A refrigerator maintains a cold environment at 2degreeC. The refrigerator steadily removes 370W from where the food is stored and discharges heat to the room through a radiator at 45degreeC. a)How much current would a reversible refrigerator draw from a 120V power supply under these conditions? b)What is the coefficient of performance for a reversible refrigerator under these conditions? c)How much heat does the reversible refrigerator discharge to the room? d)If you opened the door to a reversible refrigerator and let it run, would the room get warmer or colder? What would be the net rate of Q for the room that results from running the refrigerator with the door open? e)If a real refrigerator has a COP of 4.5, calculate how much heat it would discharge into the room under the same conditions as in (c) - i.e. with the door closed? f)Compare and discuss the results of (c) and (e). g)Determine the rate of entropy generation for the reversible refrigerator in part (a) and the real refrigerator in part (e).
a) COP = TL / (TH - TL ) = 275 / (45 - 2) = 6.395
therefore power drawn = 370 / 6.395 = 57.85454 W
Current drawn = 57.85454 / 120 = 0.4821 A
b) COP = TL / (TH - TL ) = 275 / (45 - 2) = 6.395
c) Heat discharged = 370 + 57.85454 = 427.85454 W
d) The room would get warmer beacuse the heat discharged into the room minus the heat withdrawn from the room is positive . The value of Q would be the work done by the compressor 57.854 W
e) Heat discharged = 370 + 370/4.5 = 452.22 W
f) Heat discharged in case of real refrigerator is higher than reversible refrigerator.
g) Rate of entropy generation (reversible) = 452.22 / (273 + 45) - 370 / (273 + 2)
= 0.0766 W/K
Rate of entropy generation (reversible) = 427.85454 / (273 + 45) - 370 / (273 + 2)
= 0
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