Valeooscope - Air Conditioning System Thermal comfort loop

9. The Heating Ventilation and Air Conditioning unit (HVAC)

9.6.2 Cabin air filter performances

Filter performance is defined according to the following parameters : g Efficiency & dust holding capacity The efficiency is the ratio of particles that are trap- ped by the filtration process. The efficiency is specified for a defined particle size. In practice, a cabin filter must be capable of trap- ping 100% of particles measuring 10µm in diameter and between 10% and 30% of particles measuring 0.25µm in diameter. The dust holding capacity is the quantity of solid particles a filter can retain before a defined flow resistance is reached, that is to say before the filter The difference in flow resistance upstream and downstream of the filter, is related to the air flow resistance created by the filter; it is also known as “head loss”. The head loss depends on the filter soiling. The filter must produce the lowest possible head loss to optimise the air conditioning system perfor- mances. is to be changed. g Pressure drop

g Gas absorption level This feature is applicable to active carbon filters (CA and PCA), it reflects the amount of gas that is ab- sorbed by the filter media. The cabin air filter design is a trade-off between the pressure drop and the dust holding capacity, this to assure the appropriate air flow in the cabin as well as an efficient filtration process. The service life of a filter corresponds to the maximum amount of particles before clogging occurs. The service life varies according to the use conditions (surrounding pollution, frequent use of the A/C sys- tem…)

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