Page 173 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

MODULE 7 : Engine Cooling System

LESSON 47 - 56: Engine cooling system Coolant, types,

and its properties

Objectives

At the end of this lesson you shall be able to
• explain properties of coolent
• explain types of coolent
• explain cooling system.

Introduction of cooling system

Introduction
As a result of the thermal energy generated during the operation of the engine, the temperature of the engine
keeps increasing continuously. Therefore, there is a need to control the temperature of the engine. To eliminate
unnecessary heat of the engine or to control the temperature of the engine, cooling systems are used, which are
of two types – air cooling and water cooling.
Need of cooling system
The cooling system in engines is arranged to protect the engine from the ill effects of the heat generated in it. In
the absence of a cooling system, the following defects are likely to occur inside the engine:
1 Pre-ignition
2 Detonation

3 Knocking
4 Burning of valves and
5 Damage to bearings etc. due to lack of oil.
Technical terminology related to cooling
The technical terminology related to cooling of vehicles is as follows:
1 Boiling Point
The fixed temperature at which a liquid starts converting into gas is called the boiling point or vapor point of the
liquid and this process is called boiling; For example, the boiling point of water is 100°C and the boiling point of
diesel in a diesel engine is 180°C-360°C.
2 Heat Transfer
Transfer of heat from one place to another can be done mainly through three methods – conduction, convection
and radiation. In the first two methods, a medium is required for heat transfer, whereas it is not necessary for the
radiation method.
Radiation method is the fastest method of heat transfer, in which heat is transferred from one place to another in
the form of electromagnetic radiation. A brief description of these three methods of heat transfer is given below.
i Conduction
The process of heat transmission, in which the particles of the object do not move from their place, but allow heat
to pass from one place to another. conduction process is called
ii Convection
In this process, heat transfer occurs due to the particles of the substance of the medium moving from one place
to another. This process happens in two ways
• natural convection
• Ford Conviction

160