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THERMODYNAMICS - CASE STUDY

    Introduction


Problem Description
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A refrigerator in a kitchen dissipates heat to the kitchen air through the fin coil unit located on the back of the refrigerator. If a heat engine is operating between the fin coil unit and the surrounding air, can it generate power?

What is known:

  • The coefficient of performance (COP) of the refrigerator is 3.0.
  • The power input to the refrigerator is 1.0 kW.
  • The average surface temperature of the fin coil unit is 30 oC.
  • The kitchen air temperature is 20oC.
     


How a Refrigerator Works
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  Question

  Determine the maximum power generated by the heat engine operating between the the fin coil unit and the kitchen air.
   
  Approach

 
  • Determine the heat dissipated from the the fin coil unit, which is the heat input to the heat engine.
  • Assume the heat engine is a Carnot heat engine. Its thermal efficiency is determined by
    ηth,rev. = 1 - TL/TH