Exhaust Heat Recovery - Steam Power

[Phantom]

I'm partially in the same boat as bschloop. I think that one of the best ways to get the heat from the exhaust would be to use a larger pipe.

If you go from a 3" exhaust pipe to a 3.5" and run tube inside with a size of 0.25" and the tube covers the complete stretch it should give you an effective 3" to 3" to 3" pipe.

I think that it would work best running the tube as a spiral with the inlet at the bottom of the tube shaped as a "J" and have the outlet on the top side of the pipe. Air bubbles getting trapped in the pipe should not be a problem as long as there is enough water in the system so that the inlet side water level never drops below the highest point in the loops. If the water on the inlet side is cooler than further down the pipe it will push/pull from the temp difference.

If you are really worried about trapped air seal the system and place a vacuum on the outlet side to promote the movement to the lower pressure side and place this pipe on the exhaust down-pipe so the inlet side will be much lower than the outlet side. The only issue I see there is that the hotter part of the pipe will be getting the heat first but that could help as water takes on heat 8x faster than air.

[kafer65]

What about liquid sodium like a passive nucleur power plant design. Get one end hot leave one end cool and the convection inside a vessel with liquid sodium will produce an electric field. Capture field energy and done.

[jdgFirefly]

Originally Posted by kafer65

What about liqhttp://ecomodder.com/forum/newreply.php?do=newreply&p=182486uid sodium like a passive nucleur power plant design. Get one end hot leave one end cool and the convection inside a vessel with liquid sodium will produce an electric field. Capture field energy and done.

I've heard of sodium being used as a coolant and using convection as a passive circulation system but I haven't heard of this sodium electric field thing. Got any links, it sounds interesting.

[Dr. Jerryrigger]

Okay, I'll jump back in here.
So the way I see this working well is to really try to get heat every way you can. Rap the block in rock-wool, use the boiler water as coolant, rig it up so the radiator is only used when needed
This will give you some 95C water to pump into the boiler.
For a pump you need something that can give really high pressure, like one of those 3 piston pumps used on pressure washers. There are some small 12V ones made, but it took me many hours to find one last time I looked (a few years back) and I'm not up for that right now. A belt drive one may be good. I think a computer controlled electric one is really what is needed.
With the water already at 95C hopefully you can cut back the 12sq ft : 1hp to something more reasonable for this application.
So then the high pressure hot water is run through post turbine steam (more on this later), getting the temp up to say 110C (not steam at this pressure), then into a post cat boiler. The steam is then run into a pre-cat dryer (and there are a lot of tricks for drying steam), and then to a turbine like :Slotted Disk Turbine
The steam coming out the back of the turbine will still have a lots of heat, some of which can be recovered by the water flowing to the boiler. It could also be bubbled into a water holding tank.

The hardest part of this is how to scale thing. How much heat can you really get from the exhaust? How much can you insulate the block and exhaust with out causing problems.
I generally like to try things on a small scale first, but I don't think it would work well on a smaller scale, in fact I would think it would be much more efficient on a very large engine

For a boiler I would need a few weeks with a Bridgeport.
Also, it's been a long time since I did the math on this, so this may be way off or for something else, but I seem to remember that a lot of water would be needed, something like 1gal:2miles.

[Dr. Jerryrigger]

as far as sodium, you would need a thermal exchanger to heat the sodium, and then another to heat the water. This added part would not be a big deal, but there is limited space in a car, and you will loose energy in the extra step

[jdgFirefly]

Originally Posted by bschloop

update on the AC compressor idea. I set it up again, and engaged the clutch while it was spinning. It has so little torque that I could hold it stationary with my hand. (Gloved of course) this was at 90psi, so it seems it will not work. Bummer

I find it encouraging to know that some compressors will actually turn as a motor. After doing some googleing I found that there is several types of compressors but they all look vary similar from the outside and I can't find any info on what type is on what car.

I'm a bit surprised that the thing produced really low torque. But then again the amount of air flow it would need would likely far exceed what a typical air hose can provide, especially if you used an air nozzle.

Also you can quickly check to see how good the compression is by sealing the outlet port with your thumb and turning it over a few times by hand. I found that a good piston compressor will hold pressure for a good 10s without any noticeable leakage.

[jdgFirefly]

Dr. Jerryrigger I agree with you about using the engine cooling system for pre heating the water. It will really help get the water closer to boiling before it enters the boiler.

I think that the pressure washer pump is probably overkill, they can provide 2000psi and up, I wouldn't suggest anyone build a DIY steam system at that pressure unless you do the engineering. one good thing is the pressure washer is already built for water. I was thinking a small power steering pump or oil pump might work for a cheap pump but they might not be vary eff.

That slotted turbine is cool I would like to build one some day, but why go with the DIY turbine when theirs lots of positive displacement engines and pumps that could be adapted? I just can't see the turbine being vary eff and it would be hard to size it right for the system.

[LeakyIdeas]

What about a simple co2 engine?

like in this link i can't post :-)
www animatedengines com / co2 . shtml

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Whats 12CFM of steam in water volume ? isn't it about 200ml per minute? or less than a teaspoon a second?

[LeakyIdeas]

or...for a prototype use a "live steam" model, searching for mamod on ebay should net you a few steam pistons, flywheels etc. in stock use they do 1500 rpm,

[Daox]

Originally Posted by jdgFirefly

If you already have bulky condenser and storage tank plus all the plumbing you might as well add the pump and make it a closed system.
So I'm kinda a closed system pusher...

I'm just getting back from vacation so I'm playing catch up here.

Any ideas on an inexpensive high pressure pump to use? That would probably be my main concern. Controlling that pump would be my next concern.