Non-Ideal Vapor-Compression Refrigeration Cycles

Deviations from the Ideal Vapor Compression Refrigeration Cycle

  1. Pressure drop across the evaporator is caused by fluid friction: P2 < P1.
  2. Mechanical and fluid friction in the compressor cause the entropy of the working fluid to increase. Heat transfer can also occur to or from the surroundings. Therefore, although entropy usually increases, it can decrease if enough heat is lost to the surroundings.
  3. Pressure drop across the condenser is caused by fluid friction: P4 < P3.
  4. Friction losses and heat exchange with the surroundings also occurs in the piping that connects the four processes that make up the cycle. These result in pressure drops and increases or decreases in temperature depending on the temperature of the working fluid and the temperature of the surroundings.
Process flow diagram for a practical, basic vapor-compression refrigeration cycle.
TS diagram of a real vapor-compression refrigeration cycle.
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Ch 10, Lesson B, Page 4 - Non-Ideal Vapor-Compression Refrigeration Cycles