Introduction to Refrigeration and Air Conditioning was explained in a detailed way. For more information, Visit https://mechanicalstudents.com/refrigeration-introduction-vapor-compression-refrigeration-system-vapor-absorption-refrigeration-system/

1. Introduction to
Refrigeration

2. Refrigeration may be defined as a process of
removing heat from a substance and pumping it to the
surroundings.
It also includes the process of maintaining and
reducing the temperature of a body below the general
temperature of its surroundings.

3. ● Thus in a refrigerator heat is prepared from low
temperature to high temperature.
● Theoretically, the refrigerator is a heat pump which
pumps heat from a cold body and delivers it to a hot
body.

4. ● Equipment used for removing the heat continuously
for maintaining a low temperature in a space is called
‘refrigerator’.
● Cycles on which it operates are called ‘refrigeration
cycles’.
● The working fluids used for carrying away heat are
called ‘refrigerants’ which are used in both
refrigeration and air conditioning equipment.
● Equipment used for air conditioning is called air
conditioners.

5. Applications of Refrigeration
Refrigeration is extensively used for increasing the
storage life of perishable items especially food
products, vegetables, fruits, milk, beverages, chilling
of water, ice formation, etc.

6. Unit of Refrigeration
The unit of refrigeration is expressed in terms of
“Tonne of Refrigeration” (TR).
One Ton of refrigeration: It can be defined as the
amount of refrigeration effect produced by the uniform
melting of one tone of ice (1000 kg) from and at 0°C in
24 hrs.

7. 1 Tonne of refrigeration (TR) =(335×1000)/ 24
where latent heat of ice = 335 KJ/Kg
= 13958.333 KJ/hr
= 13958.333/24 KJ/min
= 232.6 KJ/min

8. Methods for Refrigeration
● Refrigeration by evaporation
● Refrigeration by ice
● Refrigeration by the expansion of air
● Refrigeration by throttling process
● Refrigeration by dry ice
● vapor Refrigeration system

9. Refrigerants
Any substance which in the refrigeration system
absorbs heat from a low-temperature system and
delivers the heat so absorbed to a higher temperature
system is referred to as a refrigerant.
Classification of Refrigerants:
1) Primary Refrigerants
2) Secondary Refrigerants

10. ● Primary refrigerants: The working mediums or heat
carries which directly take part in the refrigeration
system and cool the substance by the absorption of
latent heat are called as Primary refrigerants.
Eg:- Ammonia, SO2, CO2, Methyl chloride, etc..
● Secondary Refrigerants: These are circulating
substances which are first cooled with the help of
primary refrigerants and then employed for cooling
purposes.
Eg:- Ice, Solid CO2, etc..

11. Desirable Properties of Refrigerants
Chemical properties:
● Non-toxic
● Non-flammable and non-explosive
● Non-corrosive to metal
Thermodynamic properties:
● Low freezing point
● Low boiling point
● High latent heat of vaporization

12. Physical Properties:
● Low specific heat
● A low specific volume of vapor
● Low viscosity
Other properties:
● Ease of leakage location
● Availability and low cost
● High COP

13. Difference between a refrigerator, heat
pump and heat engine:

14. heat engine:
In a heat engine, the heat supplied to the engine is
converted into useful work. If Q2 is the heat supplied
to the engine and Q1 is the heat rejected from the heat
engine, then the network done by the engine is given
by
We = Q2-Q1
So the performance of the engine or C.O.P is given by
Efficiency = We/Q
= Q2-Q1/Q2

15. Refrigerator:
● A refrigerator is a reversed heat engine, where heat is
pumped from low temperature (cold body-Q1) to high
temperature (hot body-Q2). So, work WR is required
to be done on the system.
WR = Q2-Q1
The performance of a refrigerator is the “ratio of the
amount of heat taken from the Cold body Q1 to the
amount of work to be done on the system WR.
● (C.O.P)R = Q1/ WR = Q1 / (Q2-Q1)

16. heat pump:
Any refrigerating system is a heat pump, which
extracts heat from a cold body and delivers it to a hot
body.
Thus there is no difference in the operation cycle of a
refrigerator and a heat pump.
The main difference between them is in their operating
temperature’s.

17. ● The main difference between them is in their operating
temperature’s.
● A refrigerator works between cold body temperature
(T1) and atmospheric temp (Ta) whereas the heat
pump operates between hot body temp (T2) and the
atmospheric temperature (Ta).
● A refrigerator used for cooling in summer can be used
as a heat pump for heating in the winter season.
so Wp = Q2-Q1
● (C.O.P)hp = Q2/ WR
= Q2 / (Q2-Q1)
Where hp-heat pump

18. For Further information, Visit
Refrigeration:Introduction, Vapor
Compression Refrigeration Cycle & Vapor
Absorption Refrigeration Cycle