How does a refrigerator manage to cool food?

How does the refrigerator cooling cycle work?#

The operation of a refrigerator is based on fundamental physical principles related to thermal behavior and fluid pressure. Naturally, thermal energy moves from warmer areas toward those with lower temperatures. In addition, the pressure and heat of a substance are closely connected, meaning that when a gaseous element has its pressure increased, its corresponding temperature also rises significantly.

Inside the appliance lies a hidden circuit known as the evaporator, where a refrigerant fluid at a very low temperature constantly circulates. By interacting thermally with the closed compartment, the heat from the stored food migrates to the chilled fluid. During this continuous absorption process, the refrigerant gas gains sensible and latent heat as it travels along the entire length of the internal tubing, reducing the temperature of the interior environment.

What is the role of the compressor and the condenser?#

To expel the heat removed from the food out of the refrigerator, one of the most vital mechanical components comes into play, the electric compressor. This component works by drastically increasing the pressure of the fluid that is in the gaseous state as it exits the internal evaporator. The intentional increase in pressure makes the temperature rise even higher, allowing the fluid to become considerably hotter than the surrounding kitchen air.

After having its pressure raised, the superheated vapor is pushed toward the condenser, commonly positioned on the exterior back of the appliance. By circulating through the tubes in contact with ambient air, the refrigerant fluid yields a large part of its thermal energy to the room. This continuous rejection of heat causes a phase transformation of the heated gas, converting it back into a saturated liquid before the next operational phase.

Read also: Why does ice float on water?

How do expansion and cooling happen?#

After completely crossing the condenser and releasing heat to the outside environment, the liquid fluid needs to cool down intensely again to restart the circuit. It achieves this goal by being forced through a special restriction, known as an expansion element. In this phase of the journey, a sudden and rigorously controlled drop in the internal pressure of the closed circuit occurs, changing its physical state to evaporate shortly thereafter.

The sharp decrease in pressure upon exiting the throat or valve causes rapid partial evaporation accompanied by an immediate and very sharp cooling. This now freezing fluid is led back to the evaporator coil inside the fridge. As soon as it returns to the internal compartment, it restarts the thermodynamic cycle by absorbing more heat from the perishable products, ensuring that the cabinet maintains constant low temperatures for better preservation.

Are there other different refrigeration systems?#

Although the vast majority of commercial models use conventional electric compressors, there are refrigerators that completely dispense with rotary motors. These alternatives are driven directly by thermal heat coming from the combustion of kerosene, diesel, or liquefied gas. They offer the great advantage of being silent and reliable for isolated locations without electrical grid infrastructure, since they operate without moving parts inside the sealed refrigeration circuit.

This differentiated thermal mechanism receives the technical name of absorption refrigeration and is based on the laws of partial gas pressures. The system employs ammonia acting as the main cooling fluid, in addition to hydrogen and water as secondary elements. The mutual solubility of these substances combined with external heat creates a continuous flow of circulation, allowing the equipment to be cooled without relying on traditional pistons or mechanical compressors.

Frequently asked questions#

How does the refrigerator remove heat from food?#

The heat emitted by food is transferred directly to an extremely cold fluid that runs through an evaporator coil inside the refrigerator, reducing the temperature of the internal air.

What is the compressor for in the refrigerator?#

The compressor works by increasing the pressure of the refrigerant gas after the evaporator, raising its temperature so that it can release heat in the external condenser.

What happens during the expansion stage?#

During expansion, the liquid refrigerant fluid undergoes a sudden pressure drop through a restriction, causing rapid evaporation and intense self-cooling before returning to the evaporator.

How does a refrigerator that uses no electricity work?#

Absorption models operate by applying flame heat to kerosene or gas to vaporize a solution with ammonia and water, making the fluids circulate through variations in partial pressures.

Keep reading#

• Why does ice float on water?
• How does the microwave heat food?
• How to choose LED light bulbs: understanding lumens, color and watts

Sources

1. Refrigerator (Wikipedia)
2. Refrigeration (Wikipedia)