When you are cruising your car along the highway, thousands of explosions occur in the engine per minute. Every explosion occurs in a sequence in different cylinders of the engine. This explosion is a combustion process which is a highly exothermic reaction producing enormous heat and if not controlled will damage the engine. To ward off this, engines use a cooling system.
Generally, energy expenditure in an engine goes like this
- Useful work ( driving the crankshaft) – 25%
- Exhaust losses– 35%
- Heat lost to cylinder walls– 30%
- Friction losses – 10%
The 30% heat loss through the cylinder walls raises the temperature of the cylinder block. Thus, it gets necessary to eliminate this heat by some system. There are two types of cooling systems for an engine.
Air cooling system in engines
In this engine, ambient air passes around the engine to extract heat. For effective cooling, there is a need for a large surface area of the engine.
Also, due to engine alignment limitations in the vehicle generate the need for additional surface area in constrained size. For it to happen, the engine has thin metal strips, called fins, on the cylinder wall. The cooler air passes effectively around the engine and takes away the excess heat.
The general application of an air cooling system is in the motorcycles engine.
- It is simple in construction as fins are the part of the engine block
- It works well where liquid cooling systems fail, like in the places having freezing temperature.
- The maintenance is easy or negligible.
- It has fewer components unlike a liquid cooling system.
- The efficiency is low, as there is no uniform cooling.
- Can draw a significant amount of power from the engine, when it uses a fan.
Liquid cooling system in engines
These engines have intricately designed cooling jackets in the engine block. These jackets contain coolant which circulates to absorb heat and transfer it to heat ex-changer outside the engine. After, moving through heat ex-changer this coolant cools and again recirculates in the engine for heat absorption.
The engine requires the ideal temperature to work efficiently, therefore, taking out excess heat from the engine doesn’t do any good. Therefore, a thermostat is placed between the engine and the heat ex-changer. When the coolant temperature plunges below the preset temperature, the thermostat close the valves to stop the coolant flow to the heat ex-changer. The coolant will continue to flow in the engine until its temperature again rises above a set temperature. This mechanism helps in keeping the engine maintain ideal temperature, therefore, getting maximum efficiency.
- It is more effective than an air cooling system.
- Consumes less power from the engine than an air-cooled system
- Heat exchanger can be placed at per the convienence.
- It is heavy and requires maintenance.
- Coolant is used for heat absorption, which needs to be replaced after some time. Also, its composition needs to be accurate, otherwise, it can corrode the engine.
Cooling systems in electric cars
The cooling system in electric cars is somewhat similar to the ones used in internal combustion engines.
The non-conductive liquid coolant can be used for cooling the batteries. However, the electric vehicles are in their nascent stage of development, so as of now we can say that there could be different methods to cool them.
Overheating Engine Problem
The combustion inside the cylinder occurs at a particular position of the valves and the piston ( valve timing diagram). This gives the maximum efficiency.
The air-fuel mixture is injected in the combustion chamber and it is ignited when maximum force can be applied on the piston. However, when the engine gets excessively heated, the air-fuel mixture pre-ignites and this disrupts the movement of piston. Therefore, the desired power is not attained from the engine.
Due to pre-ignition and not withdrawing excess heat from the engine, the heat cycle of the engine can reach up to the melting point. Thus, permanently deforming the structure of the engine and its various components.
Excess heat burns the engine oil which serves the purpose of lubrication between the moving parts. Once the lubricant is burnt, the heat from the engine and friction can seize the moving parts. This could be generally seen in piston seizing.
This all sums to keep the cooling system in your car work properly. Otherwise, the damages occurring to the engine can break your pockets.