partway through building new wood burner

[M1CDQ]

I am nearly there progress so so far.
Ive got the flue fitted and the top hotplate welded on.
Now Im just burning some wood in it to see how it performs

Well the kettle seems to be boining away nicely and a fair be of heat is given off with very little smoke out the flue so it must be burning well

its been going 2 hours now kettle is simmering away and Ive not had to put more wood in.So its looking good sofa
just need to get the rest of the red pain off then gice it a good coat of Black heat paint.

 

[Stuggi]

I'm intrigued as to why pre-heating the air in the tubes improves combustion.

Combustion depends on the mass of air, not the volume so I reckon cooling the air should improve combustion. Like you use intercoolers on turbo engines and cars seem to run better on cooler days.

Cooling of the intake air is only to be used if;

A) The combustion chamber has a small fixed size, so that the mass of the air you can ram in there takes higher priority.

B) When cooling of the combustion chamber is a something you want to achieve.

In an internal combustion engine A and B apply, therefore you use intercoolers and turbo's, at the reduced efficiency of the engine, as you're most commonly going for max power.

In a forge one does ram air into the combustion camber, as you want it as hot as possible while maintaining a lower temperature of the actual forge, so it works in your advantage to ram colder air into the combustion camber. Dunno if an intercooler would help or not, but it would decrease the efficiency of the forge. The actual practical benefits would probably be lost as the difference between inputting 20C air or 15C air into a 1500C furnace isn't much. Personally I can't really see a difference between -20C and +20C ambient with my forge.

In a wood burning stove, you want maximum heat for the minimum amount of fuel with the cleanest possible output so you preheat the intake air to increase efficiency and make the stove burn wood as cleanly as possible.

 

[rtbcomp]

.......Dunno if an intercooler would help or not, but it would decrease the efficiency of the forge. The actual practical benefits would probably be lost as the difference between inputting 20C air or 15C air into a 1500C furnace isn't much. Personally I can't really see a difference between -20C and +20C ambient with my forge.

......../QUOTE]

You wouldn't use an intercooler in a forge as the air is at ambient temperature anyway. They're used on turbo engines &c because the turtbo runs very hot and as you say, you need cool air in an engine.

 

[Stuggi]

I've seen intercoolers used on superchargers as well to increase mass of air blasted into the cylinders (lower temperature = higher gas density), but as you say they most beneficial on turbo's that need the additional cooling. And I was just hypothesizing on the forge part, no one in their right mind would even think about fitting an intercooler in front of the fan. I wonder on the other hand if using cold winter temperature air from outside the forge building would increase the temperature of the fire...

 

[Stuggi]

Oh, I forgot one of the more important aspects of hot intake air in a furnace, gas viscosity. If the intake air is pre-heated by stray heat, the air will mix more completely with the gases in the furnace, resulting in better combustion.

The reason for why colder intake air reduces efficiency of a furnace is because air is mostly made up of nitrogen, which (mostly) goes through the furnace unchanged, absorbing energy along the way as it heats up.

 

[M1CDQ]

just to update ive got a little further on it.I did a test run of it free standing in the garden and with the air vents half open I seem to be getting a clean burn with no or very little smoke.its all trial and error and Im having fun.I will soon be fitting it in my garage and putting in a new flue through the roof for it