1. Mechanical Engg. Department
Geeta Engineering College
Naultha Panipat

2. CONTENT
 Introduction
 Heat Engine
 Refrigerator
 Heat Pump
 Unit of Refrigeration
 Vapour Compression Refrigeration System
 Difference between Vapour and Air Refrigeration System
 Cooling Tower
 Evaporative Condenser

3.  Refrigeration: It is a process of reducing and maintaining the
temperature of a body below the general temperature of its
surrounding.
 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 engine, then the net work done by the
engine is given by
WE =Q2 – Q1

4.  Refrigerator: It is a device which is used to maintain the
temperature of a body lower than the atmospheric temperature.
This is done by extracting the heat Q1 from the cold body and
delivering it to a hot body. In doing so, work WR is required to
be done on the system. Its C.O.P. is given by:

5. Heat Pump: It is a device which is used to maintain the
temperature of any space or body above the atmospheric
temperature.
This is done by delivering the heat Q2 to the hot body and
extracting it from a low temperature body. In doing so, work WP
is required to be done on the system.
The cycle of operation of both refrigerator and heat pump are
same the only difference is the desired effect.
Its C.O.P. is given by:

6.  Unit of Refrigeration:
The practical unit of refrigeration is ‘Tonne of refrigeration’ (TR).
A tonne of refrigeration is defined as the rate of heat extraction
which is equal to the rate of heat supplied for uniform melting of
one tonne (1000Kg) of ice at 00C in 24 hours.
Since the latent heat of ice is 335 KJ/Kg, therefore one tonne of
refrigeration
1TR= 1000 x 335 KJ in 24 Hours
In actual practice one tonne of refrigeration is taken as equivalent
to 210 KJ/min or 3.5 KW.

7. Vapour Compression Refrigeration System:
The main parts of the vapour compression refrigeration system
are:
1. Compressor
2. Condenser
3. Expansion valve
4. Evaporator
1. Compressor: The low pressure and temperature vapour
refrigerant from evaporator is drawn into the compressor
through the inlet valve, where it is compressed to a high
pressure and temperature.
Then this high pressure and temperature vapour is discharged
into the condenser.

8. Diagram and T-S and P-V Plot
Vapour compression refrigeration system

9. 2. Condenser: The condenser consists of coils of pipe in which
the high pressure and temperature vapour refrigerant is cooled
and condensed. The refrigerant, while passing through the
condenser, gives up its latent heat to the surrounding
condensing medium which is normally air or water.
3. Expansion valve: The function of the expansion valve is to
allow the liquid refrigerant under high pressure and
temperature to pass at a controlled rate after reducing its
pressure and temperature.
4. Evaporator: An evaporator consists of coils of pipe in which
the liquid-vapour refrigerant at low pressure and temperature
is evaporated. In evaporating the liquid vapour refrigerant
absorbs its latent heat of vaporisation from the medium which
is to be cooled.

10. Difference between Vapour Refrigeration System and Air
Refrigeration system:
The components of both the refrigeration systems are shown

11. Air refrigeration systemVapour compression refrigeration system

12. Advantages of Vapour compression refrigeration system
over Air refrigeration system
 Smaller size for a given refrigerating capacity
 Higher coeff. of performance
 Lower power requirements for a given capacity
 It can be used over large range of temp.