A domestic refrigerator with both a cold space for fresh food and a freezer is m

Question

A domestic refrigerator with both a cold space for fresh food and a freezer is modeled as a 3-T refrigerator. The temperatures of the cold space and the freezer are 5degC and -5degC, and the ambient is at 20degC. if the refrigerator operates continuously, the rate of heat transfer from the cold space is twice that from the freezer, and the power input is 0.25kW, find the maximum values of the three heat transfer rates. The answers are Qf = 1.243 kW Qc = 2.485 kW Qa = 3.978kW I'm guessing you will use the coefficient of heat transfer in order to solve this problem, however I can't seem to get the right answers.

Explanation / Answer

Ideal COP for cold space = (273+5)/(20-5) = 18.53 = Q_coldspace/W_coldspace

Ideal COP for freezer = (273-5)/(20-(-5)) = 10.72 = Q_freezer/W_freezer

Q_coldspace = 2*Q_freezer

W_coldspace + W_freezer = 0.25 kW

Solving these, Q_freezer = 1.243 kW, Q-coldspace = 2.485 kW

Q_ambient = Q_freezer + Q_coldspace + (W_coldspace + W_freezer)

= 1.243 + 2.485 +0.25

= 3.978 kW

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.