Cooling a suit cooler with the car's AC system?

We're thinking about something like this since our donor car has a perfectly working R12 A/C system.    Possibly just putting the evaporator in the cool-shirt cooler, and controlling the temp with the cool-shirt circulatory pump.  If the driver gets too cold, he shuts it off, but the A/C system stays running.

I've thought of this too, except using a refrigerant to water heat exchanger and using a normal cool suit.  The compressor would cycle on when the brakes are pressed (additional braking capacity for DOMINATION) and cycle off on a WOT switch.  The LPCO and HPCO would cycle the compressor off if need be.  The cool suit would work as normal, exept no ice would ever need to be added to a cooler at any stop.  If you kept the cooler in the circuit it could be used as a buffer tank to get you through long straights where you wouldn't want the compressor on at WOT anyway.  If the compressor fails, then dump ice in the cooler and you're back to normal.  You could even start the day with ice in the cooler and only use the A/C to keep up later on.  A 1/2" 3-way valve could be used for temperature control of the cool suit itself if you use a CCOT or TXV system, a thermostat in the cooler could be used with a TXV system.  Get the biggest condenser you can fit for a R-134a conversion (or buy a new parallel flow condenser, driver comfort is budget exempt) since R-12 is rather expensive and hard to find and you'll be set.  Not that I've got this planned out or anything...... 

I'd be a bit concerned about the high pressure of the A/C system and would run this past TEO for a ruling.  In the event of an accident, you'll have a 350 psi spray of refrigerant and oil on to potentially hot surfaces as well as pressurized lines in the passenger compartment.  The high pressure lines would be especially close to the driver if you run refrigerant through the seat.  And you'd probably have trouble with oil return to the compressor anyway.

Not to mention that on most cars if the ac fails and kicks the belt off, youre also losing your water pump and alternator belt....I don't need to explaint the perils of that happening.

There is a realllllly long thread on this not that aweful long ago and it was deemed ineffective...YMMV.

When I saw this post I had to respond immediately.  I applaud your creativity and commitment to this unconventional idea.  I am not 'hating' on this idea, I'm really not.  For the last 20 years I have worked as a design engineer for a company that is the largest independently owned manufacturer of automotive air conditioning compressors.  Based on my knowledge of automotive a/c, I can only tell you that this idea is fraught with numerous very real and very dangerous hazards, and I must implore you not to proceed. 

I have been racing Lemons since 2008, and I have personally modified my own cool shirt systems, so I am familiar with all of the technology involved here.  Many of the safety hazards are obvious to most people, but many more are not.  In the best circumstances, you would have 25 psi of liquefied refrigerant wrapped around your body.  Cool shirt tubing, or any tubing other than refrigerant grade, will not cut it.  It is not thermally, mechanically, or even chemically compatible with R12 (or R134a) refrigerant.  It will quickly degrade, leak, split, and/or burst (explosively).  At that point it will fill the cockpit with an oily haze.  Then, the a/c system will continue to pump all of the liquid refrigerant (and oil) directly onto your driver's body.  Most people don't realize just how badly you can be burned by liquid refrigerant.  It's not like an ice cube, this stuff is designed to remove heat, and remove heat it does,  Imagine the worst freezer burn you possibly can.  None of these things are good in the midst of a race.

But that's the best case scenario.  A worse, but still realistic, scenario is what happens when the compressor cycles off, and the high side equalizes to the low side.  It's not 25 psi any more, try something like 120 psi.  When that pressure goes up, that's when your degraded tubing is most likely to blow.  You don't want hot oily gas spraying inside your shirt at a pressure four times higher than what's inside your tires. 

Using the a/c evaporator to cool water inside the cool shirt cooler is relatively safer, but still not a good idea for many, many, reasons.  Same thing for plumbing the seat.  For brevity I will not list all of those reasons here. 

I have described only two of the dozen or so bad scenarios that I can think of, I mean, I could go on and on here.  Dude, I love your idea, I love it so much I even want to help you build it.  Please don't get me wrong, I do not mean to rain on this parade because this kind of idea is exactly what I love about Lemons.  But the fact is that physics is not on our side in this case, and this kind of thing is just way too dangerous.

Nate
Team JB Weld / Lemon Cab Co / Buckaroo / Ratsun

Those are the reasons you should list, though! Not in a million years would I have considered running refrigerant through the shirt. Hell, I didn't even think plumbing to the seat was a good idea, and I was envisioning steel lines for that.

To be honest, I don't think running the refrigerant lines through the cooler is something I would bother doing, either, but that's mainly because at that point you're not gaining much of an advantage. You save a few seconds every pit stop and a minor headache keeping frozen jugs in the pits, but you don't lose any weight in the car, and you lose a few horsepower running an AC system. Still, if people were considering running a setup like this, I think it would be great to hear what some of the potential dangers are.

You want something like the Killer Chiller but for your cool suit. Sounds cold.

Yeah you guys are right I misinterpreted.  Sorry about that.  Please keep in mind that what I'm writing here is not meant to be negative or poo-poo the idea, I'm just stating the technical facts as I understand them.  Okay, so running the evaporator as a heat exchanger inside the cooler itself, would it be safe?  Short answer is no, I think it would not be safe even still.  I think Lemons tech guys would reject it just because you have pressurized gas, inside some homemade rig you put together yourself, right there in the passenger compartment.

So why is it not safe?  Let's walk through it.  The evaporator is located under the dash inside that big plastic evaporator/heater core/fan assembly.  Let's assume we get rid of all that hardware, except for the evaporator itself, and the two refrigerant lines running to the engine compartment.  (Keep in mind I'm talking about the refrigerant lines running to the engine compartment, not the water lines running to and from the cool shirt itself.)  The evaporator is most certainly too close the firewall for us to fit the cool shirt cooler around it, so we need to move the evaporator from its original location to where the cool shirt cooler is located (probably the passenger seat area).   This means we have to move the evaporator about two feet or so.  The existing refrigerant lines are not going to stretch that far (on most cars they are completely hard lines anyway), so we must modify or replace those lines with something custom made.  This is the dangerous part.   

If we cobble something together from the hardware store or autozone, it is just not going to work.  Any material that isn't specifically designed for a/c is going to degrade from the thermal, mechanical, and chemical effects placed on it by the refrigerant.  Now you could use something like Tygon tubing, and it would hold, but here's the thing: it would only hold for a short time.  Eventually the Tygon tubing will degrade and then one day, most likely right after a pressure increase, it will burst.  Even if it's on the other side of the passenger compartment, it's still going to burst pretty much explosively or at least hiss violently, scaring the pissie out of any driver in there, and then it will release an odd smokey-cloudy mist that will fog the cockpit, maybe not bad enough to blind the driver completely, but it's going to be real distracting.   Even if it's inside a cooler or even a fuel cell type setup, unless it's completely sealed, this stuff will find it's way out and into the cockpit.   

For modern cars, the expansion device is going to be located inside the evaporator assembly itself.  This means that one of our two homemade lines running from the firewall to our new evaporator location is on the high side of the a/c system.   Pressure inside the high side line will vary with environmental conditions, but worst case be ready for 600 psig, and about 275-300 degF of hot, oily, sticky, gas.   Tygon tubing, water hose, even fuel hose, none of it will withstand this kind of punishment.    It might hold lower pressures, for a short time.  But what I'm afraid is this scenario: your lines have degraded, it's hot out, you come in for a penatly (no ram air), and your radiator/condensor fan is busted (no fan air).  Your high side pressure will skyrocket, and that's when the line is going to burst. 

But how could we make it safer?  If you made your refrigerant lines from all refrigerant grade hardware, obtained proper o-rings and seals, and you knew how and had tools to crimp the hoses effectively, and had a rock solid radiator fan, HPCO and PRV, and you ducted everything aggressively (like you would a fuel line running through the cockpit), then you could make it relatively safer.  In that case it would be about as safe as you could make it.  Another option would be to replace the evaporator entirely with a tube-in-tube heat exchanger with water.  But even then, we gotta consider what happens when you get in a wreck, or flip the car.  If the lines are compromised in any way at any time, then to me, it's just too much of a liability.  I've personally seen what happens when an a/c system blows (we test for that kind of thing) and in the worst of cases, it's not a trivial affair.  I mean, you just do not want to be around it when it blows. 

Another unforeseen scary thing is acid.  If you don't change your desiccant and/or pull a really strong vacuum, the water remaining inside the a/c system will react with the refrigerant to form acids and other nasty chemicals.  Would they chemically burn your skin?  I don't think so, they're not that stong, but still, acid.  At the very least these acids will erode your refrigerant lines, and accelerate the rate at which they will degrade and burst. 

Again sorry guys I don't mean this as being against the idea, I love the idea, it's just seriously not the safest thing out there.  If you do decide to do it, then PM me (and this is so ironic that I'm writing this) and I will tell you all the things you could do to make it less hazardous.

That's awesome information. I had no idea the kind of pressures that go on in those systems. Thanks for increasing our collective knowledge & understanding at how to not kill ourselves in the process of trying to cool ourselves.

Good info, thanks Nate. I guess I took it for granted that you would use the proper hardware for something like this, but then again my partner-in-crime is a certified (and extremely anal) AC tech. Most teams don't have those.