Refrigeration & Equipment Engineering

Unit 2 - Refrigeration Systems

2.1.Introduction
Refrigeration contributes to the raising of living standards for the people of all lands.The advances made in refrigeration in recent years are the result of a team approach in which technicians,craftsmen,engineers,scientists,and others,pool their skills and knowledge.The foundation on which new substances and materials are built are provided by science.This knowledge is applied to the refrigeration field by those who design,manufacture,install and maintain refrigeration equipment and practical application.The application of refrigeration principle is limitless.The most common use,and one that is readily recognized is the preservation of food.Almost all products in the home,on the farm,in business,in industry or in the laboratories are in some way affected refrigeration.Thus,refrigeration has become an essential commodity in modern living.

The most important thing in refrigeration is the removal of heat.The natural tendency of the heat to flow from warm body to cold body. If two substances are at the same temperature, no heat flows between them. If there is a temperature difference between them, heat flows from the warm substance to the colder one. Thus it is said that heat is transferred from higher temperature to lower temperature. The heat that must be transferred enters a refrigerated space in the following ways.

• The heat leaks through the wall surrounding the space to be cooled.
• As the door open, outside heat rushes into the refrigerated space.
• The heat of the food stuff material is introduced into the refrigerated space.
• So all the heat enters a refrigerated space should be removed by means of refrigeration.