A refrigerator Keeps Food Cold
Most of the time when we go get a cold drink or a snack out of the refrigerator we do not think too much about the various electric parts that work together to keep our food cold and safe. Today a refrigerator is considered to be a necessity and is a common large appliance in our kitchens. However, there is actually a lot of science behind keeping our favorite foods cool and many different large and small electric components that work together to create a safe environment to store foods.
Second Law of Thermodynamics
Refrigerators actually use the nature of heat to keep foods cold. The Second Law of Thermodynamics basically states that when a cold item is placed close to a hotter item, then the cold item will start to become warmer while the warmer item becomes cooler. The way a refrigerator cools our food items is not done by lowering the temperature as much as it works using evaporation to carry the heat away. This in turn makes the refrigerator cold. Both refrigerators and air conditioners use similar principles of evaporation and electric components to cool.
Cooling System
There are two compartments on a refrigerator one which stores frozen items and the other compartment which just keeps things cool but not frozen. Surrounding these two compartments are a series of pipes that exchange heat. There is a compressor located at the bottom of the unit. The compressor is run by an electrical motor. On the back of the refrigerator are more of the heat exchanging pipes. If you look at the back side of a fridge, you’ll see these coiled up and running along the back of the appliance. Pure ammonia runs throughout the refrigerating system which is a closed system of course. Ammonia evaporates at -27 degrees. Since the system is closed up tightly there is no way that anything can be lost or added during its operation. If a refrigerator starts to leak it is very important to get it repaired or replaced at once because ammonia is a very powerful chemical.
Refrigeration Process
The ammonia is a compressed gas which becomes very hot when it is under increased pressure which is what the compressor does. Once the ammonia is compressed and gets hot it flows throughout the coils that you see on the back of most refrigerators. This allows all the extra heat to escape into the surrounding environment. Sometimes you may notice that the fridge feels warm when you touch it. Once the ammonia cools down it will turn to its liquid form which is then forced to pass through an expansion valve. Basically, the expansion valve has a very small opening and when the liquid ammonia travels through it, it turns into a fast moving, cold mist which evaporates as it moves throughout the coils in the freezer area. Because this evaporation happens at a -27 degrees F, the ammonia begins to draw heat from the area surrounding it. Basically, this is the Second Law of Thermodynamics in practice. The cold material or ammonia gas that is evaporating takes heat from the warmer objects like water in an ice cube tray.
When the evaporating ammonia absorbs more of the heat, its temperature goes back up. The coils that are used to surround the lower portions of the fridge, or the refrigerator compartment are not nearly as compact as those used in the freezer compartment. As the ammonia gets drawn back into the compressor the whole pressurization cycle begins again so that the cooling and evaporating can repeat over and over.
Cyclical Process
In one way the cyclical process that is used in a refrigerator is similar to an electrical circuit in that it continues to cycle unless it is interrupted. As the gas or refrigerant is pushed through the coils the transformation that occurs from vapor form to liquid forms releases the heat outside the fridge and gets the gases ready for another round in the cycle. The movement of the refrigerant or gas removes heat and places it outside the fridge which keeps the inside of the unit cold. Thus, the heat is transferred from the inside of the refrigerator to the outside.
Second Law of Thermodynamics
Refrigerators actually use the nature of heat to keep foods cold. The Second Law of Thermodynamics basically states that when a cold item is placed close to a hotter item, then the cold item will start to become warmer while the warmer item becomes cooler. The way a refrigerator cools our food items is not done by lowering the temperature as much as it works using evaporation to carry the heat away. This in turn makes the refrigerator cold. Both refrigerators and air conditioners use similar principles of evaporation and electric components to cool.
Cooling System
There are two compartments on a refrigerator one which stores frozen items and the other compartment which just keeps things cool but not frozen. Surrounding these two compartments are a series of pipes that exchange heat. There is a compressor located at the bottom of the unit. The compressor is run by an electrical motor. On the back of the refrigerator are more of the heat exchanging pipes. If you look at the back side of a fridge, you’ll see these coiled up and running along the back of the appliance. Pure ammonia runs throughout the refrigerating system which is a closed system of course. Ammonia evaporates at -27 degrees. Since the system is closed up tightly there is no way that anything can be lost or added during its operation. If a refrigerator starts to leak it is very important to get it repaired or replaced at once because ammonia is a very powerful chemical.
Refrigeration Process
The ammonia is a compressed gas which becomes very hot when it is under increased pressure which is what the compressor does. Once the ammonia is compressed and gets hot it flows throughout the coils that you see on the back of most refrigerators. This allows all the extra heat to escape into the surrounding environment. Sometimes you may notice that the fridge feels warm when you touch it. Once the ammonia cools down it will turn to its liquid form which is then forced to pass through an expansion valve. Basically, the expansion valve has a very small opening and when the liquid ammonia travels through it, it turns into a fast moving, cold mist which evaporates as it moves throughout the coils in the freezer area. Because this evaporation happens at a -27 degrees F, the ammonia begins to draw heat from the area surrounding it. Basically, this is the Second Law of Thermodynamics in practice. The cold material or ammonia gas that is evaporating takes heat from the warmer objects like water in an ice cube tray.
When the evaporating ammonia absorbs more of the heat, its temperature goes back up. The coils that are used to surround the lower portions of the fridge, or the refrigerator compartment are not nearly as compact as those used in the freezer compartment. As the ammonia gets drawn back into the compressor the whole pressurization cycle begins again so that the cooling and evaporating can repeat over and over.
Cyclical Process
In one way the cyclical process that is used in a refrigerator is similar to an electrical circuit in that it continues to cycle unless it is interrupted. As the gas or refrigerant is pushed through the coils the transformation that occurs from vapor form to liquid forms releases the heat outside the fridge and gets the gases ready for another round in the cycle. The movement of the refrigerant or gas removes heat and places it outside the fridge which keeps the inside of the unit cold. Thus, the heat is transferred from the inside of the refrigerator to the outside.