Question

(10) A salesman claims that the freezer he is selling operates requires 20 W of power to maintain a steady temperature of 20°F in the freezer, which gains heat from its surroundings at a rate of 240 W.

Determine:

1. The COP of the freezer.
2. Is this possible if the freezer is in a house with an air temperature of 70°F?

Answer 1

Given,

T_L = 20^oF = (20+460) R = 480 R

W_in = 20 W

Q_L = 240 W

(A)

COP of a refrigerator is given as;

$COP = \frac{Q_L}{W_{in}}$

240 COP= 20

COP = 12

...(Answer)

______________________________________________

(B)

Given,

T_H = 70^oF = (70+460) R = 530 R

Maximum possible COP;

T. (COP) mar = Tu - TL

(COP)mar = 480 530 – 480

(COP) mar = 9.6

By comparing we can see that the actual COP is more than the maximum possible COP, or;

COP > (COP)_max

Hence,

NOT POSSIBLE