A freezer has a coefficient of performance of 6.30. It is advertised as using 53

Question

A freezer has a coefficient of performance of 6.30. It is advertised as using 536 kWh/yr. (a) On average, how much energy does it use in a single day? Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. J (b) On average, how much energy does it remove from the refrigerator in a single day? Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. J (c) What maximum mass of water at 16.2 degree C could the freezer freeze in a single day? (The latent heat of fusion of water is 3.33 times 10^5 J/kg, and its specific heat is 4186 J/kg middot degree C.) Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error.

Explanation / Answer

(a) Energy used in a single day = 536 kWh/yr * 1/365 year

=1.47 kWh

= 1.47 x 1000 x60x60 = 5.27 x 10^6 J

(b) COP = Q/W = 6.3
=> Q = 6.3x5.27x10^6 = 3.32 x 10^7 J

(c) Q = mc dT + mL
=> m = (3.32x10^7) / (4186x16.2 + 3.33x10^5)

= (3.32x10^7) / (400813.2) = 82.83 kg.

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