Development of PM2.5 removal system with minimum power consumption

Abstract

Since atmospheric aerosols have an adverse effect on global climate change and human health, increasing concerns about aerosol concentrations and exposure. Various aerosols removal systems have been developed to reduce the aerosols such as a method of removing from a primary pollution source, an indoor air purifier, an outdoor large scale air purifier and face masks. Each removal systems have advantages and disadvantages. The indoor air purifiers have high aerosols removal efficiency, however, it usually use a fan to generate air flow which consumes power continuously and make noise. In the case of outdoor large-scale air purifiers, solar-assisted large-scale cleaning system(SALSCS) in Xi’an, China, it consumes less power, however, is not effective since the target is to reduce the atmospheric aerosols concentration on outdoor. The principle of SALSCS is to use solar heat to supply thermal energy to the polluted air to generate the air flow due to the buoyancy. This air flow is filtered through filters and then the clean air is emitted into the atmosphere. It consumes low power since it generates air flow with natural convection effect rather than artificial force such as fan or pump. Therefore, in this study, based on previous aerosols removal systems, we developed an indoor PM2.5 removal system with the minimum power consumption using natural convection effect. It consists of a collector that supplies thermal energy to the air and a chimney that warm air goes up. Since the buoyancy, the natural convection effect, is weaker than other artificial force. The optimal chimney shape was designed by multi-physic simulation program. When the height of chimney is 1 m, the inlet diameter is 400 mm, the outlet diameter is 200 mm, and no throat structure(height ratio is 0) is most effective. It is also most efficient when where is no temperature gradient on inlet. Based on these results, we produce prototype and conducted various experiments. For the outlet velocity(m/s), simulation results and experiment results were similar 80% on average. This PM2.5 removal system uses a film-type air filter with a low pressure drop to remove the aerosols. The optimal position of this filter is 700 mm height from the bottom of the chimney. Finally the PM2.5 removal efficiency experiment results show that the clean air delivery rate(CADR) is 0.102 m3/min when the inlet temperature is 35℃, and 0.112 m3/min when the inlet temperature is 40℃. Compared to an 23 m3(7-pyeong) indoor air purifier, the CADR efficiency is about 6%. When comparing the power consumption, it is about 62% of the power is consumed when the same amount of clean air is supplied.