Bulvot

Title restored....

NickTucker

Lotus did this on the Turbo Esprit. back in the '90's. They called it "Charge Cooling".

Seems like a great idea.

Geza

Actually, Lotus' reference to charge cooling, whether it be via an air to air, or air to water heat exchanger, was just correct technical semantics. Technically (in thermodynamics jargon), an intercooler is a heat exchanger placed in between individual stages of compression to reduce temperature (hence - intercooler). In the typical automotive application, what we normally refer to as an intercooler is really not - it is a heat exchanger placed after compression, thus "charge cooler". Or course, intercooler sounds, well, cooler. I suppose one could say, in the automotive application, the "intercooler" is in between stages of compression - between the turbo/supercharger and the engine.

Using the A/C system to cool the intake charge is something currently being employed on the Dodge Demon, though I'm not familiar with the details.

docmirror

Lotus charge cooling didn't use the AC system of the car. There were one or two air to liquid radiators mounted outboard of the center radiator. Those provided heat exchange for the liquid to air unit in a box on top of the engine after the turbo. An external fluid pump provided circulation from the charge cooler to the radiator(s).

One has to wonder about the thermodynamic efficiency to be gained by using a mechanical pump from the crankshaft to run the heat exchanger to cool in the incoming air. I don't plan to do the thermo exchange math. Turbo-intercoolers are common on larger piston aircraft engines, but are air-air with no liquid circulation. The whole driving a pump, and lines, and fluid, and losses associated with that seems a bit like a zero-sum game.

ptuomov

I don't think one has to really wonder about it! ;-)

There's one nice implementation of the idea out there. Everything else is half-baked Rube Goldberg machines. The nice implementation is the 2003 F150 Lightning Concept. It uses the liquid intercooler. There's separate storage tank that is cooled by the air conditioning circuit waste "cool". When more power is needed, this cooled intercooler fluid is run thru the intercooler and it keeps the temperatures very low for about a half a minute. I like this system because it can "load" the supercooled coolant tank over a long period of time and then release it on demand.

http://www.motorsportscenter.com/printer_75.shtml

By the way, the 928 S4 fuel cooler on the return line uses the air conditioner waste cool.

If I were building a fun turbo-diesel project with a ton of room under the hood, I'd first run a liquid charge cooler right after the compressor using the engine coolant. Then, air-to-air intercoolers. As the final stage, supercooled intercooler like that in the 2003 F150 Lightning Concept using air conditioner waste cool. It would be horribly complex and probably would never run right, but think of the theoretical thermal efficiencies! ;-)

Ian928

How about increasing pressure higher than you need, then cool it to near ambient and then use a pressure regulator to decrease pressure to what you want. That way you can get temperatures below ambient.

ptuomov

The most efficient way I know of how to do this is the air-cycle cooler. Airplanes use that. It's like a turbocharger but with air bearings. The compressor side compresses the air to be pressurized and hot. Then a heat exchanger cools the air in the very cold outside air flow. Then, the turbine decompresses and cools the air, while extracting useful work from the pressure that is used to rotate the compressor. This way, only a relatively small amount of electrical energy is needed. I think aircraft airconditioning uses the engine fresh air bleed to power the system, not an electrical motor. I'm not sure.

One could have a similar setup on a turbocharged car after the regular intercooler but before the intake valve. One would source the operating power from the pressure differential between inlet and outlet to the air-cycle cooler, analogous to a jet engine fresh air bleed, so no electrical motor would be needed. This could be built from a turbocharger. I haven't ever attempted to compute the total (in)efficiencies of such a system.

https://en.wikipedia.org/wiki/Air_cycle_machine
https://grimsby.ac.uk/documents/frpe...e_research.pdf
https://nptel.ac.in/courses/11210512...ecture%209.pdf

docmirror

This is a stored energy system where the 'dump' of chilled fluid under pressure cools the intake air for up to 30 seconds. Which reinforces my theory that it's a zero-sum game. The tank has to be charged during normal steady-state running, which uses some X amount of energy from the engine to fill a pressure chamber. At some point, a switch causes the dump of the stored energy(WITHOUT dragging the crankshaft down to provide fluid flow). One gets that X energy back(less some transfer and storage inefficiency) from the stored charge in the form of cooler incoming air.

It certainly can NOT run continuous on the dump of cooling fluid, because the reservoir can't be kept full unless the pump is run, which drags power off the crank - ergo, zero-sum. BTW, I used to do calorimitry for nuclear reactors back in the day - I'm pretty good at these scenarios, but that's why I said I'm not going to do the math. In the late-60s, there was a program called NERVA(one may google it) to provide a nuclear reactor to superheat liquid H2 and discharge it like a rocket, but it was not 'burned' as there was no Oxy on board. Speaking of Rube and his group these guys actually built a solid core reactor, and designed it as a heater to provide propulsion. Part of the hot H2 was drawn off to run the turbo-pump for the liquid H2, and when they started, the whole thing wouldn't run, because they WAY under-calculated the volume and pressure of gaseous H2 to run the turbo pump to fuel the reactor and discharge the flow out the rocket bell. That's where I learned thermodynamic efficiency rules the day, and almost everyone gets it way wrong.

If Ford were to do its total calorimitry on the process of: Pre-charge, storage, valving, plumbing, discharge, thermal transfer, and the resulting power gain, I'm quite sure it would actually be a negative total product(more energy put in, stored, than back out).

However, it does look impressive.

I edited to ADD a ")" which was missing in the second para.

Bulvot

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ptuomov

Returning to the earlier question about using AC as an intercooler:

Jeff Hartman does the thermodynamics computation on pages 158-162 of his "Supercharging Performance Handbook" under the heading "Refrigerant-cooled air-liquid intercooler". My reading is that net power _is_ increased under steady state load, but cost and complexity make it a non-sensical way to increase steady state power compared to say lowering compression and increasing boost, increasing displacement, increasing rpm, etc. The whole thing only starts making sense when there's a big supercooled liquid reservoir that can be deployed on demand.

docmirror

I've got $467,823 that says his calorimitry is -- deficient. It always is, and that's what sells 'handbooks on supercharging'. Free HP!







lolz.....

docmirror

If you are asking me if 'I'm saying....' no, I said no such thing, and do not attempt to modify EXACTLY what I wrote. It is preserved in the deep state internet forever, and I will stand behind it until proven otherwise with some 'free HP!' including total calorimitry.

Hey, I know, lets just duct the output of the air con blower right into the intake! That'll do it! Free HP for everyone.

Hey_Allen

Thank you for this summary of aircraft AC systems!

I'd worked flight-line avionics maintenance for the USAF for 12 years, but could never get an understandable explanation of how and why using HOT bleed air from the engines (or the APU) was able to generate significant quantities of chilled air for the plane's air conditioning systems.
The environmental systems techs would just gloss over it, I suspect that they didn't know the basic theory of operation and were just maintaining them by rote memorization and following the checklists.

ptuomov

I agree you on performance aftermarket stuff being generally scummy and books mostly useless. Jeff Hartman's books however have some useful simple equations for sizing stuff and they don't usually violate high-school physics.

docmirror

That's an important tool for turbo and supercharging. Most turbos are oversubscribed for the intended mission. My Ford V6 Duratec Ecoboost with intercooler uses two tiny little turbos. They spin up quick and provide gobs of air. Lots of aftermarket jobs use a ginormous turbo for a 4-5L engine. Some with crazy A/R ratios. What a waste.