The working of a car radiator

When a car engine is running there are continuous explosions in the cylinders of the engine. We know for a fact that fire creates heat, these explosions create a lot of heat within the engine. If the heat is not controlled it can damage the engine and cause it to cease. For this reason every car has a cooling system. The cooling system on a car is managed by a radiator and some other components. All cars today are liquid cooled. There are passages around the engine and the cylinders. The cooling system circulates coolant through those passages in the engine. The liquid absorbs the heat from the engine as it passes through.

In earlier times cars were cooled by passing water around those passages. Cars operate in very different conditions across the world. From well over 100 F in desserts to below freezing temperatures in snow. The liquid that is used to cool the engine cannot evaporate or freeze because if it does the cooling system will not work and the engine will overheat until it ceases. As a result the fluid used to cool the engine is a mixture of water and ethylene glycol which is called coolant. This mixture has a boiling point that is much higher than that of water at 235 F, and has a freezing point that is well below that of the freezing point of water at -55 C. In addition to this there is a pressurised radiator cap. The boiling temperature of any liquid goes up when it is pressurised, as a result the pressurised radiator cap increases the boiling point of the coolant. If the temperature exceeds the boiling point the fluid will flow out of the radiator cap through a valve. The spring pressure of the cap determines how much maximum pressure of the cooling system. The coolant flows through the overflow pipe into the bottom of the overflow tank. Once the radiator cools back down vacuum is created in the cooling system that opens another spring loaded valve that pulls the coolant back into the system. 

It may all appear to be very simple, the cooling system starts working when the engine is turned on and when the engine is turned off the cooling system goes off too. It’s not that simple however. The engine needs to run at a set temperature because at that temperature the combustion chamber is hot enough to vaporise the fuel completely, resulting in cleaner emissions. The engine oil used to lubricate the various parts of an engine is thicker at low temperatures, once the engine is heated up the viscosity of the oil goes down and it becomes thinner which makes it easier to flow in the engine and lubricate various parts. This means that the engine wastes less energy to move its parts. Also, metal parts wear out less when they are properly lubricated. 

In order to ensure that the engine reaches its set temperature as quickly as possible there is a thermostat is the radiator. At low temperatures the outlet to the radiator is blocked, no coolant flows anywhere in the system so that the engine can heat up as quickly as possible. Once the temperature rises to about 180 and 195 F the thermostat starts to open up and lets the coolant start circulating around the engine. When the liquid passing through the engine has absorbed the heat it moves onto the radiator in which there are a series of pipes and in the radiator which has air passing through it due to forward motion of the car. There is also a fan that turns on to assist airflow onto the pipes which reduces the temperature of the coolant flowing through it. A centrifugal pump connected to the crankshaft of the engine ensures that coolant is constantly pumped around the engine to the radiator and back in order to maintain a set engine temperature. The pipes in a radiator through which the coolant flows sometimes has a turbulator inserted in it so that the there is turbulence in the fluid flowing through it to ensure that the fluid in the middle of the pipe is as cool as the fluid in contact with the pipes. This ensures quicker cooling of the engine. 

Cars with automatic transmission have a separate circuit for cooling the transmission fluid in the gearbox. The oil from the gearbox is pumped to a heat exchanger inside the radiator. 

Heaters in cars also operate with the help of the cooling system. There is a heater core located in the dashboard of a car. When the heater is turned on the core draws warm coolant from the cylinder head and then returns the coolant to the pump. Air is blown onto the hot coolant through the core to pass warm air through the air vents in the car. 

Always make sure that there is enough coolant in the car so that the engine does not heat up and damage the car. If the temperature gauge shows that the engine is hotter than it should be check the coolant level. If there happens to be enough coolant take the car to a workshop to have it inspected. An overheated engine can easily cease and the cost of an engine rebuild is massive. We hardly pay attention to the temperature gauge in the instrument cluster, its best we start doing so.