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  • In a refrigerator one removes heat from a lower temperature and deposits to the surroundings at a higher temperature. In this process, mechanical work has to be done, which is provided by an electric motor.

 In a refrigerator, one removes heat from a lower temperature and deposits to the surroundings at a higher temperature. In this process, mechanical work has to be done, which is provided by an electric motor. If the motor is of 1kW power, and heat is transferred from -3^{\circ}C to 27^{\circ}C, find the heat taken out of the refrigerator per second assuming its efficiency is 50% of a perfect engine.

Answers (1)

Here refrigerator acts as a Carnot's engine in reverse order with an efficiency \eta


\eta =1-\frac{T_2}{T_1}=1-\frac{270}{300}=110
 

\eta '=0.5\times0.1=0.05

Coefficient of performance \beta =\frac{Q_2}{W}=\frac{1-\eta '}{\eta '}=\frac{1-0.05}{0.05}=19

Q2=19% WD by motor on Refrigerator

=19\times 1kW=19kJs

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infoexpert24

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