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Old 11-21-2005, 08:40 PM   #1
Jayslay420
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Question Increasing efficiency - converting heat?

Ok,

I've been pondering the fact that cars waste a huge amount of energy through heat of exhaust and the engines radiant heat. I was thinking, and wouldn't it be very usefull to try to convert this heat into more usefull energy? I've heard some numbers stated, where the loss is around 30% of the total energy stored in gas.
I was wondering if a heat conversion device like a steam engine could utilize some of this wasted heat. Perhaps convert exhaust heat to energy to run a fan for the radiator? It just seems like so much is wasted...

Does anyone have any experience with steam or other methods of converting heat to usefull energy? It seems this might be a usefull modification to high performance engines that burn through alot of gas.
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Old 11-22-2005, 12:53 AM   #2
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Re: Increasing efficiency - converting heat?

Before you leave work for home wrap your dinner in some tin foil and wire it onto the exhaust.
It should be well cooked by the time you get home.

Or, you could try a Turbo Charger.
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Old 11-22-2005, 01:36 AM   #3
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Re: Increasing efficiency - converting heat?

Quote:
Originally Posted by Jayslay420
Ok,

I've been pondering the fact that cars waste a huge amount of energy through heat of exhaust and the engines radiant heat. I was thinking, and wouldn't it be very usefull to try to convert this heat into more usefull energy? I've heard some numbers stated, where the loss is around 30% of the total energy stored in gas.
I was wondering if a heat conversion device like a steam engine could utilize some of this wasted heat. Perhaps convert exhaust heat to energy to run a fan for the radiator? It just seems like so much is wasted...

Does anyone have any experience with steam or other methods of converting heat to useful energy? It seems this might be a usefull modification to high performance engines that burn through alot of gas.
Well if 30% of the heat is lost in the exhaust, 30% is lost to the cooling system, and 10% is miscellaneous losses. There is really only about 20% of the energy left over for useful work.

Taking some of this lost energy to increase the heat lost from the radiator isn’t going to improve the engine's efficiency. Any heat lost is work lost, and no device can recover all the losses.

If you are really hard up to maximize efficiency then you need to develop of way to prevent the heat loss in the first place, not try to recover it later to run trivial devices.

On the other hand if you are only focused on dealing with recovering lost heat, Moppie is right on point and you should check out:

http://auto.howstuffworks.com/turbo.htm

and/or

http://www.amazon.com/exec/obidos/tg...04619?v=glance
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Old 11-22-2005, 09:28 AM   #4
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Re: Increasing efficiency - converting heat?

turbos increase efficiency.......and fun
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Old 11-22-2005, 10:09 AM   #5
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Re: Increasing efficiency - converting heat?

if you want increased thermo-efficiency get a diesel. they are far better than gas engines.... if you all can figure out a way to convert all that energy loss in a cost effective manner then patent it and contact all the auto makers... im sure theyd like to know how you did it
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Old 11-22-2005, 11:50 AM   #6
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Re: Re: Increasing efficiency - converting heat?

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Originally Posted by mazdatech177
if you want increased thermo-efficiency get a diesel. they are far better than gas engines.... if you all can figure out a way to convert all that energy loss in a cost effective manner then patent it and contact all the auto makers... im sure theyd like to know how you did it
I like that idea, but that takes a lot of thinking.....Diesel is a good idea, but turbo diesel..... now we're talking!
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Old 11-22-2005, 08:34 PM   #7
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Re: Increasing efficiency - converting heat?

Instead of trying to reclaim wasted heat, how about designing an engine that extracts more useful energy from the fuel by converting more of it to motion and less to heat.

Diesels are better at this than gasoline piston engines because diesel fuel can operate at higher compression ratios.

BTW rotary gas engines are less thermodynamically efficient than piston gas engines, hence their mileage is worse.

As far as I know, one way is to raise the operating temperature of an engine, without melting the pistons, rings or cylinder walls.
For years, manufacturers have experimented with ceramic coatings, ceramic parts, eliminating oiling systems (oil would just burn at really high temps anyways) and eliminating fluid cooling systems.
My guess is that no commercially-viable major tech breakthrough has been made in this field.
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Old 11-22-2005, 11:00 PM   #8
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Re: Re: Increasing efficiency - converting heat?

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Originally Posted by Schister66
turbos increase efficiency.......and fun
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Old 11-23-2005, 11:00 AM   #9
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Re: Re: Increasing efficiency - converting heat?

Quote:
Originally Posted by MagicRat
As far as I know, one way is to raise the operating temperature of an engine, without melting the pistons, rings or cylinder walls. My guess is that no commercially-viable major tech breakthrough has been made in this field.
Yep, raising the temp of the engine is good for efficiency, but not quite as good for power of course. The only viable step in this direction that I've found is Evans NPG coolant. NPG in thier case stands for non-aqueous propylene glycol. since cooling systems don't rely on the actual temperature of the water, they rely on the ability for it to transfer heat out, the actual temperature of the engine can be higher than we currently run. Since the Evans coolant doesn't get mixed with water it can't boil (well, not until something like 380 degrees). I think regular oil starts losing its life around 260 degrees, and synthetic somewhere around 280. The caddy 500 in my Bonneville runs Evans and I keep it running around 250. Detonation isn't a problem since there is no nucleate boiling to allow chamber temps to spike. It works well so far on 10w40

I wouldn't call Evans coolant a major viable breakthrough, but its at least a step in the right direction. Until then, I'll just run a turbo
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Old 11-23-2005, 12:51 PM   #10
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Re: Increasing efficiency - converting heat?

increasing engine temps would increase peak combustion temps and therefore increase NOX emissions. egr flow would have to be increased and that just takes up precious space in the combustion chamber. not to mention all that extra carbon buildup from the temps being so high
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Old 11-23-2005, 05:43 PM   #11
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Re: Re: Increasing efficiency - converting heat?

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Originally Posted by mazdatech177
increasing engine temps would increase peak combustion temps and therefore increase NOX emissions. egr flow would have to be increased and that just takes up precious space in the combustion chamber. not to mention all that extra carbon buildup from the temps being so high
As long as the coolant is taking as much heat out as the combustion puts in, it doesn't matter what the temperature of the coolant is. Its just that as water increases temp it begins to boil (nucleate boiling) and this has an exponential effect on detonation. So you are correct when discussing water based coolants.

If you need the coolant to remove 100 joules of energy and its capable of releasing 100 joules, thats all that matters. It doesn't matter to the engine if the coolant is 100 or 800 degrees. So, provided its capable of removing heat (not temperature; they're different) in the same capacity at higher temps, NOx won't increase.

Put it this way, if a typical car is tuned to not detonate at 230 degrees of coolant temp, but it might at 240, its not because its ten degrees hotter, its because the hotter water is starting to boil off the water jacket which reduces its ability to remove heat. The resulting combustion temp is much higher than 10 degrees more. Adding 10 degrees of coolant temp really doesn't matter when the combustion temps can reach 1800.

In most cars today, the cooler temps make more carbon deposits, too. I hate to directly disagree, but I wanted to make sure this part was clear.
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Old 11-23-2005, 08:16 PM   #12
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Re: Re: Re: Increasing efficiency - converting heat?

[quote=curtis73]If you need the coolant to remove 100 joules of energy and its capable of releasing 100 joules, thats all that matters. /QUOTE]
Just to clarify this to the underclasses----
Normally the ability to make, absorb, transfer, radiate heat, blah, etc. is expressed in Calories or BTUs.
The term "Joule" would be commonly used to express something like--- the amount of energy that had passed thru your Honda Civic's tires after it got hit by a bolt of lightning (and why they are all very flat...not that you would care).
However--
1 Joule is= 9.48 × 10-4 BTU
1 Joule is= 2.390 × 10-4 Calorie
I just don't want anybody to turn their Geo's engine into hot melt glue 'cause they mixed sumpthin' up on their calculator.

deleted "current" for "energy"
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Old 11-23-2005, 11:40 PM   #13
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sorry if im argumentative, but im drinking and my redneck is coming out... lol

are we talking about modern engines or the 500 caddy? there is a huge difference. higher engine temperatures have an exponential effect on metal expansion do they not? if so, then bearing clearances would have to be larger for the hotter running engines which could mean nasty knocking sounds on cold running. a 50/50 mix of ethyl-glycol coolant and water at 15psi boils at around 260, which i believe was posted above as the temp at which normal oil breaks down. so why is there any need to have your cooling system stronger than your weakest link(oil system)? a redesign of radiators, coolant temp sensors and thermostats would have to be done. not to mention the fact that on "modern cars" the emission monitors/readiness tests wont run with an intake air temp higher than 170. that value will be affected by the increased engine temps. i guess the makers could start installing intercoolers on all the cars... and last but not least, as it was stated above increased engine temps arent good for power output. i guess its up to the consumer whether they want a 10% gain in fuel economy or a 10% loss in power output.

IMO... if it were possible to do in any way, one of the manufactureres would have been on it like stink on shit a long time ago.

sorry if i pissed anyone off, have a happy turkey day if you are fortunate enough to live in the greatest nation on earth
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Old 11-24-2005, 07:53 AM   #14
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Re: Increasing efficiency - converting heat?

Just a thought.
There's a cook book called "Maniflod Destiny" about cooking on various parts of the engine.
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Old 11-25-2005, 05:10 PM   #15
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Re: Re: Re: Re: Increasing efficiency - converting heat?

Quote:
Originally Posted by Black Lotus
Just to clarify this to the underclasses----
Normally the ability to make, absorb, transfer, radiate heat, blah, etc. is expressed in Calories or BTUs.
The term "Joule" would be
Thanks for the clarification. I'm a bit "old school"
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