Topic: Refrigeration and Air Conditioning
The working temperatures in evaporator and condenser coils of a refrigerator are $-25^{\circ}C$ and $30^{\circ}C$ respectively. The COP of the refrigerator is 0.85 of the maximum COP for a power input of 2 kW. The refrigeration effect produced will be
- A. 7.6 kW
- B. 9 kW
- C. 10.2 kW
- D. 12 kW
Answer: A. 7.6 kW
Explanation: The lower temperature is $T_L = -25 + 273 = 248 K$ and the higher temperature is $T_H = 30 + 273 = 303 K$. The maximum Carnot COP is $\frac{T_L}{T_H - T_L} = \frac{248}{303 - 248} = \frac{248}{55}$. The actual COP is $0.85 \times \frac{248}{55}$. Since COP is the ratio of the refrigeration effect ($Q$) to the work input ($W$), we have $0.85 \times \frac{248}{55} = \frac{Q}{2}$. Solving for $Q$ yields approximately 7.6 kW.