Has anyone made a DSR! or II completely form castables - or is that a dumb idea
No, it's not a dumb idea. In fact, the DSR2's final development model was built from refractory castable slabs. The only part that wasn't like that happened to be the superwool liner in the riser stub. Regarding the DSR1, I didn't got as far as a final model. The design was ditched before that stage as being not a viable combustion core using hard materials and a real chimney stack.
Last Edit: Apr 28, 2021 12:22:25 GMT -8 by peterberg
Post by grootebeer on Apr 28, 2021 12:46:18 GMT -8
Thanks Peter - I am groping around to see if it feasible to make a really lightweight version in the 1kW power range. Probably the wrong thread to be asking this since I am really looking at DRSII - it's a tiny workshop, really well insulated. Thanks anyway for your reply.
What I like about the port opening on top is I can shove wood in and not worry about sticks blocking the port. I’ve been tossing my beat up bricks into a cook stove version that is a work in progress but lots of fun. I was intrigued by Peter’s latest video, the tube inferno was mesmerizing.
I have read the whole thread up to this point. Clearly Peter has done his usual yeoman's work on experimenting and recording his findings - Peter, I could easily envy your creativity, energy and stamina.
I am at the stage where I want to start a parallel vortex effort of my own, and being a lazy sod, am begging the indulgence of others to ask if anyone has summarized the dimensional and structural status to this point?
I was hoping for some kind of dimensional summary of the overall design and components.
Obviously a CAD model would be ideal, but I could work on doing one from a summary, for review and correction.
If a model is imminent, I will shut up and be patient.
There's no definitive model imminent. Mainly due to the fact that I am searching for the simplest and easiest to obtain parts and materials. I ordered four different contenders, once those are arrived, I will be able to test, evaluate and make a choice.
I'll keep you guys informed but don't hold your breath. More work on the website is in the pipeline, namely a translation in Portugese. It is important for the commercial version to be ready around September/October, for obvious reasons. So final design is quite some months off, sorry.
Not so much as progress the past month. One order didn't arrive at all, probably due to faulty adressing but I got my money back. I did put another order on hold because of worrying information regarding ceramic fibers.
Several kinds of those ceramic fiber will dissolve into lung moist and as such are able to leave the body like that. This is known as half-life or half-value time, similar to radioactive radiation. Expressed in days, not in hundreds of years. Rockwool used in building construction for example has a half-life of 40 days, Morgan Ceramics Superwool 10 days and special high refractory fibers used for vacuum formed risers 70 days. Still not good for the consumer and worse for the installer of those in heaters.
There's one catch with Superwool though: when it has been heated to a temperature above 800 ºC (1470 ºF) it will form crystals (Kristabolite) and those resulting fibers won't dissolve at all. This does sound real bad and given the fact that superwool will shrink dramatically when exposed to temperatures above 1000 ºC (1830 ºF), vacuum formed Superwool is off the table. The higher specced Ceramic fibers, also from Morgan Ceramics, doesn't show these behaviour but the best quality binder will give away much earlier. To this end, there's clay added to the binder in the vacuum process which will bake into ceramic while the normal binder is baking off. This clay addition will lower the insulation value quite a bit, by the way.
I also aquired two types of riser tubes used in iron foundries to try out, real thin and insulative but dusty and brittle when exposed to high heat. And besides that, those were a little too small diameter for what I need.
Given the fact we don't want any fine dust into our exhaust gases I tried to find an alternative. First thoughts did go to real refractory tubes, not uncommon for use as chimney liner in Germany, Austria and Italy. Hard to come by in small quantities but two German producers were willing to send me samples of their thinnest variants. So I have three kinds of these tubes here now, all reassuring hard kiln baked clay ceramics.
Two manufacturers were kind enough to send me samples, Hart Keramik close to the Czech border and Müller from Westerwäld. All these were the correct internal diameter, 140 mm (5.5"). One item of 15 mm (0.591") wall thickness, four items of 10.5 mm (0.413") and two items of two feet long sporting wall thickness of just 8 mm (0.315"). The thinnest one turned out to be very brittle and cracked and splintered while being cut using a hand grinder and diamond cutting wheel. So this was the first to reject as being not really suitable. The thicker one from Hart was split along its length and mounted horizontally in the development core. After fired for approximately two hours, running red hot at the far end and cooled down during the night this one showed two cracks in the top half. Both a little over 5" from the rear end left and right, roughly halfway above the port opening. I used this as an indication where the highest thermal stress would be. One thinner item from the same manufacturer was cut the same way and an extra cut was done at right angles over the top half, 5" from the rear end.
The partition cuts are visable, the superwool bed is there to lift the tube to the right position relative to the ceiling, not to be included in the final design of course.
This arrangement survived three hefty burns uptil now so yesterday I decided it was time for a full test. The firebox was loaded with hawthorn again with small planks of pine on top. Under the fuel there are two steel bars arranged in such a way there's some space underneath. This is better for the end of the burn, combustion being more uniform through the depth of the firebox. Combustion air supply through the door frame again, left and right starting 4" from the bottom and up, and a larger slit in the horizontal beam above the door.
This arrangement yielded good results: good enough for the EU certification tests.
No dramatic jumps in any of the lines, no overfuel situation or super low O² levels. Warming up took a bit longer as compared to an insulating tube but critical point appeared to be between 10 and 20 minutes as before. Checked the afterburner parts this morning, no cracks to be seen despite the ceramic tube has been cherry red at the far end, in and out. Some average numbers: O² 12%, eff. 91.1%, CO 713 ppm, end temp 120.9 ºC (250 ºF).
All this is very encouraging, I am happy. Outside temperature is too high now for further testing, I'll do some sketching during the coming week(s).
The information was by mail, not online as far as I know. The firm in Belgium that do the vacuum formed products for foundries was kind enough to come up with this. We had quite extensive email exchange and as a result I didn't order any of their products. In short, providing me with that specific information wasn't in their own interest but they did anyway. Good firm.
Thanks for that information. It's good when companies are fully open about their products.
I found an industry response to this concern, with links to some research papers (https://www.ecfia.eu/facts-cs/). It's not easy for me to know how independent the researchers were, but the papers suggest that the bio reactivity of heated High Temperature Insulation Wools is not high.
Post by Karl playing with geopolymers on Jun 18, 2021 11:36:17 GMT -8
Cristobalite is a rather rare mineral and a naturally occurring high-temperature modification of silicon dioxide (SiO2 quartz). Quartz and its temperature modifications are chemically extremely inert, only reacting with hydrofluoric acid and soda melts.
All ceramic materials will become chemically inert and thus are not longer solvable, once they have crystalized after exposed to high heat a single time.
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