Question

A refrigerator is removing heat from a cold medium at 3∘C at a rate of 5400 kJ/h and rejecting the waste heat to a medium at 30∘C. If the coefficient of performance of the refrigerator is 2, the power consumed by the refrigerator is
(a) 0.5 kW
(b) 0.75 kW
(c) 1.0 kW
(d) 1.5 kW
(e) 3.0 kW

Answer 1

Answer:(b) 0.75 kW

Explanation:

Given

temperature of cold region $T_L=3^{\circ}C$

Heat removal at the rate of $Q_1=5400 kJ/h$

temperature of hot region $T_H=30^{\circ}C$

COP of refrigerator =2

COP of a refrigerator is given by ratio of desired effect to the Power input

COP$=\frac{Q_1}{Power}$

$2=\frac{5400}{P}$

$P=2700 kJ/h$

$P=0.75 kW$