water chiller split from Auto Air system.

[temperacerguy]

I have an idea in mind, and I am hoping I can get some technical advice/assistance in the design, implimentation of the design.

My background is in mechanical engineering, however I am working in healthcare. I can build damn near anything out of wood/metal/composites, but I am ignorant when it comes to auto airconditioning.

I currently own an 1991 ST185 Toyota Celica Alltrac/GT4 which is a 4 wheel drive turbocharged vehicle. It has an air/water intercooler which uses a recirculating coolant to cool the intake charge for better performance.

It's an old drag racing trick to fill the intercooler resevoir with an ice water mixture, to supercool the intake charge air. However once the ice melts, then the best you can do is get ambient temperature in the water circulating through the intercooler.

Now that you know the background, here's my idea...

I would like to install an evaporator (with aluminum tube/fin design, or some type of coil design) in the resevoir tank to constantly cool the intercooler coolant, during the 90% of the time I am off boost so that I have 3 gallons of super-cooled coolant to run through my intercooler when I am on boost.

I would like to "T" off of the high side line to run to this evaporator in the "coolant chiller", and to T-back into the low side after the factory equiped evaporator...

The vehicle is running R-12 refrigerant (and I have access to R-12). The factory evaporator has a block style expansion valve.

Now, here are my questions:
Is this even possible?
Will I need a larger compressor? (I can make brackets to bolt nearly any compressor to the engine block)
Will I need a larger condensor?
What type of evaporator and expansion valve should I use in this "coolant chiller"?

As I said, my fabrication skills are pretty high up there, so as long as something is physically able to fit, I can make it work.

Thank you all in advance for your help with this project. I WILL be doing this if possible.

[Brian_UK]

Perhaps fit the second evaporator and install two solenoid valves so that you can switch from one coil to the other. Unless you want to run both at once that is.

[akachillywilly]

Unique idea you have there. I do quite a bit of auto a/c and I'm thinkin you'll have to figure out how much heat you need to pull out of the intercooler (btus) and go from there. R-12 is a good auto refrigerant but r-134a might be better for your app. cause it gets evap down under freezing.

[temperacerguy]

Sorry for the late reply, I have been dealing with some personal issues...

First of all, I am not going to swap back and forth between the two... I will need for this to be constanly cooling the resevoir, while keeping the interior cool.

As for the BTUs... it's variable. If there was a constant stream of constant temperature water coming through the system, then there would be a set heat of the coolant. However as the vehicle will not be constanly under boost, there will not be a constant heat source... Also As the intake charge temperature changes with ambient temperature, it will not be constant... It does not matter how quickly the water drops to the lowest temperature, just so that it stays near 0 degrees celcius with low demand.

What I would like to do is find a small evaporator from a small car (say a Miata) and have that sitting in the resevoir to cool the coolant. then "T" off of the High and Low side lines. However if I do this do I need to?

-increase the size of my condensor? If so, is there such a thing as "too big"
-use a larger compressor? Perhaps a unit from a 4-runner

Then with the expansion valve in the new "coolant evaporator"? does the size need to be matched to what is in the exsisting evaporator? or will the pressures just equalize flow? I just don't want one evaporator to get the full flow while the other gets nothing...

Thanks in advance.

[temperacerguy]

OK, I have done some more research into things... hopefully I will be asking the appropriate questions...

From what I have read, Auto AC systems with expansion valves have compressors of variable displacement... As such, if I go with a larger compressor it should be able to "throttle back" if the compressor is too big correct?

Now, 2nd question... Do expansion valves work by pressure, or Flow?

[mad fridgie]

It is nothing new, the load inside the car determines the evap preessure (effectivly temp) in conjuction with the compressor speed. You need to understand the your driving process, whats is the adverage engine speed, which directly effects comp speed, what ambient are you to choose. You then have a starting point, what happens then if you rev faster or slower, in warmer or cooler ambients, will you still be happy with the results, Under all conditions are you keeping the system in a safe state (ensuring long life of the equipment).
Why not just use peltiers and run of the alternator

[mikeref]

Variable displacement automotive compressors have a very low tollerence to the amount of oil in the system, so adding second evaporator will be tricky. Compressors also have a limit on safe revs so depending on engine/compressor pulley ratio, should you go over 6 thousand rpm on compressor, things wont turn out so good. Question is, will the benifits of mechanical cooling of intercooler outweigh the power consumed by engine to drive the compressor? Increase in compressor size will also require matching condenser- no short cuts there. I've heard that you guys will do anything for more horsepower to the wheels... can't you cut the a/c out and save maybe 6HP?

[Magoo]

Concider applying venturi coolers, the more air going through then the cooler the air coming out. Fixed item no mechanical cooling required. Down side is they are noisy.

[temperacerguy]

Why not just use peltiers and run of the alternator

I did some quick research on them, however it seems that is a WHOLE HELL OF ALOT of current draw, for very low cooling effect. I will need to cool approximately 3 gallons of circulating water down to near freezing.

Variable displacement automotive compressors have a very low tollerence to the amount of oil in the system, so adding second evaporator will be tricky.

Which is why I am here for advice on how to do so.

Compressors also have a limit on safe revs so depending on engine/compressor pulley ratio, should you go over 6 thousand rpm on compressor, things wont turn out so good.

It's common these days for automotive air conditioner clutches to cut out at WOT, and at higher RPMs. This was the plan.

Question is, will the benifits of mechanical cooling of intercooler outweigh the power consumed by engine to drive the compressor?

Don't think you quite understand what I am doing here... The chiller will be chilling a water reservoir... This reservoir will be slowly cooling the water, and when on boost, the cool water will be circulating through an air/water intercooler to chill the charge air.

Increase in compressor size will also require matching condenser- no short cuts there. I've heard that you guys will do anything for more horsepower to the wheels... can't you cut the a/c out and save maybe 6HP?

Let me put it this way... by running ice water in an air/water intercooler, we have seen gains of over 70 horsepower in highly turbocharged vehicles. Not only does a cooler charge temperature increase the density of the air, it lowers the detonation tendency allowing for more spark advance. The problem is that Ice melts... the idea of this system is to keep the water in the reservoir at an ultra-cool temperature at all times.


I have no problem increasing the size of the evaporator...

but again, my questions:

Will a modern variable displacement compressor "throttle back" If I go to large?

If I have two expansion valves in the system, will they "auto balance" or will one open up all the way with the other being starved?

[mad fridgie]

You have 3 gallons of water, approx 8lb per gallon so total 24lb. So total energy say from 32F to 72 F = 960 BTU
When using Ice say 50% ice by weight = (12*144)+960 = 2688 BTU. (normally work in metric) so you need to be able to have duty when the boost is on. Calculate your duty required for your engine!
Your present system is very likely to have cluth controlled by suction pressure very closes to 30F, this is to reduce the chance of freezing. But for your application you want lower temperatures to occur to get to the colder temperatures. The expansion valves are set by superheat, if the SH is reached then the valves will close (prop!)
If neither is reached then flow will occur down the system with the lowerst pressure drop.

[temperacerguy]

Excellent, thank you for the response. So let me get this straight...

If Evaporator A reaches It's superheat point, then it closes... and Flow would continue to evaporator B untill it reaches superheat and it closes... The valves would continue to open and close to maintain this level....

THIS WAS MY MAIN QUESTION ANSWERED... THANK YOU!!!

So, I need to have enough flow to allow for the expansion valves to reach this point. Excellent.