Properties of the refrigerant R134a (Solution)

Physical properties of R134a.

The vapor pressure curves of R134a and other refrigerants are sometimes very similar, which means that a clear distinction based solely on pressure is not possible.

The compressor lubrication for R-134a is achieved using special synthetic refrigerating machine oils, such as PAG (polyalkylene glycol) oils.

Behavior towards metals.

In its pure state, refrigerant R134a is chemically stable and does not corrode iron or aluminum.
However, contaminants in the refrigerant, such as chlorine compounds, can cause certain metals and plastics to corrode. This can lead to blockages, leaks, or deposits on the compressor's piston.



Critical temperature / critical pressure.

Up to a gas pressure of 39.5 bar gauge (which corresponds to a temperature of 101 °C), the refrigerant R134a remains chemically stable; above this temperature, the refrigerant decomposes (see flammability).



Water content.

Water is only sparingly soluble in liquid refrigerants. In contrast, refrigerant vapor and water vapor mix in any proportion.

In the refrigerant cycle, any water present may be carried along as droplets if the dryer in the liquid or collection vessel has already absorbed approximately 0.1 grams of water. This water flows to the nozzle of the expansion valve or throttle and freezes. The air conditioner stopped cooling.

Water damages the air conditioning system because acids are formed under high pressures and temperatures, especially in combination with other contaminants.


Flammability.

Refrigerants are non-flammable. In fact, they have flame-retardant or fire-extinguishing properties. Refrigerants decompose when exposed to flames and hot surfaces. They are also broken down by UV light (which is produced during electric welding). This process creates toxic decomposition products, which should not be inhaled. However, stimulating the mucous membranes will provide sufficient and timely warning.


Fill factor.

A container must have a vapor space connected to the liquid space. As the temperature rises, the liquid expands. The space filled with vapor becomes smaller. At a certain point, only liquid will remain in the container. After that, even a slight increase in temperature can cause very high pressures to build up inside the container, because the liquid continues to expand, but there is no more space available. The forces generated are large enough to rupture the container. To prevent containers from being overfilled, the regulations for pressure gas containers specify the maximum amount of refrigerant, in kilograms, that can be filled per liter of the container's internal volume. This "fill factor," when multiplied by the internal volume, yields the permissible fill volume. It is 1.15 kg/l for refrigerants used in automobiles.



Leak detection.

The refrigerant circuit can become leaky, for example, due to external damage. The detection of small leaks can be challenging due to the small amount of refrigerant escaping, but it can be achieved using an electronic leak detector. This device can detect leaks with a refrigerant loss of less than 5 grams per year. (For the different types of refrigerants, leak detectors must be used that are designed for the composition of the specific refrigerant. For example...) Leak detectors for refrigerant R12 are not suitable for R134a, because refrigerant R134a does not contain chlorine atoms, so these leak detectors will not respond.