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Oct 12, 2010 16:44:36 GMT
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As winter draws in, I've installed a wood burner in the shed -It's only 8x6, and has a PC and a couple of monitors keeping it warm ish, and it's mostly insulated. As such, the heater makes it steaming hot quite fast, and I can't really burn the wood slow enough to not overheat the place without the thing going out all the time. I was thinking about using it to heat a good amount of water, which I could store in an old hot water tank or similar, and then run through a radiator/old heater matrix with a fan on blowing at my feet throughout the day. That way, I could run it for perhaps an hour in the morning (with the water absorbing a decent amount of the heat so the shed shouldn't get too hot) to heat the water up and get the shed up to a reasonable temp, then use the hot water to keep it warm throughout the day. I've been thinking about how to heat the water, such as wrapping the top of the cylinder in about 10m of 8mm flexy copper pipe, or even having a coil inside the thing? Am I likely to melt the copper? - Should I just stick with steel, and weld another gas bottle on top (with the bottom cut out) to use as a water jacket and to store the water as well? Alternatively, is there a (cheap) fuel I could use that burns a lot slower than the caravan ply offcuts I have? Here is said heater:  Ta muchly! |
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mattc
Part of things
It will be done one day.....
Posts: 217
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Oct 12, 2010 17:16:29 GMT
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My mate had a set up with a chimanea (not sure how you spell it), that he ran a central heating pump that would pump water from his pool through some copper pipe rond a coil of cooper pipe in his chimanea and then heat the water back to the pool.
Worked real well and to well sometimes, so perhaps something like that your own central heating system, bit of pipe a pump nice warm shed
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Oct 12, 2010 18:41:03 GMT
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I built a garden waste furnace in my garden a few years ago and used it to heat water (mainly for fun).
Running a coil around the inside or outside won't really absorb enough heat to both heat water and stop the shed overheating.
I would suggest that you fit a fully enclosed water jacket around the whole thing. That way it keeps the heat inside the burner and absorbs as much as possible. You could then insulate the water jacket and just use the heat from the flue to head the room. That way you convert as much heat into hot water as possible, which can be used at a later date.
Google 'thermal store' and you will see propper versions of what you want to do. They are like 2000 litres of water in a well insulated tank. You can burn wood in the evening for an hour to give a bit of heat to the room, but charge the thermal store. Depending on water needs, that can last up to a couple of days before needing to be topped up
Lewis
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Oct 12, 2010 18:45:20 GMT
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To add - fitting 10m of copper tube inside would be better for absorbing heat than fitting it outside, and you won't melt the copper assuming you can keep pumping the water fast enough! But a full water jacket would be better.
Lewis
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Oct 12, 2010 20:07:47 GMT
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I like the idea. A few thoughts:
-You want a lot of surface area to collect the heat - maybe a heat exchanger matrix above the fire. The double-wall idea is good as well.
-As long as the water doesn't boil, you won't have any problem with melting the metal of the exhanger.
-The storage tank sould be open-vented, like a central heating hot water tank, so that any steam can vent without causing a big bang.
-There should be a source of water to keep the system topped up, so that it doesn't run dry.
Three options for setting up your water flow:
a)If you keep the thermal storage tank above the burner (ideally completely above), you can get a thermosyphon effect going, negating the need for a pump - although you'd need a pump to circulate the water through the heater matrix.
+no chance of the burner overheating if the electricity or pump fail, lower power pump
-big tank of water at height, need to run the pump for longer
b)Alternatively, if the tank is beneath the level of the heater matrix but at the same height as the burner, you would need to pump the water through the burner.
+water tank lower, pumps runs for less time
-chance of burner heat exhanger overheating and possibly bursting if the pump fails
c) Since it's a small burner, it might be possible to have a water tank above it, and have the heater matrix above the water tank.
+no pumps so simple and reliable
-water tank at height, needs fan to transfer warm air to low level
Personally, I'd go for option C - it seems less likely to fail, and also leaves a bit of height for a feeder tank.
I'd also want to have a method of dumping lots of heat very quickly if required - perhaps a car radiator and fan mounted outside, with two cut-off valves to reduce the loss when it's not needed.
Maybe a little over-cautious, but bursting boilers cause serious damage and while moder boilers don't do so, early systems using similar techniques as being discussed here did so fairly regularly.
James
P.s. If you want to run a hot tap from the system at some time, don't just run it from the hot water storage tank - if you run lots of water through the system, the boiler pipes could scale up and get blocked. It would be better to run it on a heat exchanger to separate the flow from the tank.
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see this guy on youtube hes been making them for yonks
think its about
used another part or side of a gas bottle welded on the back with in and out for the rads
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Last Edit: Oct 13, 2010 7:57:49 GMT by twizzle
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Oct 13, 2010 21:37:09 GMT
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Right - after running the thing today a few times I think I've made a decision - I'll cut the  out of another bottle and weld it directly on top as the water tank, and perhaps make a water jacket off the back depending on how much plate I can snaffle. I've got a central heating pump that I can use to circulate the water. I'll leave the top of the tank open so there isn't a lot of pressure, and the water can happily boil off if it wants to - there'll be a good 4 gallons of it. By my calculations, if I can heat 4 gallons of water to 80 degrees, I'll get about 90 minutes worth of foot warming heat out if it. That'll do nicely. Slowly learning with this thing - 18mm caravan board burns fast and hot, whereas 12mm ply takes a lot more lighting. An hours worth of fire takes about 1sq.ft of 12mm ply cut up. |
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Colonelk
Posted a lot
Posts: 3,740
Club RR Member Number: 83
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Oct 15, 2010 19:21:25 GMT
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BTW if no-ones mentioned it, make sure you get the water over 65 degrees when you heat it so you arent breeding legionaires disease or owt  |
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Oct 15, 2010 19:30:51 GMT
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BTW if no-ones mentioned it, make sure you get the water over 65 degrees when you heat it so you arent breeding legionaires disease or owt Yeah, I worried about that. Plan was to avoid drinking it and perhaps lob a bit of bleach in occasionally, but 65 degrees should be easy enough to get to |
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Oct 15, 2010 22:35:13 GMT
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Legionaires is spread by inhaling droplets of water, not drinking it. But yeah, just keep it good and hot. And don't drink it anyway, because it'll probably have a load of other curse word in it.
Get yourself a rain butt and use rainwater for extra "The Good Life" living-off-the-land goodness and cheapness?
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1989 Peugeot 205. You know, the one that was parked in a ditch on the campsite at RRG'17... the glass is always full. but the ratio of air to water may vary. |
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