What does an Intercooler do?
- Author: SPELAB Mechanical Engineer (focusing on car modification for 10 years)
The name ‘intercooler’ suggests that it is some type of cooling device. Indeed, an intercooler is a heat exchanger which is used to cool the air that is to be supplied to the engine for burning the fuel. The question is that what is the need to cool the air. To understand why cooling is significant, we need to be updated with the basics behind combustion process.
Basic of combustion
As oxygen plays a crucial role in the combustion process, therefore, providing quality and quantity oxygen to the engine is an integral point in combustion process and therefore is deeply focused. We all know that, for fuel to burn completely, one must ensure the following
- Sufficient amount of air to completely burn the fuel
- Availability of denser air (cold air)
From school education we all know that:
Cool air is denser, which means it has greater concentration of Oxygen as compared to hot air. The ability of the engine to burn the fuel completely, increases with the amount of oxygen supplied to the combustion chamber.
However, if limited amount of oxygen is available in the chamber at the time of combustion, then it is obvious that all the fuel won’t be burnt. The unburnt fuel is considered a waste and consequently with improper burning we will lose power and it will also contribute towards environmental emissions. Therefore, we need to provide sufficient quantity of oxygen to the engine for proper burning and eventually for better performance from the engine. The intercooler is a heat exchanger which cools the hot air and provide engine with cool dense air so that we can have better combustion.
What does intercooler do?
Intercoolers improve the efficiency of engines because it improves the quality of oxygen, which is an integral component in burning the fuel and thus ensuring better combustion eventually enhances engine’s power and efficiency.
On naturally aspirated engines, intercoolers are normally not found. For normal engines we usually use a cold air intake which provides the engine with the required cool air. However, with high performance cars and trucks which have superchargers and turbochargers involved, intercooler serves as an integral component. Because with this forced induction provided by turbochargers and superchargers, air compression is increased and consequently its internal energy but it also raises the temperature of the air, thus decreasing the density of air which means reducing the amount of oxygen for burning the fuel. The heat provided by this compression effect increases the temperature of air up to 140oC. However, for combustion it is preferred to have cool air around 30 - 60 oC. Thus, this heated air is cooled to the required temperature with the help of an intercooler. However, if this hot air is directly allowed to enter the intake manifold, then we will experience flaws like knocking, premature ignition, engine hesitation, loss of power and many other abnormalities. Thus, with forced induction it gets really important for us to cool the compressed air. This cooled air improves the combustion process and eventually engine’s output in every aspect.
Types of Intercoolers
Intercooler is a simple heat exchanger which cools the combustion air by transferring its heat to the cooling medium which is either air or water or any other liquid. Following are explained the types of heat exchanger in automobile industry.
Air to air cooled intercooler
This intercooler works similar to the radiator of the engine. Air cooled intercoolers works by directing compressed air past a number of cooling fins and via a maze of tiny tubes. These cooling fins absorb heat from the hot compressed air, which is then quickly cooled by air coming from outside the driving vehicle.
The air after it is cooled is fed to the intake manifold of the engine. Many turbocharged vehicles use air-to-air intercoolers, because due to their simplicity, light weight, and low price.
Air to water cooled intercooler
As the name suggests, this intercooler cools the compressed air with the help of water. Cool water is pumped through the unit from one side and air from another side. After the water extracts the heat from the air, air is ready to be fed to the intake manifold, whereas, that water has to be cooled now. For cooling this heated water, it passes either through the radiator or some cooling circuit before it enters again the intercooler. For even better cooling characteristics, one can change the water with some other liquid which has better heat absorbing capabilities like the coolants we have in our radiators.
These intercoolers are smaller in size because of the fact that water conducts heat better than air and is therefore suitable for a variety of temperatures. However, the increased complexity, cost and weight makes them less favorable for vehicles.