heat extraction from exhaust

[Dail R H]

   When I operated the boiler at Georgia Pacific,we tested the boiler water ,and makeup water 3 times per 8 hr shift. The system automaticaly blew down after each new 100 gals. of makeup water was added to the boiler. We changed the length of the blow down based on the test results. We also did 2 manual  blow downs per shift.
   That 1970 boiler was according to the guy who did our annual insurance inspections,the cleanest boiler he inspected.We also had the chemical co test guy by once a month to do water test.

[biobill]

  I'm building a muffler for a 6/1 out of a 100lb propane bottle. It will set vertically with inlet and exhaust on the top. I think I'll put a 3/8" copper coil in it and see what kind of hot water I get out of it. The inlet tube is fabricated from some kind of perforated stainless and runs down the center of the tank. Thought I'd make some brackets to support the coil off the inlet and tie the coil loops together to make the assembly more rigid. The copper will exit the tank through compression fittings top and bottom, the bottom one also serving as a condensate drain.
  Several different metals in what's probably a pretty corrosive environment. Any cautions, predictions? Think it'll work? How about coil length - the more the merrier?
                                                         Bill 

[dkwflight]

Hi Your ideas should work fine, with some tuning. Corrosion will be a problem over the long haull. Any system will have to be monitered. Or auto shut offs will be needed.

I personally (when funds allow) will try the gas water heater, venting the exhaust up the flue. The twisted diverter will probably viberate, but I think it could be secured. Probably a cleanout tee at the bottom will be required.
Dennis

[biobill]

Posted some pictures of my muffler/heat exchanger

http://listerengine.com/coppermine/thumbnails.php?album=131

It's a very effective muffler and a reasonably efficient heat exchanger. A large shell for space heating with a small coil to heat liquid as an afterthought.
                                             Bill

[rmchambers]

Impressive bit of work Bill.  so is the propane cylinder like a big expansion box for the exhaust?  the gas leaks out of the inner tube and heats the coil as it flows around.  How hot does the cylinder get?  what does the exhaust note sound like outside?

You'd probably get more heat from that if the copper coils were wrapped tightly around the inner pipe at least for the coil as I suspect a lot of the gas just goes right up the middle and heads out the top.

I see you went with a tire foundation for the muffler and not 4 tons of concrete. tsk tsk 

Robert

[Dail R H]

   B Bill,
   You might want to add a sleeve around the coil,something like a piece of stovepipe. That would do two things. One , force all the exaust gasses to take a longer route out of the muffler,=quieter exaust. Two, since the exaust would have to spend more time in close contact with the coil,your heat recovery should be better.

[biobill]

Robert,

  I don't have an accurate way to measure the temp. Reminds me of my wood stove with a low fire - you can touch it briefly with out getting burnt. The water stabilizes at 180F, I'm thinking the tank is in the same neighborhood. The exhaust is virtually silent outside. It exits the pipe in a mostly steady stream rather than in pulses.

You'd probably get more heat from that if the copper coils were wrapped tightly around the inner pipe at least for the coil as I suspect a lot of the gas just goes right up the middle and heads out the top.

  Actually it works the other way if I understand what you are saying. The inlet is top/center.which feeds a perforated stainless tube with internal chokes of decreasing size. The chokes were an effort to bleed off the 'pulse' over the length of the tube. The outlet is top rear and is a pipe extending to the bottom of the tank with some small bleed/equalizing holes facing the outside. The whole purpose was to try and keep pressure fluctuations to a minimum. I expect the heat is pretty well homoginized through out the tank. The coil is simply hung in the hot environment. I had some more pictures but coppermine got the best of me.

  As far as the number of coil turns is concerned, I calculated the pitch necessary to ensure a good thermosyphon and then used what I had lying around til it ran out

                                                      Bill

[adhall]

Bill:

So how dirty do the innards get??

Best regards,
Andy Hall

[biobill]

  Andy,
     I'll let you know after the heating season . Shouldn't be too hard to clean though since you can remove the core as an assembly. I did put a drain in the bottom for condensation but haven't gotten anything out of it in 130 hours.
                                                         Bill

[rmchambers]

Bill,
   you were right I did misunderstand how you routed it.  In that case the only way to get more heat out of the coil is to have more coil in there - more surface area = more heat transfer.. If you keep buying spools of copper tubing though the ATF is gonna want to know where your still is and what you're doing with the 'shine you're brewin'! 

I'm glad to hear the exhaust pulses have been moderated to the point where it's more or less silent outside.. that's ideal!

How do you get at the chokes in the inner pipe, that's about the only place I'd expect a decent amount of soot to build up (if there was any building up at all)?

Robert

[biobill]

Robert,
   Chokes were made from 2" sections of 2" exhaust pipe. The sections, 4, were collapsed on one end into a 4 leaf clover shape that gets more restrictive top to bottom. All I did was push them into place with a pipe and secure them with exhaust clamps and lots of neversieze. I expect they'll come apart the same way with a tap or two.
                                                Bill

[fattywagonman]

I like lots of small tubes instead of  big ones for better heat transfer. Counter flow is also important. Here's a photo of a Stanly boiler...
 
http://www.stanleysteamers.com/techpage/boil2.jpg

something like this (but smaller) with the exhaust being pushed down would make a good  heat exchanger... Copper tubes swedged into the sheets and a bolt on flange flange top and bottom would make cleaning easy... copper's catalytic properties make it good at shedding carbon buildup... I've used shell in tube heat exchangers like this which also do a good job..

http://www.apiheattransfer.com/en/Products/HeatExchangers/ShellAndTube/PLACShellAndTube.htm


BTW Buickanddeere I enjoyed the crane links..

I used to own some floating cranes.. My largest crane picked 100 tons @100' and sat on a 42' circle.

[adhall]

Maybe this is a crazy idea, but it's been rolling around in my mind for a while and I'm going to throw it out here anyway:
Why not capture the waste heat in the exhaust by sprinkling water through it?

I am thinking of a tank with the exhaust entering near the bottom with nozzles showering water down from the top. Any gases that don't condense or dissolve in the water would exit the top of the tank. The dirty water would be pumped from the bottom of the tank through a filter and then through a heat exchanger and, from there, back to the nozzles.

Advantages that come to mind:
  -- Should be able to collect almost all of the waste heat (even to the point of condensing the water vapor)
  -- Should remove a lot of the soot
  -- Should remove a portion of the "diesel smell" and other gasses as well
  -- Would also serve as the muffler or resonator

Downsides that come to mind:
  -- A circulating pump would be needed to feed the nozzles
  -- A filter would be needed
  -- A heat exchanger would still be needed to isolate the dirty water from the clean water
  -- The dirty water or at least the dirt in the dirty water would have to be disposed of somehow
  -- Likely corrosion problems from acid buildup in the dirty water

Unknows:
  -- Just how dirty would the dirty water get?
  -- Would pipes and nozzles tend to get plugged?
  -- Would a filter keep the dirty water clean enough?
  -- Could the acid problem be controlled well enough by adding an alkalai periodically to the dirty water (or even continuously)?
  -- And the key unknown: How much heat would this system extract compared to the alternatives?

Best regards,
Andy Hall

[rcavictim]

Andy,

I think that water spray extractor/muffler is a clever idea.  Unfortunately as you describe, it would be a rather complicated affair requiring high initial fabrication cost due to many components and maintenance which probably involves replacing a costly water filter element. A DIY sand filter may work here to save $$$.   It also requires mechanical or electrical energy to run (a water pump).  Is there a large enough return to support this and still make an energy output profit?  I think the heat available in the exhaust of a dinky little Lister/oid or othersmall diesel processing a half a litre of fuel per hour is too little to be worth the trouble, but do think this might be worth exploring on a 50 kW+ sized plant where extracting every ounce of energy was deemed necessary.

[rmchambers]

how about a non-pumping arrangement?  get a big container like Bill used (100lb propane tank) and have the exhaust feed into the bottom of it.  Put some sort of diffuser on the inlet to turn the big bubbles into lots of smaller ones which can then percolate up through the "dirty water" giving up heat etc.  you'd have a coil immersed in that same water to do the heat-exchange with the  "clean water".  You'd need a drain and a fill for the dirty water and for safety sake a vacuum breaker on the exhaust in case your engine stopped, hit compression and rolled backwards and sucked up some water.  If the pipe is long enough I doubt it will be able to suck up through 2 reverse revolutions.

What to do with the dirty water?  good question.  What would it contain?   soot, perhaps a little oil?  The oil could skim off the top, the soot might settle but even if it didn't it's not that toxic.  get some carbon eating plants and let them go to town on it.

Robert