Refrigeration Systems
Refrigeration Systems
Sep 10Installing A Refrigeration System
A refrigeration system does not produce cold air; it takes the heat out of the cabinet. The main purpose of a refrigeration system, then, is to transfer heat.
A refrigeration system takes heat out of the inside of the cabinet by blowing air over or through an evaporator coil (1). Here, the warmer air from the cabinet is transferred to the refrigerant, located inside the evaporator coil. The refrigerant then passes to the compressor (2), where it is compressed. Then, the compressed refrigerant is transferred to the condenser coil (3) where air is passed through the condenser coil and the heat is removed from the refrigerant.
The refrigerant then is returned to the evaporator coil (4) by one of two methods:
- Through an expansion valve which actually opens and allows the refrigerant to flow back into the evaporator coil; or via a capillary tube, which is a thin copper tube that meters the refrigerant flow to the evaporator coil.
- The refrigerant changes pressure and states (liquid and gas) during the refrigeration cycle.
How Refrigeration Systems Work
- Pressure and temperature of gas increases – The compressor converts gas from low temperature, low pressure gas to high temperature, high pressure gas, which moves into the condenser.
- Gas converts to liquid – In the condenser the high temperature, high pressure gas is converted to high pressure, high temperature liquid by releasing heat.
- Impurities and moisture removed – The high pressure, high temperature liquid then passes through a strainer/drier where impurities and moisture are removed.
- Flow into evaporator regulated – The metering device regulates the flow of the high pressure, high temperature liquid refrigerant into the evaporator.
- Liquid converted to gas – As the high pressure, high temperature liquid refrigerant passes through the evaporator coil, it expands and converts into a low temperature, low pressure liquid. Then, the liquid absorbs heat from the storage compartment and evaporates, turning it back into a low temperature, low pressure gas.
Purpose of a Refrigeration System
The main purpose of refrigeration is to store food at a temperature below 41° F to retard spoilage and prevent bacteria growth. There are several characteristics of a refrigeration system that can affect food’s taste, appearance, temperatures, and food yields.
Humidity – The relative humidity of the air in a refrigerator should fall between 80% and 85%. If the relative humidity of the air surrounding the food is too low, the air will pick up moisture from the food, causing discoloration, drying, and cracking. If the relative humidity is too high, the food will pick up moisture from the air, which may result in sliming, softening, and increased bacteria growth.
Air Circulation – Adequate air circulation is necessary to insure even temperature and humidity levels throughout the refrigerator.
Temperature – Temperature is the most important factor in food preservation. The temperature fluctuates every time the door to the refrigerator is opened. When the doors are opened frequently, the temperature recovery is slower and contributes to food deterioration.
Sanitation - A dirty refrigerator preserves perishable food poorly becauseunsanitary conditions promote the growth of bacteria. This one factor can negate the positive effects of sufficient humidity, adequate air circulation, and accurate temperature control.
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