Just dropped in Bill,thought I'd start an argument.... I mean, vigourous discussion.

You're right  - It's all a bit of a tradeoff. I think you'd be better off using the lister coolant circuit for heat when the engine's running and this kind of thing for when it's off.

The advantage with something that doesn't use water as storage is that you can run it at higher temps above ambient, which makes it easier to move the (limited) heat about later.  But as others have mentioned, it's all wasted heat otherwise. It's fairly low-cost and once setup it should be relatively low-maintenance soot-wise with the gaps between the aggregate.

My concern with direct water/exhaust interaction Jens is that you will tend to lose a lot of water (and heat) as water vapour out the exhaust due to the large, warm-ish surface area of the aggregate promoting  evaporation. And having seen water-based exhaust scrubbers in use in underground mining equipment - to say the water will get dirty is an understatement! There should be enough gaps between chunks in the aggregate that sooting up will take a long time.....

I'll post my back-of-envelope calcs :

Pick a material that can withstand the temps and has a reasonably high specific heat.
A list of some typical values can be found here.

Brick is good for simplicity at 1kJ/kg.K (Sorry,metric only!)

So, for each degree kelvin you heat a 1kg brick, you need to put in 1 kilojoule of energy.

Say we have.... 250kg of bricks, thus 250kJ needed to warm the bricks 1 degree.

You arrange the setup so the exhaust passes through the bricks and exits out the other side.
The bricks are at a starting temperature of 320 degrees kelvin. ( approx 50 degrees C - You used the engine yesterday)

You run your engine at load and conservatively output a constant 3kW of heat out the exhaust with at temp of, say 700 kelvin. Passing the exhaust through the bricks, you manage to cool the exhaust temp by half, to 350 kelvin , giving a net input into the bricks of 1.5kW.

You run your engine for 8 hours, charging your batteries, using your tools, warming your little arctic hut nicely with the engine coolant and eventually shut the engine off for the day.

The definition of a watt being 1 joule per second and 8 hours at 1.5kW being 8 * 3600 seconds * 1.5kJ gives you 43.2 megajoules, going into 250kg of bricks that need 250kJ to raise them 1 degree K. So, dividing 43.2MJ / 250kJ gives you an increase of about 170 degrees K, to finally wind up with hot bricks at 320K+170K = 490K, or about 220 degrees C.

You then run a heat exchanger loop around the outside of the bricks, going into your hut and a small radiator at the foot of your bed. Deliberately making use of the poor transfer from the small contact area on the round copper pipe on the outside of the drum, you manage to cool the bricks by that 170K over the next 16 hours. Working your 43.2MJ of heat energy over that time period  (57600 seconds), you get 43,200,000/57,600 or an average 750 watts output from your radiator over that period - enough to keep your toes warm, anyway. If you dick about with the heat exchanger, you could get twice as much for half the time, etc.

At the end of the day, obviously the heat has tapered off from the initial output, but the bricks, being at 50 degrees C final temp, are still at a relatively warm temp above ambient and some useful heat transfer with still take place to some extent.

Yes, there are a number of unknowns - the main one being heat transfer to the bricks. Not only is it difficult to quantify, it will taper off as the bricks heat up to exhaust temp. Too much brick and it won't get  hot enough above ambient to make the next heat transfer stage easy (low gradient heat and all that, as guy_f is fond of saying). Not enough brick and it will all reach exhaust temp too quickly, leaving wasted heat going out the exhaust.A balanced mass to match your typical engine runtime is needed. You've also got misc losses like through the brick insulation, and you'd rob heat from your hot bricks if you drop your engine to idle for any length of time before shutting off.

But, it's something to tinker with.

I've worked on 120VDC RAPS's before, let me tell you, that's a lot of 2V cells to buy and subsequently deal with, however all the equipment is readily available for that kind of voltage on the market. It's normally only used in 10KW+ systems though.....

Personally, I'd just run a 6/1 with an AC generator and via a variac+rectifier (or your electronics of choice) charge your batteries (of whatever voltage), using the remaining electrical power from your listeroid on a couple of electric heaters or for hot water.

Hmmm. Utterpower has some sort of chinese gasification plant thingo:

http://www.utterpower.com/gasification_plant.htm

In china, this unit is used to make cooking gas, in fact there's a cooking stove that comes with the unit that even has a push button igniter built in. The brief instructions that are found in the box, say this unit can be shut down for 10 hours and then restarted without re lighting the fire box. I have talked to friends in UK that suggest a setup like this makes plenty of gas to run a pickup, and the preferred fuel is charcoal because it makes such a large amount of clean and BTU rich gas. The charcoal is made by the user, and there is plenty of information on making your own. In China, they use all kinds of stalks twigs, small branches and crop stubble, the dryer the better the gas.

Dammit! Something else to tinker with. 

The pressure relief is normally a simple ball-and-spring type arrangement, with an threaded adjustment or shims to tension the spring.
If the adjustment won't go far enough, a weaker spring in there will do the trick. If you can't find the relief - sometimes it's internal - you could make a relief valve from a household water tap fairly easily as it has all the components needed except for a spring.... machine the end where the tap washer goes so that a small spring can go there to put force on the washer and you've got an instant-adjustable relief valve.

But I'd suggest driving that pump with a loose belt (or if shaft driven somehow, a shear pin) so that if something does block up and your relief doesn't work, there's a weak point in there so you don't get umpteen-bazillion PSI trying to inflate your oil filter.....

snow!?! (runs away, squealing like a little girl)

Just two seasons here, wet(hot) and dry(cool). Coldest I've seen it is about 4 or 5 degrees C.

Mount Isa in the 'wet' season:


Dry season's just the same, except the green bits are either brown (a little dry) or grey (drrry.)
And that's the way I likes it too, dammit. 

Hmm. I've never really had any trouble with the "standard" 60/40 on tinplate/mild steel with a decent acid flux. That is, all the containers I've made have never leaked......

A few things :

- 60/40 solder should do it. The triangular solder sticks about a foot long and 3/8" on each side are good for this kind of thing.
- You'll probably need a small gas torch, electric irons would be a little on the small side, unless you've got a 300-watter about the place. You can cook the solder with the gas torch, so use it to heat a seam and then sweat solder into it - just like 'normal' soldering it should flow into the seam nicely by itself. I've one that's basically a burner on top of a small disposable can, nothing special, throws maybe a 1" blue flame.
- I use "Bakers Soldering Fluid", acid based. Run it along the seam, sizzle it a bit with the torch. Don't breathe the fumes 

When I was doing this kind of thing many years ago, I used to make a "J" on the end of each piece of tin, hook them together and (gently!) hammer flat. You then solder the side that's accessible and the hammered-flat J makes a small recess to leave a nice bead of solder in. Putting the top and bottom halves of a tank on, I would probably form a lip (Kind of a sideways "S" shape) around the top of the lower piece, dished enough to hold a small amount of solder, make a matching lip on the top half, tin both parts with extra solder on the bottom part, place together, and sweat with the torch.

From the Dumb Things To Check dept:

Is it a 12 or 24V starter? 

A couple of things :

1. It's water soluble obviously as you chuck it in the pool, but I don't know if it'll mix with oil.
2. If it *is* soluble, you'd probably have trouble with the viscosity of the stuff you're trying to filter, restricting it's ability of the floc to clump particles together.

Has anyone thought of an air-bubbler arrangement for filtering out chunkier particles? Without going too much into the finer details, surface tension on the surface of tiny bubbles should make particles cling to them (similar to pepper on water) and float up where they can be skimmed off. Something like a aquarium pump and a few stones in a container, run for 10 minutes, might do something.
It might do nothing too, just trying to apply a design I've seen in various industrial plants for particle separation