HEPA filters to improve vehicle cabin air quality – advantages and limitations
Artikel i övrig tidskrift, 2024
The main protection against outdoor pollutants is from the filter in the vehicle HVAC (Heating, ventilation, and air conditioning) unit. During the past decade, the state-of-the-art solution has been synthetic filters with integrated activated carbon to also cope with gaseous pollutants. These conventional filters, however, are limited by factors including space, reduced efficiency whilst dust-loading, and relatively low efficiencies around the particle size of 100-300 nm. Widely varying efficiency values (0.2-0.9) have been reported from different vehicles.
There is now an interest to introduce filters with higher efficiencies, for example HEPA (High-Efficiency Particulate Air) filters in vehicles. Besides improved efficiencies, another advantage is that the efficiency does not decrease much whilst dust loading. The disadvantages are increased pressure-drop and space requirements, which make them harder to implement in the compact vehicle environment.
One potential improvement in the short run is to use a HEPA-filter placed in the engine bay as a pre-filter, to protect and potentially extend lifetime of the HVAC filter. The combined particle filtration efficiency is improved, and the increased pressure-drop can be acceptable when the HEPA-filter has relatively large dimension.
In this study two filter prototypes (EPA and HEPA level) were manufactured to investigate applications of pre-filtration in a production vehicle. Vehicle test with generated particles (NaCl and Di-Ethyl-Hexyl-Sebacat) and road particles were performed. The inside and outside particle concentrations were measured simultaneously under different fan speeds and combinations of prototypes. One prototype was aged and re-tested in the vehicle as well.
The tested system showed considerably improved air quality, also with an aged filter. With pre-filters applied, the in-cabin UFP and PM2.5 removal could achieve 99%, much higher than the original filter alone (76% and 87% respectively). More importantly, in the particle size range below 100 nm, higher than 97% removal was achieved for all sizes. The limitation of such system is mainly the added pressure-drop and space in the vehicle, which demands a balance [LE1] [LE2] with filter efficiency.
Pre-filtration
particulate matter
vehicle cabin
HEPA
Författare
Dixin Wei
Volvo Cars
Anders Löfvendahl
Volvo Cars
The REHVA European HVAC Journal
Vol. 61 3 45-47
Ämneskategorier
Farkostteknik
Signalbehandling