924Board.org

[Fasteddie313]

another crazy engine performance idea...

this is not an AC unit!!!!!!!

sorry but I don't have many friends that are very smart to chat with about things like this...

this works on the principle of utilizing the waste heat of the exhaust to power an absorption refrigeration unit to cool intake charge temperatures..

how absorption refrigeration works
https://www.youtube.com/watch?v=azSDHIXBcOE





this system of using exhaust heat has been proven to work to replace the air conditioning in cars but has not been adopted for any use in automobiles (besides every RV refrigerator fired by propane)...
there is far more than enough waste heat in engine exhaust to power a system like this and they don't just cool, they freeze, many degrees below 0 very efficently

this would make use of free energy witch otherwise would be nothing but waste to increase the efficiency of any car by cooling its intake air temperature (turbo, no turbo, diesel, whatever), that means more horsepower, higher boost ability, and even better cruising MPG due to increased thermal efficiency FREE just by picking up the change that the exhaust throws away

the system is completely sealed, fill it once and it works forever, NO MOVING PARTS what so ever.. NO AC COMPRESSOR JUST HEAT

these things are currently used for industrial air conditioning and refrigeration wherever there is waste heat to be had, and they were invented and used before compression refrigeration was, before common electricity even

and taking heat from the exhaust after the turbo would somewhat condense the air in the exhaust pipe reducing pressure there thereby increasing the pressure differential between the header and exhaust improving the performance of the turbo.. probably so slightly it would be immeasurable tho

I have searched a lot and have never scene even any mention of absorption refrigeration used in intercoolers, a lot of nonsense negative energy gain compression refrigeration but nothing like this...

I don't know I just need someone to bounce ideas off of..

I see no reason that this would not work and be worth the install if it proves to work.. solder copper pipe in the right places, fill it up, no maintenance, good to go

maybe one day ill come up with something useful and end the poverty cycle..

who knows maybe formula 1 will like this thing.. there all about efficiency right now, I believe this could even improve there top spec engines just that little bit more..
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80 Turbo - Slightly Modified

[Grenadiers]

If it's anything like the propane-fired fridge in our truck camper; it takes a day to cool the fridge. We turn it on, with electricity, the night before we leave (track events of course!).
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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

[Fifty50Plus]

While the ammonia cycle cooling system has been around for about a century, it is very picky about movement. RV units go bad when tilted too much and are slow responders as Dave points out.
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1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

[ideola]

I've done extensive research on refrigerant-based intercooling. Bottom line, heat soak of the refrigerant is a huge issue. Building a system with enough capacity to deal with the demands of boost cooling is not worth the weight, parasitic HP loss, complexity, or cost. The system will heat soak way too fast to be of any practical use.

The Lightning trucks had a variant of a refrigerant based system, and they were only good for drag racing. Your Porsche was meant for road racing, meaning long periods on-boost. Air-to-air is by far the most efficient arrangement for the application, especially if you can minimize pressure drop, number of bends, etc. Best part is, you can supplement it with additional charge-cooling techniques like water sprayers and water meth injection, with no incremental parasitic HP loss, and fairly minimal add'l weight/complexity/cost.
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erstwhile owner of just about every 924 variant ever made

[Fasteddie313]

[Fasteddie313]

[Fasteddie313]

[Fasteddie313]

heres some stuff from this on another forum so you guys can keep up if you like..



been crunching the numbers and as far as the efficiency of there ability to effectively turn heat into cold the numbers work


[QUOTE=67King;11432927]

Furthermore, your estimates on how much waste heat goes through the exhaust are way off. Thermal efficiency alone of an engine is higher than 25%. Will typically be above 30%. Of the at most 70% that is left, a good chunk of it, say 30% will be lost in mechanical inefficiencies, leaving about 40% of indicated power left. Of that 40%, only a portion makes its way into the exhaust system, a good deal of heat will be lost through the walls of teh combustion chamber - the piston, cylinder walls, head, and valves. Leaving the chamber, more will be lost through the exhaust ports. Now we are at the flange to the header. Your EGT's are say maybe 1000 degrees C after all of those losses. Now, I've never quantified what portion of heat is lost up to that point, but I would bet that AT LEAST half. That leaves you with 20%. A lot of heat is lost on its way to the turbo. Then some of that energy is used to turn the turbo. After the heat lost through the turbo, you are probably in the 275 degree range, only an estimate. So of the 20% left, you have maybe 550/1275 (degrees Kelvin) available in the exhaust. So that is a little over 40% of the 20%.....meaning your potential heat for recovery is likely closer to 8%. So from your example of a 200bhp engine, that would mean 800hp indicated, and [COLOR="Red"]you have 8% of that available. That is 64 horsepower at most.
[/COLOR]
Now let us look at what it would take to make this work. At 6,000 RPM at 1 bar of boost, you are looking at 60 RPS*1/2*~5L, or 150L/s of air to cool. To cool that down a single degree C would require about 200 Watts. Since this has to be an enclosed system, you need to pull the temperature down probably 125 degrees C [COLOR="Blue"](assuming from 150 to 25). [/COLOR]That is 25,000 Watts. 1hp = 746 Watts. [COLOR="red"]So that means you need 33 horsepower just to get it back down to where the stock intercooler had it.[/COLOR] That is half of your potential, which sounds like plenty of reserve, but the system will be most efficient at its hottest, and you are trying to effectively "supercool" it relative to the baseline, meaning it gets harder and harder to do so.

The next step would be to determine how big the system would need to be to first extract heat from the exhaust, and second to convert that to usable heat to remove from the intake system. I suspect a system capable of making that kind of power would be absolutely ENORMOUS. I think our refrigerator at home draws about 10 amps of current, which makes it 1200 Watts, or under 2 horsepower. Your system will need to be more than 20 times as big. Why more? Because you don't have a mechanical device to create the pressures needed to run a compact refrigerant system.

So, I don't really think it will work, personally. Guess I kind of just did most of the running it out for you. Seriously, though, back when I used to do this kind of stuff for a living, I used to do all kinds of hairbrained stuff like this, but of course you have to run it out. You may come up with 20 ideas that don't make sense for every one that will work. Again, love the creating thinking, don't get too attached to any idea or thought, just run them out. But also consider that virtually everything that does not rely on technology was figured out in the first couple of decades. One of my mentor's favorites references was a book that was published in 1929.

A much, much, much better way to improve a system would be to use a liquid injection system, which relies of phase transformation, which is orders of magnitude more efficient than trying to use just heat capacities to cool down a system.[/QUOTE]



[COLOR="red"]those numbers look quite promising to me actually[/COLOR]

ok lets say that this thing is only has the potential to almost match the performance of an intercooler, maybe 75%...

if you were to run this after an A2A intercooler that is already bringing the intake temps down from [COLOR="blue"] (assuming from 150 to 25). [/COLOR]
A2A= 150-25=125 C drop
75%= 125C drop X .75 = 93.75C drop
125C drop + 93.75C drop = 218C drop
150C start + 218C drop = -68C intake tempature....

-68C INTAKE TEMPS??? NOW THATS COLD...

I don't think we need anything near that cold of intake temps.. so lets cut that in half..

125C drop + (93.75C X .5 = 46.875C) drop = 171.875C drop

150C start + 171.875C drop = -21.875C intake temps

so if this thing can even do (75% X .5 = 37.5%) 37.5% the work our original A2A is doing then combined we get our intake temps below -20C...

so lets take whats theoretically available
[COLOR="Red"]you have 8% of that available. That is 64 horsepower at most.
[/COLOR]
8% X .375 = 3%

so we only need to capture just over a third of the 8% waste and we get
intake temps in the -20C or -7F range

now that is some cold dense air with excellent detonation resistance...

remember this thing will go far below ambient air temps ..
A2A can only bring temps down close to ambient, this will be able to get you negative below ambient temps...

I think intake temps of 0C or 32F would be a good goal and were already well past that...

time for algebra..

150C start - 125C A2A + X = 0C X = 25C drop

25/125= 20%

now we only need to get this thing to do 20% as much work as our A2A to get temps to freezing point 0C or 32F


now how much energy does it take to bring your volume of air from 25C to 0C?

compared to useable waste heat?







ok I found a ratio of 5.86 kw/ton efficiency..

and 1 RT = 3.5168525 kW

so that means 5860 watts of heat in and 3517 watts of cold out...

so an efficiency factor of about .6

still looking good

exhaust 45,000 watts in and 27,000 cold watts out..

but were gonna lose some.. cut it in half... no a third to be generous...

1/3= 15,000 watts in and 9,000 watts out

9,000 divided by 200 watts per degree C gets us a 45 degree C drop in temp at 150 liters per second of air...

so after our A2A intercooler getting us down to 25C an additional 45C drop gets us -20C intake temps

and that's estimating being able to use only a third of the available heat energy in the exhaust...

so.... numbers crunched... numbers work....

if it fits under the hood its worth putting under the hood...

now to find out if it fits as far as mass and volume of the system its self needed to do this work..


sorry I don't know how to get the html highlighting to work on this sight but you can see whats red and whats blue..... because it says red and blue..
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80 Turbo - Slightly Modified