Elements of Mechanical Engineering

1. 1

2. • What is refrigeration?
• Refrigerating effect
• Unit of refrigeration
• How refrigeration is produced?
• Main components and functions of a mechanical
refrigeration system
• What is refrigerant?
• Characteristics of refrigerant
• What are most widely used refrigerants?
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3. What is Refrigeration?
• The process of removing heat from a space or
substance to reduce its temperature and
transferring that heat to another space or
substance.
OR
The process of cooling or removing heat.
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4. • It is the amount of heat absorbed in the
evaporator (equipment used to evaporate
circulating substance) and which is the same
as the amount of heat removed from the
space to be cooled.
Refrigerating effect
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5. • The ton is normally the unit of mass. But in
refrigeration, this is used in order to compare the
capacity of the system with that of ice melting
equivalent since ice was widely used for cooling in
early days .it is very obvious to compare the
capacity of the mechanical system with that of the
heat absorbed by ice for that, the cooling
produced by melting of one ton of ice in a day is
taken as a datum.
Unit of Refrigeration
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6. • This is equal to,
= mass of ice x Latent heat of ice kj/sec
24 x 3600
= 900(kg) x 335 (kj/kg)
24(hr) x 3600(sec)
= 3.4895833 ~ 3.5kj/sec = 3.5kW
= 1Ton = 3.5kW
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7. • Mechanical refrigeration is possible because of
boiling of a volatile liquid ,called refrigerant
under proper conditions. This refrigerant will
absorb heat from the surrounding objects. The
actual cooling is produced because of this
boiling.
How refrigeration is produced?
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9. • There are mainly four main components of a mechanical
refrigeration system.
(1) Compressor
(2) Condenser
(3) Expansion device
(4) Evaporator
The cooling is produced by evaporator. The purpose of the
compressor, its drive, again. As a matter of convenience
and economy, it is not practical to permit the refrigerant
vapour to escape to the outside, and be lost by diffusion
into air.
Main components and function of a
mechanical refrigeration system.
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10. • A refrigerant is the substance used for heat
transfer in a refrigerating system. It picks up
heat by evaporation at a low temperature and
pressure and gives up this heat by condensing at
a higher temperature and pressure.
What is Refrigerant?
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11. (1) Refrigerant must be volatile or capable of
being evaporated.
(2) The latent heat of vaporization must be high in
order to minimize the flow of refrigerant.
(3) The refrigerant should be harmless to people.
(4) It should be compressed with a minimum
power.
Characteristics of refrigerant
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