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# thermodynamics Watch

1. A refrigerator is designed to make ice at –10 °C from water initially at room temperature.The energy needed to make 1.0 kg of ice at –10 °C from water initially at room temperatureis 420 kJ. The refrigerator has a coefficient of performance of 4.5.
(i) Calculate the power input to the refrigerator if it is required to make 5.5 kg of iceevery hour.

ii) Calculate the rate at which energy is delivered to the surroundings of the refrigerator.

For i) I think that the energy required to cool the ice is 420 x 103 x 5.5 = 2.31 x 106. Coefficient of performance = 4.5 and COP = Qout / Work done to cause the heat transfer.

Is Qout the energy required to cool the ice down, if so then I I assume I just divide Qout by the COP and divide by 3600.

For ii) Can I do Qin = Qout + Work done and divide the answer by 3600

thanks

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Updated: June 24, 2016
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