III) You are to select a refrigerator for frozen food processing facility. The f
ID: 2991957 • Letter: I
Question
III) You are to select a refrigerator for frozen food processing facility. The freezing of the food requires a heat rate of 250kw at a temperature of -20C. you will reject heat to the atmosphere whose temperature is 300K1. What is the upper limit on the coefficient of performance of this refrigerator?
2. The minimum rate at which you must reject heat from the refrigerator?
3. What is the minimum amount of power that must be supplied to this refrigerator?
4. What is the rate at which the entropy of the food changes?
5. What is the minimum rate at which the entropy of the atmosphere changes?
Explanation / Answer
T1 = 300 K
T2 = -20 C = 253 K
Q out = 250 Kw
1) COP max = T2 / (T1 - T2)
= 253 / (300 -253) = 5.38
3) COP = Qout / Win
5.38 = 250 / W in
Win = 46.468 Kw
2) Q rejected = 250 + 46.468 =296.468 KW
4) s = - Q out/ T2 = - 250 / 253 = - 0.988 KW/K
5) S environment = Q rejected /t1
= 296.468 / 3 00 = 0.988 KW/K