What is Cooling System?- Types, and How it Works


What is a cooling system?

A vehicle’s engine-cooling system serves not just to keep the engine cool, but to also keep its temperature warm enough to ensure efficient, clean operation.

System components include a radiator to dissipate heat, a fan or fans to ensure adequate airflow for radiator cooling, a thermostat valve that opens when the desired operating temperature is reached and a water pump (or coolant pump) to circulate coolant through the engine, hoses and other components.

Most vehicles now employ an expansion tank that allows the coolant to expand, and exit, the cooling circuit when hot, and to return when the car is turned off and the engine cools. The cooling system also incorporates elements of the cabin’s ventilation system, because engine heat is used to warm the car’s interior.

Almost all automobiles employ liquid cooling systems for their engines. A typical automotive cooling system comprises:

  • A series of channels cast into the engine block and cylinder head, surrounding the combustion chambers with circulating liquid to carry away heat;
  • A radiator, consisting of many small tubes equipped with a honeycomb of fins to convect heat rapidly, that receives and cools hot liquid from the engine;
  • A water pump, usually of the centrifugal type, to circulate the liquid through the system;
  • A thermostat to control temperature by varying the amount of liquid going to the radiator; and
  • A fan to draw fresh air through the radiator.

Cooling system of ic engine

Most internal combustion engines are fluid-cooled using either air (a gaseous fluid) or a liquid coolant run through a heat exchanger (radiator) cooled by air. In the water-cooling system of cooling engines, the cylinder walls and heads are provided with a jacket through which the cooling liquid can circulate.

A cooling system in an internal combustion engine is used to maintain the various engine components at temperatures conducive to long life and proper functioning.

How does a car cooling system work?

A cooling system works by sending a liquid coolant through passages in the engine block and heads. As the coolant flows through these passages, it picks up heat from the engine. Once the fluid is cooled, it returns to the engine to absorb more heat.

Actually, there are two types of cooling systems found on motor vehicles: liquid-cooled and air-cooled.

Air-cooled engines are found on a few older cars, like the original Volkswagen Beetle, the Chevrolet Corvair, and a few others. Many modern motorcycles still use air cooling, but for the most part, automobiles and trucks use liquid-cooled systems and that is what this article will concentrate on.

A cooling system works by sending a liquid coolant through passages in the engine block and heads. As the coolant flows through these passages, it picks up heat from the engine. The heated fluid then makes its way through a rubber hose to the radiator in the front of the car.

As it flows through the thin tubes in the radiator, the hot liquid is cooled by the air stream entering the engine compartment from the grill in front of the car.

Once the fluid is cooled, it returns to the engine to absorb more heat. The water pump has the job of keeping the fluid moving through this system of plumbing and hidden passages.

What are the Parts of the Cooling System?

The cooling system’s sole function is to regulate the temperature at which the engine operates. If the cooling system, or any part within it, were to fail it would result in the engine overheating, which can lead to a number of major problems.

Overheating can cause head gaskets to blow and even engine blocks to crack if the issue is severe enough. The following are the main parts of the cooling system. Always pay attention to signs of cooling system failure, as described below.

The major components of the cooling system are the water pump, freeze plugs, the thermostat, the radiator, cooling fans, the heater core, the pressure cap, the overflow tank, and the hoses.

Engine Cooling System

1. Cooling Fan

The cooling fan is located at the very front of the vehicle and is designed to turn on when the coolant (we’ll talk more about this in a minute) begins to get to hot. It will turn back off once the coolant has lowered in temperature.

2. Radiator

The radiator is specially designed in order to remove the heat from the coolant by transferring it to the air blown through the radiator by the fan and incoming air from driving. Radiators are prone to leaking after years of use.

3. Water Pump

The water pump is what propels the coolant through the engine. A broken water pump will prevent your cooling system from operating, thus resulting in the engine overheating while driving.

4. Thermostat

The thermostat is what controls the operation of the cooling system, specifically turning the fan on and off.

5. Hoses

A series of rubber hoses connect the radiator to the engine in which the coolant flows through. These hoses can also begin to leak after many years of use.

6. Antifreeze/Coolant

The bread and butter of the cooling system is the coolant. This sweet-smelling, bright green fluid flows through passages in the engine, attracting heat from the engine. It collects the heat and transfers it to outside air inside the radiator.

Necessity of Cooling System

The cooling system serves three important functions. First, it removes excess heat from the engine; second, it maintains the engine operating temperature where it works most efficiently; and finally, it brings the engine up to the right operating temperature as quickly as possible.

The need of cooling systems in an IC Engine because of the following reason:

  • During the operation of an engine, the temperature inside the engine can go up to 2500 degrees centigrade (Source: How Stuff Works), which is above the melting point of the components used to make the engine. So, we need to use the cooling system to dissipate the heat as much as possible.
  • As we know, we also need a lubrication system for the proper functioning of the engine, but due to the high heat, the property of lubricating oil can be changed. That result seized the engine. So to avoid that we need to use a cooling system.
  • Sometimes due to the enormous heat, thermal stress is built-up inside the engine, so to minimize the stress we need to keep the engine temperature as low as possible.

What are the Types of Engine Cooling Systems?

Generally, there are two types of cooling systems, and those are:

  • Air Cooling System
  • Water Cooling System

1. Air Cooling system

Air cooling is a method of dissipating heat. It works by expanding the surface area or increasing the flow of air over the object to be cooled, or both. The addition of fins to a heat sink increases its total surface area, resulting in greater cooling effectiveness.

An example of the former is to add cooling fins to the surface of the object, either by making them integral or by attaching them tightly to the object’s surface (to ensure efficient heat transfer). In the case of the latter, it is done by using a fan blowing air into or onto the object one wants to cool.

There are two types of cooling pads are used in air cooling one is a honeycomb and another one is excelsior.

In all cases, the air has to be cooler than the object or surface from which it is expected to remove heat. This is due to the second law of thermodynamics, which states that heat will only move spontaneously from a hot reservoir (the heat sink) to a cold reservoir (the air).

When operating in an environment with lower air pressure like high altitude or airplane cabins, the cooling capacity has to be derated compared to that of sea level.

A rule-of-thumb formula 1 – (h/17500) = derating factor. Where h is the height over sea level in meters. And the result is the factor that should be multiplied with the cooling capacity in [W] to get the cooling capacity at the specified height over sea level.

Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures. In all combustion engines, a great percentage of the heat generated (around 44%) escapes through the exhaust, not through the metal fins of an air-cooled engine (12%).

About 8% of the heat energy is transferred to the oil, which although primarily meant for lubrication, also plays a role in heat dissipation via a cooler. Air-cooled engines are used generally in applications that would not suit liquid cooling, as such modern air-cooled engines are used in motorcycles, general aviation aircraft, lawnmowers, generators, outboard motors, pump sets, saw benches, and auxiliary power units.

Advantages of Air-Cooling System

These are some advantages of using Air Cooling Systems:

  • Light in weight
  • No antifreeze is required
  • This system can be used where water scarcity is there
  • Simple in design
  • Require less space
  • No tapping up of water, etc.
  • Prevents Electronics From Overheating.
  • Improves Work Performance

Disadvantages of Air-Cooling System

Air-Cooling Systems also has some disadvantages, and those are:

  • More noise in operation.
  • The coefficient of heat transfer of air is less, hence less efficient in working.

Examples of Air-Cooled Engine:

It is used in scooters, motorcycles, and tractors.

2. Water Cooling System

This type is the most commonly used type of system.

In a water cooling system, water jackets are provided around the engine cylinder or liners. The circulating water in these jackets absorbs the heat from the cylinder surface and then heated water is cooled by the air passing in the radiator.

The water cooling system consists of water jackets, water pump, radiator, thermostat valve, fan, belt, and pulley, etc. Although, water is the most commonly used cooling agent whereas, special coolants having better and desired properties like corrosion-free, higher boiling point, etc. are also available in the market and recommended also for obtaining and marinating higher engine efficiency.

Water Cooling System

The water is made to circulate in the water jackets continuously with desired pressure and speed with the help of a water pump driven by a belt. Generally, water pumps are of a centrifugal type and consist of water inlet and outlet with an impeller which makes the water to come out from the pump outlet by a centrifugal force.

The pump inlet is connected with the radiator at bottom to draw the coolant/water from the radiator. When the engine is cooled, the thermostat valve remains open and the same water/coolant is being circulated through the water jackets.

By the time, water/coolant gets heated, the thermostat valve is opened to make water pass through the radiator to dissipate heat by coming intact with the air passing through the radiator.

The radiator is located in the front of the tractor/vehicle and it consists of a water/coolant tank, tubes, and pressure cap on the tube. This pressure cap is used to prevent water evaporation and increase the pressure within the cooling system.

The temperature difference between the air outside and water inside the radiator is high, and the heat is dissipated more quickly from water to the air. The air is generated with help of fan and also by the forward movement of the tractor.

Generally, engine operates efficiently in the temperature range of 800C to 900C and it is always desired that the engine temperature should reach to this temperature as early as possible in cool weather conditions and remain in this temperature range only under excessive hot weather conditions.

The thermostat is designed to maintain this temperature range by regulating the temperature of water/coolant circulating in the water jackets.

Types of Water Cooling system

There are two types of water-cooling systems.

  • Thermosyphon
  • Pump circulation system

Thermosyphon System

The pump is not fitted in this system. Circulation of water is done due to the difference in densities between hot and cold water.

However, in these cooling systems, the rate of cooling is low. Nowadays its usage is limited because we need to maintain the water to a certain level. It is simple in construction and cheap.

Working of Thermosyphon System

The thermosyphon cooling systems operate on the principle of natural convection. Thermosyphon water cooling system is based on the fact that water becomes light on heating and,

The top and bottom of the radiator are connected to the top and bottom of the cylinder water jacket respectively with the help of pipes. The radiator is cooled by causing air to flow over it. Airflow is achieved by vehicle motion or a fan provided.

The heated water inside the cylinder water jacket becomes light and moves out of the upper connection pipe into the radiator and travels down from the upper tank to the lower tank, and rejecting heat as it travels.

This cooled water from the lower tank is passed into the cylinder water jacket and hence circulated again for the process.

The limitation of this systems is that this cooling depends only on temperature and is independent of engine speed.

Pump Circulation System

In this cooling system, the circulation of water is done by providing a centrifugal pump. Due to this pump, the rate of flow of water is more. And the pump is driven by a belt from a crankshaft.

Here radiator may be fitted at any place convenient to the designer.

Working of Pump Circulation System

In this system, the direction of cooling water flow is upward from the cylinder head to the top tank of the radiator, then down through the radiator core to the bottom tank. From the bottom tank, it moves through the lower radiator hose to the cylinder block water jackets by the help of the water pump, which circulates the water.

Water enters the engine at the center of the inlet side of the pump. The circulating pump is driven by a belt from the crankshaft. As engine speed increases, the flow of coolant increases.

Advantages of Water-Cooling System

These are some advantages of a Water-Cooling System:

  • In these types of cooling, we see a high heat transfer rate.
  • This type of cooling system is used where the size or power of the engine is more.
  • Thermal Conductivity is more
  • Water is easily available
  • Liquid has a high enthalpy of vaporization so that the efficiency of water cooling is more.

Disadvantages of Water-Cooling System

The disadvantages of Water-Cooling Systems are mentioned below:

  • Sometimes corrosion occurs inside the radiator or pipe or storage.
  • Due to scaling heat transfer rate is goes down after the long run, so it needs regular cleaning and maintenance.

Examples of Water-Cooled Engine:

All the modern engines (Cars, Bus, Trucks, etc.) nowadays use this type of cooling system.

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