On a cold winter day, the outside temperature is -20°C and the inside temperature is maintained at 20°C. There is a net heat flow to the outside through the walls, roof, etc., of 25 kW. At what rate is the air outside the house gaining entropy as a result of this process?
A) 13 W/K
B) 25 W/K
C) 85 W/K
D) 99 W/K
E) 0 W/K

Question

Quizplus · Accepted Answer

The rate of entropy gain is given by the heat flow divided by the temperature difference. In this case, the heat flow is 25 kW and the temperature difference is 40°C, so the rate of entropy gain is 25 kW / 40°C = 0.625 kW/K = 625 W/K.

On a Cold Winter Day, the Outside Temperature Is -20°C