heat exchanger cold to touch after hard driving educate me

[8600RPM]

Can someone give me science behind how heat exchanger or intercooler gets cold to touch after hard drive? The silver one on top of engine, not radiator

[Cyberdemon]

The intercooler is cooled by water flowing through it. The heat exchange is happening elsewhere so the IC stays cold to cool the charge air and the heat is sent to the exchanger.

In hot temperatures with hard driving it would still be susceptible to heat soak.

Drag guys often add ice to their reservior to further drop the temps.

[8600RPM]

Originally Posted by Cyberdemon

The intercooler is cooled by water flowing through it. The heat exchange is happening elsewhere so the IC stays cold to cool the charge air and the heat is sent to the exchanger.

In hot temperatures with hard driving it would still be susceptible to heat soak.

Drag guys often add ice to their reservior to further drop the temps.

But how us it literally cold? Thete is no fluid I can think of in a car that is ice cold?

[CanAutM3]

Originally Posted by Cyberdemon

In hot temperatures with hard driving it would still be susceptible to heat soak.

What makes you so sure about this assumption?

[8600RPM]

It's clearly not susceptibe to heat soak as I just beat the crap out of the car for 30 mins of red line runs and wot, and it's almost ice cold to the touch. Still trying to understand, clearly some endothermic reaction of the metal heat exchanger or what as fluid passes through? Feels like 8ce water ran through. It's 70 degrees outside

[CanAutM3]

Originally Posted by 8600RPM

clearly some endothermic reaction of the metal heat exchanger

I seriously doubt there is any chemical reaction taking place here.

I think it has more to do with a very well designed heat exchange system in the intercooler and the radiator.

[8600RPM]

Again coolant isn't ice cold. There is some rapid dissipation of heat within there but I'm so unfamiliar with the details of intercoolers

[Merli]

I'm not really sure what answers you're looking for in this thread... That's simply how an intercooler works?

Let's start at the basics.... This is the air/air intercooler on my GTR:



After a few laps of the track, if I touch the turbo-side end tank, I will literally sear the fingerprints off my poor little digits. However, if I touch the throttle body-side end tank (after the compressed intake air has passed through the intercooler), that end tank is still cool to touch.

So the BMW's cooling setup is a little more complicated, being a water/air intercooler.

It comprises of two heat exchangers. One on top of the engine, and one in front of the car that cools the water down.







The heat exchanger that you're touching on top of the engine has water flowing over each of the rows of the core, unlike the air through my single core system in my GTR. This water obviously heats up, and then gets pumped through the second front mounted intercooler that uses the flowing air through the front of the car to cool the water back down before it makes it's way back up to the top heat exchanger to cool the intake air down again.

I'm not sure what the insides of that top water/air intercooler core looks like, but it's possible that you're touching the part that gets the cool water that has just come from the front intercooler and hasn't had a chance to heat up yet. Perhaps the bottom of that core gets quite hot, but through intelligent design they hasn't allowed silly backyard mechanics to pop the hood and burn themselves touching hot bits of the engine after a back-road blast?

I'm not 100% confident of the BMW design, as I haven't pulled it apart (and probably never will), but I'm using my previous knowledge of how intercooling works and trying to help out a little bit.

[8600RPM]

I guess I'm surprised it's cold to the touch. Luke warm or just slightly cool or cooler than the engine would all make sense but cold cold surprised me since outside air of 70 doesn't seem cold but then again 70 degree water is cool. I'm new to turbos but I'm impressed with their cooling system as I bear on my car hard for 30 mins and ice cold still. Heat soak on stock power cars will be very hard to do in my view.

[gsrbri]

Water to air intercoolers are highly efficient (more so than air/air) - the M3/4 intercooling system is very well designed and thermally efficient given the power output. Would be curious to see an IAT sensor read-out during high boost. You didn't mention what the ambient temperature outside is, but the system will certainly cool the charge to that temperature relative to the hot engine compartment - as long as the car is moving and the intercoolers receive good airflow. It's just physics, after all. A 30 minute lapping session on a racetrack might be a different story - I won't find that out until springtime, unfortunately. 15 degrees F here around Boston today.

[Cyberdemon]

Originally Posted by CanAutM3

What makes you so sure about this assumption?

The laws of thermodynamics.

Heat soak with water to air systems is a matter of physics - but that's not to say the rate at which it would happen is ever going to be a PROBLEM.

I'm sure the system is very well designed, and you could throw the car around a track for a while in very hot conditions with no problems at all. The simple question is what will the intake temperatures look like after 30 minutes of hard use vs when you started the car, and the answer (no matter what the figure) is going to be "higher". Even with great airflow it's simply a matter of physics that all of the heat generated + high ambient temperatures has to go somewhere.

To the OP - to answer why it's cold, think of the same reason your air conditioner might freeze up on a hot summer day. The heat is being moved from point A to point B.

In reality you could tell what the actual temperature is with an IR thermometer. In reality I would expect the temperature to be close to ambient (which surrounded by a scorching block of metal probably feels near freezing).

[CanAutM3]

Originally Posted by Cyberdemon

The laws of thermodynamics.

Heat soak with water to air systems is a matter of physics - but that's not to say the rate at which it would happen is ever going to be a PROBLEM.

I'm sure the system is very well designed, and you could throw the car around a track for a while in very hot conditions with no problems at all. The simple question is what will the intake temperatures look like after 30 minutes of hard use vs when you started the car, and the answer (no matter what the figure) is going to be "higher". Even with great airflow it's simply a matter of physics that all of the heat generated + high ambient temperatures has to go somewhere.

Law of heat exchange: If the heat extraction capacity is always greater than the heat generation, it will never heat soak .

Disclaimer: I am not saying it the case for the F8X, but the system does seem to have good margin.

Originally Posted by Cyberdemon

To the OP - to answer why it's cold, think of the same reason your air conditioner might freeze up on a hot summer day. The heat is being moved from point A to point B.

The difference with an air conditioning system is the compression/expansion of the cooling medium. Something not possible with an incompressible fluid such as the water in the intercooler system.

[Cyberdemon]

Originally Posted by CanAutM3

The difference with an air conditioning system is the compression/expansion of the cooling medium. Something not possible with an incompressible fluid such water in the intercooler system.

It's the best Layman's analogy I could come up with.

It would be easy to test all of these assumptions with a racetrack and an IR thermometer plus an M4 and some hot weather, but at the moment all I have is an IR thermometer and a snow covered 335 so...

[8600RPM]

I've read a lot last night and to be more accurate all these are air to water to air so heat soak is no risk if enough water is in the system and it flows to an adequate radiator. We will see over summer I'm sure but for 99 percent of drivers I think they hit a home run with this. Less lsg, cooler temps and pretty resistant to heat soak I feel

[Needsdecaf]

Simple answer is that the cooling medium is running through a radiator that has substantial airflow going over it. Think about how much cooler you felt in an older car with no AC when you had airflow going over you. No, the ambient air isn't any cooler, but the airflow is moving heat off of YOU, so you feel cooler.

Likewise, the air flowing over the water radiator in the front is stripping heat out of the intercooling liquid passing through it. It's certainly possible to have the temperature of the coolant drops below ambient.

[CanAutM3]

Originally Posted by Needsdecaf

Simple answer is that the cooling medium is running through a radiator that has substantial airflow going over it. Think about how much cooler you felt in an older car with no AC when you had airflow going over you. No, the ambient air isn't any cooler, but the airflow is moving heat off of YOU, so you feel cooler.

Likewise, the air flowing over the water radiator in the front is stripping heat out of the intercooling liquid passing through it. It's certainly possible to have the temperature of the coolant drops below ambient.

Nope, that goes against physics and heat exchange principles.

Having an airflow certainly helps with the rate at which heat is transferred (how fast it is transferred), but from a tempearure standpoint, you cannot reach a lower temperature than the temperature of the ambient air.

[Needsdecaf]

Originally Posted by CanAutM3

Nope, that goes against physics and heat exchange principles.

Having an airflow certainly helps with the rate at which heat is transferred (how fast it is transferred), but from a tempearure standpoint, you cannot reach a lower temperature than the temperature of the ambient air.

Yeah, you're right. My thermodynamics classes were a long time ago, and mechanical engineering is not my specialty! I could have sworn that it was possible, but dusting off the cobwebs via google, I remember the laws and you are correct, it's not possible. .

If one were to get technical about it, I wonder if heat added to the water in the air to water intercooler in the engine pressurizes the water to an extent enough that as it cools, it decompresses and makes almost a mini-refrigeration cycle, thus lowering the water slightly below ambient?

Probably not...

[Mandi90TT]

Originally Posted by CanAutM3

Nope, that goes against physics and heat exchange principles.

Having an airflow certainly helps with the rate at which heat is transferred (how fast it is transferred), but from a tempearure standpoint, you cannot reach a lower temperature than the temperature of the ambient air.

Correct. Or so says my BS in Physics from...too many years ago. However, what might be happening is that the heat exchanger that you are feeling that feels cool to the touch is, in fact, made of metal, and metal's heat conduction capabilities are quite strong. Given that 'ambient' air temp is usually less than 98.6 (body temp), the say 70 degree (for example) heat exchanger will be pulling heat from your hand pretty quickly, thus feeling cold.

[CanAutM3]

Originally Posted by 8600RPM

Can someone give me science behind how heat exchanger or intercooler gets cold to touch after hard drive? The silver one on top of engine, not radiator

My interpretation of this phenomenon is that the intercooler system on the F8X is very efficient at maintaining a temperature very close to ambient. I have witnessed the same thing as you, where I did 2 back to back 30 minutes session on the track, popped the hood and touched the intercooler. I could not believe that it felt COLD to the touch when everything around it was scorching hot.

The intercooler core is made of aluminum and it is cooled by the water that circulates in the system. It is then the cool aluminum that extracts heat from the air entering the engine. Aluminum has very high heat conductivity. Touch any aluminum surface in a room and it will feel cold to the touch because it absorbs the heat from you body. In contrast touch a piece of wood in the same room and it will not feel as cold, even if it has the same room temperature as the aluminum object.

The good news is that the intercooler does not seem to be prone to retain much heat (heat soak), hence it is cold to the touch. However, I seriously doubt that its temperature is below ambient. Best way to test this would be with an IR gun.

[CanAutM3]

Originally Posted by Dave 90TT

Correct. Or so says my BS in Physics from...too many years ago. However, what might be happening is that the heat exchanger that you are feeling that feels cool to the touch is, in fact, made of metal, and metal's heat conduction capabilities are quite strong. Given that 'ambient' air temp is usually less than 98.6 (body temp), the say 70 degree (for example) heat exchanger will be pulling heat from your hand pretty quickly, thus feeling cold.

Bingo!

I posted the same thing, but you beat me to it while I was typing

[Needsdecaf]

Originally Posted by CanAutM3

The good news is that the intercooler does not seem to be prone to retain much heat (heat soak), hence it is cold to the touch. However, I seriously doubt that its temperature is below ambient. Best way to test this would be with an IR gun.

This is the most important thing, and certainly seems to be the case!

[Mandi90TT]

And here I was about to quote you, saying something along the lines of 'I just said that'