Question
Sun February 10, 2013 By:
 

Assuming that a domestic refrigerator can be regarded as a reversible engine working between temperature of melting ice and that of atmosphere (17 degrees celcius) . find the energy which must be supplied to freeze i kg of water at 0 degree celcius.

Expert Reply
Wed February 13, 2013
So T2=0+273=273K
T1=17+273=290K
heat energy required to freeze 1 kg of water at 0 degree celcius=mL=4.2x80J=Q2
This much heat has to be extracted from the sink(freezer) at 0 degree C.
Q1=amt of heat released to source(surrounding) at 17 degree C
W=work done on the refrigerent by outside machine
W=Q2-Q1
now coeff of performance=Q2/W
W=Q2/coeff of perf
coeff of perf=T2/T1-T2
so :
W=Q2(T1-T2)/T2=20.9J
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