Chapter 2 Thermodynamic Analysis of refrigeration cycle

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Chapter 2 Thermodynamic Analysis of
refrigeration cycle
Refrigeration Technology
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Refrigeration Technology
Chapter2 Thermodynamic Analysis of refrigeration
cycle
Chapter 2 Thermodynamic Analysis of
refrigeration cycle

• The Laws of Thermodynamics and Their Relation to
  Refrigeration
• The Refrigeration Cycle and its Main Components
• The Performance of Refrigeration System
• Entropy Analyses method of Refrigeration System
• Work and Heat Operated Refrigerators
• Lorenz Cycles for Variable Temperature Heat
  Source and Heat Sink
• REFERENCES

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Refrigeration Technology
Chapter2 Thermodynamic Analysis of refrigeration
cycle
The Laws of Thermodynamics and Their Relation to
Refrigeration
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Refrigeration Technology
Chapter2 Thermodynamic Analysis of refrigeration
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• (1)The 0th Law of Thermodynamics
• The Zeroth Law of Thermodynamics states
• (1)If two systems are each equal in
  temperature to a third system, then the
  temperatures of the two systems themselves are
  equal.
• (2)If two closed systems (together
  isolated), with different temperatures are
  brought into thermal contact, then the
  temperatures of the two systems will change to
  approach the same temperature. That is, the
  temperature of the system which is at a higher
  temperature will decrease and the temperature of
  the system with the lower temperature will
  increase. They will eventually have the same
  temperature.

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Chapter2 Thermodynamic Analysis of refrigeration
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• (2)The 1st Law of Thermodynamics
• The First Law of Thermodynamics involves the
  conservation of energy. It states
• The energy of an isolated system remains
  constant.
• The First Law of Thermodynamics can be expressed
  as a mathematical interpretation as

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Chapter2 Thermodynamic Analysis of refrigeration
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(3)The 2nd Law of Thermodynamics There are
several alternate but equivalent ways to describe
the 2nd Law 1. Heat Transfer Heat flows
spontaneously from a hot body to a cool body in
absence of other effects, not the opposite. 2.
Mass Transfer Fluid flows spontaneously from a
high pressure to low pressure in absence of other
effects, not the opposite. 3.Diffusion Two
gases, when placed in an isolated chamber, will
mix uniformly throughout the chamber, but will
not separate spontaneously once mixed. 4.It is
impossible to convert heat completely into useful
work. 5.For an isolated system, any change over
time of entropy S is either positive or zero,
that is
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Chapter2 Thermodynamic Analysis of refrigeration
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(4) The 3rd Law of Thermodynamics There are
several alternate but equivalent ways to describe
the 3rd Law 1.The entropy of any pure substance
in thermodynamic equilibrium approaches zero as
the absolute temperature approaches zero 2.It is
impossible to cool a body to absolute zero by any
finite process. Although one can approach
absolute zero as closely as one possible, one
cannot actually reach this limit.
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Chapter2 Thermodynamic Analysis of refrigeration
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The Refrigeration Cycle and its Main Components
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Chapter2 Thermodynamic Analysis of refrigeration
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• Fig.2-1 illustrates a refrigerator operating in a
  thermodynamic cycle. There are a refrigerator and
  two heat reservoirs (a hot heat reservoir with
  temperature TH and a cold heat reservoir with
  temperature Tc ) to make up of the heat transfer
  process from low temperature Tc to high
  temperature TH .

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Chapter2 Thermodynamic Analysis of refrigeration
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• (1)Heat reservoirs---heat source and heat sink
• A heat reservoir is a sufficiently large system
  in stable, to which and from which finite amounts
  of heat can be transferred without any change in
  the temperature of the heat reservoir A heat
  source is a heat reservoir from which heat is
  transferred.
• A heat sink is a heat reservoir to which heat is
  transferred.

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Chapter2 Thermodynamic Analysis of refrigeration
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• (2)Refrigeration cycle
• As the refrigerator cycle is referred to as the
  system, and the two heat reservoirs as the
  environment, when the system has completed a
  refrigeration cycle, it has undergone a series of
  processes and returned to its original state.
• All the parameters (such as pressure P,
  temperature T) and all the thermal properties
  (such as enthalpy h, entropy s, inner energy u)
  of the refrigerant at the end of the cycle are
  the same as they are at the beginning

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Chapter2 Thermodynamic Analysis of refrigeration
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• (3)Main Components of vapor compression
  Refrigeration cycle
• The refrigeration cycle shown in Fig.2-1 is
  called