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. The dryer is often attached to the condenser and sometimes they even form a single unit.
The refrigerant is routed 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 previously converted the refrigerant from gaseous to liquid state, allowing it to be filtered more effectively.
Operation:
Among other things, the dryer is responsible for removing dirt and moisture from the refrigerant. It is crucial to keep the air conditioning system free of moisture. When moisture is present in the system, for example due to a saturated drying 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 reduced cooling capacity of the air conditioning. As a result, the interior of the car will heat up. After the air conditioning has been turned off for about fifteen minutes, the evaporator has had time to defrost, and the air conditioning will then function normally again for a few minutes.
The drying element is filled with silica gel or silicate beads that contain moisture-absorbing silicate crystals. These beads absorb moisture from the refrigerant as efficiently as possible. The other internal filter elements ensure that wear particles and dirt particles are retained. The clean and dry refrigerant then leaves the dryer via the riser tube (see image) and is then routed to the TEV (Thermal Expansion Valve), which is attached to the evaporator, where the refrigerant continues to flow.
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). This smooths out pressure waves. This can be compared to the operation of an accumulator.
Maintenance:
The dryer/filter element can become saturated when the drying element (the silica gel or silicate beads) has absorbed so much moisture that it is no longer absorbent. The moisture is absorbed once and is 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 several times at an air conditioning service station. Each time the station is connected, or when work is carried out on the system where lines are disconnected, a small or large amount of outside air can enter the system. The dryer/filter element immediately absorbs all the moisture from the outside air that enters the air conditioning system. Therefore, it is advisable to replace the filter/dryer element after work has been carried out on the air conditioning system.
Another cause of saturation can be incorrect installation of the filter/dryer element. When a new element is installed, protective caps are present. These caps should only be removed when the corresponding lines of the system are being connected. If these protective caps are removed too early and the lines are only mounted on the dryer a few minutes later, the drying element is exposed to outside air for too long. This allows a certain amount of moisture to enter. For this reason, it is wise to replace the complete filter/dryer element every time 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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