What are intercoolers?
- Author: SPELAB Mechanical Engineer (focusing on car modification for 10 years)
It is a cooling device, as implied by the name "intercooler." In actuality, an intercooler is a heat exchanger used to cool the air that is to be fed to the engine for fuel combustion. We must become more familiar with the fundamentals of the combustion process in order to see why supplying cool air to engine is a stringent requirement.
Basic of combustion process
The combustion process relies heavily on oxygen, thus feeding the engine with a sufficient amount of high-quality oxygen is an important part of that process. We all know that in order for fuel to burn entirely, the following conditions must be met
- Sufficient amount of air to completely burn the fuel
- Availability of denser air (cold air)
From school education we all know that:
Since cool air is denser than hot air, it has a higher concentration of oxygen. The amount of oxygen delivered to the combustion chamber affects how efficiently an engine can burn its fuel.
However, it is evident that not all of the fuel will be burned if there is a restricted supply of oxygen in the chamber at the time of combustion. Unburned fuel is seen as trash, therefore if it is burned improperly, we will lose power and produce more pollutants into the environment. Therefore, we must supply the engine with enough oxygen to ensure proper combustion and, ultimately, improved engine performance. The intercooler is a heat exchanger that reduces the temperature of hot air and supplies the engine with cool, dense air for improved combustion.
What does intercooler do?
An intercooler is a device that is used to cool the compressed air that is produced by a turbo charger or a supercharger before it enters the engine. It works by reducing the temperature of the compressed air, which allows the engine to burn more fuel and produce more power. Intercoolers are commonly used in high performance engines, such as those found in sports cars and race vehicles, as well as in some heavy-duty diesel engines. Intercoolers improve the efficiency of engines because it directly improves the combustion of the fuel.
In most cases, intercoolers are absent from naturally aspirated engines. For most engines, a cold air intake is typically used to supply the engine with the necessary cool air. However, intercoolers play a crucial role in high-performance automobiles and trucks that use superchargers and turbochargers. The forced induction produced by turbochargers and superchargers increases air compression and subsequently its internal energy but also elevates air temperature, which reduces air density and hence the amount of oxygen available for fuel combustion. The heat generated by this compression effect raises the air's temperature to 140oC. However, air between 30 - 50 oC is ideal for combustion. Thus, an intercooler is used to reduce the temperature of this heated air to the desired level. However, if we allow this hot air to reach the intake manifold directly, we may encounter problems like knocking, early ignition, engine stuttering, power loss, and many other anomalies. Therefore, cooling the compressed air becomes extremely crucial for us while using forced induction. The combustion process benefits from the cooled air, which ultimately increases the engine's output in all respects.
Types of Intercoolers
A straightforward heat exchanger known as an intercooler cools combustion air by transferring its heat to a cooling medium, such as air, water, or any other liquid. The various heat exchanger types used in the automotive sector are described here.
Air to air cooled intercooler
An air to air cooled intercooler is a type of intercooler that uses ambient air as a cooling medium to reduce the temperature of compressed air produced by a turbocharger or a supercharger before it enters the engine. It typically consists of a heat exchanger with a series of fins that increases the surface area for heat dissipation. The compressed air is passed through the intercooler where it is cooled by ambient air that flows through the fins.
This type of intercooler is normally found in vehicles with limited space and are typically mounted in front of the radiator or front bumper. The advantage of air to air cooled intercooler is its simplicity and low cost but in very hot environment their efficiency is not up to the mark.
Air to water cooled intercooler
An intercooler that employs coolant, often water combined with antifreeze, as a cooling medium to lower the temperature of compressed air produced by a turbocharger or supercharger before it enters the engine is known as an air-to-water cooled intercooler. It typically consists of a heat exchanger with a series of tubes and fins, through which the compressed air and the coolant flow in separate channels. The compressed air is passed through the types of intercooler where its heat is taken away by the coolant flowing through the fins.
This type of intercooler is more efficient than air to air cooled intercooler as it can dissipate heat more effectively, because coolant/ water conducts heat better than air and therefore is suitable in hot temperatures. Being more compact, it is an ideal fit for tight engine bays, but is usually more expensive and complex than air to air intercoolers.