Refrigerant
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| Illustration 1 | g01076998 |
The substance that is used in air conditioning systems is called refrigerant. Many refrigerants are available. In fact, any liquid that will boil at temperatures near the freezing point of water can be used as a refrigerant. However, a good refrigerant should be non-poisonous and non-explosive in order to be safe. A good refrigerant should be noncorrosive, odorless, and mix well with oil.
The refrigerant that is used in current Mobile Air Conditioning Systems is known as Refrigerant HFC-134a. HFC-134a is made from Hydrogenated Fluorocarbons. HFC-134a has the same advantages of R-12 plus HFC-134a will not harm the atmosphere.
The following precautions should be followed when you are servicing air conditioning systems, operating air conditioning equipment, or handling refrigerants.
- Do not weld near vehicle installed air conditioning lines. Do not steam clean near a vehicle installed air conditioning lines. The heat can cause excessive refrigerant pressure.
- Do not transport refrigerant in a passenger compartment of a vehicle.
- Do not expose refrigerant to open flames, high temperatures or direct sunlight.
- Wear safety goggles. Refrigerant that comes in contact with the eyes can cause serious injury.
- Do not use excessive heat on refrigerant containers during the charging process. Never use direct heat. Use a container of water that does not exceed 52 °C (125. °F).
- Do not discharge refrigerant to the atmosphere. In addition to being harmful to the earth's ozone layer, Refrigerant 12 results in a very poisonous phosgene gas, when the refrigerant is subjected to an open flame
- Always work in a well ventilated area. Inhaling refrigerant, even in small amounts, can be cumulative and cause you to become lightheaded. Refrigerants can also cause irritation to the eyes, the nose, and the throat.
- Do not weld or steam clean an air conditioning system. Excessive pressure could build up in the system.
- Do not mix R-134a with air for the purpose of leak testing. When R-134a is under pressure the mixture could explode.
- When you charge a system with the engine running, be sure that the high pressure gauge valve is closed.
- Be alert when the engine is running. Stay clear of rotating components.
- Do not recover or transfer refrigerant into a disposable tank. Always use a DOT approved tank. Look for DOT4BA or DOT4BW on the tank.
- Do not fill a storage tank to more than 80% of the gross weight rating.
Basic Air Conditioning System
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| Illustration 2 | g01077001 |
Illustration 2 shows an open flask of Refrigerant HFC-134a at room temperature. When at atmospheric pressure (14.7 psi), HFC-134a boils at -27 °C (-16 °F). The heat in the room causes the refrigerant to boil. As the refrigerant boils, heat is drawn away from the surrounding area. The absence of heat makes the surrounding area cooler. However, such a system is not economical nor is the system good for the atmosphere.
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| Illustration 3 | g01077002 |
In Illustration 3, a compressor and a high pressure flask have been added. As the liquid refrigerant boils, the vapor is drawn through a hose into the compressor. The compressor increases the pressure of the vapor and the intensity of the heat. Since temperature is a measurement of the heat intensity, the temperature of the vapor increases. The high pressure, high temperature vapor flows into the high pressure flask. The temperature of the high pressure vapor is higher than the temperature of the surrounding area. Therefore, heat flows from the high pressure vapor to the surrounding area. The high pressure vapor cools. Then, the high pressure vapors change into a high pressure liquid.
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| Illustration 4 | g01077003 |
Complete the system by adding a hose to connect the flask of high pressure liquid to the flask of low pressure liquid. An orifice is inserted in the hose in order to maintain a pressure difference between the high pressure liquid and the low pressure liquid.
When the flask of low pressure liquid refrigerant boils, the boiling process collects heat from the surrounding area. The low pressure refrigerant vapor is drawn through a hose into the compressor. The compressor raises the pressure and temperature of the vapor and stores the vapor in the high pressure flask. The high pressure, high temperature vapor gives up heat to the cooler surrounding area. This causes the high pressure vapor to cool and to condense into a high pressure liquid. The high pressure liquid refrigerant flows through a hose and an orifice to the flask for low pressure liquid refrigerant. The low pressure liquid refrigerant boils, and the cycle is repeated.