Hello all I am new to this Cye has been steering me in the right direction on a coil heat exchanger I have been forming,, and suggested I post some pictures,, sadly its a bit late in the day for me to picture the actual "coil" as it is now insulated and hidden.. but having had a snoop around the forum I am sure you are all far more advanced than I and have seen it all before!
The fire and heat coil is meant to keep me warm in at an off grid property (project) that I have in Spain, I had intended to build a nice fire but time ran away with me and the list of other things to do wasn't getting shorter, build a trailer, convert the cooker to LPG etc etc.. so I built a quick and dirty one hopefully it will do the job,, its drawing too much air at present but I think some fire rope around the ash door will help.. recycling seems to be a recurring thread on this forum so you will all be pleased that in real terms the fire was free 2x old gas cylinders a broken IKEA toilet roll holder for a handle a spring from inside a beer barrel for the other handle and the used brake disk that seems to be compulsory (but useless save than for added mass) on a gas cylinder fire. I had to buy the 5" flue and 20m of 10mm pipe but the twin wall stainless one was salvaged from a job I did.
ok my photos are too big! If people want to see them I will try again
Orange, that is a very nice construction thanks. How did you bend the coil and avoid kinking the pipe?
Caveman suggested that you may benefit from a baffle in the top of the stove, perhaps made from another brake disk. This will slow the flue and hopefully get more of the flue gases and tars burnt before they 'see' the water-cooled flue. Of course you'll only really know what further refinements are required when you fire the thing up and see whether you have excessive tar/creosote in the flue.
I think the 'stack coil' (flue coil) idea you've used is certainly better than the traditional boiler stove design where the boiler sits in the stove itself. Caveman (I think) describes the latter as a 'water cooled' fire, as cooling the fire too much in the firebox creates conditions which do not encourage efficient wood burning. For efficient wood burning, one needs very high temperatures, then, once the fuel gases are burnt off, it is ok to take some heat from the flue provided there is enough heat left in the flue gases to maintain an adequate draught.
If it were me, i'd consider partially lining the sides of the firebox with some refractory, e.g., some fondu cement mixed with sand and vermiculite. This will make for a hotter fire and a more efficient burn.
I'm only thinking out aloud, not criticizing. It is a lovely job altogether and you should be proud of your work. I wish I could make one as nice!
You may well have read this already, but if not, I think your type of stack coil is broadly described in the american booklet here:
I already have a baffle plate, it was the most difficult part to make! its a segment of gas cylinder turned horizontally (does that make sense? imagine a skateboard ramp upside down) so it channels the flame forward I kept the flue as far back as possible to keep the fire in the box as long as possible. I intended to put a damper in the flue also ( I built an offset smoker in the summer which was a great help in learning about exhaust gasses air movement etc) but like I said so many projects so little time. and I was worried about a cold chimney,, though personally I think too much is made of this (my smoker burns for 8 hours with a cooking chamber temp of 125 degrees with no evidence of creosote)
Plumbing wise once out of the coil I am stepping up to 15mm pipe, for this visit I will be fitting 2 rads, pumped by the one I bought from you I have a "normally closed" thermo switch which I plan to mount on the pipework which from memory "opens" at 55 degrees and closes at 30,,, I might have to also fit a manual switch as I am worried the pump will "pulse" at start up until water temp stabilizes, but I want it all to be automatic if I can, As my primitive fire certainly wont stay lit overnight and I wont want the pump running for no reason..
I have been eyeing up a beer keg today wondering if I have time to insert a coil in it and connect it to an old radiator painted black on the roof and maybe sleeve a meter of my heating "flow" pipe with 22mm pipe for a small heat exchanger.. as I have as yet no means to heat water and even in December I might get some heat in the water.. I was last out there in June and had the bright idea to paint an old 10 gallon antifreeze drum black and connect a hose to it for an alfresco shower... it worked well enough but by day 5 it looked like I had a spray tan... schoolboy error I had forgotten about rust.
lastly 10mm pipe around a 5" flue requires no tools or skills I just cut off the packaging put the coil around the flue (which was suspended between 2 trestles with a fence pole through the middle) stretched the coil and wrapped it tightly around simplz ,, mind if I do fit a coil in my beer keg it will be 22mm and need to thread in through a small hole not so simplz I will probably just take a gas ring and my homebrew boil pot this time.. I will download the link you suggest, do you have any downloads of differential temperature switches just in case by some miracle I do form a coil insulate the keg etc in the next 4 weeks and manage to make a living and finish all my other to do list!?
We have made a very simple differential temperature switch by adapting the 12v Maplin (Vellemann) thermostat using an additional NT10k thermister, also available from maplin. if you don't mind soldering, the PCB can be made up for <£10. you then need some 2 core lighting flex for the two sensors, and a tube of 'pound shop' epoxy resin to pot (waterproof) the sensors.
a few of these modified kits have been working successfully now for two seasons in solar heating applications, they're very basic but they do the job and are very inexpensive.
if you get a hold of the kit first, i can talk you through the minor mod that is required to turn it into a DTC.
it's great to see folks such as yourself making their own kit - grateful to you for sharing the info, and i'm sure it will encourage others to do likewise.
I made time to form my coil this evening (Saturday night the other half is away and I made a coil instead of going to the pub,,,, must be my age!) 22mm was a bit more of a challenge than 10mm but its done.. if I manage to thread it into my keg and make it watertight I will be in Maplins Monday or Tues and will be looking for a crash course in in switch design ..
the weather has been kind today so I have been trying to finish my trailer (as its booked on a ferry in a few weeks) so I have not progressed any with my cylinder/heat store, its a real ale type keg I have not really paid much attention to it I am guessing about 40l volume I will check/confirm.. I formed the coil using 2x 3m lengths of standard (straight) plumbing pipe,, once I got into the swing of it its straightforward. the second is much better than the first (both soldered together) if I knew how to add a picture to this reply would show you,, I used a chepo pipe bender (I didn't buy it especially for this) which I modified by taking one of the arms off and holding in a vice.
the jury is out on how to form the seal I am leaning towards solder as I intend to encase the whole lot in an insulated timber box and am suspicious of rubber gaskets that I cant see, more so when the cylinder will be dry for months on end I guess it will depend ultimately on how accurately I can drill the holes!? since the sides are angled its going to be awkward! speak soon
hi Cye I am familiar with what my Dad calls an Essex gland.. my main challenge will be getting the coil into the keg and lining it up with the two holes I make and fish them back out,, I might just buy (I hate that word) a plastic drum with a removable lid fit all the gubins and seal the lid on it wont have much pressure so it should be ok,, I do wonder if the keg has enough volume to be worth the work,, I had rationalised this with,, its in the Med.. so it should heat quicker than here,, and at present I have no water on site. I wont spend enough time there to justify (or can afford) a well, the same applies to having a tanker deliver water (minimum charges apply) so I have to bring water in from a tap in the village! and filling a large hot water cylinder and keeping the header tank full will be a full time job.,, and I was also thinking that I might be better of with 2 or three small stores dedicated to serve a specific room that the thermal response times would be quicker!? I will email you the photo of the coil being formed, but I doubt its anything you have not seen,, the next one I make will be more even now I have worked it out.