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Post by Vortex on Feb 16, 2017 9:41:17 GMT -8
Bit more done. Decided to use some of the storage heater bricks for the base layer, only whole ones though, I cast 2 pieces to fill the remaining space. It leaves me 3 short for the channels but hopefully I'll find some more before I get to those. The front steel panel will be slotted in later - makes it easier to work on.  |
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Post by Vortex on Feb 20, 2017 11:08:21 GMT -8
Made some more progress on the new stove, and found 50 more storage heater bricks   |
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Post by patamos on Feb 22, 2017 19:25:56 GMT -8
Nice work Trev,
Is that going to be a hollow bell heat exchanger?
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Post by Vortex on Feb 23, 2017 11:06:25 GMT -8
Hi Pat,
It can be anything; single hollow bell, mini bells, up and down labyrinth, descending channels or any other way I come up with. The idea is it can be configured and reconfigured with a minimal amount of work to change it.
The internal size of the chamber is twice the width of a storage heater brick, so I can use them to arrange all sorts of systems. The internal chimney will be made of steel, roughly 6 inch square, and will be wrapped in ceramic blanket.
The first configuration is going to be descending channels, with 3 horizontal runs and will contain 26 heater bricks. I'm about to start fitting them in so I'll post a pic soon.
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Post by patamos on Feb 26, 2017 9:16:27 GMT -8
Very cool,
Gets me thinking of those old russian diagrams showing all kinds of bell mass layouts…
On another note; Been chatting with A nearby fellow who builds Finnish contraflow heaters. Talking about start up bypass, he leaves a 1.5" x 1.5" permanent bypass at the most direct path into the chimney, and figures this works well enough. I know some of the old grundofen bypass dampers leave 5% gap regardless, which is much the same on an 8" CSA system.
So maybe there is something to play around with there… ?
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Post by Vortex on Feb 26, 2017 10:46:06 GMT -8
That's probably a good way to idiot-proof a stove for the cost of a little loss in efficiency. Means if someone unfamiliar with the stove and/or bypass dampers is lighting it they cant mess it up. Here's the bottom layer of storage heater bricks, they're supported on steel C channel which holds them up 4.5"/120mm from the bottom. (The nearest heater brick has been left out so you can see the steel support.) The square steel insulated chimney will fit down the center, which leaves a vertical channel on the right near side of the picture.  Here you can see the steel support for the top layer of heater bricks with the first 2 bricks in position. (The top layer is in a reverse L shape of the bottom layer). The hot flue gases will pass over the top of the top layer, drop down and pass between the top and bottom layers, then drop down again and pass under the bottom layer before exiting up the chimney.   |
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Post by patamos on Feb 28, 2017 8:44:38 GMT -8
Cool Something between a descending flue run and contraflow (which is often acts a bit like a bell anyways…) No shortage of storage mass |
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Post by Vortex on Feb 28, 2017 10:18:49 GMT -8
Exactly, Pat. In this bell I'm aiming for the maximum mass in the available space, but with as much surface area in the flow path of the flue gases as I can get - If it doesn't work it only takes 15 minutes to change it. I've been totting up the weight of the parts as I build it and it's just passed 500 Kg (1100 Lbs). I made the internal square steel chimney pipe this afternoon. It will be wrapped in ceramic blanket to fill the rest of the gap around it. Bypass damper is still to be done. The idea of it is that a masonry chimney that is part of the bell will always be shedding heat off the inside up the chimney, drawing heat out of the rest of the mass by convection, even when the stove is shut down with an air tight door. The rest of my chimney is insulated steel, so why not the bit inside the bell?     |
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Post by patamos on Feb 28, 2017 10:39:03 GMT -8
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Post by 1967gto on Feb 28, 2017 21:09:36 GMT -8
Won't the thickness of the mass cause an efficiency problem?
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Post by Vortex on Mar 1, 2017 3:14:27 GMT -8
The firebox will have a complete insulated layer all around it and an insulated secondary burn chamber on top, so in theory, no. My present firebox has no insulation from the mass but less mass. I've been experimenting with different mixes for the insulating layers. The best one I've found so far (center) is a mix of 4 parts Perlite, 1 part furnace cement and 1 part Calcium Aluminate cement. It is very light and hard, reminds me of burnt coal clinker. The 2 most promising ones have just been put in the firebox to see how they stand up to the intense heat.  |
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Post by fzurzolo on Mar 1, 2017 7:42:14 GMT -8
This is starting to look really good! I'm excited to see how it performs.
I have a bit of experience with making firebox insulation with outdoor clay ovens. The design I use is a black oven. The inner dome (directly exposed to the flame) is about 75mm of clay sand mix. That would be the equivalent of the non-insulating firebrick in this case. Then I do about 100-120mm of insulation. To make the insulation I mix perlite, a bit of clay (for stickiness) and lime (Type N or S). Then just enough water to get it to stick together enough to pack it over the clay dome.
I then apply a lime plaster directly to the dried insulation which has enough structural integrity to hold the plaster.
This insulation does a great job and the exterior of the dome only just gets warm to the touch after firing the oven for 3 hrs. Nowhere is it even close to "hot".
For this or other stove applications where the insulation is contained, I think this roughly pourable mix might work really well. The lime tends to shrink as it cures which increases the space between the perlite balls and I think adds to the insulating value.
And, once, when I ran out of perlite, I used a mix of perlite, and chopped flax shiv (think very tiny sticks). Once that was fired, the flax shiv seemed to have been burned away leaving air gaps again and that stuff has been working great too.
Not sure if anyone else has tried this, but it might be a cheaper option than the aluminate cement, or a good alternative if that stuff isn't available in the area. |
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Post by drooster on Mar 1, 2017 10:34:44 GMT -8
Owning only nine of these very heavy magnetite bricks I'm jealous of the sheer MASS in that contraption!
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Post by drooster on Mar 1, 2017 10:44:25 GMT -8
The best one I've found so far (center) is a mix of 4 parts Perlite, 1 part furnace cement and 1 part Calcium Aluminate cement.... Keep us updated on your test results. I love my lime/perlite mixes for insulating 'building' stuff, and for lowish-temp 'firebricks' in ny lowish-temp stove, but worry about the meltingness in a high-temp flame path. |
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Post by Vortex on Mar 1, 2017 10:44:46 GMT -8
This is starting to look really good! I'm excited to see how it performs.
I have a bit of experience with making firebox insulation with outdoor clay ovens. The design I use is a black oven. The inner dome (directly exposed to the flame) is about 75mm of clay sand mix. That would be the equivalent of the non-insulating firebrick in this case. Then I do about 100-120mm of insulation. To make the insulation I mix perlite, a bit of clay (for stickiness) and lime (Type N or S). Then just enough water to get it to stick together enough to pack it over the clay dome.
I then apply a lime plaster directly to the dried insulation which has enough structural integrity to hold the plaster.
This insulation does a great job and the exterior of the dome only just gets warm to the touch after firing the oven for 3 hrs. Nowhere is it even close to "hot".
For this or other stove applications where the insulation is contained, I think this roughly pourable mix might work really well. The lime tends to shrink as it cures which increases the space between the perlite balls and I think adds to the insulating value.
And, once, when I ran out of perlite, I used a mix of perlite, and chopped flax shiv (think very tiny sticks). Once that was fired, the flax shiv seemed to have been burned away leaving air gaps again and that stuff has been working great too.
Not sure if anyone else has tried this, but it might be a cheaper option than the aluminate cement, or a good alternative if that stuff isn't available in the area. That sounds like a perfect mix for a pizza dome where the insulation's protected inside the masonry. Unfortunately I need to cast slabs 1.5" / 38mm thick, so I need something more durable. If I add clay to the mix I get a more durable cast but it's noticeably heavier and less insulating. I'll probably have to use clay in the mix for the base insulation layer as it's going to have to support all the weight of the firebox and secondary burn chamber above. I found the best technique was mixing the furnace cement and calcium aluminate cement with a little water until it's the consistency of melted chocolate, then dribble it over the perlite and gradually mix in until it will hold together like a snowball, and press it into the mold using a small block of wood. I haven't tried any lime in my mixes yet, I'll have to get a bag and try some with it in. The two I test fired in the firebox this morning both came out glowing red and are still in perfect shape, so there's hope it'll work for the sides of the secondary burn chamber. |
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