What makes stoves so efficient?

[Woodworks]

11 minutes ago, slim reaper said:

An interesting read ?

http://www.soliftec.com/efficiency.htm

Great link and look at the numbers for an open fire!

[difflock]

32 minutes ago, slim reaper said:

An interesting read ?

http://www.soliftec.com/efficiency.htm

 

Hmm, I recalled wood to have a calorific value of 4.xx kW,

I  just checked and got 4.44kW, so where does this site get 5kW, presumably for bone dry = zero % moisture content wood.

A tad offputting in respect of the likely veracity of the rest of this sites info imho.

 

[Woodworks]

12 minutes ago, difflock said:

 

Hmm, I recalled wood to have a calorific value of 4.xx kW,

I  just checked and got 4.44kW, so where does this site get 5kW, presumably for bone dry = zero % moisture content wood.

A tad offputting in respect of the likely veracity of the rest of this sites info imho.

 

Yes but the rest of it does have a ring of truth about it. 

[openspaceman]

16 minutes ago, difflock said:

 

Hmm, I recalled wood to have a calorific value of 4.xx kW,

I  just checked and got 4.44kW, so where does this site get 5kW, presumably for bone dry = zero % moisture content wood.

hardwoods bone dry are about 18.6 MJ/kg lower heating value, softwoods a bit more, this is about 5.2kWh(t), at 20% mc wwb this would only have 4.13 kWh(t)  potential energy but would also have to boil off 200 grams of water.

 

I think we should really work in higher heating values and then work out total losses as steam in the exhaust.

 

As an old chemist once told me wood is a good energy source but a poor fuel.

16 minutes ago, difflock said:

A tad offputting in respect of the likely veracity of the rest of this sites info imho.

 

I gave up reading as soon as I saw he didn't know the difference between power and energy.

[billpierce]

Have you got any info on that system, I am in the near future going to render some stone walls but was going to use lime with cork pellets incorporated. 

Not really no, a local builder has done it to the inside of his house and really rates it as it still allows the stone to breathe I.e no damp condensation issues. Also gives a nice finish. Will try and get back to you with details, think it will be many thin coats totalling about 2inchs of render.

[AHPP]

2 hours ago, openspaceman said:

the difference between power and energy.

What is it?

 

[neiln]

power is a rate of doing work, ie energy per unit of time.  Watts.  Watt = Joule per second.  

energy is Joule, or power multiplied by a time period, kWHr.

[Woodworks]

17 hours ago, slim reaper said:

Have you got any info on that system, I am in the near future going to render some stone walls but was going to use lime with cork pellets incorporated. 

Used to be talked about quite a bit on the Green Building Forum. http://www.greenbuildingforum.co.uk/newforum/search.php?PostBackAction=Search&Keywords=hempcrete&Type=Topics&btnSubmit=Search

[billpierce]

Some good reading here. And there is another good one with designs of frontier type DIY woodstoves and ovens from folded tim/ barrels etc.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.fastonline.org/CD3WD_40/JF/425/20-461%2520-%2520Wood%2520Stoves%2520-%2520Ole%2520Wik%25202.pdf&ved=2ahUKEwjLm-DK69vfAhWKyIUKHWjMBbgQFjAbegQIARAB&usg=AOvVaw2ae0wVUiXVNaiQ2AnyAXRs&cshid=1546869962294

[Steven P]

Thanks for the info

 

So for efficiency I need (and I think in the order of importance):

- Limit the air going up the chimney, use a door then

- Insulated fire box, hotter fire = more efficient

- Make sure the flame can burn fully before its extinguished and goes up the chimney.  In a stove this is using a baffle plate, I might be wrong but isn;t this so they can increase the flame length and make the stove shorter? In a traditional fire the flame fully burns out but part way up the chimney first.

- Air gap around the stove lets heat get out by convection currents and not just by radiated heat

 

Is that about it?

 

So thinking to my small upstairs fire, I could get a local blacksmith to make a suitable door on a hinge (complete with vents and clips to hold a glass window in), bolt that on and the open fire might double its efficiency? A door would be god because it can be  kept closed and stop draughts up the chimney when not in use? After that I would want to get a builder in to open up the fire place to install a stove