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Tango Charlie 08-21-2008 08:47 PM

There's gotta be a better way
 
...to air condition my car.
We all know the AC compressor saps a lot of power. I don't run my AC as much as I can stand it, but some days are just too much. It gets very humid here. I was wondering if there might be a better way. Here are my 'requirements';

1. Be more efficient than the current standard compressor/refrigerant system. i.e.; not affect mpg.

2. Not require recharging or servicing before every trip.

3. Be contained within the vehicle. (Can't be ruining aerodynamics, now.)

And don't be telling me about swamp coolers (see #2), ice water vests (see #2), and beaded seat covers (already got 'em). I did do a search but found nothing promising. And I don't wanna hear useless prattle about windows up/down vs. AC above/below 45mph. If you do, I'll break your arm. Or sick JohnnyMullet on you. :D I want to hear some NEW ideas. C'mon. Let's think.

Anyway...

I ran across this today;
THE HILSCH VORTEX TUBE

It's a VERY intriguing concept. I'm wondering if this design would work at a lower psi. Could you optimize the dimensions and make it work off of ram air pressure from the front of the car? Or would it require too big of an inlet and destroy your Cd?
How about an electric blower? Or would you just be trading compressor drag for alternator drag?
Or maybe operate it off a high pressure carbon fiber air tank. Sounds expensive. I do have an aviator's breathing oxygen tank sitting in my shed that I removed from a Cessna 401 several years ago... But it's pretty heavy.
Hmmm...

Johnny Mullet 08-21-2008 08:54 PM

A very large block of ice in the back seat would do great. For a little while.

Tango Charlie 08-21-2008 09:00 PM

O.K. Wiseguy. :D

dentprone 08-21-2008 10:42 PM

Yeah, I saw that tube in a 50's era popular mechanics book. They called it "Maxwells' Demon". Looks like there are enough drawings to work off on that site, but if you need another set of plans, I can scan the page and send it to you. Seems like you could run it temporarily off one of those crappy 12V tire inflators just to see if it is remotely practical. I don't think it would meet criteria #1 on your list, tho. Best of luck, and keep us posted.

Vince-HX 08-22-2008 12:19 AM

Quote:

Originally Posted by Johnny Mullet (Post 55222)
A very large block of ice in the back seat would do great. For a little while.

:thumbup:


The vortex tube is cool idea also but I think with the air requirements you would have to run a high pressure air tank. So $$$ for refills and you still would have to have it charged as a normal compressor will not be able to output the same psi. I do like the idea of no moving parts though :thumbup:

Daox 08-22-2008 08:47 AM

I don't know if you have seen this, but dremd was working on an interesting project that might help. Check it out here: http://ecomodder.com/forum/showthrea...ject-3884.html

My wife was also very thoughtful and picked me up a few of these seat covers recently. They were very reasonably priced and are a step up from the normal beaded seat cover. I haven't had a chance to put them in the car and try them. I'll be sure to write a full review once they are in. She is an A/C junkie (75 degees and that sucker is on :(), so I really hope they work good.

Amazon.com: Wagan Universal-Fit Air Circulating Ventilated Seat Cushion: Automotive
http://ecx.images-amazon.com/images/...TL._SS400_.jpg


None of these options are actually air conditioning, but direct cooling is much more effective than blowing air on you. I've read the OEMs are looking into in seat cooling as a way to cool down passengers. This allows them to downsize the A/C system considerably.

Tango Charlie 08-22-2008 09:42 AM

At the risk of splitting hairs, your seat cushions are blowing air on you. But the direct, localized cooling does sound tantalizing. You'd be consuming less power to produce such focused cooling. I did read dremd's thread, but have not seen hugely successful results. I'm not crazy about cutting up my seats and running fluid through them. In contrast, your forced-ventilated cushions seem desirable. I look forward to your review. Please post a link here when you do.

Now how about if we take those cushions and use the cold air output from the vortex tube to feed it?

Daox 08-22-2008 09:49 AM

I would think that system would be quite a bit more efficient than conventional A/C.

Also, I haven't looked extensivly at the seat cover, so I'm not sure if the air cools down the cover itself, or if it leaks it out slowly and it blows on you. I assume it would be the later.

Tango Charlie 08-22-2008 09:59 AM

I was assuming the same thing, based on the wavy blue arrows emanating from it in the picture. :p

moorecomp 08-22-2008 10:14 AM

In my former life as an aircraft mechanic, our airplanes used what is called an Air Cyle Machine. Look on Wikipedia for an explanation. Basically it uses high temp - high pressure bleed air from the turbine engine compressor and cools it and then allows it to expand, which results in a cooling effect. Maybe you could do a similar thing with a turbocharger and an intercooler and then allow the expansion.

Sounds like a lot of work!

Best regards

Vince-HX 08-22-2008 10:49 AM

Quote:

Originally Posted by moorecomp (Post 55337)
In my former life as an aircraft mechanic, our airplanes used what is called an Air Cyle Machine. Look on Wikipedia for an explanation. Basically it uses high temp - high pressure bleed air from the turbine engine compressor and cools it and then allows it to expand, which results in a cooling effect. Maybe you could do a similar thing with a turbocharger and an intercooler and then allow the expansion.

Sounds like a lot of work!

Best regards

Two turbo's and three intercoolers, yeah that a bit of work

really neat idea though

wagonman76 08-22-2008 12:35 PM

I think the absorption principle would be a great idea. Like what is used in camper fridges. It uses no evergy except for a heating element to boil a fluid which cools the air inside the fridge and the freezer works well too. Set up the coils inside the car and divert some exhaust heat to boil the fluid. Ive also thought for a long time that this would work well for home cooling too, use the sun to boil the fluid and the hotter the sun beats down, the cooler it gets in the house.

trikkonceptz 08-22-2008 12:59 PM

Having the same car I too have put thought into the same idea. Here is what I have been contemplating;

-A dry Ice cooler, attached to the a/c recirc intake inside the car under the dash. This cooler would have an ambient temperature fan to keep it cool as long as possible, but it would draw the cooled air through the vent thus providing a/c for as long as the dry ice lasts. You would have to test to see how long that is, but it may work.

Second option;

Remove the compressor from the belt system, research the smallest compressor possible, like the motorcycle ones used on goldwings, etc and drive it with an electric motor. The draw from that could be offset with solar panels or a second battery off the system that you could charge nightly.

Try that see what sticks ..

sohl 08-22-2008 01:02 PM

Quote:

My wife ... is an A/C junkie (75 degees and that sucker is on):(
Ooh, mine too! She doesn't like how the wind from open windows buffets her ears, even though she sometimes doesn't drive on any roads above 25 mph, and usually not over 45 mph. 70 degrees and sunny and that AC is on. :rolleyes: I think this is a big reason we are not even getting EPA mpgs in our Honda Odyssey. But hey, in our house, she loves it to be 80+ degrees and we only run the AC a few days a year. :(

azraelswrd 08-22-2008 02:12 PM

I like wagonman's idea of an absorption cooler:

Solar air conditioning - Wikipedia, the free encyclopedia
Inexpensive Home Building: Passive Cooling Solar Cooling: Use Heat To Cool
Home Built IcyBall
Building Your Own Larry Hall Icyball
HowStuffWorks "Gas and Propane Refrigerators"

Size, weight and safety are issues to consider but I like the idea of using all that "free" exhaust heat. Also, it probably wouldn't cool very fast (or until more heat is generated) at first. But the principle is sound. It is practical and is on the commercial market (see gas/propane refrigerators)

SuperTrooper 08-22-2008 02:19 PM

Quote:

Originally Posted by wagonman76 (Post 55365)
I think the absorption principle would be a great idea. Like what is used in camper fridges. It uses no evergy except for a heating element to boil a fluid which cools the air inside the fridge and the freezer works well too. Set up the coils inside the car and divert some exhaust heat to boil the fluid. Ive also thought for a long time that this would work well for home cooling too, use the sun to boil the fluid and the hotter the sun beats down, the cooler it gets in the house.

It's been tried. It works well in a well insulated box or even a building, but the greenhouse of a car requires way too many BTUs/hr for a system that would fit in a car.

Tango Charlie 08-22-2008 02:25 PM

Hey, moorecomp. Former A&P, eh? Me too! The puddlejumpers I worked on didn't have air cycle machines, but I have heard of them. I'm afraid running a turbo to get the compressed air would rob as much or more power than the AC compressor. I like the 'outside the box' thinking, though. :thumbup:

wagonman, since I live in the mecca of RV manufacturing, you'd think I'd know about camper refridgerators. But I don't. Do you have any links that might explain the... oh! thanks, azraelswrd! :o

Trik, your dry ice idea violates my requirement #2, but your electrically-driven compressor idea is intriguing. I didn't know Goldwings had AC!

millenniumtree 08-22-2008 02:37 PM

Route the exhaust pipe to a stirling engine, which then runs the A/C compressor.
A/C from the engine's waste heat!

I'm not sure how large the stirling would need to be to power the A/C compressor... 1-2 hp maybe?

Chiefdruid 08-22-2008 03:33 PM

Ok, here's what I've got rolling around in my head. A bank of 12v thermoelectric coolers avalable from All Electronics | Electronic and Electro-Mechanical Parts and Supplies at Discount Prices cooling a heat exchanger (manifold) of sorts. Pull the vented air seat covers input air through this manifold.
Years ago, I built a water cooler for an overclocked PC. With just one TEC chip, I could get frost on the cold block in 20-30 seconds at room temp. The only problem is getting rid of the waste heat from the hot side of these coolers. You would have to vent a heatsink to the outside to pull a sufficient amount of heat to keep these cooling properly...

Here's a link if anyone's interested:

40MM X 44MM THERMOELECTRIC COOLER | AllElectronics.com

Daox 08-22-2008 03:38 PM

Not a bad idea, but yikes, those things pull 5 amps each! That would add up fast. I wonder how many you'd need to get descent cooling.

Chiefdruid 08-22-2008 04:09 PM

It depends on the manifold design, I think. If a 'honeycomb' design could be machined in copper or aluminum, keeping the passages reasonably small, I'd Swag (scientific, wild-a$$ed guess) maybe six...
For a total of 30 amps. Now, this is where I get lost. How does that relate to what the alternator produces? Electrical theory was never my strong suit... lol

aerohead 08-22-2008 04:10 PM

My middle brother once worked at a steel mill near El Paso,Texas.His job was down in a pit,cutting white-hot steel as it emerged from extrusion dies.He wore an insulated asbestos fire suit,equipped with a vortex-tube for cooling.He claimed that it required a remarkable amount of air(pressure and volume) to make the thing operate.I know thats a very subjective comment,buts thats all I have.

aerohead 08-22-2008 04:20 PM

absorption
 
Quote:

Originally Posted by wagonman76 (Post 55365)
I think the absorption principle would be a great idea. Like what is used in camper fridges. It uses no evergy except for a heating element to boil a fluid which cools the air inside the fridge and the freezer works well too. Set up the coils inside the car and divert some exhaust heat to boil the fluid. Ive also thought for a long time that this would work well for home cooling too, use the sun to boil the fluid and the hotter the sun beats down, the cooler it gets in the house.

My partner in crime is a boiler operator and baby sits a natural gas-fired turbine-generator(5-MW),which utilizes waste heat to operate absorption cycle chillers for space cooling.The system uses Lithium Bromide as the working medium,and I understand that it will operate at temps as low as 210-degree F.

aerohead 08-22-2008 04:31 PM

Question.Is the air conditioning system on a Prius a non-engine-belt-driven, hermetically-sealed,electrically-powered system? I'll wait 'til I hear back before I go any more stupid.

Daox 08-22-2008 04:41 PM

The Prius uses the main battery pack to power its electric compressor pump. I think this is mainly to provide A/C while the engine is off though.

SuperTrooper 08-22-2008 05:40 PM

It's called an "electric inverter" A/C system. Here is a Toyota slide presentation on how it works:

http://www.epa.gov/cppd/Presentation...20inverter.pdf

trikkonceptz 08-22-2008 06:32 PM

OK after seeing that presentation ... lets break it down to simplest form and argue backwards ...


Why can't we buy a Prius Compressor, make hoses and brackets with the proper fittings and wire it up with a switch we control to a seperate battery or in line with our current battery?

SuperTrooper 08-23-2008 07:55 AM

Quote:

Originally Posted by trikkonceptz (Post 55462)
OK after seeing that presentation ... lets break it down to simplest form and argue backwards ...


Why can't we buy a Prius Compressor, make hoses and brackets with the proper fittings and wire it up with a switch we control to a seperate battery or in line with our current battery?

If the whole point of this mental exercise is to save gas by reducing the load on the engine, then running it off a separate battery makes the most sense.

chuckm 08-23-2008 02:15 PM

A spin off of an idea mentioned earlier: Sterling engines. Use the heat from exhaust gas to power several Sterling engines. Then use the Sterling engines to power directly coupled Sterling cycle cryocoolers.
Additionally, you could also couple the cryocoolers to motors (powered by solar panels) to maintain cooler temps out in the parking lot. This would help lower the time to effective cooling.

Randy 08-24-2008 03:33 PM

Vortex tubes aren't very efficient at all. They only use them when compressed air is handy (like supplied breathing air, or a shop) to get more cooling than the air alone. They're light and simple, but loud and take a lot of air.

A commercial source of them lists BTU/h cooling here. The biggest they have is 6000 BTU/h... the A/C in my Civic is listed at 14800. It also requires 100 scfm, which would take a huge (~30hp) compressor. So standard
A/C is about 10-20 times more efficient, not counting the air-drying effect.

Thermo-electric coolers are also less efficient than refrigerant systems. Also, ice has more cooling for the same weight as a battery, so if you want a rechargeable system, just use a cooler full of ice.

I think the fan seat cover is the closest you'll get to all your requirements.

Tango Charlie 08-24-2008 06:17 PM

Rain on my parade, will ya, Randy? :p
I figured the (lack of) efficiency of the vortex tube might be what makes it undesirable.

Schlepping ice before every trip just doesn't appeal to me.

I like the fan-cooled seat cushion idea, too. Waiting for Daox's review.
I also like Trik's idea of the electrically-driven Goldwing compressor. Just haven't had time to research it yet. I suppose I could put up with recharging a battery every night.

azraelswrd 08-24-2008 09:43 PM

An ice filled cooler with a small electric fan to blow air over it will do a lot too -- add in some calcium chloride to the ice and now it will act as a desiccant and PULL water out of the air (and solve some of the high humidity issues).

But I still like the absorption cooler only because it speaks to the MacGuyver in me. :D

chuckm 08-27-2008 06:44 PM

Okay, let me drop a different idea. What if you had a vehicle powered by propane (or LNG for that matter) instead of gas? Tap off the bottom of the propane tank and run the liquid fuel through the AC evaporator set prior to sending it to the engine. When you are not using the AC, use exhaust gas to warm up the evap. In fact, you could use the exhaust gas to preheat the propane to the optimal combustion temp as necessary.

HaPPI 08-27-2008 09:06 PM

The coolest cooler takes advantage of God's brain
 
The most efficient cooler is the one God built into all of us, evaporation from the lungs, sinuses and skin interfacing to the bloodstream, and what feels best beside. So think in terms of moving the air a little bit (so some kind of fan for one end and maybe the seat cushion gadget for the other) and drying the air in the car when it goes above a certain percent relative humidity. Some kind of chemical humectant that can be re-dried out at home in the microwave would be lots more efficient that current compressor coolers. No moving parts is good. Not sure about cost.

You'd want to keep the air recirculating to keep out the outside humidity. So the air temp might not be 70, but a dry, moving 90 degree airstream will feel cooler to you than a still, clammy 75, you crazy mammal you.

Oh, and tint your windows with heat-reflective film. And paint the car white if it isn't.

I once drove across West Texas in July with no A/C. The key was block out the window to keep the sun directly off ya, and keep the air moving. 110 degrees and it wasn't all that uncomfortable.

Tango Charlie 08-27-2008 10:04 PM

Yup, tinting the windows is definitely on the to-do list.
Doax's cushions might be the simplest solution yet. Or at least the start of an efficient system.

forgottenmindset 08-27-2008 11:44 PM

Get it done
 
Yall guys are making this too complicated, lets actually get it done instead of adding tripple turbos, and solar shenanigans

Plan A) Basic, redneck approach

1) Get a 12v oscillating fan from walmart that plugs into the cig adapter.
2) Coil Copper tubing behind it
3) Use an aquarium pump to circulate ice water through the coils
4) Draw the ice water from a super insulated ice box (like the orange gatoraide coolers)
5) Make sure there is an emergency 6 pack in the ice box at all times

Plan B) Nicer approach

1) Use the car's existing blower motor to drive the cool air, and use existing ac controls
2) Stick a copper coil in the duct work, or in the blower motor assembly
3) Circulate the water from the icebox from the trunk, rout it down below the vehicle near like a fuel line, and install a heat exchanger (small heater core) inline to keep the ice water (or whatever fluid) cooler, longer.

You could even put the heat exchanger up near the grill or in a fender well, anywhere it will get cool air.


You shouldn't need to add ice but every few days

HaPPI 08-28-2008 12:50 AM

One more thought about a fan
 
I'm a fan of fans, TC. I just had a great idea for where it would cool you off best - mounted on your headrest, on the side or top, pointed at the back of your head. A little muffin fan extracted from dead electronics such as a PC power supply is 1) free, 2) 12VDC, 3) draws maybe .3A and could even be run from a 4.5 watt solar cell (WalMart auto dept, around $40, as I recall) on the back window ledge.

With it so close to your ears though, you'd have to pick a quiet one with a slow rpm to not drive you deef. Or if the headrest has an arch to it and a gap between it and the seat like some cars do, put it behind the headrest at the bottom so that the air goes between em.

chuckm 08-28-2008 07:24 AM

forgottenmindset,
I can assure you that it will be more often than just "every few days." I know a little about the gatoraid coolers... Back in my high school days, I played football. Just before school started, we had summer "two-a-day" practices. First practice was ~8:30am, second around 3:30pm. The junior varsity guys had to make the ice water and they were, um, encouraged to get to the ice machine early before the afternoon practice. Why? The ice from the morning practice would be practically gone by the 3:30 practice, even when stored in the shade. (And the last group to make up their jug didn't get much ice.) Sure, we are talking about Louisiana heat. But you're looking at storing your ice inside a vehicle, where the temps can go over 130F pretty quickly.

forgottenmindset 08-28-2008 11:01 AM

Hmm, ok so just add ice everyday


But with the window tint and the cooler in the trunk, I think it would stay pretty cool in the cabin already

What about this, seal the circulating system water (just like the r134 gas is sealed), and keep dry ice in the cooler which has no direct contact with the copper lines, I dunno just thinking out loud here

Also a mabey better idea is to have a really high pressure water pump shoot mist through you blower motor, it wont be enough to make you wet, but it will cool in blowers intake air down tremendously

That's what they do at disney world, they shoot atomized water at fans way high up to shoot cool mystified air at the guests waiting in line. Works amazing.

Tango Charlie 08-28-2008 11:54 AM

No
No
No
and
NO.
I'm not putting a swamp cooler in my car. It's already too humid in there.
And I am NOT schlepping ice before every trip. See requirement #2 in the OP.


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