Efficient removal of indoor particulate matter using water microdroplets generated by a MHz-frequency ultrasonic atomizer

Abstract

Airborne particulate matter (PM) has emerged as an important global environmental and social issue due to its harmful health effects. Various techniques have been introduced to remove indoor PM. However, an effective and sustainable method has not been established yet because of complex mechanisms and various factors. Here, we propose the use of water microdroplets generated by a MHz-frequency ultrasound, and experimentally examine the effects of the generated microdroplets on PM removal. The PM removal efficiency and PM deposition constant are analyzed by measuring the temporal variation of PM concentration. The measured experimental results are compared with analytical deposition constants. Two collection efficiencies derived in previous studies are employed to substitute a mathematical model used for determining the analytical deposition constants. In addition, the mean diameter and the moving velocity of the microdroplets are experimentally measured via a digital holographic microscopy and particle image velocimetry generated by a MHz-frequency atomizer. The present results demonstrate that water microdroplets generated by the atomizer can be effectively used to remove PM.