I am tinkering with some low cost stoves and am using "baldosas", which is essentially a cheap terracotta floor tile that is mass produced where I am. One side and the outer edges are smooth while the underside is rough (I presume because they dry on the dirt before being fired in the kiln). Lots of loose dust/grit can be brushed off of the underside when you first buy them, but then it is relatively durable afterwards.
Would it be beneficial to build with the rough or smooth side facing inwards? I've been doing smooth as I was under the impression that smooth flow would be better, but now I'm learning about all the things that have been devised (ports, tripwires, etc...) to encourage turbulence. I also figure that the smooth side is more "durable" and the rough side would wear away faster, though that's not a tremendous concern.
Is the answer as it generally is - give it a try - or is there some tried and tested rationale behind smooth or rough in different sections of the stove?
Thanks. This isn't for a heater/heat exchanger, but increased surface area makes sense for those applications - look at any radiator or heat sink and it's exactly like that.
It's also fairly well established here that some obstructions (sometimes called tripwires) in the elbow or riser can help with mixing - some very good work on that has been done by peterberg. This is the reason that i figure that a rough surface with a million "micro obstructions" could be helpful.
In fact, it could be even more useful than a single obstruction in that the flow tends to cling along the walls and this would continuously "trip" the flow.
I have no real way of measuring any of it but I'll probably set up two identical stoves - one smooth and one rough - and see if there's a noticeable difference.
fuegos why do you say that? They, themselves, were fired in high temperature kilns and people regularly recommend using various ceramics/bricks. Moreover, they are working just fine so far for me and many others (based on reports I've found). Moreover, if/when they break, they are practically free and simple for anyone to replace
thermal shock & repeated cycling will destroy any tiles in high temp zones like a riser , burn tunnel or firebox .This is the experience of others on this board .The composition of refractory materials is very different to ordinary tiles.
Fair enough. I will continue using these as the stoves I'm designing are for people in extreme poverty. The cost has to be kept to an extreme minimum, as well as needs to use materials that are widely available. I couldn't care less if they lose 10 or even 30% efficiency - it's still 3+ times more efficient and incomparably cleaner than open fires. If they have to replace some tiles, so be it - it'll be easy and cheap to do with tiles that are available everywhere here.
So, back to my question, would a smooth vs rough surface make a difference for mixing?
"I couldn't care less if they lose 10 or even 30% efficiency " I'm not sure if a rough or smooth surface will give a gain ? the design of the port incorporating a sharp corner is i think more important. If your'e not worried about a 30 % loss in efficiency why bother with such marginal gains ? sticking to the design parameters as published here & on Batchrocket.eu is i think much more important. The early work of Ianto Evans covers low cost , simple stoves that meet your criteria. A good rule of thumb in in my opinion is that the materials should conform to the design not the other way round.
Fair enough - smooth vs rough probably is quite marginal, but it's a matter of flipping the tiles around so why not find out which way is better? Without a measuring device I doubt I can really find out through experimenting, so I figured I'd ask folks here who have such technical experience if they have an opinion on the matter. Surely it is a relevant design factor for any stove, no?
I agree about materials conforming to the design - my primary design criteria are 1) lowest possible cost, 2) widely available and easy to transport materials 3) materials easy to work with 4) design easy to fabricate with minimal skill and tools, 5) no chimney (cost $, rusts out and doesn't get replaced). These tiles along with pumice stone insulation fit the bill perfectly, even though I'm surely losing 10 or even 30% efficiency as compared to the wonderful stoves made here with fancy materials and complicated designs.
I tried making a BBR version, but its just too complicated and didn't even work well for me at a 3" riser size (which is the constraint given available materials and budgets). But I'll be trying to incorporate some of its features, like a horizontal port in a shorter 4" diameter riser and a feedtube/batchbox that is larger than the riser CSA. It'll be a sort of hybrid between a peterberg BBR and standard L Tube cookstove, and should only cost a few bucks for people who barely have even that.
Are these cooking stoves or heating stoves, or both? Where exactly are you since there may be factors necessary to help answer your questions.
As far as smooth vs rough, air flow is KING in rocket stoves and RMH. Since rough introduces random friction without much in the way of usable turbulence, smooth is better. Plus that puts the larger surface area to the outside so that heat transfer to the outside is improved.
Besides pumice and tiles, what other materials are available there. One of your other threads mentions a steel drum. Are they widly available? Sand? Portland cement? Clay from the ground?
You obviously have wood, what about straw, flax, river reeds? I'm just trying to brain storm some solutions.
sand/clay mortar and cob are cheaper than tiles and give you flexibility in the design. "no chimney" so maybe a simple J would be a solution , cooking directly over the riser ? i assume the stoves will be used in a semi outdoor setting ?
TexasGonzo: Sooooo glad I found this site! Its always rewarding to find such a super group of folks! To any and all, feel free to PM me anytime. Thanks for having me!
Mar 11, 2019 18:56:41 GMT -8
jlmtech: GADGET: CONSIDER USING A JET PUMP INSTEAD OF A BLOWER FAN TO INDUCE DRAFT; NO CLOGGING.
Mar 26, 2019 8:19:28 GMT -8
michaelegan: i am unable to open the sketchup files on my mac. I used sketchup a few years back but apparently the company now requires a subscription. does anyone have any advice/instructions on how to use the program or how to view pictures without spending money?
Aug 20, 2019 18:41:48 GMT -8
mannytheseacow: michaelegan: download AutoCAD student version for free... import .SKP
Aug 23, 2019 13:33:44 GMT -8
topbaza: hi everyone, been searching all over net and this is were i need to be i think!!
Sept 28, 2019 6:16:25 GMT -8
anounaki: Hi, why I cant upload photos when I make new tread to this forum?
Feb 28, 2020 2:09:40 GMT -8
ahansen: photos under 1 mb not possible?
Jun 4, 2020 0:09:21 GMT -8
belgiangulch: Photo's are possible. They must be downloaded elsewhere and the image url (adress) is copyied.
Sept 14, 2020 7:26:15 GMT -8
belgiangulch: While creating a thread click on the small picture in the banner above the reply. A box pops up, paste the image url in the box. Pay no attention to the huge list of numbers and such.When you finish and hit reply your post with pictures will come up.
Sept 14, 2020 7:29:27 GMT -8
deadstarsstillburn: Hi there. I was directed this way by folks on the Permies.com website and am hoping I can get some information on how a total newbie can get started designing, siting, building, and not-dying-in-a-horrible-house-fire with a new RMH in a 160-year old home
Oct 21, 2020 6:52:10 GMT -8
deadstarsstillburn: The people over there recommended either a 6" batchbox or an 8" J-tube. I don't know what those are but am going to try to figure that out. What I need is a blueprint that I can scale to fit the need for my house. I have something likne 5000 square feet
Oct 21, 2020 6:53:00 GMT -8
deadstarsstillburn: but I do not need to heat all of it by any means. probably only need to heat half of that, maybe less.
Oct 21, 2020 6:53:15 GMT -8
deadstarsstillburn: moreover, the house has 3 storeys (large attic) so I assume if I get very efficient heating on the ground floor, that will go a long way toward heating the upstairs as well, no?
Oct 21, 2020 6:53:59 GMT -8
BenAlexanderT: Happy new year everybody. I wish you the best
Dec 31, 2020 15:06:14 GMT -8
Solomon: Anybody in Southern Oregon, in Jackson or Josephine counties?
Jan 16, 2021 21:54:43 GMT -8
gnomedome: i realsie this is from 2009
Apr 14, 2021 8:30:44 GMT -8
gnomedome: i realize this is from 2009 id love to see the photos from this ..as im looking to build a sauna soon similar to this .... if anyody sees this post email@example.com..... the photos in this post did not show up
Apr 14, 2021 8:32:00 GMT -8