Flue Cube - any thoughts or experiences of this??

[Stubby]

It shouldn't be much of a surprise, consider a car engine, it works at near a perfect mix of fuel and air but there are only milliseconds to complete the combustion. As there is not quite perfect consumption the hot gases ( about 500C) travel on to the catalytic converter. Now as I said previously the catalyst just seems to lower the threshold at which a chemical reaction takes place. So any surviving oxygen molecules and any remaining part burned fuel can have a second chance to meet on the catalyst and combine. Of courser then their energy is given up as heat in the catalytic converter.

 

A couple of points here, if one cylinder misfires persistently then all its fuel and oxygen end up burning in the cat, which will get very hot.

 

The other is that prior to cats being mandatory lean burn petrol engines were being developed, these were challenging diesel engines for economy. However a catalytic converter would be receiving far too much oxygen to fuel gases from a lean burn and hence legislation made put paid to their development.

 

Running on from this you'll begin to see that fuels burn in fixed ratios of fuel to air, e.g. one carbon atom requires 1 oxygen molecule (this is two oxygen atoms) but because air consists of 21% oxygen and 78% Nitrogen you have to supply 5 times more volume of air to get the right amount of oxygen. The correct ratio of fuel to air is known as the stoichiometric ratio. This stoichiometric mix is what is needed for a car engine.

 

Wood is more difficult to burn but we have much more space and time to complete the combustion, we don't want smoke ( which is products of incomplete combustion) so we increase the opportunity for an oxygen molecule meeting a fuel molecule. We do this by adding excess air and maximising the three Ts, retention Time for the reactions to complete in the burner, Turbulence to increase mixing and the chances of an oxygen molecule to meet the fuel and Temperature to provide the energy to dissociate the molecules and facilitate complete combustion.

 

I understand most of what you are saying . I have a plain and simple open fire with a very good draw on it . Apart from innitial light up ( a few mims) I cant tell , from the out side of the house , if its alight or not . Above the pot , on the roof I can't see smoke at all . Come indoors and there is a nice warm fire with bright yellow flame . I assume this is good .

[Goaty]

I will guinea pig. Ordered one and will let you know how it goes. Our problem is trees nearby and sometimes hard to light and smoke comes into room. Etc.

[Alycidon]

I understand most of what you are saying . I have a plain and simple open fire with a very good draw on it . Apart from innitial light up ( a few mims) I cant tell , from the out side of the house , if its alight or not . Above the pot , on the roof I can't see smoke at all . Come indoors and there is a nice warm fire with bright yellow flame . I assume this is good .

 

That is burning well, only problem is that 80% of you heat is going up the chimney. A stove properly installed would resolve that for you, up to about 80% of the heat generated by your fuel comes out into the room rather than up the chimney.

 

A

[Craig Johnson]

I will guinea pig. Ordered one and will let you know how it goes. Our problem is trees nearby and sometimes hard to light and smoke comes into room. Etc.

 

look forward to that. i wounder if it would cure my smoke in the room when feeding the stove?

[slasherscot]

Chimney Products Direct - Chimney Cowls, Caps, Flue Pipe Systems and Accessories

 

i use this cowl..............stops the downdraught and gives u an excellent draw..first class

[Stubby]

That is burning well, only problem is that 80% of you heat is going up the chimney. A stove properly installed would resolve that for you, up to about 80% of the heat generated by your fuel comes out into the room rather than up the chimney.

 

A

 

I understand about the heat going up the chimney but when its been alight for an hour or two all the bricks ( old clamps they are called ) that make up the surround and the chimney breast are all warm to the touch . When you come down next morning they are still warm . . I put a big old lump of holm oak os similar and it keeps in . just stir the embers i bit of smaller ash or syc and away it goes again . Can't fault it really.

[Goaty]

look forward to that. i wounder if it would cure my smoke in the room when feeding the stove?

 

That is when we get smoked, but not always. So will advise as we go and maybe try it with it off then put it on to know if it does make a difference.

[openspaceman]

I understand about the heat going up the chimney but when its been alight for an hour or two all the bricks ( old clamps they are called ) that make up the surround and the chimney breast are all warm to the touch . When you come down next morning they are still warm

 

I thought I replied to this earlier but apparently it didn't send.

 

Warming bricks or stone by a fast hot burn and then allowing the heat to seep out over time is the principle of a masonry stove but they do control combustion air.

 

Alycidon is right, an open fire loses a lot of heat up the chimney in warming excess air, the chimney still needs to be hot at the top to avoid fouling so dumping more flue gases than necessary at this temperature robs heat from the building. Indeed if the building is warm ( say a fire in one room and central heating elsewhere) the open fire can eject more heat up the chimney than the small amount of heat it emits by radiation or heating the brickwork. This of course still happens once the fire is out and the flue still warm.

[Stubby]

I thought I replied to this earlier but apparently it didn't send.

 

Warming bricks or stone by a fast hot burn and then allowing the heat to seep out over time is the principle of a masonry stove but they do control combustion air.

 

Alycidon is right, an open fire loses a lot of heat up the chimney in warming excess air, the chimney still needs to be hot at the top to avoid fouling so dumping more flue gases than necessary at this temperature robs heat from the building. Indeed if the building is warm ( say a fire in one room and central heating elsewhere) the open fire can eject more heat up the chimney than the small amount of heat it emits by radiation or heating the brickwork. This of course still happens once the fire is out and the flue still warm.

 

Ok so what you are saying is I would be better of with a stove . The thing is I am reluctant to fix what aint broke !

[openspaceman]

Ok so what you are saying is I would be better of with a stove .

 

 

No, I wasn't being at all prescriptive just pointing out that your comments that the bricks were warming up and increasing efficiency of the fire was wrong. I like a good blaze in and open fire and if the wood is free...