Refrigerant R134a Characteristics

Refrigerant R134a Characteristics

Commercial Names and Designations
The refrigerant R134a is currently available under the following trade names:
- H-FKW 134a
- SUVA 134a
- KLEA 134a

NOTE:
- Different trade names may be used in other countries.
- Of the wide range of refrigerants available, this is the only one which may be used for vehicles. The designations Frigen and Freon are trade names. They also apply to refrigerants which may not be used in automotive vehicles.

Color
Like water, refrigerants are colorless in both vapor and liquid form. Gas is invisible. Only the boundary layer between gas and liquid is visible. (Liquid level in tube of charging cylinder or bubbles in sight glass). Refrigerant R134a fluid may appear colored (milky) in a sight glass. This cloudiness is caused by partially dissolved refrigerant oil and does not indicate a malfunction.

Vapor Pressure
In a partially filled, closed vessel, the quantity of refrigerant evaporating from the surface equals the quantity returning to the liquid state as vapor particles condense. This state of equilibrium occurs under the influence of pressure and is often called vapor pressure. Vapor pressure is dependent on temperature.

R134a Physical Characteristics
The vapor pressure curves of R134a and other refrigerants are sometimes very similar, therefore it is not possible to make a certain distinction solely by pressure.

With R134a, the A/C compressor is lubricated with special synthetic refrigerant oils, e.g. PAG oils (polyalkylene glycol oils).

Affect on Metal
In its pure state, refrigerant R134a is chemically stable and does not corrode iron or aluminum.

Refrigerant impurities such as chlorine compounds however cause corrosion of certain metals and plastics. This can lead to blockage, leaks or deposits on the A/C compressor piston.

Critical Temperature/Pressure
The refrigerant R134a remains chemically stable up to a gas pressure of 39.5 bar (corresponding to a temperature of 101 degrees C). Above this temperature, the refrigerant decomposes (refer to "Combustibility").

Water Content
Only very small amounts of water are soluble in liquid refrigerant. On the other hand, refrigerant vapor and water vapor mix in any ratio.

Any water present in the refrigerant circuit is fed with it as droplets. The dryer, dryer bag or dryer cartridge contained in the reservoir can absorb approximately 7 grams of water. They are then saturated and cannot absorb any more water. If water is still present in the refrigerant circuit, it flows up to the expansion valve nozzle or restrictor and becomes ice.

The air conditioning system stops cooling.

Water destroys the air conditioner as it combines with other impurities at high pressures and temperatures to form acids.

Combustibility
Refrigerant is non-flammable. In fact, it has a fire-retardant or extinguishing effect. Refrigerant decomposes when exposed to flames or red-hot surfaces. UV light (occurring for example during electric welding) also causes refrigerant decomposition. The resultant decomposition products are toxic and are not to be inhaled. However, irritation of the mucous membranes provides an adequate and timely warning.

Charge Factor
A vessel must have space for vapor as well as liquid. As the temperature rises, the liquid expands. The vapor-filled space becomes smaller. At a certain point, there will only be liquid in the vessel. Beyond this, even a slight increase in temperature causes great pressure to build up in the vessel as the liquid attempts to continue expanding despite the absence of the necessary space. The resultant forces are sufficient to rupture the vessel. To avoid overfilling of vessels, regulations governing compressed gases specify the number of kilograms of refrigerant with which a vessel may be filled per liter of internal vessel volume. The product of multiplying this charge factor by the internal volume of the vessel is the permissible capacity. The figure for refrigerant used in vehicles is 1.15 kg/liter.

Evidence of Leaks
External damage, for example, can cause a leak in the refrigerant circuit. The small quantity of refrigerant escaping from minor leaks can be detected for example using an electronic leak detector or by introducing a leak detection additive into the refrigerant circuit. Electronic leak detectors are capable of registering leaks with refrigerant losses of less than 5 g per year. (Use must be made of leak detectors designed for the composition of the respective refrigerant. For example, a leak detector for R12 refrigerant is not appropriate for R134a, as R134a refrigerant has no chlorine atoms and the leak detector does not therefore respond).