Cedric Noussan

thank you so much for the explanation
now I can start designing the rest

Fox James wrote:That might depend if you intend to use the actual chimney or how the chimney is constructed, ie is it rough stone or brick or do you plan to insert an insulated flue. Other factors might be … high the chimney is, what is its overall condition, is it straight up or have bends?
What style of stove you want to use and how much draw you will require, ie if it is a batchbox with a 4’ high riser or a small riserless core that need a strong draw through an insulated chimney?

Hi, I intend to use the chimney how It Is: in brick, not isolated, 5 meters high, straight. I thought of a stratification bell, I have not yet decided whether to make a batch or a shorty, of the maximum power that I can

I'm planning my next rmh, I have a rectangular chimney measuring 15x30 cm (6"x12"), what csa I consider?

I improved the heater, here is the result!
if you want to see the photos of the construction:
https://drive.google.com/drive/folders/12YY8_NI_vQbA4DZElZedj9IRtCDZsi2L
Whats do you things?

Phil Stevens wrote:

The firebrick riser will mean that it takes longer to reach optimum temperature from startup, but once you get there it should be fine. Is there insulation around the riser?

Riser not insulated

Phil Stevens wrote:Have you opened it up to inspect things? Any deposits of ash indicating constrictions in the flow path? Dark stains, soot or creosote would be a definite sign of trouble.[/quote

The Wall of bench are black, see the video on my YouTube Channel
https://youtube.com/@cedricnoussan4893?si=-f-OAzjMYP1UxkoE

Glenn Herbert wrote:

A well-burning J-tube should emit no significant amount of creosote, so you definitely need to let it get hotter through insulating the outside. You might also want to partly cover the feed tube to restrict airflow, allowing the combusting gases to stay in the core longer and burn more completely. Your feed should in any case be tall enough that the fuel can be covered and airflow closed completely, for safety reasons in case something goes wrong. This will take care of the issue with the fire climbing the fuel and smoking into the room.

I am currently burning wood with double the length of the feed, I will cut the wood and do some tests by partially closing the entrance with a brick.
today I also added a p channel

Glenn Herbert wrote:The bench cross section is not large enough for stratification, it will all move through the channel as one flow. This is essentially a square brick duct. What is the surface temperature of the brick channel, both from the barrel exit and upstairs?
For such a long burn, there ought to be a ton of heat being released somewhere from the system, and not much could be getting up the chimney. An 8" J-tube should produce enough heat to bake a space in 5 hours with temperatures above freezing outside. Also, the bench being just maybe 10-12 cm thick, it does not have much mass and will cool quickly.
.

unfortunately I don't have a thermometer at the moment, I'll try to explain my feelings, after 3 hours of ignition the bench is pleasantly warm, after 5 hours you can still sit down, the exit pipe of the bench after 5 hours you can still touch it with your hands for a few seconds. instead the lower level becomes nice and warm, you can wear a t-shirt with an outside temperature of 10 degrees

Glenn Herbert wrote:I agree that the absence of insulation will allow too much heat to be lost from the core, lowering combustion efficiency. It would be interesting to know how much soot there is in the channels... .

On my YouTube channel I posted a video of what you can see from the inspection port near the barrel and another video of the inside of the bench in the last section

Glenn Herbert wrote:The very small copper tubing would be an obvious culprit for lack of water heating, except for the pump in the circuit. Tubing of that size would not thermosiphon well by itself. How hot is water coming out of the coil when the fire is going well? Is the coil one run, or multiple in parallel? That length of small tubing would have a lot of friction in one run.

the coil is made up of 4 pipes in parallel.
when turned on about 30° after 5 hours the temperature of the water exiting the coil was 80°.

thomas rubino wrote:Hi Cedric;
I have not yet had time to read your post properly.
But regarding your last question.
Insulate the riser for sure.
I'm not sure what you mean by the barrel, but if it is easy then give it a try.

I mean, to isolate the riser I would just have to open the barrel from the top, while to isolate the whole j I would have to disassemble the whole rocket

Consideration: since I do not have an insulated riser, the combustion is not completely complete, it produces a bit of ash and creosote that over time (it will have burned for 80 hours now) have accumulated on the copper coil (I read in a book that 1mm of soot reduces efficiency by 6%) this would explain why during the first ignitions the water accumulation heated up more quickly in addition to reaching higher temperatures (80° maximum while now I reach a maximum of 60°)
What do you think?
Here is a video recorded with the phone entering from the inspection vent
https://youtube.com/shorts/Gx8m9X4I_XA?si=_kaqQgXymiA-HCMH