The evolution of particle size distribution （PSD） of fine polydisperse particles at high number concen- trations （7105 cm-3） was simulated through a combined model employing direct quadrature method of moments （D...The evolution of particle size distribution （PSD） of fine polydisperse particles at high number concen- trations （7105 cm-3） was simulated through a combined model employing direct quadrature method of moments （DQMOM） with heat and mass transfer equations. The PSD was assumed to retain log-normal distribution during the heterogeneous condensation process. The model was first verified by exact solu- tion and experimental data prior to investigating the influence of initial conditions on final PSD under an octadecane-nitrogen atmosphere. Low particle number concentrations and high vapor concentrations were beneficial to shift the PSD to larger particles having a narrower distribution. Additionally, vapor depletion has more influence on the final PSD than the heat release parameter for a number concentra- tion of 10^6 cm^-3. This study may assist the design process of a gas-solid separating cyclone, to eliminate dust from high-temperature volatiles by pyrolysis of solid fuels.展开更多
Three types of water-based condensational growth systems, which can enable particles to grow in size to facilitate sampling and subsequent chemical analysis, were evaluated. The first one is a mixing type growth syste...Three types of water-based condensational growth systems, which can enable particles to grow in size to facilitate sampling and subsequent chemical analysis, were evaluated. The first one is a mixing type growth system where aerosols are mixed with saturated water vapor, the second one is a thermal diffusive growth system where warm flow enters cold-walled tube, and the third one is a laminar flow type where cold flow enters a warm wet-wall tube. Hygroscopic sodium chloride （NaCl）, ammonium sulfate （（NH4）2SO4） and ammonium nitrate （NH4N03）, and non-hygroscopic polystyrene latex （PSL） particles, in the size range of 50-400 nm, were used to determine their growth factors through the growth systems. Our data showed that the third-type growth system could enable particles to grow most efficiently regardless of their hygroscopic property. Collection efficiency of particles in the size range of 0.05-2.5 μm, in a continuous aerosol sampler after they passed through the third-type growth system was about 100%, suggesting that the third-type growth system would he the most useful among the tested growth systems for sampling and subsequent chemical analysis of fine and ultrafine particles.展开更多
基金This work was supported by the National Basic Research Pro- gram of China （973 Program, 2014CB744300）, by the National Natural Science Foundation of China （51476180）, and by Meso- science Innovation Fund （COM2015A004）. Discussion with Dr. Susanne Hering on his experiment and effects of initial size is acknowledged.
文摘The evolution of particle size distribution （PSD） of fine polydisperse particles at high number concen- trations （7105 cm-3） was simulated through a combined model employing direct quadrature method of moments （DQMOM） with heat and mass transfer equations. The PSD was assumed to retain log-normal distribution during the heterogeneous condensation process. The model was first verified by exact solu- tion and experimental data prior to investigating the influence of initial conditions on final PSD under an octadecane-nitrogen atmosphere. Low particle number concentrations and high vapor concentrations were beneficial to shift the PSD to larger particles having a narrower distribution. Additionally, vapor depletion has more influence on the final PSD than the heat release parameter for a number concentra- tion of 10^6 cm^-3. This study may assist the design process of a gas-solid separating cyclone, to eliminate dust from high-temperature volatiles by pyrolysis of solid fuels.
基金supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MEST)(NRF-2011-0015548)the Basic Research Project through agrant provided by GIST
文摘Three types of water-based condensational growth systems, which can enable particles to grow in size to facilitate sampling and subsequent chemical analysis, were evaluated. The first one is a mixing type growth system where aerosols are mixed with saturated water vapor, the second one is a thermal diffusive growth system where warm flow enters cold-walled tube, and the third one is a laminar flow type where cold flow enters a warm wet-wall tube. Hygroscopic sodium chloride （NaCl）, ammonium sulfate （（NH4）2SO4） and ammonium nitrate （NH4N03）, and non-hygroscopic polystyrene latex （PSL） particles, in the size range of 50-400 nm, were used to determine their growth factors through the growth systems. Our data showed that the third-type growth system could enable particles to grow most efficiently regardless of their hygroscopic property. Collection efficiency of particles in the size range of 0.05-2.5 μm, in a continuous aerosol sampler after they passed through the third-type growth system was about 100%, suggesting that the third-type growth system would he the most useful among the tested growth systems for sampling and subsequent chemical analysis of fine and ultrafine particles.
