Refrigeration PPT to present.ppt

SUBJECT: FUNDAMENTAL OF MECHANICAL ENGINEERING
AND MECHATRONICS
Mr. Bodhisatwa Seal
Assistant Professor ( Mechanical Engineering Department)
IIMT Engineering College, Meerut

REFRIGERATION & AIR-CONDITIONING
 Introduction to thermodynamic system
 Introduction of Refrigeration System
 Definition of Refrigeration
 Unit of Refrigeration
 Coefficient of performance ( COP )
 Difference between Heat engine, Heat pump & Refrigerator
 Method of Refrigeration
 Construction & working of domestic refrigeration
 Introduction of air-conditioning system
 Psychrometric terms
 Comfort condition
 Construction & working of window air conditioning

INTRODUCTION
• Refrigeration : Refrigeration is defined as the process of
extracting heat from a lower temperature heat source,
substance, or cooling medium and transferring it to a higher
temperature heat sink.
• A refrigeration system is a combination of components and
equipment connected in a sequential order to produce the
refrigeration effect.
• Refrigeration may also be defined as the process of achieving
and maintaining a temperature below that of the
surroundings, the aim being to cool some product or space to
the required temperature.

 It is based on 2nd law of Thermodynamics. As per Clausius
Statement, heat cannot flow from a body at lower temperature to
a body at higher temperature unless assisted by some external
means.
 In refrigeration, heat is continuously removed from the system at
a lower temperature and same heat is rejected to the
surroundings at a higher temperature. This is done by using an
external source like a compressor (or) a pump.
 Heat from a system at lower temperature is abstracted by using a
working fluid/medium called refrigerant.
PRINCIPLE OF REFRIGERATION

High Temperature Reservoir
Low Temperature Reservoir
R Work Input
Heat Absorbed
Heat Rejected
Refrigeration and air
conditioning is used to
cool products or a
building environment.
HOW DOES IT WORK?

Applications of refrigeration:
• Food processing, preservation and distribution
• Chemical and process industries
• Special Applications such as cold treatment of metals, medical,
construction, ice skating etc.
• Comfort air-conditioning
Storage of Raw Fruits and Vegetables
• Dairy Products
• Meat and poultry
• Beverages
• Candy
Necessity and Applications

REFRIGERATION EFFECT
In a refrigeration system ,the rate at which the heat is
absorbed in a cycle from the interior space to be cooled is
called refrigerating effect.
Refrigerating Effect (N): It is defined as the quantity of
heat extracted from a cold body or space to be cooled in a
given time.
N= Heat extracted from the cold space
Time taken
T

CAPACITY OF A REFRIGERATION UNIT :
 Capacity of a refrigerating machines are expressed by
their cooling capacity.
 The standard unit used for expressing the capacity of
refrigerating machine is ton of refrigeration.
SPECIFIC HEAT OF WATER AND ICE :
It is the quantity of heat required to raise or lower the
temperature of one kg of water (or ice), through one
kelvin or (10 c) in one second.
Specific heat of water, Cp water = 4.19 kJ/kg K
Specific heat of ice, Cp ice = 2.1 kJ/kg K.

 TON OF REFRIGERATION
One ton of refrigeration is defined as, “the quantity of heat
abstracted (refrigerating effect) to freeze one ton of water
into one ton of ice in a duration of 24 hours at 0o c”.
Heat extracted from water at 0o c = latent heat of ice
Latent heat of ice = 336 kJ/kg
i.e., 336 kJ of heat should be extracted from one kg of water
at 0o C to convert it into ice.
One ton of refrigeration = 336x1000 kJ/24 hrs.
= 336x1000 kJ/min
24x60
One ton of refrigeration = 233.333 kJ/min
= 3.8889 kJ/sec

C O P
 The performance of a refrigeration system is expressed by
a factor known as the co-efficient of performance
 It is the ratio of heat absorbed or extracted in a given time
to the work supplied
Q=Heat absorbed or removed (KW)
W=Work supplied (KW)
C O P = Q / W
The COP is always greater than 1 and known as theoretical
coefficient of performance.

REFRIGERATORS AND HEAT PUMPS
• The transfer of heat from a low-
temperature region to a high-
temperature one requires special
devices called refrigerators.
• Another device that transfers heat
from a low-temperature medium to a
high-temperature one is the heat
pump.
• Refrigerators and heat pumps are
essentially the same devices; they
differ in their objectives only.
• The objective of a refrigerator is to
remove heat (QL) from the cold
medium
• The objective of a heat pump is to
supply heat (QH) to a warm medium.

Coefficient of Performance
The performance of refrigerators and heat
pumps is expressed in terms of the
coefficient of performance (COP),
defined as,
Both COPR and COPHP can be greater than 1.
For fixed values of QL and QH
COPHP = COPR + 1

Can be classified as non-cyclic, cyclic and thermoelectric.
Non-cyclic refrigeration - cooling is accomplished by melting ice
or by subliming dry ice (frozen carbon dioxide). Are used for small-
scale refrigeration i.e. laboratories and workshops, or in portable
coolers.
Cyclic refrigeration - Consists of a refrigeration cycle, heat is
removed from a low-temperature space/source and rejected to a
high-temperature sink with the help of external work
Cyclic refrigeration can be classified as Vapor cycle and Gas cycle
Vapor cycle refrigeration can further be classified as:
Vapor-compression refrigeration
Vapor-absorption refrigeration
Methods of Refrigeration

Methods of refrigeration
 Gas cycle - Air is most often the working fluid. The hot and
cold gas-to-gas heat exchangers are used. Less efficient than
the vapor compression cycle because the gas cycle works on
the reverse Brayton cycle instead of the reverse Rankine cycle
 Thermoelectric refrigeration - Thermoelectric cooling uses
the Peltier effect to create a heat flux between the junction of
two different types of materials. Commonly used in camping
and portable coolers
 Thermoacoustic refrigeration uses sound waves in place of
a compressor to create cooling power.

In this method the ordinary ice is used for
keeping the space at temperature below the
surrounding temperature. The temperature of
ice is considered to be 0 degree Celsius hence
it can be used to maintain the temperatures of
about 5 to 10 degree Celsius. To use the ice for
refrigerating effect a closed and insulated
chamber is required. On one side of the
chamber ice is kept while on the other side
there is a space which is to be cooled where
some material to be cooled can be placed. If
the temperature below 0 degree Celsius is
required, then the mixture of ice and salt is
used. This method of cooling is still being used
for cooling the cold drinks, keeping the water
chilled in thermos, etc.
Ice Refrigeration:

Dry ice refrigeration: Dry ice is the
solid carbon dioxide having the
temperature of -78 degree Celsius.
Dry ice converts directly from solid
state to gaseous; this process is
called as sublimation. Dry ice can be
pressed into various sizes and shapes
as blocks or slabs. Dry ice is usually
packed in the frozen food cartons
along with the food that has to be kept
frozen for long intervals of time. When
the dry ice gets converted into vapor
state it keeps the food frozen. The
process of dry ice refrigeration is now-
a-days being used for freezing the
food in aircraft transportation

COMPONENTS OF A REFRIGERATOR SYSTEM
Condenser
Evaporator
Expansion
device Compressor
The basic components of a refrigeration system are:
- Evaporator
- Compressor
- Condenser
- Expansion Valve
- Refrigerant; to conduct the heat from the product

 To compress and circulate the low temperature and low
pressure working fluid into high temperature and high-
pressure vapour.
 They are power absorbing mechanical devices and need
input power. An electrical motor supplies power to these
drives.
1. COMPRESSOR (OR) PUMP:

2. CONDENSER
 Condenser consists of a series of coils in the form of U –
tubes.
 The high pressure, high temperature refrigerant from the
compressor enters condenser
 Where the refrigerant rejects its heat to the surrounding
atmosphere.
 The latent heat of the refrigerant is given to the
surrounding atmosphere, which results in change of
phase of the refrigerant.

3. EXPANSION VALVE:
 The high pressure and temperature liquid refrigerant expands
in the expansion valve to low pressure & low temperature
two-phase mixture.
 The temperature of the refrigerant drops in the expansion
valve due to partial evaporation
 The expansion valve is located at the end of the liquid line,
before the evaporator. The high-pressure liquid reaches the
expansion valve, having come from the condenser.
 The valve then reduces the pressure of the refrigerant as it
passes through the orifice, which is located inside the valve.
 On reducing the pressure, the temperature of the refrigerant
also decreases to a level below the surrounding air.
 This low-pressure, low-temperature liquid is then pumped in
to the evaporator.

4. EVAPORATOR
It has cooling coils arranged in form of U – tubes.
 The function of the evaporator is to reduce the
temperature of the refrigerator cabinet.
 The low temperature two phase mixture of refrigerant
passing through the evaporator coils absorbs heat from
the cabinet and changes into vapour phase.
 This effect of cooling is also known as refrigerating
effect

REFRIGERANT
In a refrigerator, a medium called refrigerant continuously
extracts the heat from the space within the refrigerator
which is to be kept cool at temperatures less than the
atmosphere and finally rejects to it.

PROPERTIES OF REFRIGERANTS
Thermodynamic properties
1. Boiling point – low
2. Freezing point –low
3. Latent heat of evaporation - Very high

 Physical properties
1. Specific volume – low
2. Specific heat – low
3. Viscosity – low

 Safety working properties
1.Toxity-non toxic
2.Flammability-non flammable
3.Corrosiveness-non corrosive
4. chemical stability - non reactive

 Other properties
1. C O P – high
2. Action with lubricating oil - non reactive

LIST OF COMMONLY USED REFRIGERANTS
 AMMONIA (NH3) -in vapour absorption refrigeration
 CARBONDIOXIDE(CO2) -In marine refrigeration
 SULPHUR DIOXIDE(SO2): - In house hold refrigerator
 METHYL CHLORIDE - In small scale refrigeration and
domestic refrigeration
 FREON-12 -In domestic vapour compression refrigerators
 FREON-22 - In air conditioners

Vapour Compression Refrigeration System

Vapour Compression Refrigeration System -
Construction
 This system consists of a
compressor, condenser, a receiver
tank, an expansion valve and an
evaporator.
 Compressor : Reciprocating
compressors generally used.
For very big plants centrifugal
compressors directly coupled
with high speed rotating
engines (gas turbine) are used.

Construction
 Condenser : It is a coil of tubes made of copper.
 Receiver tank: It is the reservoir of liquid refrigerant.
 Expansion Valve: This is a throttle valve. High
pressure refrigerant is made to flow at a controlled
rate through this valve.
 Evaporator : It is the actual cooler and kept in the
space to be cooled. The evaporator is a coil of tubes
made of copper

Working
Working :
1. The low pressure refrigerant vapour coming out of the evaporator
flows into the compressor.
2. The compressor is driven by a prime mover.
3. In the compressor the refrigerant vapour is compressed.
4. The high pressure refrigerant vapour from the compressor is then
passed through the condenser.
5. The refrigerant gives out the heat it had taken in the evaporator (N)

Working
Working :
6. The heat equivalent of work done on it (w) on the compressor.
7. This heat is carried by condenser medium which may be air or
water.
8. The high pressure liquid refrigerant then enters the expansion
valve.
9. This valve allows the high pressure liquid refrigerant to flow at
a controlled rate into the evaporator.
10. While passing though this valve the liquid partially
evaporates.

Working
Working :
11.Most of the refrigerant is vapourised only in the evaporator, at a
low pressure.
12. In the evaporator the liquid refrigerant absorbs its latent heat of
vapourisation from the material which is to be cooled.
13. Thus the refrigerating effect (N) is obtained.
14. Then the low pressure refrigerant enters the compressor and the
cycle is repeated.

Condenser
Evaporator
High
Pressure
Side
Low
Pressure
Side
Compressor
Expansion
Device
1 2
3
4
Working

Condenser
Evaporator
High
Pressure
Side
Low
Pressure
Side
Compressor
Expansion
Device
1 2
3
4
The superheated
vapour enters the
compressor where its
pressure is raised.

Condenser
Evaporator
High
Pressure
Side
Low
Pressure
Side
Compressor
Expansion
Device
1 2
3
4
The high pressure
superheated gas is cooled
in several stages in the
condenser

Condenser
Evaporator
High
Pressure
Side
Low
Pressure
Side
Compressor
Expansion
Device
1 2
3
4
Liquid passes
through expansion
device, which
reduces its pressure
and controls the flow
into the evaporator

Condenser
Evaporator
High
Pressure
Side
Low
Pressure
Side
Compressor
Expansion
Device
1
2
3
4
Low pressure liquid
refrigerant in
evaporator absorbs
heat and changes to a
gas

Layout of Domestic Refrigerator

Layout of Domestic refrigerator

 House hold refrigerators use vapor compression cycle
 Less energy: (90 W to 600 W)
 Due to small and high efficiency motors and
compressors,
 better insulation materials,
 large coil surface area,
 better door seals
 Designed to maintain:
 Freezer section -18 °C
 Refrigeration section at 3°C
DOMESTIC REFRIGERATOR……

 Insulation materials:
 Fiber glass, k= 0.032 W/m °C
 Urethane foam, k= 0.019 W/m °C
 Wall thickness for foam
 For freezer section reduced from 90 to 48
mm
 For refrigeration section reduced from 70
to 40 mm
 Works better up to the environment of 43°C
 Ice maker (2 to 3 kg/day)
 Vapor absorption is more expensive and less efficient

 Energy consumption can be minimized for practicing
good measures
 Open the refrigeration doors fewest times possible
 Cool the hot foods to room temperature
 Clean the condenser coil behind the refrigerator
 Check the door gaskets for air leaks
 Avoid unnecessary low temperature settings
 Avoid excessive ice build up
 Use the power saver switch
 Do not block the air flow passages to and from the
condenser coil.

AIR CONDITIONING:
Air Conditioning is the process of conditioning the air
according to the human comfort, irrespective of external
conditions.
AIR CONDITIONING
Applications of Air Conditioning
 Used in offices, hotels, buses, cars.,etc
 Used in industries having tool room machines.
 Used in textile industries to control moisture.
 Used in printing press.
 Used in Food industries, Chemical plants.

CLASSIFICATION OF AIR CONDITIONING
Air conditioning systems are classified as
1) According to the purpose
a) Comfort Air conditioning.
b) Industrial Air conditioning.
2) According to Season of the year
a) Summer Air conditioning.
b) Winter Air conditioning.
c) Year round Air conditioning.

TERMINOLOGIES
1) Dry air: The atmospheric air which no water vapour is
called dry air.
2) Psychrometry: Psychrometry is the study of the properties
of atmospheric air.
3) Temperature: The degree of hotness (or) Coldness is called
the temperature.
4) Moisture: Moisture is the water vapour present in the air.
Humidity: mass of water vapor present in 1kg of dry
air
Absolute humidity: mass of water vapor present in
1cu.m of dry air

TERMINOLOGIES
5) Relative humidity: Relative humidity is the ratio of actual
mass of water vapour in a given volume to the mass of
water vapour actually can withhold by the same volume.
6) Dry bulb temperature: The temperature of air measured by
the ordinary thermometer is called dry bulb temperature
7) Wet bulb Temperature: The temperature of air measured
by the thermometer when it is covered by the wet cloth is
known as wet bulb Temperature.

TERMINOLOGIES
8) Dew point Temperature: The temperature at which the
water vapour starts condensing is called dew point
Temperature
9) Wet bulb depression: (DBT- WBT) indicates relative
humidity
10) Dew point depression: (DBT- DPT)

For Support notes, please visit: www.arpradeep.
Window Type Air Conditioner

Window Type Air Conditioner - Working
 The low pressure vapour refrigerant from
the evaporator is sucked by compressor
through the open inlet valve.
 The compressor compresses the vapour
refrigerant.
 The high pressure and high temperature
vapour refrigerant then flows to the
condenser through the open outlet valve.
 In the condenser, the outside
atmospheric temperature in summer
being around 42o C, air is circulated by
fan.
 After condensation, the high pressure
liquid refrigerant formed passes through
an expansion valve which reduces its
pressure

 The low pressure refrigerant then
enters the evaporator and evaporates,
thus absorbing latent heat of
vaporization from the room air.
 The equipment which is used for
evaporating the refrigerant is called
evaporator.
 After evaporation, the refrigerant
becomes vapour.
 The low pressure vapour is again
passed to the compressor. Thus the
cycle is repeated.
 A partition separates high temperature
side of condenser, compressor and low
temperature side of evaporator

 The quantity of air circulated can be
controlled by the dampers.
 The moisture in the air passing over
the evaporator coil is dehumidified
and drips into the trays.
 The unit automatically stops when the
required temperature is reached in the
room. This is accomplished by the
thermostat and control panel.
 Generally, the refrigerant monochloro
difluro methane (CHCLF2) is used in
air conditioner. It is called Freon 22.

Merits and Demerits of Window type air conditioner
 Merits :
 A separate temperature control is provided in each
room.
 Ducts are not required for distribution.
 Cost is less.
 Skilled technician is required for installation.
 Demerits:
 It makes noise.
 Large hole is made in the external wall or a large
opening to be created in the window panel. This
leads to insecurity to inmates.
 Air quantity cannot be varied.

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