How does a refrigerator work?

How does the refrigerator, an appliance with an indispensable presence in every home (also at the workplace), produces the cold that allows food to be kept and preserved for a long time? In order to find that out, we’ll have to take a look at the working of the refrigerator in detail.

Working of a refrigerator

In fact, a refrigerator takes heat from a container (the internal compartment that is thermally insulated) that is cold and pours it into the surrounding outdoor environment, characterized by higher temperature. Refrigerating machines are systems in which the evolving fluid called the refrigerant undergoes transformations.

Different types of refrigerant exist for substantial physical properties. In the past, the most common evolving fluid was “Freon”, which was used in the construction of refrigerators since 1970. However, it was banned due to its aggressive properties with respect to atmospheric ozone, and for this reason, supplanted by the less harmful R134a (CH2FCF3).

The thermodynamic cycle

In the refrigerator, the R134a undergoes a cyclical succession of transformations within the different components of the system, so that, once the useful effect is obtained, the refrigerant returns to the initial conditions, thus resulting in the so-called thermodynamic cycle.

A refrigerator is essentially made up of:

1.      A refrigerator is essentially made up of.

2.      A closed environment that needs to be cooled.

3.      A tube in which the refrigerant flows.

4.      A compressor powered by electricity.

5.      A lamination valve applied precisely between condenser and evaporator.

The volumetric compressor, consisting of a piston that slides inside a cylinder compresses the gas. In addition to the temperature, the pressure flowing inside the condenser, a heat exchanger where the tube in which the refrigerant flows is wound on itself to serpentine (coiled set of pipes inside the refrigerator to maximize the heat exchange and to transfer heat to the external environment).

Once the passage inside the condenser has been completed, the fluid, which used to be gas becomes saturated liquid (i.e., without any trace of the vapor phase).

In the liquid phase, the refrigerant flows through the “L” lamination valve, which is simply a narrowing of the duct the liquid flows into. Due to the sudden reduction of the passage section, the pressure at which the liquid is found suddenly drops and the variation induces the evaporation process due to certain physical properties of the refrigerant. 

This transformation, activated downstream of the lamination valve, proceeds and is completed inside the evaporator located inside the refrigerator, i.e., the environment to be cooled. The refrigerant evaporation process involves subtraction of heat inside the refrigerator compartment, which at this point is, therefore, colder than the external environment.

Once the phase transition is complete, the steam, now saturated (i.e., without traces of liquid) passes inside the compressor where it is brought to a higher pressure, this allows the restoration of the initial conditions, thus concluding the cycle thermodynamic.

The refrigerating machine requires a certain amount of electrical energy to operate, the greater the higher the external temperature of the refrigerator. For this reason, paradoxically, the efficiency of the machine is lower in the summer, since the speed with which the refrigerant gives heat to the surrounding environment is less than in winter. This leads to a significant increase in consumption and eventually inflated electricity bills. The simplest way of optimizing consumption is to properly place and store the food in the refrigerator.