Question

The working temperatures in the evaporator and condenser coils of a refrigerator are $-{30}^{0}C$ and ${32}^{0}C$ respectively. If the actual refrigerator has a COP of 0.75 of the maximum, the required power input for a refrigerating effect of 5 kW is nearly.

• A. 4.0 kW
• B. 2.94 kW
• C. 1.7 kW
• D. 3.92 kW

Answer 1

The correct option is C 1.7 kW

$(COP{)}_{max}=\frac{T_1}{T_2-T_1}=\frac{243}{305-243}=3.919$
$(COP{)}_{actual}=0.75\times (COP{)}_{max}$
$=0.75\times 3.919=2.939$
Now,
$(COP{)}_{actual}=\frac{\text{Actual refrigerating effect}}{\text{Power input}}$
$\text{Power input}=\frac{5}{2.939}=1.7kW$