different technologies and i have idea how they all works regardless brand. I have the right to make my point if i have to and to explain to a person that can have the wrong idea how things works with an specific product that i know and have plus use.

Regards

 

[Woody Stover]

I dont see problem with the BK radiating heat from the sides because of the inner shields, they are just covering the upper part of the stove just in a partial way plus there is like 2" space between them and outer wall. I know you have that in mind. Any stove with outer side shields regardless the technology has no good radiation of the heat from the sides. After all that is why manufactures installed them or give you the option to have it or not. The main purpose like you already know is clearance to combust

The external side shields also serve to intercept radiation and convert it into heat. Radiation traveling through the air doesn't heat anything until it hits an object. When radiation hits an external side shield, the shield is heated and then that heat can be pulled off passively as in the BK by convection of the air rising between the shield and the side of the stove, or actively as in the Liberty and the Buck 91 by the blower moving air between the side and the shield.
It would be interesting to have the side shield off the BK, then shoot all over the side of the box with an IR gun, both toward the front where the shield stops and the flame and coals can radiate directly into the sidewall of the stove, and further back where the side is complete shielded from radiation of the flames and coals. I'd like to see what the different temps would be. I think the inner shields probably serve to intercept radiation off the coals/flames and keep it in the stove, as opposed to letting it hit the stove walls and allowing some of that heat to leave the box. That may allow the cat temp to stay up at lower burn rates. Now, that heat should eventually leave the box, but is probably best stripped at a low burn rate where the heat doesn't go up the flue, but has a chance to get out the top of the stove. I think that stoves that allow more radiation to the walls, and have blowers that cover the side walls, will get more heat out of the box, faster, at high burn rates than a BK will. It all comes down to engineering decisions.
As has been stated here, all stoves operate on a combination of radiation and convection, and the two are inextricably linked.

 

[lsucet]

The external side shields also server to intercept radiation and convert it into heat. Radiation traveling through the air doesn't heat anything until it hits an object. When radiation hits an external side shield, the shield is heated and then that heat can be pulled off passively as in the BK by convection of the air rising between the shield and the side of the stove, or actively as in the Liberty and the Buck 91 by the blower moving air between the side and the shield.
It would be interesting to have the side shield off the BK, then shoot all over the side with an IR gun, both toward the front where the shield stops and the flame and coals can radiate directly into the sidewall of the stove, and further back where the side is complete shielded from radiation of the flames and coals. I'd like to see what the different temps would be. I think the inner shields probably serve to intercept radiation off the coals/flames and keep it in the stove, as opposed to letting it hit the stove walls and allowing some of that heat to leave the box. That may allow the cat temp to stay up at lower burn rates. Now, that heat should eventually leave the box, but is probably best stripped at a low burn rate where the heat doesn't go up the flue, but has a chance to get out the top of the stove. I think that stoves that allow more radiation to the walls, and have blowers that cover the side walls, will get more heat out of the box, faster, at high burn rates than a BK will. It all comes down to engineering decisions.
As has been stated here, all stoves operate on a combination of radiation and convection, and the two are inextricably linked.

I totally understand what you say and is good to have a civil conversation thru this forum without the use of "BS" and all those attitude. I think that i was just communicating with you and letting you know my experience. If it comes to the point that my experience is with a brand that some don't like to hear about it, well so be it.
Your comment is welcome and is well put together.

 

[bholler]

well for what i can see the bs is just coming from you cause i said most of them.

Yes I read exactly what you said. And again do you have anything at all to base that on?

I have absolutely no problem at all with blaze kings of the fact that you like yours and it works well for you. But when you make wild generalizations like you did all while saying that bk's can do it all as well as any others it sounds like the same old fan boy stuff. Yes blaze kings are great stoves for low and slow without a doubt. But they typically run with much lower temps in the firebox because of that they are not good radiant heaters at all heat shields or not. I work on and burn many different technologies. I understand them just fine. And yes for many people cat stoves and blaze kings are a great fit. and for them I would absolutely recommend those stoves. But for someone looking for a high btu output radiant heater a bk is not the right fit.

 

[lsucet]

well you see, if i really give the correct answer to you question and statement, then we will be making this a BK stove vs any other stoves and i think, if i understood correctly, this is not what you want plus it was not at all my intention with my post above.

My statement about over fired stoves in the past is reality, like it can happen now also. just people are more educated about now. but i will leave it at that. there is no point of get into that. back in the day not many wood burners use thermometers and other aids that are available now a days. most just toss wood in there and lets stay warm, that was what was important. but it is ok if you don't think so

 

[Marshy]

Time to get educated.

(broken link removed to http://www.healthyheating.com/Thermal-Comfort.htm#.WJQO55FOnqB)

 

[begreen]

well you see, if i really give the correct answer to you question and statement, then we will be making this a BK stove vs any other stoves and i think, if i understood correctly, this is not what you want plus it was not at all my intention with my post above.

My statement about over fired stoves in the past is reality, like it can happen now also. just people are more educated about now. but i will leave it at that. there is no point of get into that. back in the day not many wood burners use thermometers and other aids that are available now a days. most just toss wood in there and lets stay warm, that was what was important. but it is ok if you don't think so

How far back you going son? Many of us here have heated with wood for decades without overfiring the stove. Our 1979 Resolute came with a thermometer and it has been on every stove we've owned since then.

 

[tpenny67]

How far back you going son? Many of us here have heated with wood for decades without overfiring the stove. Our 1979 Resolute came with a thermometer and it has been on every stove we've owned since then.

I can go back further than 1979, but only vicariously

My father in law had a small cabin in Vermont he built back in the early 60s and it had an old (probably new at the time) box stove with no air control except the damper. He always told the story of the time his dad put a piece of fir in by accident and the entire stove glowed red, so they opened the door wide to let all the heat up the chimney. I didn't bother to point out that he probably created a blast furnace by doing so. There's still a small scorch mark on the wood near that stove, as it doesn't even have 3 feet of clearance to combustibles.

We just bought the house across the street from that cabin, and that came with an old Jotul 118 that shows signs of overfiring. With the 118, it's very easy to get the side temperatures up to 600 and the top up to 700. I don't stuff it full of wood and keep the air turned down because I don't want the cracked sides hitting 800+.

Anecdotal evidence to be sure, but that makes 2 out of 2 old stoves I know of that have been over fired. I'm pretty sure that with a modern stove it's hard to get anything other than the stove top to glow in an overfire condition.

 

[bholler]

How far back you going son? Many of us here have heated with wood for decades without overfiring the stove. Our 1979 Resolute came with a thermometer and it has been on every stove we've owned since then.

And my father has been supplying them to customers pretty much since he started in 1975.

 

[JA600L]

I like radiant heat better from the basement. It warms the slab and walls better in the basement which brings the heat up the stairs. My Ideal Steel is claimed to be a radiant heater but has some convection to it.

My Quadra fire 4300 with shields worked a lot harder

 

[lsucet]

How far back you going son? Many of us here have heated with wood for decades without overfiring the stove. Our 1979 Resolute came with a thermometer and it has been on every stove we've owned since then.

Begreen is ok if you think that, was not common back in the days. We still seeing that happening but it is ok if you don't see it or think is not true and possible.
There is a history behind everything. rules and regulations are created to stop the salvage/crude/cruel way that something is done. That apply to anything.

This site is one of the greatest informative site for an individual get educated and learn about wood burning but there is a reality. WE ARE JUST A SMALL COMMUNITY. lot of people burn wood to stay warm and they have no interest in knowing what you, me or somebody else has to say. After all they are doing this all their life.lol. That is the way many here think also. New people has no saying. i can tell you many stories related to wood burning and crazy things i am seeing over the x amount the years without has to be a hard core wood burner. Just in the village where i have the ranch, things i can't believe cause i know better. I guarantee you that bholler will be out of the job here.lol finding something else to do cause nobady needs his services here.

His job is a creation from rules/regulations and codes plus insurances companies enforcing those regulations in some areas as much they can. there are lot of people that they don't need insurances, they own the house etc and don't see the need to anything like that. I am an example of that. the Ranch is paid off and if i want i can keep everything the way it was with that old stove. if somebody take me to court, well i bet it will be grandfathered because it was like that before me. was my choice to do everything by code and regulation to insurance the property.

 

[lsucet]

And my father has been supplying them to customers pretty much since he started in 1975.

What is the point? wood burning start since 1975?

 

[bholler]

I guarantee you that bholler will be out of the job here.lol finding something else to do cause nobady needs his services here.

I know several sweeps who work in New Mexico. And I work in a rural area where many heat with wood and do their own maintenance. I still dont see what that has to do with most stoves being overfired then or now. Yes lots of people over fire their stove and lots of people used to as well but most people even before thermometers were readily available knew how to run their stoves. And most did not over fire them.

His job is a creation from rules/regulations and codes plus insurances companies enforcing those regulations in some areas as much they can.

Really you think the profession of chimney sweep is a creation of insurance companies and codes???? Any evidence to support that? Becasue there is tons of evidence to refute it. And I almost never do anything just to satisfy code or insurance I do it because it is the best and safest way to do it. Where I work we very rarely have any inspections most insurance companies dont inspect so we could in theory do what ever we wanted but we choose to do it right.

What is the point? wood burning start since 1975?

No but I am still waiting for any evidence to support your claim.

 

[lsucet]

you know bholler, what happening here is the some people are lack of the ability to understand what they read. i said not many wood burners.....
I never said nobody.

also i never said that thermometer don't exist at that time or any time. tell me where is the statement from me saying so. i never said or mentioned any year in particular. not 1800, not 1870, not 1975, not 1979 or 2017. I know lot of wood burners that don't have an stovetop thermometer and they can care less of it. the question still, what is your point? And i stand firm on what i said. back in time it was just a hole in the roof and a piece of pipe going thru the roof, length was not a requirement or concern for most. and i am a witness of that with the piece of pipe for chimney this house had for who know how long. Oh and i used to burn on it too. I don't think somebody with those setups need your services.

Here are pictures of my own, I found one and the other from now. I can get down the road and take pictures of other houses chimneys but it is not my business. Now tell me if i don't know what i am saying

 

[bholler]

In the past people had all that heat from old stoves but i take the liberty to says that most of them, were over fired most of the time.

So you didnt say that most of them were over fired most of the time????

also i never said that thermometer don't exist at that time or any time. tell me where is the statement from me saying so. i never said or mentioned any year in particular. not 1800, not 1870, not 1975, not 1979 or 2017. I know lot of wood burners that don't have an stovetop thermometer and they can care less of it. the question still, what is your point?

My point is that your claim that "most of them, were over fired most of the time." Is competly innacurate and you have no evidene to back it up. Yes I know very well that lots of setups used to be and still are far from perfect but that does not mean they were being overfired all the time.

And your claim that chimney sweeps are a creation of insurance and code is absurd and you have nothing to back it up.