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M501.4 1
Name : A.V.Raghunatha Reddy Designation : Lecturer Branch : Mechanical Engg.Institute : E.S.C.Govt.polytechnic,NandyalYear/Semester : V semesterSubject : Refrigeration and Air conditioningSubject Cod : M-501Topic : Fundamentals of Refrigeration
and Air Refrigeration Duration : 50 min.Sub Topic : Unit of refrigerationTeaching Aids : PPT, Animations
DEPARTMENT OF TECHNICAL EDUCATION ANDHRA PRADESH
M501.4
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In the previous class we had studied about
• Steam jet refrigeration
• Liquid nitrogen refrigeration
• Applications of refrigeration
M501.4
Recap
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Objectives
• Define the unit of refrigeration
• Define the Coefficient of performance
• Solve the problems on the above
On completion of this period you would be able to
M501.4
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In this period we will study
• unit of refrigeration
• Coefficient of performance
• problems on the above
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The unit used in the field of refrigeration to
measure the rate of heat transfer is known
as Ton of refrigeration
Unit Of Refrigeration
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Ton of Refrigeration
The amount of refrigeration effect produced by
uniform melting of one ton of ice from and at 00c in
24 hours
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• As per American units, 1ton = 900 kg.
• Latent heat of fusion of ice = 336 kj/kg
Ton of Refrigeration
• Refrigeration effect of 1ton ice in 24 hours = 336X900 kj
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1 TR = (336 X 900) / 24 = 12600kj/hr
Ton of Refrigeration
1 TR = 12600 / 60 = 210kj/min
1 TR = 210 / 60 = 3.5kj/sec
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A refrigerating machine having capacity
cooling effect of 210kj/min or 3.5kj/sec is
rated as one ton machine
One Ton Machine
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The amount of heat required to change the
temperature with out the change of state of substance
is called sensible heat
Sensible heat
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Latent heat
The amount of heat required to change the state
of substance without change of temperature is
called Latent heat
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Latent heat of vaporisation
The amount of heat absorbed during change of
state from liquid to vapour is called Latent heat
of vaporisation
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Latent heat of condensation
The amount of heat rejected during change of
state from vapour to liquid is called Latent
heat of condensation
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The cooing effect produced by a refrigerating
machine in given time is known as
refrigerating effect
Refrigerating effect
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Coefficient Of Performance
It is defined as ratio of refrigerating effect
produced by a refrigerating machine in a given
time to the work supplied during the same time
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• COP is also called as Energy Ratio
• COP =
Coefficient Of Performance
N = Refrigerating effect in kj/min
W = work supplied in kj/min
W
N
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The theoretical values of N and W may be
obtained by the application of laws of
thermodynamics. The COP obtained in this way
is known as Theoretical COP
Theoretical COP
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Actual COP
The actual measured values of N and W
obtained during a test. The COP obtained with
these values is known as Actual COP
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Relative COP
The ratio between actual COP and theoretical
COP is known as Relative COP
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COP of Heat pump
In a heat pump heat is extracted at ambient
temperature(Ta) and rejected at higher
temperature(Th) to the body to be heated
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COP of Heat pump
HP
Tc
Th = Temp. of source
HS
SK
Win
SK = Sink
Tc = Temp. of sink
Qh = Heat taken from sourceQc = Heat rejected
HS= Heat sourceTh
Qh
Qc
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COP =
COP of Heat pump
=
=
in
h
W
Q
ch
h
Q
ch
h
TT
T
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COP of Refrigerating machine
In a refrigerating machine heat is extracted at
lower temperature(Tc) and reject it to
surroundings at ambient temperature(Ta)
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SK = Sink
Tc = Temp. of sink
Qh = Heat taken from sourceQc = Heat rejected
HS= Heat source
COP of Refrigerating machine
Ta = Ambient temp.
R
Tc
HS
SK
Win
Qh
Qc
Ta
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COP Of Refrigerating machine
COP =
=
=
in
c
W
Q
ch
c
Q
ch
c
TT
T
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Problem
• Find the COP of a refrigerating system if the work
input is 250 kj/kg and refrigerating effect produced is
400 kj/kg
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Solution
Given data,
Work input, W = 250 kj/kg
Refrigerating effect, N = 400 kj/kg
COP =
= 400 / 250
= 1.6
W
N
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Problem
• The capacity of refrigerating system is designated
as 15 tons. Calculate cooling rate of this machine
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Solution
= 52.5kJ/sec
Cooling rate of 1 ton machine = 3.5kJ/sec
Cooling rate of 15tons machine = 3.5X15kJ/kg
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Summary
• Ton of Refrigeration
• Coefficient of Performance
• Problems solved
So far we have discussed about
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Quiz
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• 1 Ton of refrigeration is equal to
a) 210 kj/sec
b) 35 kj/sec
c) 3.5 kj/sec
d) 3.5 kj/min
Quiz
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• A refrigerating machine having capacity
cooling effect of 7kj/sec is rated as
a) 1 ton machine
b) 2 ton machine
c) 7 ton machine
d) 3 ton machine
Quiz
M501.4 34
The amount of heat absorbed during change
of state from liquid to vapour is known as
a) Latent heat
b) Latent heat of vapourisaton
c) Latent heat of Condensation
d) Sensible heat
Quiz
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The ratio of refrigerating effect produced and
work supplied is known as
a) Efficiency of refrigerating machine
b) Efficiency of heat engine
c) COP of refrigerating machine
d) COP of heat pump
Quiz
M501.4 36
4. If the rate of cooling of refrigerating system is 4,20,000 kj/hr what is the tonnage of the system
1. Define unit of refrigeration
2. What is Ton of refrigeration? Explain briefly
3. Define the term coefficient of performance
5. Distinguish between heat pump and refrigerator
Frequently asked questions
M501.4 37
Assignment
3. If the rate of cooling of refrigerating system is
2,20,000 kj/hr what is the tonnage of the
system
1. What is Ton of refrigeration? Explain briefly
2. Define the term coefficient of performance
M501.4 38
Thank You