Evaluation of an ultraviolet photocatalytic oxidation air cleaner. Impact on volatile organic compounds and ozone
Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Publicerad
2011
Författare
Thorel, Mathieu
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The technology of ultra violet photocatalytic oxidation (UV-PCO) in indoor air quality studies is relatively new and to test the VOCs and ozone removal efficien-cies of each new device is essential. A lot of research has been done in laboratory applications; often tests have been done at low airflow rates – from 1 to 100L/min (i.e. a long contact time) – with rather high VOCs concentrations. In building ap-plications, the parameters are completely different: short contact time 100 to 350ms, high airflow rates, and with typical indoor concentration (levels < 20-30ppb in most of the cases) for VOCs. This report presents a set of laboratory tests of a commercially available UV-PCO unit. The study deals with the decom-position of VOCs and ozone under 254nm and 185nm UV wavelengths, the influ-ence of relative humidity of the air, the contact time (i.e. airflow rate) and the identification of by-products generated with rather low VOCs concentration injec-tions. 254nm UV wavelength seems to be good in removing ozone, with a single pass efficiency reaching 60%, in specific conditions: a relative humidity of 35% and long residence time (350ms). Some studies claim that the addition of ozone with 185nm UV lights, enhances the VOCs removal efficiency with long contact time (> 2s). In our case, the 185nm UV wavelength or a combination of 254nm + 185nm UV wavelengths, generates too high concentration of ozone for building applications (>50ppb). The addition of 185 nm UV-light did not seem to improve the VOCs removal efficiency. However, the addition of ozone, obtained by the 185nm UV wavelength irradiation, is suspected to enhance transformation of sty-rene into formaldehyde and possibly also benzaldehyde as by-products. Another part of the report assesses the air flow resistance of the tested UV-PCO unit. The pressure drops were verified and are quite low in comparison with common sorption or active carbon air cleaners, a key point to reduce the energy consumption in HVAC systems. An evaluation of Chalmers test-rig and instru-mentation equipment has been performed, in order to help the new users in their use of these devices in other projects.
Beskrivning
Ämne/nyckelord
Building Futures , Byggnadsteknik , Building Futures , Building engineering