This years Rocket Stove developements

[MIGNAL]

What does it matter which way a chimney exits a building, so long as passers-by can't burn themselves on the exhaust? Heat goes upwards dunnit? Or does this mean you can't put a cowl over the top of a vertical chimbley?
H&E gone mad with power again?

Chimney/flue, all the same. They do exit in a number of ways, vertically or horizontally. Virtually all Combis have a flue that is horizontal, even though they are fan powered. Some are balanced flues, without a fan.
Stoves certainly do need to be safe. Not only from carbon monoxide but from the ever present danger of fire spreading throughout a building. The consequences can be too severe to ignore.

 

[bugbear]

A stove delivers the energy in the form heat. What else can you measure ?

Sorry, you're quite right . Heat is a form of energy, although a bügger to measure. As is
the energy in wood.

BugBear

 

[Benchwayze]

What does it matter which way a chimney exits a building, so long as passers-by can't burn themselves on the exhaust? Heat goes upwards dunnit? Or does this mean you can't put a cowl over the top of a vertical chimbley?
H&E gone mad with power again?

Chimney/flue, all the same. They do exit in a number of ways, vertically or horizontally. Virtually all Combis have a flue that is horizontal, even though they are fan powered. Some are balanced flues, without a fan.
Stoves certainly do need to be safe. Not only from carbon monoxide but from the ever present danger of fire spreading throughout a building. The consequences can be too severe to ignore.

Yes MIG.

I see your point, and appreciate a flue can set fire to a building if certain safety factors are absent. However, I was wondering what difference a horizontal or vertical exhaust makes. As long as it's far enough from the fabric of the building, and people, then the exhaust gasses are hot and go upwards. Just like some lorries have vertical exhausts (With cute little 'flippy-tinkly' lids on them! :lol: ) and most cars horizontal. The fumes still find their way upwards.

 

[MIGNAL]

I don't think they are too worried about fumes once it exits a building. Combi flues have certain clearances but I'm fairly certain that they can be within arms reach, just protected by a small cage which is required by the regulations.
Given the amount of smoke (or rather lack of) and the miniscule amount of Ash that rockets stoves produce all suggests that they are extremely clean burning. They may even have higher efficiency than an A rated combi.

https://www.youtube.com/watch?v=W3TwEhjTwb4

5 months of ash! My wood burner produces that amount in 2 or 3 days.

 

[Jacob]

A stove delivers the energy in the form heat. What else can you measure ?

Sorry, you're quite right . Heat is a form of energy, although a bügger to measure. As is
the energy in wood.

BugBear

Yep heat is energy. And it isn't difficult to measure - you need to know the temperature change and the specific heat of the material being heated.
The specific heat of dry air is about 1.006 kJ/kg.K.
You can get approx calorific value of wood from tables

Or if you wanted to rate a stoves output you could get the room up to a sustained steady air temp and calculate the room's heat losses (knowing k values of the structure, temps in adjacent rooms / outside etc etc). This'd give you the output at that point.

 

[bugbear]

[Heat] it isn't difficult to measure - you need to know the temperature change and the specific heat of the material being heated.
The specific heat of dry air is about 1.006 kJ/kg.K.
You can get approx calorific value of wood from tables
[/quote]

That approach works nicely for measuring something like this:

http://www.amazon.co.uk/Relags-travel-i ... B000KBEWQW

Dump it in a insulated jug of water, turn it on for a measured time, and see how much hotter the water has got. Bit of maths later,
you know what heat came out of your heater. Easy.

But a wood stove can't be switched on and off like that, and the stove isn't burning "properly" during run up and run down, where it's still onsufming wood. So it's all a bit tricky. Worse, what object is the fire heating? The stove? The room? The air in the room? The flue? Not a good experimental set up.

Or if you wanted to rate a stoves output you could get the room up to a sustained steady air temp and calculate the room's heat losses (knowing k values of the structure, temps in adjacent rooms / outside etc etc). This'd give you the output at that point.

That's better (not saying much, the first option is awful), but the errors involved in estimating the rate of heat loss are very large, leading to a very inaccurate measurement of power/heat/efficiency. A real house in the a real world with varying weather, night/day etc is a complex thing.

All these issues can be, and have been (designing proper experiements is fun!) solved, but it's far from easy,

My concern (that I stated earlier) is that some of the proponents may have come by their efficiency figures in very imprecise (to be polite) ways.

BugBear

(for those who want to see how careful you have to be to do even a "simple" experiment properly, take a look
at Joule's original heat experiments)

 

[Graham Orm]

1500 degrees, dosen't steel melt at 1500 degrees?

Pete

Lower actually according to a quick search 1350c. Some of the guys I've discussed it with on YT reckon that a year is the max for a steel fire box and stainless 2 years. They simply disintegrate because of the heat. The next option is to build the rocket tube and firebox from fire bricks or high temp concrete, which has already been done by one of the guys so I'm following his developments this year.

 

[DMF]

The next option is to build the rocket tube and firebox from fire bricks or high temp concrete, which has already been done by one of the guys so I'm following his developments this year.

Hi Grayorm,

there is a huge amount spent globally on concrete research programmes for the obvious reasons, many requirements for it in a lot of industry's and of course fire safety where the are primarily concerned with structural integrity and stability when exposed to high temperature changes (not a all encompassing statement), think the industrial studies are the applicable one's primarily focused on transmission and cycling (hot /cold) and the stresses evident there after, not least in this very application mentioned. I'm sure I remember reading a paper regarding a partnership between a university and a commercial incinerator but I can't for the life of me find it again! A Quick google on concrete research will give a clue as to how he will do though but last few years lots more info gleaned, even the Americans had a good go at it and with the budgets they have for research when they want it's well it's worth reading some. Seems a interesting subject and one on my list to explore when I have somewhere for a rocket stove to play with!

Anyway point was just to say interesting thread and if you fancied a go you don't have to wait for him! There's lots of info out there somewhere lol!

Dean

 

[Graham Orm]

Thanks Dean. I've just about come to the end of my development phase with the steel version so I'll be seeing how many seasons I get out of this, I'm hoping to at least get this year and next out of it. This is his video of the casting process. https://www.youtube.com/watch?v=yK93KkFT7sE

 

[DMF]

Thanks for that link, had a proper go at it hasn't he! Obviously a clever bloke and I'm sure I could learn many things from him but he does need a shuttering lesson from me! From what he used though for the shuttering and the fact its quite a complex shape I think it was a sterling effort, as he acknowledged I'm sure there's a better mix out there and I don't see why he went so thin with the walls, I think that was half his problems with casting, but I don't know all about rocket stoves so who am I to say anything!

The most important thing is he has a prototype to test and observe and that's the route to success when trying anything like that surely? I hope he hasn't got any large fissures within the structure to de rail that process though and it might take a mark2 or 3 but this is a complex structure under a range of stresses so to even achieve a working stove first time is proper impressive and hats off to him.

Like wise your efforts, you must be chuffed to be where you are with yours and thanks for posting your adventures up, lots of interesting little tangents with something like this and the more I see the more drive I get to crack on

Thanks for that,

Dean

 

[Graham Orm]

Thanks dean. Yes he's well ahead of me with development. He was trying to set one up to heat the house last year, I don't know where he's up to with it. If you look at his channel you'll find some excellent Damascus knife making vids using his own forge.

He's done a few like this https://www.youtube.com/watch?v=MwsAn7zrLwg

 

[DMF]

If you look at his channel you'll find some excellent Damascus knife making vids using his own forge.

Don't please, forge is banned from the wants list for now! I've just got past the bench drill stage so I have a few steps yet and I have many points to score before I can mention such things, def best if I don't start telling her about forges. Especially as she knows that wouldn't be allowed at the folks place so it'll be in our kitchen :lol:

Cheers,

Dean