Question
How does an air conditioner differ from a refrigerator? Define the coefficient of performance of an air conditioner and express it in terms of heat current.
✓
Answer
The working of an air conditioner is exactly similar to that of a refrigerator, but the volume of the chamber/room cooled by an air conditioner is far greater than that in a refrigerator. The evaporator coils of an air conditioner are inside the room, and the condenser outside the room. A fan inside the air conditioner circulates cool air in the room.The coefficient of performance, $K$, of an air conditioner is defined as $K=\left|\frac{Q_C}{W}\right|$, where $Q_c$ is the heat absorbed and $W$ is the work done. The time rate of heat removed is the heat current, $H =\frac{\left|Q_C\right|}{t}$, where $t$ is the time in which heat $\left|Q_c\right|$, is removed.
$
\therefore K=\left|\frac{Q_{ C }}{W}\right|=\frac{\left|Q_{ C }\right| / t}{|W| / t}=\frac{H}{P} \text {, }
$
where $H =\left| Q _c\right| / t$ is the heat current and $P (=| W | / t )$ is the time rate of doing work, i.e., power.
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