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Introduction:
The dryer/filter element (2 functions in 1 component) is installed in air conditioning systems with a TEV valve (Thermal Expansion Valve). The dryer/filter element (hereafter simply referred to as “the dryer”) is placed between the condenser and the TEV valve. Often, the dryer is attached to the condenser and sometimes they even form a single unit.
The refrigerant is directed in liquid form from the condenser through the dryer. The compressor provides the pressure and circulation of the refrigerant in the system. The condenser has already converted the refrigerant from a gaseous to a liquid state, enabling better filtration.
Operation:
One of the tasks of the dryer is to remove dirt and moisture from the refrigerant. It is crucial to keep the air system moisture-free. When moisture is present in the system, for example, from a saturated dry element, there is a risk that it will freeze at a certain point in the system, such as at the evaporator, because this is the coldest point. This can lead to blockages and a reduced cooling capacity of the air conditioner. As a result, the car’s interior will warm up. After the air conditioner has been turned off for about fifteen minutes, the evaporator will have had time to defrost, and the air conditioner will function normally again for a few minutes.
The dry element is filled with silica gel or silicate beads containing moisture-absorbing crystals of silicate. These beads absorb moisture as efficiently as possible from the refrigerant. The other internal filter elements ensure that wear and dirt particles are retained. The clean and dry refrigerant then exits the dryer via the riser tube (see image) and is then directed to the TEV (Thermal Expansion Valve), which is attached to the evaporator, where the refrigerant flows further.
Another function of the dryer is to store refrigerant. This storage allows any gas bubbles to escape, ensuring the expansion valve receives a constant flow of refrigerant (in liquid form). As a result, pressure waves are flattened. This can be compared to the operation of an accumulator.
Maintenance:
The dryer/filter element can become saturated when the dry element (the silica gel or silicate beads) has absorbed so much moisture that it is no longer absorbent. The moisture is absorbed once and never released again. When the dryer/filter element can no longer function effectively due to the large amount of moisture, we refer to this as “saturation.”
Over time (often years), there is a risk of saturation, especially if the air conditioning system has been emptied and refilled multiple times at an air conditioning station. Every time the station is connected, or when work is carried out on the system involving the disconnection of lines, a small or large amount of outside air can enter the system. The dryer/filter element immediately absorbs all the moisture present in the outside air into the air conditioning system. Therefore, it is advisable to replace the filter/dryer element after any work on the air conditioning system.
Another cause of saturation can be incorrect installation of the filter/dryer element. When a new element is installed, there are cover caps present. These caps should only be removed when the system’s lines are being installed. If these cover caps are removed too early and the lines are only mounted on the dryer several minutes later, the dry element is exposed to outside air for too long. This allows a certain amount of moisture to enter. Therefore, it is wise to replace the complete filter/dryer element whenever the system is emptied and refilled.
This can be compared to replacing an oil filter in a car when changing the engine oil.
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