All residential refrigerators operate in a similar fashion. All refrigerators have these components: a compressor, condenser, evaporator, capillary tube, and a thermostat. Refrigerators with an automatic defrost cycle have small heaters in strategic places to defrost ice buildup. The basic principle of refrigeration is that you remove heat. Some people think refrigeration works by cooling something, but it’s just taking heat away. The refrigeration process is really simple. Your refrigerator takes warm air and makes it cooler by transferring the heat using evaporation principles.
Refrigeration starts with the compressor. The compressor is the workhorse for the refrigerator. The compressor is turned on when electricity is sent to it by the thermostat. It mechanically compresses, or squeezes, a refrigerant gas. This compression causes the gas to become a hot, high-pressure gas. Next, this hot gas flows through a set of condenser coils where it dissipates its heat, and condenses into a liquid.
The condenser coil is a system of bent tubes that run through thin pieces of metal. These thin pieces of metal are sometimes referred to as fins. These fins resemble a radiator that you would see in a car. The high-pressure gas from the compressor flows into the condenser coils and changes state to become a liquid. As this change takes place, the tubes radiate heat from the refrigerant gas. This heat is conducted away from the coils by the fins attached to the tubes. The capillary tube connects the condenser coils to the evaporator coils, and it controls the pressure of the refrigerant as it enters the coils.
As the refrigerant passes through the exit of the capillary tube, the liquid refrigerant expands, boils, and evaporates into the evaporator coils, and it becomes a cold, low-pressure gas. This cold gas flows through the evaporator coils, which allows the gas to absorb heat, and by absorbing that heat; it cools down the air flowing past the coils. The fan inside the freezer’s compartment circulates the air to keep the temperature uniform and constant. Because the evaporator coils are so cold, they cause any humidity in the air to freeze onto the evaporator coils as ice or frost. The refrigerant is then sucked back into the compressor where the process is repeated. A thermostat controls the process, helping to keep frozen foods at the desired temperature to maintain freshness.
The fan that is located inside the refrigerator’s freezer compartment circulates the air to keep the temperature uniform and constant. The process is regulated through the use of thermostats and switches, which help to keep your foods at a desirable temperature to maintain freshness without freezing the food, or leaving it so warm that it spoils. When the temperature is cool enough, the thermostat senses it, and tells the compressor and fan to take a break. When it gets too warm again, the same thermostat tells the compressor and fan break time is over.
Most modern refrigerators have an automatic defrost system which includes three major components: the defrost timer, defrost thermostat, and defrost heater.
The defrost timer, approximately every 6 to 12 hours, cuts off the power to the compressor and cooling system, and switches on the defrost heater. As the ice melts, it drips through a drain hole, through a tube, and into an evaporation pan where it evaporates with the help of a fan that blows warm compressor air over it to improve evaporation. The defrost heater has an electric heating element and is located just beneath the evaporator coils. This heater element gets hot, and due to its proximity to the coils, any ice or frost build-up usually melts pretty fast. When the defrost timer advances, or the defrost thermostat, located near the evaporator coils, detects that the temperature by the coils has raised up to a certain pre-set temperature, the cooling unit kicks back in.
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