--- Recover heat from exhaust --- I got just the right heat exchanger!

[Christ]

Originally Posted by basslover911

^ Well if it is, that probably how aftermarket mufflers are tested as well (to get "good" numbers). Which is where I got my -2psi (from a magnaflow website I think)... dont you think? (It only makes sense I guess.)

That's how mufflers have to be tested - there is no heat exchanger in a muffler, besides ambient air exchange (wholly inefficient, so negligible at best.)

The problem comes in when you start extracting heat from the exhaust. The exhaust will lose velocity because of the heat exchange.

I'm not saying it won't work, and by all means, please, try it. I'd do it, but I don't have $160 + shipping to spend on it right now.

Please, keep us updated with your results!

[RobertSmalls]

Originally Posted by basslover911

A water to air intercooler;



Replace your muffler with one of these, run a water line in/out, and power a small pump to make electricity. (a la BMW, but much simpler).

Theory;
The drop on these intercoolers is VERY low, about .1 psi. The drop on a normal car muffler is of excess of 2 psi. So not only will you get a heat exchanger, but also a free-er flowing muffler.

Since they are made to effectively convert temps from water-air, it will effectively convert temps from air-water.

I think this is the best thing to use as a energy recovery system and easy to implement... what do you think?

It's pretty, but there are a few problems with it.

That's just a heat exchanger, not a heat engine. Its output is hot water, not electricity. So you need a heat engine in addition to it. Maybe you can recover enough energy from your exhaust to generate pressurized steam and run a turbine, which in turn runs an alternator?

However, setting up a turbine and condenser under your car and filling them with a working fluid that won't freeze could be a challenge.

The real killer here is those components will add weight, volume, and aerodynamic drag. Will you recover more energy than you spend? Depends on your implementation.

As to its muffling properties, I'm sure they're minimal.

[vtec-e]

This was discussed here before and there was talk of using a refrigerant as the working fluid. Getting that to turn a turbine with enough power to drive a generator to power the car...will be a whole other thing.
I suppose another benefit of this would be the condensing of particulates etc. from the exhaust. If it did happen then you would be reducing your emmissions! Not bad at all.

ollie

[aerohead]

Originally Posted by basslover911

The point is to remove the alternator, and if electricity generation is that much then yes covert everything to electric.

I tried copper tubing and it's nit efficient AT ALL. That's why I thought about using this. How many watts would this need to produce in order to completely remove the alternator though?

to compensate for the total available power the alternator could produce,your "net" power (after all the pump/generator system losses) would have to match your alternator's full current output (amps) which would be listed in the owner's manual.You could typically do with less,until the time,if ever,that you were running all your accessories.

[Christ]

Originally Posted by vtec-e

This was discussed here before and there was talk of using a refrigerant as the working fluid. Getting that to turn a turbine with enough power to drive a generator to power the car...will be a whole other thing.
I suppose another benefit of this would be the condensing of particulates etc. from the exhaust. If it did happen then you would be reducing your emmissions! Not bad at all.

ollie

No, sir. The water and air never come in contact with each other in this setup.

The exhaust flows through a sort of radiator that is surrounded by water flowing. They're two different circuits.

[basslover911]

"Maybe you can recover enough energy from your exhaust to generate pressurized steam and run a turbine, which in turn runs an alternator?"

Yes, like i've been saying, that IS the whole idea. Through natural convection the liquid will flow to spin a turbine and back into the heat exchanger.

And you ideally want the lowest possible exhaust velocity after this exchanger, because thats how you know you are extracting energy from the system (in the form of heat)- so low exhaust velocity would be a good thing not a bad thing...

[Christ]

Originally Posted by basslover911

"Maybe you can recover enough energy from your exhaust to generate pressurized steam and run a turbine, which in turn runs an alternator?"

Yes, like i've been saying, that IS the whole idea. Through natural convection the liquid will flow to spin a turbine and back into the heat exchanger.

And you ideally want the lowest possible exhaust velocity after this exchanger, because thats how you know you are extracting energy from the system (in the form of heat)- so low exhaust velocity would be a good thing not a bad thing...

Keep in mind, you have the efficiency of the engine to worry about, as well. You can't think of one system at a time, you have to think of both systems working together. Decreased exhaust velocity means higher back pressure, which is not good for your engine (unless it's a 2 stroke, of course, and then only to a given extent.)



Ideally, you could get 100% of the heat from the exhaust system. This would choke out the host engine, though, defeating the intended design.

Realistically, you probably won't be able to recover more than about 25% of the exhaust's heat without causing severe performance degradation.

You will want to shield and insulate the exhaust from front to back, to minimize the heat loss that isn't providing energy for your setup, which will help a few % with efficiency, and still allow you to have enough heat in the exhaust to maintain positive flow with minimal pressure build.

[Daox]

What kind of turbine are you thinking of using?

[basslover911]

Originally Posted by Christ

Keep in mind, you have the efficiency of the engine to worry about, as well. You can't think of one system at a time, you have to think of both systems working together. Decreased exhaust velocity means higher back pressure, which is not good for your engine (unless it's a 2 stroke, of course, and then only to a given extent.)



Ideally, you could get 100% of the heat from the exhaust system. This would choke out the host engine, though, defeating the intended design.

Realistically, you probably won't be able to recover more than about 25% of the exhaust's heat without causing severe performance degradation.

You will want to shield and insulate the exhaust from front to back, to minimize the heat loss that isn't providing energy for your setup, which will help a few % with efficiency, and still allow you to have enough heat in the exhaust to maintain positive flow with minimal pressure build.

Yes but remember your replacing a muffler for this, so the back pressure should be the same or less than how the car came from factory since your not adding anything to the system just replacing something

And what turbine? Well more like a water pump that turns an alternator.

[basslover911]

Of course you could SKIP all of this and simply place a turbine in the exhaust (turbo) attached to an alternator.

But then your not really using the wasted exhaust heat but rather the normal (not-wasted) exhaust velocity and that WILL add way more back pressure... Unless a turbo also uses heat to spin it? (although it might, I think its main source of energy is the velocity of the exhaust)