Gasoline engines have improved tremendously over the last several decades. Still, even if today’s engines are night and day compared to earlier models, they’re still inefficient at transforming chemical energy into mechanical power. Anyone with auto technician training knows that when a car is active, a lot of the gasoline’s energy will be transformed into heat. The main task of the cooling system, therefore, is to keep the engine from overheating. To do so, it will need to transfer all this heat to the air.
Cooling System 101
Fuel is constantly burning inside the engine. Some of this heat is expelled through the exhaust system, but the rest stays inside and heats up the engine. The intention of the cooling system isn’t to make the engine cold. Instead, it seeks to keep the engine at a constant temperature, which allows it to be more efficient and emit less pollution. The engine runs optimally when its coolant is about 93 degrees Celsius in temperature. Metal parts wear out less quickly at this temperature, while the combustion chamber is warm enough to vapourize the fuel. The oil used to lubricate the engine is also thinner, meaning the engine parts can move more freely.
Most cars today are liquid-cooled, though it might interest students of auto mechanic schools to know that several older models used to be air-cooled. With a liquid-cooled car, the cooling system circulates a fluid through pipes in the engine. As this liquid passes, it absorbs some of the heat from the engine. When the liquid exits the engine, it passes through the radiator, which blows the heat into the air through an exchanger.
Type of fluid
The fluid that most cars use is a mixture of water and ethylene glycol, also known to anyone with auto mechanic training as antifreeze. Adding ethylene glycol to water improves the boiling and freezing points of water, which can’t be used by itself as a fluid to hold heat.
The cooling system itself uses pressure to further raise the boiling point of the coolant. Not unlike a pressure cooker, in which boiling temperature is higher, the boiling temperature of coolant is higher if you add pressure to the system. By adding pressure, the boiling point is raised by another 25 Celsius, meaning the coolant can withstand the higher temperatures. The antifreeze added to the coolant also contains additives, which allow it to resist corrosion.
Aluminum radiators are what most modern cars use. These radiators are made by flattening aluminum tubes, creating thin aluminum fins. The coolant flows through many tubes mounted in a parallel arrangement, and the fins take the heat from the tubes and transfer it to the air flowing through the radiator.
Radiators also usually have a tank on each side. Inside the tank is a transmission cooler, which functions not unlike a radiator within a radiator. However, instead of exchanging heat with the air, the oil exchanges heat with the coolant in the radiator.