Bell size...

[xabre]

Hi everyone,

I'm new to the subject of batch box rocket stoves, so I'm sorry for any stupid questions, or if I step on any toes

However, when it comes to bell sizing, the latest information I've found is Peter vdB's old list: 

Recommended bell size is:
150 mm system, 5 m2

180 mm system, 7.15 m2

200 mm system, 8.85 m2

This means that for a 150 mm system, using a barrell, the barrell would need to have a diameter of 0.8 m (D) and a height of 1.8 m (H):

Internal surface area = (D*pi*H + (D/2)^2*pi) = 5 m2  (I'm excluding the bottom of the barrell).

This just sounds 'extremely' large to me      ... I've never seen a YouTube video for a 150 mm system using such a big barrell. Are they sub-optimized or has the recommendations changed?  

Thank you for any comments! 
Henrik  


 

[peterberg]

You are assuming the barrel and bell are one and the same. They aren't. Have a look at my website, batchrocket.eu/en/. In the applications department there's a 150 mm system, virtually without mass, consisting of three barrels. You could have a barrel and a masonry bell and/or bench behind it in order to reach the desired Internal Surface Area.

[xabre]

Thanks Peter. I need to find a way to increase the ISA in my basement. The ceiling is very low

[peterberg]

More barrels side by side?

[fiedia]

1.8m bell height seems not necessary.

May be you can present your project in terms of materials you want to use (barrels, bricks, clay...) and dimension constraints.

If you want a lower bell, why no bench ?

[xabre]

Great, a living community! Thanks everyone.

Well... I need to build the rocket stove in my basement, since there is no space in my main living areas. Also, my hardwood floors are quite expensive The height in the basement is ca 180 cm in total and there is no way of digging deeper. The soil here in southern Sweden consist of cement in a natural form and it takes heavy equipment to dig deeper. I think I will stick to a classic batch box layout given the space I have. However, my main goal is to heat water which I can circulate in the house. I've been searching for different solutions to this but most information consists of prototypes with copper coils wrapped around stove pipes. Do you have any input / experiences on do's and don'ts? Please excuse my drawing made in Powerpoint below, but i hope you get the idea... Looking at it, I probably don't need the coil in the tank over the rocket stove at all... 

Thanks.
Henrik 



Rocket stove draft

[fiedia]

Well, I have no experience for such a set up. There are several threads about rocket stove for boilers. Did you have a look at them ?

[xabre]

Thanks! I've tried to find information using keywords like water, heating etc but your word "boiler" returned more relevant threads 🙂

[serg247]

donkey32.proboards.com/thread/1961/russian-rocket

[xabre]

Thanks!

I have most of the materials to start experimenting now, but I'm not sure about the best solution for the heat exchange between gas and water. I have a number of water tanks available and the first three ideas that came to my mind involved a small tank fixed to the bell and then a circulation pump and piping taking the hot water to a bigger tank in the house.

Riser / bell / water heating:  Water heating concepts

1. Welding the rocket stove bell into a boiler tank, like a hat. 
2. Same as no 1, but keeping the top of the bell free. Not sure why, but since this part may have to be replaced due to stress, perhaps the shape of the water tank should be more of a "doughnut"? 
3. Placing the water tank on top of the bell like a kitchen water cooker. Probably less efficient, but very easy. 

Also, not sure what is best in terms of the water volume (blue)? I know the diameter of the pipes circulating the water matters but what about the water volume encapsulating the bell? Should I just maximize the surface area between water tank and bell...? 

Best regards, 
Henrik 
 
 

[fuegos]

I think that heating water is probably the biggest challenge for a rocket stove, mainly because of the very high temperatures compared with a conventional wood burning stove.The subject has been discussed at length on this forum and the biggest problem is with direct systems as shown in your second drawings, because of the likelihood of the water flashing to steam & causing an explosion.

this thread discusses some of the issues. For safety I think that an indirect system as shown in your first drawing is probably the best, but progress is made through failure !