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Author Topic: Exhaust heat recovery- Exhaust to water exchanger  (Read 48567 times)

Grael

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #60 on: January 27, 2008, 06:05:04 AM »
I if may add my 2 cents to the Maytag & Iron horse engine discussion, I have one of the opposed twin Maytags, It'll start up nicely whenever someone wants to see it run. I also have probably 6 Iron horse engines 4 kick starts of all different designs, 2 pull starts and a few junked ones kicking around for parts. I'd love to have one of the ol' Iron horse with the 12VDC generator attached, I'd make a lovely backup when the other generators go down. I even had that Maytag of mine running a alternator for a while when we first moved up here and had no power at all, 5/8HP does not make many amps. :P

Ramble over. :D
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dpollo

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25 HZ and DC
« Reply #61 on: January 28, 2008, 02:02:56 AM »
Here on the wet west coast, the town of Comox ran 25 cycles  back in the 30s from the Puntlege River Power Station. In the 60s, there was still one 25 cycle unit in place for use in the mines nearby. If you tried to use fluorescent lighting, the flicker was noticeable.

The Empress Hotel in Victoria had a steam plant and the whole hotel used DC until about 1963. Part of the reason for change over was the closing of the coal mines and I believe the plant was oil fired for a couple of years before final shut down. I wish I had been bold enough to knock on the door and ask to see it in operation. I was too shy. Too bad, I'm sure the engineer would have been pleased to show it to me.

 Hotel staff were constantly under abuse from American tourists who plugged electronic gadgets into the DC power despite the fact that outlets were all marked with a warning.  It was the policy of Canadian Pacific Hotels to generate their own Power.  Lake Louise had a gorgeous Hydro Plant, AC,  still running in the 60s but gone now. 

adhall

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #62 on: January 28, 2008, 04:22:31 AM »
Apparently, 25 Hz power was more common than I had realized.

For what it's worth, Minnesota Power and Light Company (where my father used to work) was providing 25 Hz power to customers in Duluth, MN at least as late as the 1980's--perhaps they still do. I remember my father telling me about a hydro plant near Duluth which had a 25 Hz generator and a rotary convertor that could convert between 60 and 25 Hz (either way).

And the city of Proctor, MN (just outside Duluth) was all 25 Hz up to at least the late 1940's. My father repaired radios and TV's after returning home from WWII and told me about modifying radios to work on 25 Hz for customers in that town. If I remember right, they got their power from an electric railroad the operated in the area.

There is also a dam on the Mississippi river at Keokuk, IA which was generating 25 Hz power at least as late as the 1980's--and may still be, as far as I know. I did some work at a plant in Keokuk which used this power to produce calcium carbide in large electric furnaces. (Calcium carbide is used to make acetylene.) It was weird to work around this equipment because it sounded "wrong". 25 Hz hum sounds a lot different from 60 Hz hum.

Best regards,
Andy Hall
JKSon 6/1, 5 kW ST Head, 1992 Dodge RAM Cummins 5.9L Turbodiesel, 2001 VW TDI 1.9L Turbodiesel, 2006 Jeep CRD Turbodiesel, Yanmar FX22D Diesel Tractor

listerdiesel

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #63 on: February 03, 2008, 08:38:01 PM »
I'm just sitting here at the scanner, starting out on an 8000-page scan of the UK Abridged Patents for Class 7 Air and Gas Engines.

One thing that is currently going across the screen is the 1905 Patents, and in there, we have a lot of schemes for heat recovery from cooling water and the exhaust.

Patent No 12769 Dated July 4th 1904 and granted in 1905, also refers back to another scheme dated 1887, so there's not a lot that is new....

Peter

mkdutchman

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #64 on: February 04, 2008, 01:10:17 PM »
I'm just sitting here at the scanner, starting out on an 8000-page scan of the UK Abridged Patents for Class 7 Air and Gas Engines.

One thing that is currently going across the screen is the 1905 Patents, and in there, we have a lot of schemes for heat recovery from cooling water and the exhaust.

Patent No 12769 Dated July 4th 1904 and granted in 1905, also refers back to another scheme dated 1887, so there's not a lot that is new....

Peter


8000 pages.........good grief. Would sure like to see that, will it be publicly accessible?

listerdiesel

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #65 on: February 04, 2008, 02:02:43 PM »
8000 pages.........good grief. Would sure like to see that, will it be publicly accessible?

Subject to agreement by HMSO (Her majesty's Stationary Office) yes it will.

We have had a trial section running since 2005, we are currently working on the 1905-1908 Part section, this has 368 pages, plus the names and subject indices pages. The main pages for the current work is at:

http://www.stationary-engine.co.uk/Patents7/ABPatent2.htm

there is also an improved page (same details, better font) at:

http://www.stationary-engine.co.uk/Patents7/ABPatent3.htm

Note that the names and subject pages are fully operational, but only the first 12 pages are in place for the main part.

We have scanned the 368 pages, just have to clean them up and put them into carrier pages.

That will be 368 out of 7930...

Peter

Guy_Incognito

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #66 on: April 08, 2008, 05:58:52 AM »
Hmm. I hesitate to bring the thread back to the top, but........

I wonder if an intermediate storage step would help.

Consider :

- A large drum (or taller) full of loosely-packed aggregate (about 2"). Bits of brick, rocks, steel, whatever.
- A water pipe wrapped around the outside,
- The entire assembly is then wrapped in some insulating substance like your typical water storage heater.
- Exhaust gas is piped in under the aggregate and is directed through it out the top.
- Engine is run for 8 hours (or whatever), heating the aggregate eventually to a few hundred degrees above ambient.
- Water is run through the outer pipe to heat whatever you want to heat.
- Heat transfer out is limited by the gaps in the aggregate and the contact area between water pipe and drum, hopefully alleviating the problem of water flashing to steam in the pipe and allowing a simple thermosiphon arrangement.

Doing the math indicates one could get a usable amount of heat from the hot aggregate for a number of hours after the engine is shut off until its temperature tapers down closer to ambient. A phase change material in place of the aggregate would be ideal, although something with the temperature range needed is hard to find. Waxes are too low for exhaust operating temps. 60/40 solder would be pretty good, except for the quantity needed......

Thoughts?

biobill

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #67 on: April 09, 2008, 01:50:45 PM »
  Guy,
 Haven't heard from you in a while. In from the outback?
 
I think your scheme would be a bit of a trade off - heat storage potential in exchange for long warm up times. Might have some advantages if it was designed for a specific length run but that would be difficult to stick to in my situation, perhaps not in yours. I'm thinking that on shorter runs the agregate (thermal mass) would not receive enough BTU's to push the delta into a useful range. I question whether the backside advantage would be worth the frontside disadvantage if heat extraction is your primary goal.
          Bill
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Guy_Incognito

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #68 on: April 09, 2008, 02:23:21 PM »
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.

biobill

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #69 on: May 23, 2008, 02:32:57 AM »
Jens,
  Just checked the clock and it's got 318 additional hrs. since I opened it at 125 hrs. Haven't touched it and it hasn't given me any reason to.  I can still hold the exhaust pipe (post heat ex) with my hand, my somewhat less than scientific method of determining that heat is being extracted, and the engine shows no signs of being "plugged up" or down on power. It seems that in my circumstances, annually maybe 500 hrs. battery charging during the short days, a once a year check will suffice. At some point I may install a better condensate trap which is currently collecting in a muffler I made from a propane bottle.
  The dang thing worked really well for a "run what yer brung" set up.  A friend stopped by a while ago and mentioned he'd never seen so much firewood in my shed this time of year.
  I've seen two varieties of shell and tube exchangers. In some of them the tubes are individually connected with "U" shaped pieces to reverse the flow. I didn't want that type as I'd have no idea how to clean it. The one I have has tubes swaged into plates at each end and the end caps have partitions that direct the flow. I simply made new end caps with no partitions
                      Bill
Off grid since 1990
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blacksea7

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #70 on: June 14, 2008, 10:49:02 PM »
Hi all,

A waste heat recovery system is really simple. We've hooked them up to old steam registers out of old buildings all the way through Hayden tube and shell recovery units... the latter of which work incredibly well and they're easy to clean... just dump the water out and let the unit get hot... that's it. You can make one out of a piece of 12" pipe, couple ends and 2" tubes running throughout... want a picture, I can draw one up for you... The best use we had for the exhaust was baseboard heating in trailers in Alaska... exhaust did the heating... electricity off the generator did the rest.

Bill

jzeeff

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #71 on: August 25, 2008, 02:34:55 PM »

IMO, if the $.25/hr or so in heat is of interest and you have a design to deal with the condensate and soot cleanout, then exhaust heat recovery is a good idea.


biobill

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #72 on: September 09, 2008, 02:04:17 AM »
Quote from: jzeef

IMO, if the $.25/hr or so in heat is of interest and you have a design to deal with the condensate and soot cleanout, then exhaust heat recovery is a good idea.
  If it's only about finances than yea, there's better ways to go. But circumstances enter into it too. If you're out in the boonies, with grid power miles away (to run the central heating system you'd have to buy), on a road where fuel trucks fear to tread, it might be worth thinking about.
  or, you might just like to putter
Off grid since 1990
6/1 Metro DI living in basement, cogen
6/1 Metro IDI running barn & biodiesel processer
VW 1.6 diesels all over the place
Isuzu Boxtruck, Ford Backhoe, all running on biodiesel
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oliver90owner

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #73 on: September 09, 2008, 11:17:52 PM »
It is simple economics.  You pay for the fuel, you want the maximum return for your hard earned money. 

if the $.25/hr or so in heat is of interest

10 hours a day, is $2.50 .  That is $17.50 each week. 

The value of the collected energy is always increasing.....the cost of energy is 'going through the roof'..... Power stations (fossil) are only about 40% efficient.......It  takes time and fuel to collect and cut wood...... every little helps.  And it reduces any effects it might have in advancing global warming.  'Go for it' is what I say. :)

Regards, RAB

Grael

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Re: Exhaust heat recovery- Exhaust to water exchanger
« Reply #74 on: September 14, 2008, 05:59:40 AM »
I was thinking about exhaust heat recovery today and thought about the idea of putting a catalytic converter before the 'recover area' to heat up the exhaust gas a bit more as the converter 'burns' the unburnt fuel in the exhaust gas from the engine, thus more heat; it also would help clean up the exhaust emissions a bit as well. :)

Any thoughts?
GTC 8-1

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