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Post by Karl L on Jun 23, 2020 11:12:41 GMT -8
A DSR2 radiates a lot of heat from the top box window. Then, a steel bell would also radiate a yet more heat.
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Post by Karl L on Jun 23, 2020 11:09:31 GMT -8
That's useful information, though I don't know if the boards are made from the same material?
With the board I have, it was only after firing that the disintegration happened.
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Post by Karl L on Jun 23, 2020 5:37:22 GMT -8
I've been building a DSR2 batch rocket core using Superwool HT board for the heat riser and top box lining. Superwool is biosoluable, which is why I am using it.
This board was rated at 1300C by the seller. However the datasheet says Classification Temperature: 1275C Continous use temperature: 1177C
When I pulled the core out of the bell after the first burn, I noticed that *some* edges of the Superwool board were 'fluffy' and disintegrating. I noticed this on *one* of the two very small pieces to either side of the top box exit port (the piece on the other side was OK!). I didn't notice this kind of damage in the heat riser, even though I've heard this is the hottest part of the system.
Anyone got any experience of using Superwool HT board in a batch rocket or DSR2? Any one seen this kind of damage?
Thanks!
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Post by Karl L on Jun 22, 2020 9:32:10 GMT -8
I did the first burn today, in the open air.
The combustion seemed good - no smoke after a while, and 'damp charcoal' smelling exhaust.
When I pulled the core out of the bell after the burn, I noticed that some edges of the ceramic fibre board were 'fluffy' and disintegrating. I noticed this on one of the two very small pieces to either side of the top box exit port (the piece on the other side was OK). I didn't notice this damage in the heat riser, which I guess might be hotter?
I am using Superwool HT board, which was rated at 1300C by the seller.
The datasheet says Classification Temperature: 1275C Continous use temperature: 1177C
Anyone got any experience of using Superwool HT board in a batch rocket or DSR2?
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Post by Karl L on Jun 21, 2020 10:21:41 GMT -8
Thanks, yes, I took a look at that calculator at some point.
There are several factors that mean I don't need so much heat on average: We don't get very cold winters here, usually. I sleep in this room, and like it not as warm at night (hence the low-ish themal mass) The room has several internal walls and a ceiling, to rooms which are heated by other sources. I don't mind lighting extra fires if necessary.
(Re. the calculator, I thought it odd that the heat requirement is calcuated from the volume of the house (or room), rather than it's area.)
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Post by Karl L on Jun 15, 2020 23:56:32 GMT -8
how large is the space that needs heat, 125mm sounds weak? 125mm is 5", which is the size Peter first used to develop the DSR2 concept. The space is a large room 6m x 4m x 2.5m (20' x 13' x 8'). I've already used a (very rough) experimental rig with 100mm (4") riser size, coupled to an oversized firebox, suitable for a 125mm system. There was no thermal mass, just a steel bell. It was easily powerful enough! I'm not going to use a lot of thermal mass -- all I need is enough to stop the heater overheating the room. I also found that the room itself stores a lot of heat when that heat is radiant, and the charcoal phase of the burn 'tops up' the heat over a long time.
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Post by Karl L on Jun 12, 2020 3:36:29 GMT -8
i'm not sure i understand but if the heatriser blows very hot air on top there could be some danger if metal is covered. maybe overheating but a 45 degree aluminium foil directing top heat right way out the air can also circulate up the outsides of metal over top and down through hollow brick wall cool and back up fore distribution combined whit alumium on inside of bricks so all heat is forced more out when "doors" are open (There isn't a heat rise in the DSR2, but still the hot gases will rise to the top.) Insulating the top isn't a problem, partly because the top surface will radiate heat inside the bell, thus cooling it and warming the other surfaces of the bell. (I've done this a number of times with no problems.) The 45 Deg. Al foil does work -- I've also tried that.
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Post by Karl L on Jun 11, 2020 22:50:12 GMT -8
The other think to think about in a bell, is that the top half of the bell absorbs more of the heat energy than the bottom half, due to the thermal stratification. A brick near the top will absorb more heat energy, reach a higher temp, and stay hot longer than low ones. Are you suggesting a particular distribution of bricks to make use of this?
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Post by Karl L on Jun 11, 2020 22:47:04 GMT -8
A top that is insulated with rock wool should work to force more heat to come out the sides and could be lifted to expose the radiant surface when fast heat is desired... I’m thinking made of thin sheet metal with rock wool sandwiched between... it could be light enough to be on hinges, or lifted by a cable or light chain? Yes, thanks, I've also been thinking about similar ideas. The rig I've built should allow me to test things like that quite quickly. I've noticed that Aluminium foil is very effective at reflecting radiant heat, and so could be used over some heat resistant board to achieve a similar effect to your idea.
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Post by Karl L on Jun 10, 2020 7:25:02 GMT -8
Thanks for the suggestion - but my experience says that warm air is not such a 'nice' form of heat, compared to radiant heat. So the design tries to maximise radiant heat and minimise convective heat.
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Post by Karl L on Jun 8, 2020 6:21:58 GMT -8
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Post by Karl L on Jun 7, 2020 10:10:55 GMT -8
I am constructing a 125mm DSR2 heater with a steel inner bell and dry stacked firebricks for the thermal mass. The problems this heater is trying to address are these:
Heat up a room quickly from cold. Store heat in a thermal mass when the room is hot. Work with a non-ideal chimney (that probably can't be lined), with an unknown flue gas exit temperature requirement to generate sufficient draught. Overcome the risk of cracks in a single skin bell. Flexible/adjustable/experimental design to deal with the many unknowns.
The core will built inside a sheet steel box using Vermiculite board, split fire bricks and SuperWool board.
The primary air system has equivalent CSA to Peter's welded steel tube design, but is constructed differently.
The door is a sliding type, salvaged from a previous experimental stove.
The bell is constructed from welded sheet steel. It will be surrounded on 3 sides with bricks (thermal mass) and open at the front (for radiant heat).
The amount of heat extracted by the bell (and so the flue gas exit temperature) can be varied by adjusting the air gap between the bricks and the steel bell, and also by adjusting the area of the radiant surface. These are both 'build options' - but it should not take very long to do the rebuild because the bricks are dry stacked around the steel bell.
It may also work to close a 'door' over the radiant surface, to reduce the heat into an already-warm room. This might push some of that heat in the the thermal mass instead. This has to be tested.
I will try to load photographs...
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Post by Karl L on Jun 1, 2020 8:24:42 GMT -8
Thanks, that's good to hear about the doors.
I would expect more draught when the doors are closed, because the gas temperature in the chimney would increase, because less heat is being extracted from the barrel.
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Post by Karl L on May 31, 2020 10:07:11 GMT -8
Hi,
I am in the middle of constructing a 125mm DSR2 heater that tries to meet some of the requirements you have specified. When I have time, I'll post some pictures in a new thread. The problems this heater is trying to address are these: - Heat up a room quickly from cold.
- Store heat in a thermal mass when the room is hot.
- Work with a non-ideal chimney (that probably can't be lined), with an unknown flue gas exit temperature requirement to generate sufficient draught.
- Overcome the risk of cracks in a single skin bell.
- Flexible/adjustable/experimental design to deal with the many unknowns.
My design uses a welded sheet steel bell, surrounded on 3 sides with bricks (thermal mass) and open at the front (radiant heat).
The amount of heat extracted by the bell (and so the flue gas exit temperature) can be varied by adjusting the air gap between the bricks and the steel bell, and also by adjusting the area of the radiant surface.
These are both 'build options' - but it should not take very long to do the rebuild because the bricks are dry stacked around the steel bell.
It may also work to close a 'door' over the radiant surface, to reduce the heat into an already-warm room. This might push some of that heat in the the thermal mass instead. This has to be tested.
Karl
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Post by Karl L on Feb 29, 2020 10:48:55 GMT -8
Thanks, Yasin. Do you know what temperature the primary air must be heated to, in order to produce the clearn burn without secondary air?
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