Yield wood stove and flue gas temperature

Heating, insulation, ventilation, VMC, cooling ... short thermal comfort. Insulation, wood energy, heat pumps but also electricity, gas or oil, VMC ... Help in choosing and implementation, problem solving, optimization, tips and tricks ...
Christophe
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by Christophe » 12/11/10, 14:23

We will stop beating around the bush on my measurements ... our fireplace is inside and goes into a living room (glued to an exterior wall insulated in ytong) so there are still a few calories that will be "useful" recovered ...

I mean that measuring the T ° at the outlet of the stove exchanger will not give the overall balance but only that of the stove even if there is a good chance that more than 90% of the calories are provided before the chimney.

So :

a) I just wanted to go up to what correspond to the smoke t ° for a given stove for 74% yield. That's all.

b) On the other hand I would like to see other comparative measurements of T ° on stove (no matter the method if it is valid) from other people ...

c) Bonding a thermocouple on the stove or nozzle will give you a much less accurate value of the surface temperature (decreased or increased depending on the ambient T °) than by infrared. You're wrong!

I tested. The infrared method is valid even if you think otherwise. Example: my skin in the palm of the hand is at 33.7 ° C ... it is impossible to get this value by not strongly sinking the thermocouple in the hand (just glued on the skin it will give a lower value). ..

ps: pkoi do you think medical thermometers put themselves where I think ... or are they just infrared?
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bernardd
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by bernardd » 12/11/10, 14:30

Christophe wrote:b) On the other hand I would like to see other comparative measurements of T ° on stove (no matter the method if it is valid) from other people ...


Very good initiative, I find it very interesting.

I would also like to test by putting a plate heat exchanger type vmc to recover all the thermal energy and see what happens. By compensating of course the pressure drops by a fan.
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See you soon !
dedeleco
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by dedeleco » 12/11/10, 14:37

The thermocouple should be thin, flattened, like a sheet (less than 1 / 10 is mm and a bit insulated, because of the DIY fine wires Cu Iron) because the thermal air boundary layer is around 3, 5mm to 1cm ( as for the double glazings) on which the greatest variation of T occurs, and so we better measure the surface T as well as the infrared T with its unknown emissivity.

If not, does the stove have a draft air inlet near the exit ???
It is necessary to evaluate the excess of air as explained by Chatelot16 !!
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by Christophe » 12/11/10, 14:38

bernardd wrote:I would also like to test by putting a plate heat exchanger type vmc to recover all the thermal energy and see what happens. By compensating of course the pressure drops by a fan.


Because of the fouling and incompatibility of materials (T °), you can forget this idea ... in my opinion ...

It makes me think that there are wood stove catalysts but they never pierced commercially for individuals (expensive, efficiency ?, wear ...) so hard to find if it still exists. We have an old topic on the question: https://www.econologie.com/forums/catalyseur ... t3518.html

One can also imagine putting an old catalytic converter (anti-CO) or a particle filter ... but it must be regenerated periodically. So on a boiler oil it should work well (gas plant anyway) ... So the assembly of maloche is much more interesting: https://www.econologie.com/forums/ameliorati ... t5172.html
(to avoid pollution is better than to clean up)

dedeleco wrote:The thermocouple should be thin, flattened, like a sheet (less than 1 / 10 is mm and a bit insulated, because of the DIY fine wires Cu Iron) because the thermal air boundary layer is around 3, 5mm to 1cm ( as for the double glazings) on which the greatest variation of T occurs, and so we better measure the surface T as well as the infrared T with its unknown emissivity.

If not, does the stove have a draft air inlet near the exit ???


Ok on (I) waiting for your photo reportage measurement with your method.

No there is no air intake.
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dedeleco
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by dedeleco » 12/11/10, 14:49

YES, better combustion, pseudo gasifier and assembly Maloche with little soot, then good exchanger with scraper for automatic cleaning of the remaining soot, it is the right solution that exists close enough in good expensive boilers (20000 €) and it would take Japanese strenuous to turn this into a cheap stove or consumer insert, as for the microwave oven cheap, expensive radar become cheap!
French, we will never do it !!
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by chatelot16 » 12/11/10, 14:50

Christophe wrote:Urban artist the T ° gradient between the top, the side and the bottom of the nozzle tends to prove that the measured T ° is close to the container ...

Measurements on the nozzle with emissivity of 0.45:

- High: 88 ° C
- side: 61 ° C
- down: 52 ° C

If one measures these differences of T ° on the nozzle, it is good that these measurements are significant of the T ° of the fumes (I say not in the middle of the nozzle but at least on the circumference of the gas vein ...) ...


I draw a different conclusion!

I think the completely turbulent interior flow is at a uniform temperature

on the other hand, on the outside, it is a rising air flow caused by convection: the bottom of the pipe is thus better cooled by this flow of air at ambient temperature.

the top of the pipe is cooled only by air which is already heated by making the pipe turn so temperature closer to the inside temperature than outside

if you do not want to pierce the pipe put it in glass wool, with a hole in the glass wool as small as possible for the infrared thermometer: I think the temperature will rise

I also think that with glass wool you will find the same temperature at the top and at the bottom
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by Christophe » 12/11/10, 14:57

Rahh, you keep going around the pot instead of taking your thermocouple (or whatever) and doing your own measurements ... : Evil:

For convection, I had thought ... but I do not know: given the T ° of the air behind the stove is relatively homogeneous (radiation of the nearby stove and refractory wall behind 20 cm) and knowing the conductivity of steel, well, I do not really believe this explanation ... Although some stainless steel are bad conductors of heat. As I do not know which one is used there ...

To know it must be measured. So yes, I will try to measure with a piece of rockwool and a thermocouple. It is sure that the T ° will be more homogeneous but not that it is fully ... we will see well.

By cons I do not think at all that is turbulent ... for the air must be very fast to get into turbulent if I remember my waves cours mecan fluid ...
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dedeleco
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by dedeleco » 12/11/10, 15:08

For the air on meters we are always turbulent, even with paper plane, and in the water we can swim because turbulent, otherwise we would sink!
The classes are a lesson for students, forgetting to insist on simple points of reference and privileging an armada of formulas!
Laminaria is the jar of jam or quicksand (where it flows) or spermatozoa with their flagellum!
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by Christophe » 12/11/10, 15:24

Uh ... do not agree ... There are many more laminar regimes than that.

You talk about sperm, so stay in the area: you've already pee standing I guess? If you're not in too much of a hurry to drain, you should see the laminar flow of the jet ... which is accelerated by gravity and so goes from one regime to another ...

I am wrong?
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dedeleco
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by dedeleco » 12/11/10, 15:39

Exact with tap too, but a dead leaf also falling is in the turbulence !! Without turbulence not possible to fly and the same for air in a room and requires double glazing to avoid convection turbulence (cm)!

Read the free books!
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