BASIC REFRIG. CYCLE

1. Presented By :
Hussein Lateef Thamer

2. Introduction
A major application area of thermodynamics is refrigeration, which is
the transfer of heat from a lower temperature region to a higher
temperature one .
Devices that produce refrigeration are called refrigerators, and the
cycles on which they operate are called refrigeration cycles.
The most frequently used refrigeration cycle is the vapor compression
refrigeration cycle in which the refrigerant is vaporized and condensed
alternately and is compressed in the vapor phase

3. Principles Of Refrigeration
 Liquids absorb heat when changed from liquid to gas
(latent heat of vaporization)
 Gases give off heat when changed from gas to liquid.
(latent heat of condensation)

4. The Ideal Vapor-compression Cycle:
1-2 Isentropic compression .
2-3 Constant pressure heat rejection .
3-4 Throttling in an expansion valve.
4-1 Constant pressure heat addition.
T-S diagram for the ideal vapor compression refrigeration cycle

5. The P-h diagram

6. Components of the vapor compression refrigeration cycle:
The refrigerant
comes into the
compressor as a low
pressure gas, it is
compressed and then
moves out of the
compressor as a high-
pressure gas.
1. Compressor

7. 2. Condenser
The gas then
flows to the
condenser. Here
the gas condenses
to a liquid, and
gives off its heat
to the outside air

8. 3. Expansion Valve
The liquid then
moves to the
expansion valve
under high pressure.
This valve restricts
the flow of the fluid,
and lowers its
pressure as it leaves
the expansion valve.

9. 4. Evaporator
The low-pressure liquid
then moves to the
evaporator, where heat
from the inside air is
absorbed and changes it
from a liquid to a gas, the
refrigerant moves to the
compressor where the
entire cycle is repeated

11. Co-efficient Of Performance (COP)
 The performance of refrigerators and heat pumps is expressed in
terms of co-efficient of Performance, defined as
 A rule of thumb is that the COP improves by 2 to 4 percept for
each °C the evaporating temperature is raised or the condensing
temperature is lowered.

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