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The Refrigeration Process In Your Refrigerator: The refrigerator found in the common kitchen uses a cycle that is very similar to the previously described, generic cycle. In the original home refrigerator, the refrigerant used was essentially pure ammonia. Ammonia is a fairly volatile substance that has been found to be toxic to humans, and since then has been replaced. Chlorofluorocarbons (CFC's) were created to reduce danger levels to humans. CFC's were later determined to be harmful to the environment, so other substitutes were created in the early 1990's. Freon is the common refrigerant found in home refrigerators today. However, for this example, the cycle will be explained using the original refrigerant of ammonia. To begin the cycle, the ammonia is compressed. The compress gas heats up (the orange region) and the heat is released to the atmosphere through the heat-exchanging pipes or coils often found on the back of the refrigerator.
The ammonia then begins to condense as it heads towards the expansion valve (the red to purple region). The once high-pressure ammonia then heads through the expansion value, sending the ammonia into a low-pressure zone. This pressure change causes the ammonia to boil and vaporize (the light blue region). This causes the cooling inside the refrigerator. After the ammonia travels through the network of coils, it travels back through the compressor and begins the process again (How Refrigerators Work 5).
The above picture is of the back of the average home refrigerator. It does an excellent job of showing the heat exchanging pipes used for external cooling, as well as the compressor located at the bottom. The Refrigeration Process In Other Types of Refrigerators: There are several other types of refrigerators on the market today. Some refrigerators are powered by propane, kerosene, or gas. It should be noted that the processes these machines undertake are similar to that of the above "standard" refrigerator, but not identical. Some notable component differences that the propane fridge posses are as follows (How Refrigerators Work 6):
Below is a diagram of how the gas refrigeration system works.
These pieces allow for the cooling process to take place without electricity. Since electricity has been removed from the equation, another substitute is required to power this system. This substitute is propane. Propane allows for the application of heat to the ammonia generator. This heating causes ammonia to reach its boiling point. The boiling mixture then travels through a separator, where water and ammonia are partitioned. The ammonia is the important portion of the mixture, as it proceeds from this step up towards the condenser. The condenser allows the ammonia to cool at a rapid rate, allowing the boiling ammonia to liquefy. Once the ammonia has changed states it heads towards the evaporator, where it is mixed with hydrogen gas. This mixing allows for evaporation, which produces the cold temperatures that can be found in the fridge. What is left of the ammonia and hydrogen gas flows into the absorber. The ammonia and water mix to form a liquid state, and the hydrogen gas travels back up into the evaporator. Once this has been competed, the cycle can begin again (Propane Refrigeration Units). Lets now examine other types of cooling methods, such as peltier coolers.
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