Final answer:
Refrigerators work on a cyclical process involving coolant evaporation and compression, reversing the natural flow of heat and conserving energy as dictated by the first law of thermodynamics.
The efficiency is measured by the coefficient of performance, the ratio of heat transfer versus the work done.
Step-by-step explanation:
During the cycle of a refrigerator, when the door remains closed, several processes occur for heat transfer, work, and energy conservation. A refrigerator uses a cyclical process involving a coolant with a low boiling temperature.
At the evaporator, the coolant extracts heat from inside the refrigerator, causing it to vaporize. This transfer of heat is an example of work being done to actively move energy from the air inside the refrigerator to lower its temperature, countering the spontaneous heat flow from hot to cold.
The vaporized coolant is then compressed, increasing its temperature and pressure, and pushed through the condenser where it releases heat to the outside environment.
This cycle is an engineered reversal of a naturally occurring process, consuming work (electricity) to transport heat from the colder interior to the warmer exterior.
The first law of thermodynamics states that the energy within the system is conserved, meaning the work done by the refrigerator equals the net heat extracted from the coolant plus the net heat transfer into the surroundings.
Afterward, the coolant is allowed to expand and cool down before starting the cycle over again.
Efficiency of a refrigerator is measured by its coefficient of performance which is the ratio of heat transfer from the cold interior to the work required to remove that heat.
It is a critical parameter in understanding the energy and cost-efficiency of a refrigerator.