EFFECTS OF INDOOR VENTILATION AND AIR MIXING ON DISINFECTION EFFICACY OF UPPER-ROOM UVGI SYSTEM

摘要

With a validated Computational Fluid Dynamics (CFD) method, this paper investigated the effects of room air exchange rate (ACR), and ceiling fan's operation on the disinfection efficacy of an upper-room ultraviolent germicidal irradiation (UR-UVGI) system. UR-UVGI disinfection efficacy was evaluated by the index called "fraction of microorganism remaining (FR)", which was the ratio of the volume-averaged concentration of airborne microorganisms calculated with the UVGI turned "on" (Con) to that calculated with UVGI turned "off" (Coff). Three ACRs (2 ACH, 4 ACH and 6 ACH), and four fan speeds(40 rpm, 80 rpm, 150 rpm and 235 rpm) at two directions (upward and downward) were considered in this investigation. According to the simulation results, UR-UVGI disinfection efficacy was determined by ACR, and could be further improved by using ceiling fan. On the other hand, ceiling fan's rotational direction showed a slight influence. In conclusion, it seems an appropriate application to use the UR-UVGI system with ACR of 2 ACH and fan speed of 150 rpm.