All of us have a refrigerator at home and the fundamental idea of having a refrigerator at home is that it helps in keeping the food items colder and fresher for a long time. Refrigerator acts by the principle that the cold air will slow down the multiplication of bacteria in food, and thus it takes a very long time for the bacteria to spoil the food that is kept inside the refrigerator. Apart from the refrigerator portion of the fridge, the freezer also helps in preserving food items from spoiling for a longer time. It helps in maintaining a freezing temperature for frozen food items.
While the interior portions of the refrigerator are essentially cold, the outer portions of the refrigerator are warm. It is dissipating heat through its walls to maintain a colder temperature in its internal compartments. Refrigerators will generate a lot of heat and let out hot air, during the process of making cold air and maintaining colder temperatures.
To cool down this heat, several heat dissipation pipes are installed on the outer walls of the refrigerator. When the refrigerator is being operated, the heat will get generated on the side walls of the refrigerator. Also, to maintain this cool temperature inside the refrigerator, the heat that is generated when the compressor is operated periodically will dissipate to both the front and the sides of the unit.
Now a common question that arises in the minds of people is that when the back and the sides of the refrigerator are generating so much heat, why is the rear portion of the refrigerator painted black? We all know that black color absorbs a lot of heat compared with other dull colors, and still the back portion of the refrigerator is painted black. Do you think that the refrigerator manufacturing companies paint them in black because black paint is cheaper? May not be.
The back portions of the refrigerator are painted black for the scientific reason that, a color that is better at absorbing heat is also the color that is better at radiating heat. According to scientific theories, “The rate at which the body radiates or absorbs the thermal radiation will depend on the nature of the surface in which it operates”. The Objects that are good emitters of heat are also very good absorbers, according to Kirchhoff’s radiation law.
Why is the back portion of the refrigerator painted black?
A black surface is both an excellent emitter and an excellent absorber. If the same surface is painted in silver or any other dull colors, then it becomes a poor absorber and a very poor emitter of heat.
Thus, black is both good heat-absorbing color and it is also a good radiating color. This is the reason why the external coils of the refrigerator are painted black. The condenser coils or the external coils of the refrigerator that are present on the bottom of the back of the refrigerator are the pipes, where the vapor refrigerant condenses into liquid form when the compressor keeps increasing the pressure. As the condensation process in the refrigerator keeps happening, the refrigerant will keep releasing the heat, which gets pushed out into the outside air. This is the heat that we feel when we stand near the refrigerator.
Now that we know the condenser coils are letting out heat from the refrigeration process, the manufacturers ensure that they paint these external coils black to radiate heat as much as possible. This blackened surface will keep releasing the heat away from the refrigerator and ensures that the fridge will continue to work in an optimal condition, by remaining cool.
The compressor of the refrigerator is also known as the heart of the refrigerator. It helps in circulating the refrigerant throughout the system and it also helps to add adequate pressure to the warm portions of the circuit, thus making the refrigerant hot. This works similarly to the principle of pumping air back into the bicycle tube. We will be able to sense the heat increasing in the pump when we compress the air. The compressor is also present in the rear portion of the refrigerator and it is also predominantly painted black for the same reason that the black color will absorb and radiate more heat compared with other colors.
When the refrigerator is working, it will absorb the heat from the food and cool it down. It will dissipate heat through the condenser pipes at the rear of the refrigerator. Common sense tells us that black color absorbs more heat and will thus make the back portion of the refrigerator even hotter if it is painted in black. Still, the rear portion of these units is painted in black, for the simple reason that, the black color not only absorbs more heat, but it also dissipates it faster, maintaining easy release of hot air into the atmosphere.