V.c. CYCLE

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R.A.C. Assignment
Topic: V.C. Cycle
Submitted To, Submitted By,
Mr. Aditya Mishra Sir Chinmay Sharma(K10881)
B.tech (Mechanical)
sem./year:- 6th/ 3rd

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COP of Vapour Compression Cycle
Definition of Refrigeration:
Refrigeration is the process of Producing lower temperature as
compared to surrounding. To maintain lower temperature
continuously, heat must be extracted continuously. Hence
Refrigeration system must operate in a cycle.

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Vapour compression Refrigeration System:
There are four component in Vapour compression cycle.
1. Compressor:- Compresses the refrigerant to high pressure and
temperature from low pressure and temperature.
2. Condenser:- The latent heat of refrigerant is removed by circulating water
or atmospheric air.
3. Expansion Valve:- In the throttle valve where the pressure is reduced at a
controlled rate.
4. Evaporator:- A liquid-Vapour mixture refrigerant then enters the
evaporator at low pressure where the latent heat of evaporation is converted
into vapour and the cycle repeats.

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Fig:- The P-h diagram is another convenient
diagram often used to illustrate the refrigeration
cycle.

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Determination of COP:
Assumptions made for drawing T-S and P-h Diagram:
1. The refrigerant leaving the evaporator is dry and saturated.
2. The compression of vapour in the evaporator is isentropic.
3. There is no sub cooling of the refrigerant in the condenser.
4. There is no pressure losses in the system.
Conditions of vapour at the end of compression:
There are three different conditions at which the refrigerant from the compressor.
a. Vapour is dry and saturated.
b. Vapour is wet condition.
c. Vapour is superheated condition.

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COP Of V.C. Cycle
Apply Steady flow energy equation ( Neglect K.E & P.E changes)
1. Compressor:
Q1-2 + C1
2/2 + Z 1 + h1 = W1-2 + C2
2/2 + Z 2+ h2
W1-2 = - ( h2 – h1)
2. Condenser:
Q2-3 + C2
2/2 + Z 2 + h2 = W2-3 + C3
2/2 + Z 3+ h3
Q2-3 = - (h2 - h3)
3. Throttle Valve:
Q3-4 + C3
2/2 + Z 3 + h3 = W3-4 + C4
2/2 + Z 4+ h4
h3 = h4 (Isenthalpic process)
4. Evaporator:
Q4-1 + C4
2/2 + Z 4 + h4 = W4-1 + C1
2/2 + Z 1+ h1
Q4-1 + h4 = h1
Q4-1 = h1 – h4

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Co-efficient of Performance: It is the ratio of net refrigerating effect to the
work required to produce that effect.
Co-efficient of performance = Refrigerating effect/ Work input
= ( h1 – h4 ) / (h2 – h1)

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Effects of variation of properties on the performance
of Vapour compression cycle:
Case 1:- Decrease in Evaporator:
RE= h1-h4
Win=h2-h1
COP= RE/Win

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• Effects:-
Reduction in Refrigeration effects
Increase in work input
Decrease in COP
Decrease in volumetric efficiency due to increase in pressure
ratio.

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RE= h1-h4
Win=h2-h1
COP= RE/Win
• Case 2:- Increase in condenser pressure

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• Effects:-
Reduction in Refrigeration effects
Increase in work input
Decrease in COP
Decrease in volumetric efficiency due to increase in pressure
ratio.

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RE= h1-h4
Win=
COP= RE/Win
• Case 3:- Superheating

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• Effects:-
Increase in Refrigeration effect
Increase in work input due to temperature at the inlet to
compressor increase.
COP may increase or decrease depending on the refrigerant. In
case of R- 12 superheating result in increase in COP where as in
case of NH3 superheating results in decrease in COP.

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