A refrigerator is an electrical appliance with a thermally insulated compartment that keeps contents cool.
These devices have a refrigerant that flows through a sealed system, drawing heat out of the fridge. They preserve food by keeping it cold enough to slow microbial growth. Refrigeration does not stop all microbes or make food safe indefinitely.
Over time, the design and functionality of a refrigerator have evolved drastically. Nonetheless, the purpose remains the same.
Let’s try to understand how it works in closer detail.
Important Components of A Refrigerator
At the heart of a refrigerator is a compressor. It’s a pump that constricts the gaseous refrigerant and releases it into the condenser coils.
Now, the refrigerant is a fluid that changes from liquid to gas and vice-versa during the refrigeration process.
The main function of the refrigerant is to suck heat out of the fridge compartment and pump it to the outside. Hence, it’s a liquid that evaporates inside the refrigerator, creating cold temperatures.
An important characteristic of a refrigerant is that it changes from liquid to gas and back during the process.
Apart from the compressor and refrigerant, refrigerators have three components. The first is a condenser coil. These coils are located outside the refrigerator.
The condenser releases heat from the refrigerant into the surrounding room. The evaporator absorbs heat from inside the refrigerator.
Next, are evaporator coils located on the inside of the refrigerator. Finally, there is an expansion device.
Principle of Operation of A Refrigerator
When you rub alcohol on your skin and leave it on, it evaporates, leaving your skin feeling cold. This is similar to how refrigerators work.
When the refrigerant evaporates, it traps heat and produces a low ambient temperature. So, how does this happen? Let’s find out.
Refrigerators have long serpentine pipes running back and forth along the outside and inside compartments.
In older units, these pipes were filled with Freon gas. But Freon was linked to various environmental issues. Hence, it was replaced by other gases as refrigerants.
As Danfoss explains the refrigeration cycle, the compressor takes in low-pressure refrigerant vapor and compresses it. The hot, high-pressure vapor then travels to the condenser, where it releases heat and becomes liquid.
After passing through an expansion device, the refrigerant enters the low-pressure evaporator and absorbs heat as it boils. Heat leaves the compartment through this sealed circuit; the system does not pump the compartment’s air outdoors.
The vapor returns to the compressor, and the cycle repeats. A capillary tube or another expansion device maintains the pressure difference between the condenser and evaporator.
The entire process repeats continuously.
As heat is removed, the compartment cools. Depending on the design and cooling demand, the controls cycle the compressor on and off or vary its speed.
A refrigerator releases the heat removed from its compartment, along with heat associated with its electrical operation, into the room. That is why parts of its exterior can feel warm.
A Closer Look at The Different Components of A Refrigerator
Here are the various components of a refrigerator.
Compressor
The compressor is the heart of a refrigerator. It’s responsible for compressing the refrigerant gas and increasing its pressure during the cooling cycle.
The main function of this part is to compress the low-pressure refrigerant gas from the evaporator.
In a reciprocating compressor, an electric motor drives a piston through a suction and compression cycle.
When the piston moves downward, it creates low pressure. This enables the refrigerant to enter the compressor.
When the piston moves upward, it compresses the gas, increasing its pressure and temperature. This process will expel the gas into the condenser coils.
Hence, the compressor plays an important part in maintaining the flow of the refrigerant through the system.
Compressor designs vary across refrigeration equipment. Household refrigerators commonly use compact hermetic compressors; large industrial systems can use different designs.
Household refrigerators typically have reciprocating compressors.
Condenser
A condenser removes heat from the compressed refrigerant and condenses it into a liquid.
The coils of a condenser are usually made of copper or aluminum. They provide a large area for heat exchange.
When the condenser cools the refrigerant, it undergoes a phase change from gas to liquid. This liquid then flows to the expansion device for the rest of the process.
There are different types of condensers, like air-cooled condensers, water-cooled condensers, evaporative condensers, shell-and-coil condensers, and plate heat exchangers.
The choice between them will depend on factors like the size of the refrigeration system, cooling requirements, and installation conditions.
Expansion Device
The expansion device restricts the flow of high-pressure liquid refrigerant toward the evaporator. Household refrigerators often use a capillary tube rather than an adjustable expansion device.
It creates a pressure drop to control the amount of refrigerant entering the evaporator.
This pressure drop allows the refrigerant to evaporate rapidly and absorb heat, allowing the refrigerator to cool rapidly.
Evaporator
The main task of an evaporator is to facilitate the evaporation of the low-pressure liquid refrigerant.
When the liquid refrigerant enters the evaporator, it comes into a low-pressure environment created by the expansion device.
This makes it evaporate and absorb heat from the surroundings. Like the condenser, the evaporator coils are also made of copper or aluminum to increase the area of heat exchange.
The design and functionality of an evaporator depend on various factors, like the size of the refrigerator, cooling requirements, and space availability.
Refrigerant
Refrigerants have unique properties that enable them to effectively undergo a phase change from low-pressure gas to high-pressure liquid and vice-versa.
This phase change creates the heating and cooling effect that drive the refrigeration process.
Some of the essential properties of a good refrigerant are a low boiling point, high latent heat of vaporization, good thermodynamic properties, stability, and low environmental impact.
Commonly used refrigerants include HFCs (hydrofluorocarbons), HCFCs (hydrochlorofluorocarbons), HCs (Hydrocarbons), Ammonia, and Carbon Dioxide.
Various factors like safety considerations, system requirements, and environmental impact decide the choice of refrigerant.
Modern Refrigerator Features
Over the years, refrigerators have evolved significantly.
Modern refrigerators have advanced technological and innovative features that make them more convenient and energy-efficient. They also have better storage capabilities.
A notable advancement in refrigerator technology is the emergence of smart refrigerators. These appliances have various intelligent features like internet connectivity for remote monitoring and control.
Higher energy efficiency is also an added advantage of many newer refrigerator models.
These refrigerators optimize power usage and reduce energy consumption through energy usage tracking and the use of energy-efficient components.
Some models have a vacation mode. Follow its manual carefully, especially if the mode requires the refrigerator compartment to be emptied.
Some models offer flexible shelving or specialized storage zones. Check the particular model’s features and temperature instructions.
Door-in-door design refrigerators usually feature an additional compartment that is accessible from the outer door.
It lets users access some items without opening the main compartment. Actual energy use still depends on the model, settings and how it is used.
They also come with special compartments and shelves with temperature optimization capabilities to store special food and produce.
This helps users to store deli meats, beverages, and delicate produce at the optimum storage condition.
These additional features vary by model. Compare the actual specifications and energy label rather than assuming that every modern refrigerator is connected or uses less electricity.
