InterviewSolution
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InterviewSolution
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Explain the energy flow in a refrigerator and define the coefficient of performance of a refrigerator. |
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Answer» In a refrigerator, QC is the heat absorbed by the working substance (refrigerant) at a lower temperature TC , W is the work done on the working substance, and QH is the heat rejected at a higher temperature TH . The absorption of heat is from the contents of the refrigerator and rejection of heat is to the atmosphere. Here, QC is positive and W and QH are negative. In one cycle, the total change in the internal energy of the working substance is zero. ∴ QH + QC = W ∴ QH = W – QC ∴ -QH = QC – W Now, QH < 0, W < 0 and QC > 0 ∴ |QH| = |QC| + |W| The coefficient of performance (CoP), K, or quality factor, or Q value of a refrigerator is defined as K = \(\frac{|Q_C|}{|W|}\) = \(\frac{|Q_C|}{|Q_C|-|Q_H|}\) [Note: K does not have unit and dimensions or its dimensions are [M°L°T°.] |
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