refrigeration-air-conditioning-training ppt

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CHAPTER : Refrigeration and Air Conditioning
BASIC MECHANICAL ENGINEERING (3110006)
Subject : Basic Mechanical Engineering
Chapter : Refrigeration and Air Conditioning
Prepared by, MEHUL CHHOWALA

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Content
• Refrigeration, Refrigeration effect
• Refrigerant, Commonly used refrigerant & it’s Properties
• Performance Assessment Parameter
• Co-efficient of Performance
• Ton of Refrigeration
• Specific Power Consumption
• Energy Efficient Ratio
• Classification of Refrigeration Cycle
• Vapor compression refrigeration system
• Vapor absorption refrigeration system
• Domestic Refrigerator
• Air conditioning & its Application
• Components of Air Conditioning System
• Classification of Air Conditioning System
• Window Air Conditioner
• Split Air Conditioner

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Refrigerator and Heat Pump

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What is
Refrigeration?
Refrigeration is process in which the transfer of heat from a low temperature level
to a high temperature level by using a refrigerant.
It is also defined as the process of removing heat from a substance (i.e. process of
cooling a substance).
OR
What is
Refrigeration
Effect?
It is define as the amount of heat absorbed by refrigerant from the space to be
cooled. The capacity of refrigeration system is expressed in tons of refrigeration
which is unit of refrigeration.

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What is
Refrigerants ?
Refrigerant is a compound typically found in either a fluid or gaseous state. It readily
absorbs heat from the environment and can provide refrigeration or air conditioning.
The refrigerant is a heat carrying medium which absorbs heat from space (desired to
cool) and rejects heat to outside the refrigerator (in atmosphere).
OR

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Properties of a Ideal Refrigerant
The high specific heat of vaporization
The critical temperature and the triple point are far beyond the
operating range
Chemically stable, compatible with construction materials and
mixtures containing lubricants
Non-corrosive, non-toxic and non-flammable
High dielectric strength
Environmentally friendly
Low cost

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• Properties : Highly toxic, flammable, good thermal properties, highest
refrigerating effect per kg of refrigerant.
• Uses : It is widely used in large industrial and commercial refrigeration
system. It is mostly used with Vapour absorption refrigeration cycle like
ice plants, cold storage, packing plants etc.
NH3 (Ammonia)
• Properties : Colorless, non-toxic, non-flammable and non-corrosive
gas. It gives low refrigeration effect.
• Uses : It is used in marine refrigeration system.
CO2 (Carbon dioxide)
• Properties : Easily available without cost, non-toxic, completely safe
refrigerant, low COP.
• Uses : It is used in aircraft air-conditioning system.
Air
Common used Refrigerants and Properties

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• Properties : Non-toxic, Non-flammable and Non-corrosive.
• Uses : It is used in Small office buildings and factories for refrigeration.
R-11 (Trichloro monofluoro
methane) OR Freon-11
• Properties : Non -toxic, Non-flammable, Non-explosive, high COP and
most suitable refrigerant..
• Uses : It is used in domestic vapour compression refrigeration.
R-12 (Dichlaro - difluro
methane) OR Freon -12
• Properties : Non-toxic, Non-flammable, Non-explosive Required less
compressor displacement.
• Uses : It is used in commercial and industrial low temperature
applications (in air conditioning).
R-22 (Monochloro - difluro
methane) OR Freon -22
Common used Refrigerants and Properties

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Coefficient of Performance
It is the ratio of cooling capacity in kW to the total power
input in kW, at any given set of rating conditions.
The Theoretical Coefficient of Performance(Carnot)
• COPcarnot - a standard measure of refrigeration efficiency of an ideal
refrigeration system- depends on two key system temperatures, namely,
evaporator temperature (Te) and condenser temperature (Tc).
COP(carnot) = Te / (Tc - Te)
• This expression also indicates that higher COPcarnot is achieved with higher
evaporator temperature and lower condenser temperature.
Performance
Assessment
Parameter

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Tons of Refrigeration (TR)
It is defined as the rate of heat transfer that results in the
freezing of 1 short ton of pure ice at 0 °C in 24 hours.
1 TR of refrigeration = 3024 kCal/hr heat rejected
= 12,000 BTU/h
= 3.5 kW
The refrigeration TR is assessed as TR = Q x Cp x (Ti – To) / 3024
Where Q is mass flow rate of coolant in kg/hr
Cp is coolant specific heat in kCal /kg deg C
Ti is inlet, temperature of coolant to evaporator (chiller) in °C
To is outlet temperature of coolant from evaporator (chiller) in °C.
Note: The above TR is also called as chiller tonnage.
Performance
Assessment
Parameter

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Specific power consumption(kW/TR)
It is defined as the ratio of energy consumption in kW to the
rate of heat removal in tons at the rated condition.
In a centralized chilled water system, apart from the compressor unit,
power is also consumed by the chilled water (secondary) coolant pump as
well condenser water (for heat rejection to cooling tower) pump and
cooling tower fan in the cooling tower.
• Compressor kW/TR
• Chilled water pump kW/TR
• Condenser water pump kW/TR
• Cooling tower fan kW/TR
The overall kW/TR is the sum of the above.
Performance
Assessment
Parameter

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Energy Efficiency Ratio (EER)
It is defined as the ratio of net cooling capacity of a refrigeration
compressor, a packaged unit, or other device, in BTU/h, to the
electric power input to that device, in W, under designated
operating conditions.
Performance
Assessment
Parameter

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Refrigerators
(A machine produce
cooling effect)
Natural refrigerator
(The cooling effect produced by
evaporation of liquid or
sublimation of solids)
Mechanical refrigerator
(The cooling effect produced by
external source of mechanical
energy or heat energy)
Vapour compression
refrigerator
Vapour absorption
refrigerator
Air refrigerator

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Refrigeration System
Vapour Compression
Refrigeration System(VCR)
VCR uses mechanical energy as
the driving force for refrigeration
Vapour Absorption
Refrigeration System (VAR)
VAR uses thermal energy as the
driving force for refrigeration

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Vapour Compression Refrigeration (VCR)
1-2 Compressor
Isentropic compression
s = constant
W
t˙n = N
˙ (ℎ2 −̇
ℎ1)
2-4 Condenser Isobaric condensation Qḣ = N
˙ (ℎ3 −̇ℎ2)
4-5 Expansion valve Isenthalpic expansion ℎ4 = ℎ3
5-1 Evaporator Isobaric evaporation Qṙ = N
˙ (ℎ1 −̇ℎ4)

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Compressor
• The type of compressor may be either reciprocating, rotary, or centrifugal.
• Its function is to receive refrigerant at a particular temperature and pressure and to
deliver it after compression at higher temperature and pressure.
• The temperature of the refrigerant delivered will be higher than the temperature of the
cooling fluids used; so that heat will flow from the refrigerant to the cooling fluid
which is at higher temperature than that of refrigerating space.
Condenser
• The high pressure and high temperature compressed vapour is discharged into the
condenser where heat is transferred to the cooling fluid which is normally water or air.
• The vapour cools and then condenses, at saturation temperature which corresponds to
the pressure in the condenser.
• The vapour after condensing, the high pressure liquid then enters the throttle valve or
expansion valve.

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Expansion valve
• This is a throttle valve in which throttling process is carried out.
• It is a valve with narrow passage through which high pressure liquid passes and
expands from high pressure to a low pressure at constant enthalpy.
• The liquid after expansion becomes low temperature wet vapour and is transferred
to the receiver from where it passes to the evaporator through a control valve.
Evaporator
• In the evaporator, liquid vapour absorbs heat from the space to be cooled for its
vaporization.
• The evaporator is in the form of a coil or bare pipe or tubes, as the case may be,
through which liquid vapour flows.
• The evaporated vapour is sucked by the compressor from the evaporator and
delivered to the condenser. Thus, the cycle is completed.

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Process 1-2: Inlet of compressor (at point 1), low pressure and low temperature vapour enters the compressor.
Compressor compresses the vapour at high temperature and pressure.
The condition of refrigerant at exit to compressor (at point 2) is high pressure and high temperature vapour.
Process 2-3: High pressure, high temperature vapour coming from compressor condenses in the condenser by the rejecting
heat to cooling medium.
Cooling medium is usually air or water.
The condition of refrigerant at exit to condenser (at point 3) is low temperature saturated liquid.
Process 3-4: The saturated liquid coming from condenser passes through expansion device (throttling valve) where
pressure of saturated liquid decreases from condenser pressure to evaporator pressure.
The condition of refrigerant after throttling is low temperature and low pressure liquid.
Process 4-1: Liquid refrigerant coming from expansion device enters into evaporator where it absorbs latent heat of
evaporation from space to be cooled (refrigerator compartment).
Due to absorption of heat liquid refrigerant converted into saturated vapor or superheated vapour at low
pressure and low temperature.
Again this vapour enters into compressor and the cycle is repeated.

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Domestic vapour compression Refrigerator

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Domestic vapour compression Refrigerator
Construction
• It consists of an evaporator installed in the freezing compartment of the
refrigerator.
• One end of evaporator connected to the suction side of the compressor and
other end connected to condenser through throttle valve.
• Normally condenser installed at the backside of refrigerator.
• The delivery side of compressor is connected to a condenser.
• Available in capacities of 65 liters, 100 liters, 165 liters, 275Iitres,360
liters,500 liters, 1000 liters etc with star rating.

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Vapour Absorption Refrigeration System (VAR)

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Construction
• This system is shown in figure consists of (i) evaporator, (ii) condenser, (iii) generator,
(iv) absorber, (v) pump and (vi) expansion device.
• In this system the refrigerant coming from evaporator is absorbed by absorber.
• The absorbing medium may be solid or liquid.
• In VAR system, the compressor is replaced by an absorber and generator.
• Ammonia is refrigerant has characteristic as it is easily absorbed by water at low
pressure and temperature, but at high pressure and temperature, the solubility of
ammonia in water is reduced.
• Therefore when mixture of water and ammonia is heated by generator, the ammonia
vapour is separated from water.
• This principle is used in the vapour absorption refrigeration system. Here the ammonia is
refrigerant and water is absorbent.

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Working
• Low pressure and low temperature vapour ammonia coming from evaporator enters in
the absorber where ammonia is absorbed by weak solution coming from generator
through throttle valve.
• Due to absorption of NH3 in water, solution becomes strong. [In the mixture of NH3 and
water, if amount of NH3 is less than water is called weak solution and if amount of NH3
is more than the water is called strong solution.]
• During absorption process heat is released and rejected to cooling water.
• The strong solution from absorber is pumped into generator, where it is heated and NH3
vapour separated from solution.
• In generator is supplied from external source. The weak solution at point 4 is flowing
back to absorber through throttle valve.
• Again weak solution in absorber absorbs NH3 vapour coming from evaporator.
• NH3 vapour coming from generator passes through condenser and condensed in
condenser and reject heat to cooling medium. Then liquid NH3 throttled through
expansion device and it enters

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Air Conditioning
Basic processes of
Air Conditioning
system
Sensible
cooling/heating
Humidifying
Dehumidifying
Air cleaning
Air change
Air movement
Applications of
Air Conditioning
For Human comfort
Industrial Air Conditioning

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Components of Air
Conditioning System
Fans For circulation of air
Filters For cleaning air
Heating element
Heating of air (It may be electric
heater, steam, hot water)
Control system
It regulates automatically the
amount of cooling or heating.
Grille
It adjusts the direction of
conditioned air to the room.
Tray It collects condensed water

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Classification of Air Conditioning System
Air conditioning
system
According to
arrangement of
equipment
Unitary system
Window Air
Conditioner
Split Air Conditioner
Central system
According to the purpose
Comfort air
conditioning system
Industrial air
conditioning system
According to season of
year
Winter air
conditioning system
Summer air
conditioning system

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Window Air Conditioner

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Working
• The hot air coming from room is flowing on the evaporator (cooling coil), the cooling coil absorbs
heat from air.
• The moisture of air gets removed on the cooling coil surface by process of condensation of air.
Thus the air is cooled and dehumidified to meet the requirement comfort air conditioning in the
room.
• The filter clean the air coming from room before passes through the cooling coil. The tray is
provided below the cooling coil (evaporator) to collect moisture which condenses from
recirculation of air.
• The flow of hot air (from room) and cooled air (to room) is taking place by the evaporator blower.
The refrigerating unit provides cooling effect at evaporator. The condenser fan circulates air on
outside of condenser tubes, the refrigerant in condenser reject heat to outside atmospheric air.
• Necessary fresh air is allowed to mix with the recalculated room air to meet the ventilation
requirement.
• Ventilation air is controlled by ventilation damper. The room -temperature is controlled by a
thermostat using on-off power supply to compressor motor.
Limitations :
• It produce noise in the room because of compressor is very near to the room.
• It requires appropriate size of window or hole in wall to fit the conditioner.

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Split Air Conditioner

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Construction
This unit differs from window air conditioner. In terms of splits of unit into two parts. In split air
conditioner, the window air conditioner divided (split) into two parts.
• First part: Includes the evaporator, filter, evaporator fan and grille (cooling coil). They placed inside
the room.
• Second part: Includes condenser, condenser fan, and compressor. This placed outside the room.
• First part (inside of room) and second part (outside of room) is connected by small diameter tubes.
Therefore, small hole required in wall for installation of split air conditioner.
Advantages
• The compressor is outside of room, therefore no compressor noise in the room.
• No window opening and fixing needed..

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Thank You...

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