ample: A Camot r at0C·The air in the kitchen is at 25 C. refrigerator is used to
ID: 1871926 • Letter: A
Question
ample: A Camot r at0C·The air in the kitchen is at 25 C. refrigerator is used to remove enough heat from I kg of water at 20 C and change it to is a) How much heat must be removed from the water in order change it to ice? (Will this involve a change in Carnot cop- 273 k b) Determine the Camot COP of this refrigerator operating at these temperatures. c) How much work must be done by the refrigerator in order to change the water to ice? d) How much heat is rejected to the kitchen during this process? Related Question: If a person left the door to the refrigerator/freezer open would the temperature of the air in the room increase, decrease or remain constant as a result? Explain your reasoning using science by comparing the values of removed heat Qe and rejected QuExplanation / Answer
Given
a)
mass of water is m = 1 kg , at T1 = 20 C
turns into ice by removing heat Q at 0 0C
the heat required is Q = mc*DT +mL
Q = 1*4200*20+1*3.33*10^5 J
Q = 417000 J
energy requiered to remove heat from the water to convert it ot ice at 0 C is Q= 417000 J
yes there is phase change that is from water (liquid) to ic soli
first it has to cool down and at 0 C , from liquid to solid phase change
b)
coefficient of performance COP = Qc /W
COP = Qc/(Qh -Qc)
COP = T2/(T1-T2)
COP = 273.15 /(293.15 -273.15)
cop = 13.6575 = 13.7
c)
work done W = Q = 417000 J
d) heat rejected to the kitchen is Q = COP*W = 13.7*20 = 274 J
if the refrigerator is open in the room , the temperature of the room increases , because the COP is always >=1 so the
heat is transgered from cool region to the hot region continuously , so the temperature of the room increases
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