How does intercooler work??????
 

This is a very fundamental question to most of you but I do not have an intercooled truck. I am assuming intercooling helps hold down temps as you make modifications for more fuel. I have read intercooled units have bigger radiators so they must use coolant, not air to achieve their goal. Enlighten me, please.

i think they just happened to put the cross flow radiators on about the same time that they put in the intercooler (or aftercooler) the intercooler looks just like a radiator. it is an air-to-air cooler on our trucks. when the turbo compresses the air it heats up. the air then flows through the aftercooler and the outside air cools it by keeping the fins cool. the cooler the air is the more dense it becomes allowing more air into the cylinder each time it fires. the fact that the air is cooler helps to lower egt's. the fact that it is more dense allows you to burn more fuel (though i think that part of it is miniscule) those are the basics. you can buy aftermarket air-to-liquid coolers but they do not come stock on the truck.

Intercooler
 

Thanks for the the class 101 on "Intercooler".

no problem :)

Limitedslip is right about how and why they went to intercoolers. You are removing a lot of heat from the compressed air. This is really why they need a bigger radiator. The intercooler is in front of the radiator heating the air going into the radiator making them less efficient.

boatnik that makes a lot of sence. never thought that once the air took the heat it still had to try to cool the radiator!

As I understand things, those who know better, please speak up. ;)

If one ignores any friction involved in the compressor wheel spinning in the air, etc. . . . . .

The turbo does not heat the air.

The following numbers are simply thrown out as an example. ;)

You take one (1) cubic yard of outdoor air. Let's say it contains 100btu of energy. At that point, per unit of measure, it's temp is equal to it's surroundings.

Compress that same cubic yard to one (1) cubic inch.

Without any further change, it still has the original 100btu of energy. The only thing(s) that have changed are the density of the air/pressure/volume occupied.
In this state, the one cubic inch of air is much warmer than it's surroundings.


Hold those thoughts.

Heat's natural thing is to move to something cooler. Equilibrium is never really reached. With that, when you send the compressed charge air described above through an inter-cooler (actually, and After-Cooler), The energy (heat) of the charge air wants to flow into the metal of the inter-cooler, which in turn passes said heat to the cooler, outdoor air.


Further, as as the temperature of the charge air drops, it's density increases. It gets thicker. The act of cooling the charge air is in itself, a means of increasing boost as it were. A fine example of this is when you open the refrigerator door to get a cool one, the cold air falls out to the floor across your feet. It's because it's denser. The warm thinner air of the room, is pulled into the frig to replace the cold. When you shut the frig door, only to remember you need more dip, you go to open the door again to fine it nearly stuck shut! Huh?! That warm air you just let in is now shrinking as it looses its heat, holding the door shut with the reduced pressure in the fridge.

For our needs, the thicker air contains more oxygen as compared to warmer, so you can add more fuel. :D


Getting back to the expanding/shrinking thing. Our engines work by simply expanding air by way of adding heat. That expansion pushes the piston down. By filling the cylinders with the compressed, and cooled charge air (denser). We can have a higher expansion ability as compared to natural aspiration.

The higher density charge air, with the appropriate, additional fuel means more power. ;)

Adding an intercooler to our engine without changing the fuel will certainly drop EGT's simply because you're moving more (denser) air through the engine.


It's kind of a long winded, readers digest version of how it works. You've got to keep in mind how it effects the whole engine to fully understand it.

Hope this helped more than confuses. :D

how do you compress air without any additional energy? you cant. you are adding energy to the system by compressing it, which is why it increases in temperature.

I'm thinking the energy involved in the compression is held as potential energy in the form of the additional pressure (again, ignoring friction).

I think that's how it works. :confused:


Work is work, is work, is work, . . . .

You can't create, nor destroy energy. Merely change it's state.


Consider taking some of the boost pressure from a twin setup. 50# boost into your pneumatic air wrench. The energy put into the act of compression by the turbo is released as work by the wrench. With that, notice the cool air exhaust from the tool.

Remember you cooled that high pressure charge with the inter-cooler to room temp. Expanding it through the tool does not add heat to it, so it's cool compared to the original turbo intake.

That heat difference represents that removed by the inter-cooler. ;)


NOTE: I keep saying "ignoring friction". Yes, the turbo does heat the air by way of frictional losses due to aerodynamics, fluid dynamics, etc that are inherent with centrifugal compressors like we use. Those are fairly small if one stays within the properly designed/applied footprint of a turbo.

British thermal unit (n. Abbr. BTU or Btu):
The quantity of heat required to raise the temperature of one pound of water from 60° to 61°F at a constant pressure of one atmosphere.

heat is energy. you increased the temperature of the air and therefore the BTUs do not remain at 100 (per your example) but rather increase. p*V=m*R*T in a closed system, so an increase in pressure increases the temp and therefore the energy (BTUs).

pressure alone is not energy. pressure*(change in volume) is energy <--in a very simplified form.

Weird science. :D

i was merely commenting on your example, not the turbo as that is an open system.

LOL, I think we're singing the same song albeit in different keys. ;)

pgilles has it exactly right. Any time you compress a gas, you also heat it. The more efficient a compressor is the closer it comes to the above equation, but it will always add more heat than the theoretical minimum. Thus the need for an intercooler. OK, technically it's an aftercooler because it's not between stages of compression, but in the U.S. almost everybody calls it an intercooler. Cummins literature typically calls it a CAC (Charge Air Cooler).

On Cummins engines, water-to-air CAC's are usually found in stationary or slow moving installations where airflow through the CAC would be poor. They are also popular on marine installations. For a drag or dyno-only truck, a water-to-air CAC plumbed to an ice water tank in the bed (rather than into the engine coolant) is the ultimate setup.

As found here~ http://en.wikipedia.org/wiki/Gas_compressor#Temperature

We're dealing with the latter two primarily. :)

Finally, Combined gas law