# Can in intercooler reduce the air temp lower than ambient?



## kenan (Apr 29, 2003)

Say the outside air temp is 5 and after passing the turbo it 7 say. Could an intercooler reduce the temp below the outside temp of 5 without CO2 cooling, water injection etc.

I know it may seem a stupid question but having a "dissagreement" with someone about it


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## Bassman (Dec 17, 2003)

Good question that, on the face of it it would be obvious that it could not reduce the charge temp below ambient but then again if the car were moving what about the 'wind chill effect'?
On balance I would think it is highly unlikely that you will see a reduction below ambient given the typical usage an intercooler experiences during it's operation.


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## slippyr4 (May 2, 2002)

This is all theoretical. 

The intercooler could cool the charge not lower than the intercooler's temperature. The intercooler could, in theory be lower than ambient if it was wet and much air rushing past/through it was evaporating the water quickly.

It won't happen in practice though. And the turbos would heat up the air waaaay more than 2 degrees- not only by compressing the air (this makes it hot), but also conduction from the fairly warm turbos themselves.


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## SteveN (Aug 6, 2002)

Well in the real world, if ambient is say 20deg C, once it thru the turbo it usually 100degC+, so the likelyhood of getting it back below ambient is slim even IF it is possible.

Lowest ive ever seen was 6degC after the intercooler and it was about minus 10 windchill that day 

Itd be VERY interesting to see a GTR intercooler test, on the standard AND the various aftermarket ones, as ive yet to ever see one, and looking at various coolers, i think the results would be interesting, lol...


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## kenan (Apr 29, 2003)

Bugger, I was hoping that in theory if the intercooler were big enough with all hte air flowing over it you could get it lower than the ambient temp. The temps were just for explaination as I didn't have a clue on the temps.

Thanks guys, no my mate can trully say TOLD YOU SO DOH


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## slippyr4 (May 2, 2002)

> if the intercooler were big enough with all hte air flowing over it you could get it lower than the ambient temp


Sadly, the laws of physics apply even to really big intercoolers.


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## GTuned (Mar 21, 2002)

In the US I have had frost form on the "cold" side of my intercooler.. after a long drive... so *theoretically*...


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## ATCO (Feb 2, 2003)

Kenan, it depends how smart you want to be! I have a theoretical cunning plan!

The above posts are correct in real terms. However, think of this.

Lets assume that the I/C is around ambient. Then in principle the temp drop cannot be lower.

However, subject to where you are measuring the temperature, plus the external environment think of this:

1. Its raining, therefore the I/C is getting wet. The "wind-chill" airflow forced across the cooler would cause the water too evaporate, thereby causing a drop in temperature. That is, you do get a significant wind chill effect.

2. Whilst compression does heat up the air, when it hits the expanded area of the I/C it experiences a pressure drop. Pressure drop causes a (further) reduction in temperature. So provided you measured the temp within the I/C, ideally at a cold spot, and definitely before the I/C outlet then the temp is lower! 

Its all bu11sh1t of course, but depending how smart your chum is it might save your pride! ;-)

DaveG


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## Mycroft (Apr 13, 2002)

Yes it can but the circumstances have to be rather particular, it is NOT going to happen here in the UK, the most likely places that it can occasionally occur is in the high humidity and high temps of the tropical regions, where the combination of surface evaporation and the chill effect of movement of air makes it possible...


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## slippyr4 (May 2, 2002)

Hello mycroft, not seen you for a while.

I'm sure that one of these would help. Guffaw.


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## weka (Jul 3, 2001)

A question on wind chill factor.


You don't feel colder becuase of temperatures being lower than ambient? Is it not that we 'feel' its colder due the lost of heat removed by the wind?


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## Mycroft (Apr 13, 2002)

Weka, correct more calories are lost...

That is why [regarding the original question] only if the air has a high moisture content can an inversion occur...

I just did some calcs and if the intake air was 35c and 90% humidity and you had a rather good IC and a car travelling throught the same air at 90mph the air temp within the IC will drop [assuming an OA 90% efficiency] to 31c.


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## Scott (Jun 29, 2001)

Just reading this thread I though, I'd bet Mycroft would know if he was still around!  

Then BAMMMM, out of the blue like a sience super hero!   

Glad to see your still around.


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## lynchy (Aug 21, 2004)

As above, I thought that wind chill is not measureable as such. For example the external temp sensor on my last car which was located in the brake duct didn't change because of air movement or lack of it. The way I understand it wind chill relates to how cold it feels and cannot be measured with a thermometer but is more a calculation that takes into account the wind speed and temperature.

Regarding ICs, a 100% efficient cooler will lower the charge air to ambient. A 0% efficient IC would not cool the charge air at all. However from what I have read anything over 80% would be classed as highly efficient and to get the extra efficiency above that figure would be very difficult and most probably result in a negative impact on other aspects of the ICs performance. 

In the books I've read the only coolers that can exceed 100% efficiency are air to water coolers loaded with ice water or marine applications that use sea water which again is cooler than the air. But that's a bit of a cheat as in both circumstances the cooling medium is cooler than the ambient air.

Also from what I've read water injection is progressively less effective at cooling charge air the cooler it is.

So IMO it could MAYBE be possible to get the charge below ambient when the ambient is very high and a super efficient IC is used along with water injection but even then it is very unlikely.


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## NIGHTMARE (Dec 4, 2001)

Because wind chill is based on removing heat from the human body, there is no wind chill for inanimate objects, such as car radiators and intercoolers. However, there is a faster heat loss with increasing winds, so the amount of time for an object to cool to the actual air temperature is less. Regardless, the inanimate object cannot not cool below the actual air temperature. Thus, if the temperature outside is -5 degrees Fahrenheit and the wind chill temperature is -31 degrees Fahrenheit, then your intercooler will not drop lower than -5 degrees Fahrenheit.


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## NISFAN (Oct 11, 2003)

Correct Typhoon, an IC works on Wet bulb temps, we measure ambient in a dry bulb thermometer. There is adifference in these two temps depending on humidity level, height above sea level, etc. 
Theoretically possible to have lower outlet temps, but not in practice.


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## Pavlo (Sep 12, 2002)

Mycroft,

If the air with 90% relative humidity is flowing on the exterior of the intercooler, how does the air lower the temp of the intercooler below it's ambient temp, given the water in the air is already evapourated. Surely the water would need to be a mist of liquid suspended in air, in order to evapourate and lower the temperature of the bulk fluid below ambient temp as it passed over the intercooler. This in turn would like the temp of the intercooler potentially below that of the ambient air.

Paul


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## Jabberwock (Jun 24, 2003)

Perhaps 'wind-chill' and water evaporation can be considered as separate effects?

When water evaporates from a surface, that surface becomes cooler because energy (in the form of heat) is drawn from it to aid the transition (latent heat).

The wet-bulb temperature is the temperature of the surface of (in this case) the wet intercooler.

Whether it is possible or not will depend on how long the air spends in the I/C so I suppose size does matter  

Is that right Iain? it was all a long time ago..........

Ken.


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## Jabberwock (Jun 24, 2003)

Right, here's some more bunk.........

Drybulb temp. is the ambient temp. of the air.
Dewpoint temp. is the temp. at which a given quantity of air becomes saturated with moisture.
Wetbulb temp. is the temp. of the surface of a material being dried.

Wetbulb depression is the difference between the drybulb and wetbulb temps, and is a measure of potential rate of evaporation.
Although the dewpoint is independent of temp, decreasing it also decreases the wetbulb.


So in theory, the best conditions for attempting the above could be:

High ambient temp.
Low dewpoint (ie dry air)
LARGE intercooler surface, sprayed with water or something else
Rapid forward movement creating massive air flow.


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## Inline 6 (Nov 10, 2003)

Just how can air charge of well above atmospheric pressure possess a lower temperature (molecular kinetic energy) than atmospheric air itself? Without going into the laws of Thermodynamics, temperature and pressure and volume has its interelationships, you simply can't change one without affecting the other. 

"Cold air" at the inlet ports isn't a good idea anyway, as the fuel mixture and atomisation will be poor under that kind of condition. Poor economy, reduction in BMEP, etc

High humidity levels slows down flame development and propagation of the gas charge, so allow that. 

The key to the extra power, reliability and all that stuff, is through optimisation, not by the more is more, bigger is better approach.


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