ESTIMATING THE EFFECTS OF AMBIENT CONDITIONS AND AGING ON THE PERFORMANCE OF UVGI AIR CLEANERS

Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure Hg vapor lampsto control biological air contaminants. Lamp UV output depends on multiple factors, includingaccumulated operating time (age) and the thermal effects of ambient air temperature and velocity.Additionally, the life of some lamp types depends on the frequency of on-off cycles. Models of lamplife as a function of cycling rate and lamp output as a function of age and ambient conditions aredeveloped for three common standard output lamp types based on heat transfer theory andmanufacturers lamp performance data. Example results are presented and a parametric study in theform of a 3k factorial experiment is used to identify significant factors affecting output and theirinteractions. A typical range of ambient conditions reduces lamp output by more than 30% of ratedcapacity and the inclusion of aging effects reduces capacity by as much as 70%. For given ambientconditions, performance varies substantially across lamp types due to their differing heat transfercharacteristics. It is concluded that short term and long term variation of lamp output is highlysignificant and that modeling of such effects is necessary for accurate system design and analysis.