Air Conditioning vs Windows Down [Archive] - Australian LS1 and Holden Forums

BLKVYSS

14-03-2007, 05:03 AM

I'm Curious about this question.. as I do a bit of freeway driving at the moment..

Basically I am aware of the fact that the Air Con makes the engine work harder, there for more petrol is used.. but then Having windows down creates Drag and makes the engine work harder, more fuel.. yaddda yadda..

So a question I have.. is has anybody tested.. or perhaps noticed which might actually be better for Economy? Windows down on the freeway is a little noisy at times and just irritating..

But I'm wondering which would be the better alternative on a Warm, not sweltering day..

I'm going to be conducting a few tests over the next couple weeks of my own to see which is better.. Anyone out there already done such a thing?

I'm curious to say the least..

CAPTIVALX

14-03-2007, 05:22 AM

myth buster done the test a few years ago but i'll be buggered if l can remember which one won.

Vulture

14-03-2007, 05:26 AM

I think you'll find that it depends on the speed that you are travelling. Higher speeds will place it in favour of windows up, lower speeds windows down aircon off, but the difference may actually be so small that it might be hard to measure.

HSVMAN

14-03-2007, 05:26 AM

At open road speed the engine is not under any real extra load from Air cond :teach:

mmciau

14-03-2007, 05:29 AM

Windows up - less drag

Fuel use by air con is minimal after cabin reaches set temperature

Mike

STATIE

14-03-2007, 08:10 AM

Basically I am aware of the fact that the Air Con makes the engine work harder, there for more petrol is used.. but then Having windows down creates Drag and makes the engine work harder, more fuel.. yaddda yadda..

So a question I have.. is has anybody tested.. or perhaps noticed which might actually be better for Economy?

I'm going to be conducting a few tests over the next couple weeks of my own to see which is better.. Anyone out there already done such a thing?

I'm sure OzTrack has done some logging, programmed a few spread sheets and made a pie chart or 2 on the differences in the two.:lmao:

GHZ28

14-03-2007, 08:11 AM

Fairly extensive testing (read as thousands of km of highway travel) by my brother and I point to around 1.5 l/100km more fuel used by having the a/c on, at least up here in Queensland where it would normally work harder than in the Southern States.

If you have a 3 window cluster, instantaneous fuel use will rise by around 1.8 l/100km with the compressor, in LS1 vehicles. Up here, in the Queensland sun, compressor duty cycle is around 80%.

Just a note, most of the non-airconditioned travel has been at night, or days which are overcast, still warm up here, but without the bite of the burning sun. So some of the difference could be accounted for by that, the the instantaneous readout, coupled with observed duty cycle of the compressor would indicate 1.5 l/100km to be about right.

Oh, and winding the driver's window down at highway speeds does not change the instantaneous display by a measurable amount.

YMMV literally.....gh

vxssgurl

14-03-2007, 08:18 AM

On a highway stretch, I tend to watch my RPM's more than my speedo (cause I too am curious about loading and its effects)... plus I use cruise control all the time.

Personally, on my VX, I've noticed that at 110 travelling the Hume with aircon on makes about 200 - 210 rpm difference to non-aircon. Highway driving fuel economy for me is roughly 650 kms to the tank, and having the aircon on shortens that by about 20 or so k's.

Windows open makes no noticeable difference to RPM's, however, the noise factor makes it pretty unbearable after a while... BUT, with a bit of trial and error, I discovered that I find it easiest to drive in "windows open weather" to have all four down about 2 - 3 inches, rather than just the driver's window or both front, open all the way.

Have not noticed any real drop in economy with windows open though.

Bazz

14-03-2007, 08:24 AM

myth buster done the test a few years ago but i'll be buggered if l can remember which one won.

I remember that. They drove a car around an oval track for a lengthy period to see which one was more economical. From memory it turned out to be aircon on windows up.

Personally at 110 I like the windows up just for the sheer noise factor. I cant remember the exact speed but it is proven that the wind noise causes hearing damage too. But I'm not the best person to say cause I drive around Darwin with the windows open and the aircon on!!! You may ask why, well the aircon just takes the edge off the heat and I love driving with windows down.

chillicatqld

14-03-2007, 08:31 AM

:doh: ummmm - buy a Charade if you that worried. :doh:

swingtan

14-03-2007, 08:44 AM

I remember that. They drove a car around an oval track for a lengthy period to see which one was more economical. From memory it turned out to be aircon on windows up.

Personally at 110 I like the windows up just for the sheer noise factor. I cant remember the exact speed but it is proven that the wind noise causes hearing damage too. But I'm not the best person to say cause I drive around Darwin with the windows open and the aircon on!!! You may ask why, well the aircon just takes the edge off the heat and I love driving with windows down.

Yep, that's the one. Though the whole test was bogus ( like many they do ). They were going to fill the tanks and then drive till the cars ran out of fuel, but when they started testing ( in the huge Yank 4x4's they decided would make the best test bed ? :doh: ) they found out that they would be driving for 7 hours straight at high speed. they were on a closed track and the safety stewards decided that the std. tyres wouldn't last at the required speed for that period of time ( think about an oval banked track ).

So they syphoned the tanks :doh: :doh: and then refilled with a set amount, maybe it was 5 gallons. So now they had 2 identical trucks, with differing fuel amounts as syphoning will not give you the same starting point. Then they just drove the trucks untill they ran out of fuel. Their test showed that the open windows were better for fuel economy, but let's face it, drag on a 4x4 isn't going to change much whether the windows are open or shut.

Mind you though, I still like their show.

VX BY DESIGN

14-03-2007, 08:54 AM

JimmyXR6T04

14-03-2007, 09:09 AM

at the end of the day, how much extra is it gonna cost to drive around with the air con on?? maybe a few bucks per tank? i know that the original poster wasn't complaining about this fact, but some people out there refuse to turn the air con on because it uses more fuel. I have some mates who are hesitant to turn it on, even though i'm sweating up a storm!! I always offer to leave $5 in the glove box to make up for the extra fuel :cussing:

To me, they're either complete idiots, complete tight asses, or poor as buggery. I leave my air con on pretty much 24/7 in the summer, and i'll even forget to turn it off during the winter when defrosting windows (using heat) of course. I just turn the heat up a bit of it gets cold and leave it somewhere in the middle. Nothing worse then turning it off, and 5 seconds later you have to crank it and find that comfy level again.

I'd rather be comfy then worry about how much fuel it's using... by the way, with 300rwkw, if i was worried about fuel economy, i'd have to take myself to a psych ward ;) In saying that, i still return around 12-13L for city driving.. i'm a bit of a nanna these days.

Anyways, back on topic... i still think it's more economical to drive with AC on and windows up. Especially in todays cars. Even if it costs 5c extra per km, at least i won't have wind noise or that damn annoying helicopter noise that surfaces now and then.

From memory, mythbusters suggested that driving with windows down in slow traffic/low speeds was best, but the difference was so insignificant you'd be just about crazy to drive with windows down on the basis it's saving fuel. Sure, if you like the fresh air or wind through the car, but not for saving fuel.

Oh, and doof doof people like windows down so that everyone can hear their fully sik stereo :teach:

RED R8

14-03-2007, 09:56 AM

I'm sure OzTrack has done some logging, programmed a few spread sheets and made a pie chart or 2 on the differences in the two.:lmao:

Hehe,I dont care either way my aircons on just about every day I dont think my little bit of comfort is costing me a fortune.

Shmacky

14-03-2007, 10:00 AM

Windows up - less drag

Fuel use by air con is minimal after cabin reaches set temperature

Mike

Not all of us have climate control in our LS1's.

Shmacky

Fnomna

14-03-2007, 10:04 AM

With climate A/C I find I just leave it on and windows up anytime it gets over about 26 and it's sunny.
When the cabin temp has cooled to a steady temp, there doesn't seem to be much load on the engine when cruising along. When doing about 80km/h I have noticed on the trip computer instantaneous L/100km goes down by about 0.5L/100km if I switch the A/C off. Suppose I should then see if it goes up again when I open the windows, while maintaining constant speed..

I think more noticeable increase in consumption occurs during acceleration.
For times when I know I'll be accelerating from say a standstill to 80km/h at a moderate pace, I just press the A/C off for those few seconds, then back on when at steady speed. The cabin doesn't warm up much during that time. But even then I don't bother doing this if it's not that hot and I don't need to accelerate too rapidly.

Wingnut

14-03-2007, 10:21 AM

The mythbusters test was flawed, as previously stated. There have been a number of tests on this in the past, most come to the conclusion that the speed where the drag coefficient and the extra fuel usage from the AC even out is at around 80 km/h. If you are going above 80, windows up, AC on, under 80, windows down, AC off.

Mythbusters also had a program where they were re-evaluating the tests that they did, and also stated the same as the above.

GHZ28

14-03-2007, 10:24 AM

A/C will automatically disable at approx 4500 rpm or 100% throttle anyway.

so if you nail it off the line, no A/C drag at all.

Oh and I forgot earlier on, most of the people here have SV8 and SS which do not get the 3 window dash/trip computer so don't have instantaneous fuel readout. Those of you with it, Calais, Berlina and HSV should have a look some time.

But as nearly everyone else has commented, economy is not that important, the small cost for the comfort far outweighs the cost. At $2 an hour I will sit in a/c thanks. Mind you that is 20 times the cost of a/c my office during our hot summer days.

On the mythbusters thing, the other one often quoted is their test on tailgate up or down for economy/drag. Their test was again to run out of fuel, not use real time consumption gauges, which would be more accurate, and only take 60 seconds, not good for a TV show. Good TV but not necessarily good science.

gh

I think more noticeable increase in consumption occurs during acceleration.
For times when I know I'll be accelerating from say a standstill to 80km/h at a moderate pace, I just press the A/C off for those few seconds, then back on when at steady speed. The cabin doesn't warm up much during that time. But even then I don't bother doing this if it's not that hot and I don't need to accelerate too rapidly.

vh-holden

14-03-2007, 10:29 AM

It's nice for those that have a choice.

$1800 to get the aircon in the vs to work again.

SICK SS

14-03-2007, 10:42 AM

in my ss ute i drive around with the windows down and arm on the sill in the ssv its windows up and ac on the sills are to high to comfortably rest my arm on it while im crusing

JimmyXR6T04

14-03-2007, 10:44 AM

It's nice for those that have a choice.

$1800 to get the aircon in the vs to work again.

bugger dude!! mind you, if it were me and i was planning on keeping the car a while i'd get it for sure, i can't stand not having AC. My other run about car doesn't have AC, and during the summer it just sits there and the other two cars get used. I better spray it for spiders before i jump back in :shock:

vh-holden

14-03-2007, 10:52 AM

bugger dude!! mind you, if it were me and i was planning on keeping the car a while i'd get it for sure, i can't stand not having AC. My other run about car doesn't have AC, and during the summer it just sits there and the other two cars get used. I better spray it for spiders before i jump back in :shock:

it has done 270000km. everything in the system leaks.

VYII_R8

14-03-2007, 05:51 PM

it has done 270000km. everything in the system leaks.

Not wanting anyone to jump on the Holden vs Ford bandwagon, but the aircon on my 92 Falcon still works just as good as ever... and it has just ticked over 500,000kms!

pteropid

14-03-2007, 05:55 PM

Just did a Sydney to Melbourne run at 8.5L/100klm with the air con on all the way. For me it's not the heat that annoys me but the humidity.

Aus8

14-03-2007, 06:12 PM

As mentioned above Mythbusters did this ages ago and found 60mph+ its more efficient to have the aircon on windows up. below 60mph windows open.

Drewie

14-03-2007, 07:29 PM

Slightly different topic, but do you think being in an air cond car for a long period is more tiring than driving with the windows down, the reason I mention it is I often do a 6 hour drive (round trip) to the in-laws farm in country Victoria, always use the SS with the air on, last weekend I had to tow a trailer full of stuff and not having a towbar on the SS had to take the family hack a VC commodore, drove all the way with the windows down and I was surprised how alert and fresh I felt when I got home. May have been a one off but I did wonder if the open window all the way was the reason, and I usually have the A/C in the SS on fresh air not recycle.

Mojo

14-03-2007, 07:44 PM

Wouldn't be in start stop freeway gridlock without the windows up and the aircon on recycle...there's so much toxic crap floating around in that air with the exhaust of 10,000 vehicles spewing their guts out.... I'll gladly pay a couple of extra bucks/100k's.. just gotta give the smokes up now :p

Slightly different topic, but do you think being in an air cond car for a long period is more tiring than driving with the windows down, the reason I mention it is I often do a 6 hour drive (round trip) to the in-laws farm in country Victoria, always use the SS with the air on, last weekend I had to tow a trailer full of stuff and not having a towbar on the SS had to take the family hack a VC commodore, drove all the way with the windows down and I was surprised how alert and fresh I felt when I got home. May have been a one off but I did wonder if the open window all the way was the reason, and I usually have the A/C in the SS on fresh air not recycle.

Gday Drewie
Didn't have the a/c on recycle did ya - that'll stuff you up after a few hours as no fresh oxygen coming in.

Dilan

14-03-2007, 09:12 PM

I remember reading in a RACV mag (questionable credibility) that as a rule of thumb, for speeds <80km/h windows down....>80 clicks aircon is better.

jerrel

14-03-2007, 09:52 PM

Noah

14-03-2007, 10:11 PM

my estimate is that my car uses 30% more petrol with the a/c on. i always have windows down.

Question: does having the fan speed on 3 or high (with a/c), use more petrol then if the fan speed is on 1?

Would be the opposite.

Faster fan speed will get the cabin temp lower, faster! This will bring the thermostat into play faster. The fan only varies the heat transfer rate through the condenser.

Noah

JimmyXR6T04

14-03-2007, 10:14 PM

my estimate is that my car uses 30% more petrol with the a/c on. i always have windows down.

Question: does having the fan speed on 3 or high (with a/c), use more petrol then if the fan speed is on 1?

30% more petrol??? i think your estimate is highly out.. a 30% variance is massive, and i'd suggest 30% more fuel is attributed to your right foot. Unfortunately, there is no way anyone could reliably, and accurately test the fuel consumption. Traffic, acceleration, and way too many other factors will influence your fuel consumption to say that 30% more fuel is used from air con.

Basically, what you're saying is.. if you have a 100L fuel tank, you'll use 30% more if the AC is on.. 30% of 100, is 30.. so you'll use 30L more with the AC on.. i'll go nearly 300kms on 30L.. i think you may need to re-adjust your estimate, or do your math again.

brh26

14-03-2007, 10:16 PM

Noah

14-03-2007, 10:19 PM

How is it "dry Air". Aircraft yes, car??

Bazz

14-03-2007, 10:20 PM

CV8Monaro

14-03-2007, 10:25 PM

Just did a Sydney to Melbourne run at 8.5L/100klm with the air con on all the way. For me it's not the heat that annoys me but the humidity.

That's great economy....cruise control and 110 all the way? Best I got was 9.5 but I do give it a boot when overtaking...

I was always under the impression with the A/C that it was the smaller engines that suffered most...A/C in the V8 should have virtually no effect on the fuel economy...

Noah

14-03-2007, 10:28 PM

Not necissarily as the efficiency of the transfer of heat from the air reduces as the air rushes past it faster. So air can be made cooler by coming out slower and allowing the transfer of heat more therefore cooling the inside of the car quicker.

Very true.

You will still find, faster is better in A/con (for a modern sys). See what Climate Control will do.

JimmyXR6T04

14-03-2007, 10:31 PM

I drive long highway stints and to help break up the trip, I have tried different AC settings, windows up windows down and different speeds. My testing indicates turning the AC on at speeds above 80kph results in instantaneous fuel consumption increases from 0.7 to 1.5L per 100km. It seems to be dependant on outside temp. Different fan speeds don't seem to affect the fuel consumption.
Windows up or down a few cm's seem to give the same and also the best fuel consumption figures(if you can tolerate the lack of airflow).

AC on is dry air, and therefore will increase the likelihood of dehydration if you do not keep up fluid intake. So yes, you will be more likely to be fatigued.
FYI, fatigue is being considered to be the #1 contributing factor in the road toll up here.
I have done more than 200hrs of testing on this in the same vehicle. Take it for what it is.
Cheers

sounds solid enough :thumbsup:

personally, if it's only 1.5L per 100km.. then i'll use AC everytime. What's that gonna cost over a 500km trip?? a few bucks max. 1.5L might cost say $1.80 per 100km... over 500km it'll cost around $9..

hardly worth worrying about.

When on a long trip, i'll often go between re-circulate and fresh air, and occasionally put the window down for a bit fresher air.. stop revive survive :thumbsup:

Edit: i hope my maths is correct... i only did it very rough and quick.. it's late ;)

brh26

14-03-2007, 10:53 PM

jerrel

14-03-2007, 10:53 PM

30% more petrol??? i think your estimate is highly out.. a 30% variance is massive, and i'd suggest 30% more fuel is attributed to your right foot. Unfortunately, there is no way anyone could reliably, and accurately test the fuel consumption. Traffic, acceleration, and way too many other factors will influence your fuel consumption to say that 30% more fuel is used from air con.

Basically, what you're saying is.. if you have a 100L fuel tank, you'll use 30% more if the AC is on.. 30% of 100, is 30.. so you'll use 30L more with the AC on.. i'll go nearly 300kms on 30L.. i think you may need to re-adjust your estimate, or do your math again.

i wish ur thinking was true. my calculations are fine. i drive from berwick to glen waverley everyday, it is 20-25km. my "distance to empty" drops in that range normally. when the a/c is on it drops between 30-40km, pre trip.

vh-holden

14-03-2007, 10:58 PM

Not necissarily as the efficiency of the transfer of heat from the air reduces as the air rushes past it faster. So air can be made cooler by coming out slower and allowing the transfer of heat more therefore cooling the inside of the car quicker.

i found that (when the aircon was working, and as it was dying) the car would cool quicker on 2 than on flat out.

brh26

14-03-2007, 11:16 PM

I agree, it is only a small cost incurred with running AC on a warm or hot day compared to comfort level. I haven't even thought about testing in city traffic. Mind you, we don't even have traffic lights where I live, so not going to be much validity to said testing......lol

JimmyXR6T04

15-03-2007, 10:04 AM

i wish ur thinking was true. my calculations are fine. i drive from berwick to glen waverley everyday, it is 20-25km. my "distance to empty" drops in that range normally. when the a/c is on it drops between 30-40km, pre trip.

mate, i wouldn't hold much faith in the distance till empty reading. The only real way to test it would be drive to those locations for a week, in exactly the same traffic conditions (perhas late at night), and exactly the same throttle application and then re-asses where you're at.

I think if you fill the car to full.. drive 100kms with AC on, then re-fill it and see how many litres of fuel it used. Then drive another 100km (similar roads) with AC off.. i think you'll find the difference in fuel usage to be minimal. Best way would be on a freeway or similar using cruise control so that the test is more accurate.

It's like the average fuel consumption readout... mine will say it's 13.5L/100km. But when i fill the tank to full, drive it 100km then re-fill to full again, it'll only accept maybe 12.8L of fuel.. They're a very basic guide.

On interstate trips, with some hilly roads and some WOT overtaking, i'll still return 8.5-10.5L on a variety of roads and towns. Cruising up to sydney from canberra will see around 9L. depending how many times i take it off cruise control :yahoo:

Dacious

15-03-2007, 05:52 PM

I'd go with 0.8-1.5 l/100km with the a/c on. Interestingly my car is reasonably quiet with the windows down at 100km/h and it seems to have a marginal effect on cunsumption except into a headwind. Or maybe I'm just deaf from too much geetar amp and mudderboiks.

Went to Mt Gambier last weekend and until I got to a bit of private road where I do a little 'low flying' I was sitting on 7-8l/100km. I found I am more economical than cruise control by 0.5l/100km at 100-110. I am very cautious on the Western Hwy - saw a Plod VE in Lake Bolac and a TOG VZ pull someone over near Dunkeld.

I filled at and drove from Ballarat to Hamilton and the distance to empty was still over 550km. When I rolled into Gambier I had half a tank on the guage and 450km to empty showing even with a bit of 'overtaking'. Sitting on 140 @2500rpm my car chews exactly 10l/100km on the flat and pretty much ignores anything other than major hills.

I personally prefer, if air is moving in and out of the car, to not use aircon because I too have delicate skin and it goes all icky dry :limpy: Not really, I just prefer air flowing, as a paid-up Temporary 'Stiryan.

Oztrack Tuning

17-03-2007, 12:07 AM

I havent logged it propelry but last weekend on a 30 deg sunny day at 110kph i think having the air con turned on was using about 0.4-0.8L/100kph

Have no idea about windows - but any air that makes it into the car surely has to be drag - the air is going 110kph and has to be supplied with a forward force to make it stop.

JimmyXR6T04

17-03-2007, 12:38 AM

but even if it's using 1L/100km more with AC.. who in their right mind would choose windows down based on fuel consumption?? you'd have to be a complete tight ass to even consider it.. it's fair enough if people prefer windowns down based on air flow and comfort, but to save fuel?? c'mon... it's saving $1.20 per 100km... fark me, what's the point of owning a V8 or any performance car if people are worried about saving $1.20 over a few hundred kms.

VB2VT

17-03-2007, 07:46 PM

i remember a test was done some years ago and they found that on average the fuel consumption was quite the same so if its hot wack it on! Why leave it off and be uncomfortable to save $1 every 400ks? if the dollar does make a difference sell the commodore and but a toyota or something smaller and cheaper!! or just buy a bike!

djgelling

17-03-2007, 08:03 PM

I believe it is the adiabatic process that removes moisture from the air to deliver cool air. The relative humidity can drop 50-70% as the air is cooled.
Also, cold air can retain less moisture than warm air.

Hmmmm. My belief is that it is a fact that the refrigerated (cooled) air is quite cold (ever stuck a thermometer in front of a vent with aircon on??). This will cause the moisture in the air to condense on the ice cold heat exchanger bits (ever seen what happens to the outside of a cold beer glass in North Queensland??), rather than have all this water gush all over the place and spray out at you through the vents, it is separated and drained away externally by a drain tube under the car (ever noticed the pool of water under the car when you pull up for a while after running the aircon on a humid day?). Thus you remove a large % of the water form the air, thus drying it out!!

Glenn@Autowerks

17-03-2007, 08:09 PM

Air will be de-humidified before cooling takes effect !!

Simple !!

djgelling

17-03-2007, 08:12 PM

Air will be de-humidified before cooling takes effect !!

Simple !!
And what's your take on how "dehumidifed" is effected??

Glenn@Autowerks

17-03-2007, 08:15 PM

30 years in the Commercial Air Conditioning Industry !!!

djgelling

17-03-2007, 08:24 PM

30 years in the Commercial Air Conditioning Industry !!!

Sorry. I meant "can you please explain the physical process so that everyone can learn (including myself).

How is "dehumidifying prior to cooling" achieved??

Thanks.

EDIT: This is a genuine query as obviously my understanding is obviously incorrect.

Capt.LS2

17-03-2007, 08:25 PM

30 years in the Commercial Air Conditioning Industry !!!

and take that!! :teach:

Glenn@Autowerks

17-03-2007, 08:34 PM

Simple terms, a high humidity day everyone sweats, the evaporator will extract the moisture 1st...(major water..condensate run off) then the cooling effect takes place. Like your beer example, the glass will obtain the moisture 1st - thats the principle of ac systems, it takes the water from the air first, then when all the moisture is gone the cooling effect starts. Go into an air conditioned place in a high humidity area, will the glass build up the moisture real quick ? The answer is no, the ac system has already taken it out !!

Another example, middle of Aus, temps are high but no humidity, does it affect you that much, the answer is no - no humidity !!!

Hope that explains a bit !!

and take that!! :teach:

I love it..... Cheers :beer:

djgelling

17-03-2007, 09:17 PM

Simple terms, a high humidity day everyone sweats, the evaporator will extract the moisture 1st...(major water..condensate run off) then the cooling effect takes place.

OK this is the bit that I can't quite get my head around. The sweating thing is a different process as the car doesn't sweat. It is the evaporation off the skin that cools us. The body can provide sweat via the sweat glands.

The car can't "sweat". Can you explain further how the evaporator extracts the moisture........... What physics are involved here?? Are we talking about expansion of a known volume, thus cooling the air which will result in condensation. Where does this take place? How does this relate to the Refrigerant gas in the AirCon system, which I believed was involved in the heat exchange system (ie cool the refrigerative gas via compressor in the engine bay, pump this cold gas this through an exchanger in the cabin, over which cabin air is blown, cooling it, resulting in the heat being pumbed out to the engine bay, a.k.a. reverse cycle refrigerative household systems.

Evaporative air conditioning would work as you described, not refrigerative.

Still confused.

Glenn@Autowerks

17-03-2007, 09:42 PM

OK this is the bit that I can't quite get my head around. The sweating thing is a different process as the car doesn't sweat. It is the evaporation off the skin that cools us. The body can provide sweat via the sweat glands.

The car can't "sweat". Can you explain further how the evaporator extracts the moisture........... What physics are involved here?? Are we talking about expansion of a known volume, thus cooling the air which will result in condensation. Where does this take place? How does this relate to the Refrigerant gas in the AirCon system, which I believed was involved in the heat exchange system (ie cool the refrigerative gas via compressor in the engine bay, pump this cold gas this through an exchanger in the cabin, over which cabin air is blown, cooling it, resulting in the heat being pumbed out to the engine bay, a.k.a. reverse cycle refrigerative household systems.

Evaporative air conditioning would work as you described, not refrigerative.

Still confused.

Point 1. There is no such thing as Evaporative air conditioning.

Point 2. Go do a refrigeration course at tech.

Point 3. End of conversation.

Sorry but I dont get where this is headed apart from sucking knowledge, if you want any more info pm me. Will be glad to help if I can !! Have a great day !

Cheers
Glenn

Fnomna

18-03-2007, 05:29 PM

The car can't "sweat". Can you explain further how the evaporator extracts the moisture...........
http://home.howstuffworks.com/question76.htm

What physics are involved here?? Are we talking about expansion of a known volume, thus cooling the air which will result in condensation. Where does this take place?
More like just water vapour in the air hitting the cold coil and turning into liquid. Then it drips and drains away.
Water vapour has a higher temperature than liquid water. Removing this 'warm' water vapour from the air/water mixture entering the system will take away some heat too.

How does this relate to the Refrigerant gas in the AirCon system
It doesn't really. The major heat exchanging via refrigerant and the moisture extraction from the air are separate processes that can occur at the same time.
You don't need moist air for the refrigerative process to cool it.