4unit of refrigeration & cop

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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

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In the previous class we had studied about

• Steam jet refrigeration

• Liquid nitrogen refrigeration

• Applications of refrigeration

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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

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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

QQ

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

QQ

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

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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

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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

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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

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Thank You