Fig 1.1 Content of chapter 1 


 Refrigeration :
Refrigeration is process of removing heat from lower temperature of body and transferring to higher temperature of body. In simple word creating lower temperature than surrounding.It works on the second law of thermodynamics.

Refrigerating machine :
It is device which transfer heat from lower temperature of body to higher temperature of body. It maintain the temperature of body below surrounding temperature.

Necessity and applications of refrigeration : 
1. Ice making. 
2. Transportation of food items above and below freezing. 
3. Industrial Air – Conditioning. 
4. Comfort Air – Conditioning. 
5. Chemical and related industries. 
6. Medical and Surgical instruments. 
7. Processing food products and beverages. 
8. Oil Refining. 
9. Synthetic Rubber Manufacturing. 
10. Manufacture and treatment of metals. 
11. Freezing food products. 
12. Manufacturing Solid Carbon Dioxide. 
13. Production of extremely low temperatures (Cryogenics) 
14. Plumbing. 
15. Building Construction 
16. Food processing, preservation and distribution. 
17.Chemical and process industries. 
18.Industrial, such as in textiles, printing, manufacturing, photographic, computer rooms, power plants, vehicular etc. 
19.Special Applications such as cold treatment of metals, medical, construction, ice skating etc. 

Difference between Heat engine,Heat pump and Refrigerator 

1. Heat engine 
It is device in which heat is supplied as input and it convert this heat into useful work. we can understand by following diagram. 
Fig 1.2 Heat Engine 
Above figure shows basic diagram of heat engine will clear all doubts regarding heat engine.
Figure shows two bodies hot body which is at T2 temperature and cold body which is at T1 temperature.E indicate heat engine. Heat supplied to engine is Q2 and heat rejected is Q2 and work done shown by W as above.
Hence we can say than heat engine takes input Q2 as input and converted into useful work W, but all heat can not be converted into useful work some amount of heat is rejected and is indicated by Q1. we discuss in details in next blog why all heat can not converted into useful work.The performance of heat engine is expressed by its efficiency.Efficiency = work-done/ heat supplied
Work-done = Q2 - Q1
Heat supplied = Q2
Fig 1.3 Efficiency of heat engine 
we can relate this example to our day to day life bike engine. In our bike we feel petrol as fuel, heat generated by petrol is input to bike engine. and useful work by engine is moving bike foreword and heat rejected by exhaust outlet of bike. I think we have cleared all about heat engine.

2. Heat Pump
It is device used to maintain the temperature of body or system higher than that of surrounding by supplying heat to the room.For example , in a winter season, where the temperature of surrounding is very low says 7 degree. In this case heat is supply to room maintain temperature above the surrounding.
Fig 1.4 Heat Pump
Above figure shows basic diagram of heat pump in which output is hot body that is Q2. Heat is adsorbed from low temperature body with the help of some external work Wp and transferred to high temperature of body.The performance of heat pump is expressed by COP term.

 COP(Coefficient of performance) :
It is the ratio of desired effect to the external work supplied to the system. we discuss in detail in next blog.
Fig 1.5 COP of heat pump

3. Refrigerator
As mention in starting It is device which transfer heat from lower temperature of body to higher temperature of body. It maintain the temperature of body below surrounding temperature.
Fig 1.6 Refrigerator 
Above figure shows basic refrigerator diagram. Extracting the heat from cold body(Q1) and delivering it to a hot body (Q2). In doing so, work
WR is required to be done on the system.
According to First law of thermodynamics,
Wr = Q2 - Q1
The performance of refrigerator is expressed by COP term.
Fig 1.7 COP of refrigerator 
from above heat pump and refrigerator we can find that relation is ,
(C.O.P)pump = (C.O.P)refrigerator + 1 

Some Basic terms
1. Refrigeration effect: the removal of heat from cold body is known as refrigerating effect.
2. Capacity of Refrigerator : The rate at which the heat is removed from cold body is called capacity of refrigerator.
3. Unit of refrigeration: Refrigeration effect is expressed in watt or kilowatt. Apart from this, refrigeration effect also expressed in 'tons of refrigeration' or 'TR' 
4. 1 TR : amount of heat required to convert 0 degree water to 0 degree ice in 24 hours. 
1 TR = 210 kJ/min = 3.5 kW 
5. Refrigerant : It is the working media or working substance (liquid or gas) which works in heat pump and which extract heat from cold body and gives it to hot body. 
In next blog we are going to see Non conventional methods of refrigeration system.