The Simulation For The Capture Capability Of Electrostatically Charged Monolith Filter Based On Microchannels

HEPA filters are widely promotion and popularization for it is the most important late-stage filter of clean room. HEPA is the key equipment for the development of air cleaner technologies,and it is an important measure of a country’s standard level of filter technological development.Energy efficient and inexpensive equipment is the key points for HEPA’s equipment. Therefore, the exploratory experimental study on low resistance and high efficiency air filters is a breakthrough to further tap the market potentiality.Monolith structure of the filter has little resistance, and a high level of sub-micron particle filtration efficiency. Good characteristics of Simple structure, low cost make it be an important direction for the development of new high efficiency air filter. Meanwhile, with the development of micro-nano processing technology, micro-nano-aperture processing technology has matured.The current holes density can be made into 1 million / cm2 or more, making the research on monolith filter based on the micron channel gradually be taken seriously attention. However, the monolith filter is still on the main stage of the theoretical study at home and abroad, the relevant literature reports are still relatively rare and the study on filter filtering mechanism is not perfect, which adds a lot of trouble for the monolith filter design and manufacturing. In response to this situation, the paper made a comprehensive study on monolith filters with conventional fiber filters for comparison, to provide a theoretical basis for the design and manufacture of more energy-efficient and more efficient filters.Single-channel theoretical model has been used for the analysis of the filtration properties of electrostatic charged monolith filter in this paper. First the characteristics of a single particle motion in the monolith microchannels has been studied. The results show that when the particle diameter Dp <0.1μm,Brown force and static electricity dominant.With the increase of Dp, the movement of particles is gradually dominated by the flow resistance.Next, we study effection of the inlet velocity and direction of airflow, static electricity the particle diameter and other factors on the monolith filter efficiency.The results show that when Dp < 0.1μm, inlet velocity u0 increases, the capture efficiency drops rapidly;u0> 3m / s, the capture efficiency is close to 0 and will not longer be influenced by the aerosol inlet velocity; the particle capture efficiency hardly increases with the incident aerosol angle.And when Dp> 1μm, with the increase of u0, the capture efficiency of passage decreases and then increases;the particle capture efficiency increases obviously with the increase of the incident angle of aerosols.Electrostatic effect on the monolith channel capture efficiency is very significant. Studies show that when the particle diameter is small(Dp <0.1μm), particles with the heterogeneous charge of passage with capture efficiency of the channel significantly enhanced. Therefore, the use of artificial means to make monolith filter surface with a stable of high-density charge is important, the most commonly used method is to embed the channel surface electret filter manufacturer. Therefore, the use of artificial means to make monolith filter surface charged with a stable of high-density charge is important. The most commonly used method is to embed the channel surface electret filter. Diameter of the particle is a most important factor for capture efficiency of the channel.With the increase of particle diameter, particle motion mainly dominating by action of Brownian forces and electrostatic forces gradually transforms into dominating by the flow resistance. when Dp is in 0.01μm ~ 1μm,the capture efficiency decreases with the particle diameter increase and then increases.There is a minimum value of efficiency,which called the largest particle penetration diameter Dpmax = 0.1 ~ 0.4μm.Particles deposited position distribution along the monolith filter channel is also analyzed in this paper.Results show that most of the particles deposited on previous 10% area of the channel,depositing less and more evenly distributing in the other location.In engineering applications, monolith filter cleaning should be focused on previous10% of the position of the channels. When Dp = 0.05μm, the particle distribution and the deposit location along the channel has little relationship with inlet airflow velocity direction, while the particle deposit location along the channel significantly moves backward with the gas flow velocity increases; When Dp=0.5μm, the speed increases and angled of the airflow into the channel both make the deposition position of the particle backwards.Finally, we compare the filtration performance of monolith filter with fiber filters under comparable conditions in all respects. The results show that ensuring the flow inlet velocity conditions, monolith filter has a significantly higher efficiency for small particles(Dp <0.1μm); u0 = 0.1m / s, the fiber filter filtration resistance ΔP = 160 Pa, while monolith filter filtration resistance ΔP = 50 Pa, less than 1/3 of the fiber filters, which once again confirmed that the monolith filter have a low-power high efficiency characteristics in the processing of submicron particles compared to conventional fiber filter.