Coefficient of performance

Definition

Coefficient of performance (COP) is the ratio of useful heating or cooling provided to work required in heat pumps and refrigerators. It measures the efficiency of these devices.

5 Must Know Facts For Your Next Test

1. COP for a heat pump is defined as $\frac{Q_{H}}{W}$, where $Q_{H}$ is the heat delivered to the hot reservoir and $W$ is the work input.
2. COP for a refrigerator is defined as $\frac{Q_{C}}{W}$, where $Q_{C}$ is the heat removed from the cold reservoir and $W$ is the work input.
3. The COP of a refrigerator or heat pump can be greater than one, indicating that more energy is transferred as heat than is consumed as work.
4. Higher COP values indicate more efficient systems because they deliver more heating or cooling per unit of work input.
5. COP depends on operating temperatures; it decreases as the temperature difference between reservoirs increases.

Review Questions

• How do you mathematically define COP for a heat pump?
• Why can COP values be greater than one?
• What factors affect the COP of a refrigeration system?

Related terms

Heat Pump:

A device that transfers heat from a colder area to a hotter area by using mechanical energy.

Refrigerator:

A device that removes heat from a space to lower its temperature, typically transferring it to another space.

Work:

$W$ represents the energy transferred when an object is moved over a distance by an external force.