What Is a Freezer?
Freezers are electrical appliances that create a low-temperature space below -10°C and are used primarily for storing food.
A freezer is distinguished from a refrigerator in that it creates a low temperature of -18°C or lower and freezes and stores food. Refrigerators and freezers work in exactly the same way, just at different temperatures.
How Freezers Work
The principle of freezers is almost the same as that of air conditioners, using a mechanism called a heat pump. A heat pump is a mechanism that exchanges heat between a low-temperature place and a high-temperature place. The heat inside freezers is absorbed and dissipated to the outside of the freezers to keep the inside of the refrigerator cool.
A substance called a refrigerant is used as a medium for heat exchange, taking advantage of the physical laws of the substance, such as taking heat from the surroundings when it vaporizes and dissipating heat when it liquefies.
Heat pumps are mainly composed of four components: compressor, condenser, expansion valve, and evaporator. Each of these four devices have the following roles.
1. Compressor
Compressors compress gaseous refrigerants. Since heat is generated during compression, the compressor is located outside of freezers. In most freezers, the compressor is installed on the back. If the space on the back is not enough, heat cannot escape, resulting in lower cooling efficiency and higher power consumption.
2. Condenser
The condenser has the role of liquefying the high-temperature, high-pressure gaseous refrigerant compressed by the compressor. The condenser is also installed outside freezers.
3. Expansion Valve
The expansion valve is responsible for lowering the pressure of liquid refrigerant liquefied by the condenser to lower its boiling point. Expansion valves are installed inside freezers.
4. Evaporator
The evaporator vaporizes the liquid refrigerant with reduced boiling point sent from the expansion valve. As the liquid vaporizes, it removes heat from its surroundings, keeping the inside of the refrigerator cool. The vaporized refrigerant is then fed to the compressor, which releases heat to the outside, repeating this cycle to keep the freezers cool inside.
Types of Freezers
Freezers are generally classified according to the cooling method, and there are three main types: direct-cooling type, fan type, and Peltier type.
1. Direct Cooling Type
This is a method in which an evaporator is installed inside freezers and the inside is cooled by natural convection. It has the advantage of high cooling efficiency and low electricity costs. It has the disadvantages of not being able to set temperatures for each room and the need for defrosting.
2. Fan Type
This is a method in which an evaporator is installed outside of freezers and cool air is supplied by a fan. This method has the advantages of allowing temperature settings for each room and eliminating the need for defrosting. The disadvantages are that the main unit is larger due to the installation of a fan and that it operates more noisily.
3. Peltier Method
This cooling method uses a Peltier element that absorbs and releases heat by passing an electric current through it. 5-15°C cooling is possible. It has the advantages of being quiet with no startup or vibration noise, compact, and requiring no defrosting. Compared to direct cooling and fan cooling, it has the disadvantage of not being able to maintain temperatures lower than 5°C.