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Just Part C and D A refrigerator is characterized by a number called the coeffic

ID: 1617285 • Letter: J

Question

Just Part C and D

A refrigerator is characterized by a number called the coefficient of performance (COP), which is defined as the heat removed from the cool place (inside the fridge) divided by the work required to remove that heat: COP = Q_l/W. If you are buying a new fridge is it better to buy one with a higher COP or a lower COP? higher lower it doesn't matter Let's say that a fridge operates between temperatures of 4 degree C and 33.0 degree C. A particular fridge has a COP of 4.80. (b) If 600 of work is done by the compressor in the fridge to extract heat from inside the fridge, how much heat is removed from inside the fridge? 2880 J (c) How much heat is dumped by the fridge into the surroundings, in this case? J (d) What is the maximum possible COP that would be achieved by an ideal fridge operating between the two temperatures specified above?

Explanation / Answer

Heat extracted from inside the fridge, Qcold= 2880J

Coefficient of Performance, COP= 4.80

Temperature of cold reservoir, Tc= 4oC= (4+273)K= 277K

Temperature of hot reservoir, Th= 33oC= (33+273)K= 306K

c). Let heat dumped by the fridge into the surroundings be Qhot

Then we can write Coefficient of Performance as

COP= Qcold/(Qhot- Qcold)

using given values in above,

4.80= 2880/ (Qhot-2880)

Qhot-2880= 600

Qhot= 3480 J (ANS)

d). COP for Ideally operating Fridge is given as

COP= Tc/(Th-Tc)

using given values in above,

4.80= 277/(306-277)= 9.55 (ANS)