Browsing by Author "Varghese, S.K."
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Item Generation of monodisperse aerosols through condensation nuclei control(2007) Kadlimatti, H.M.; Gangamma, S.; Varghese, S.K.A device for the generation of monodisperse aerosols through condensation nuclei control has been designed and tested in the present study. A continuous flow, evaporation-condensation aerosol generator has been designed to produce monodisperse aerosols of low vapor pressure organic liquids, such as dioctyl phthalate (DOP), at flow rates over 2.5 1pm. Nebulised NaCl particles are passed through the particle number controller to reduce the number concentration close to 105/cc to suppress homogeneous condensation. The condensation nuclei with nitrogen as a carrier gas are passed through a bubbler containing DOP, producing a nuclei-vapor mixture. The mixture is condensed producing the aerosols of narrow size distribution. A heater section previous to the condenser section provides complete evaporation across the tube diameter, while the condenser walls in free convection create a low temperature gradient, both of which enhance aerosol monodispersity. The results show that controlling the nuclei number concentration as well as vapor source can produce aerosols with sufficient monodispersity. 2007 WIT Press.Item Generation of monodisperse aerosols through condensation nuclei control(WITPress marketing@witpress.com, 2007) Kadlimatti, H.M.; Gangamma, S.; Varghese, S.K.A device for the generation of monodisperse aerosols through condensation nuclei control has been designed and tested in the present study. A continuous flow, evaporation-condensation aerosol generator has been designed to produce monodisperse aerosols of low vapor pressure organic liquids, such as dioctyl phthalate (DOP), at flow rates over 2.5 1pm. Nebulised NaCl particles are passed through the particle number controller to reduce the number concentration close to 105/cc to suppress homogeneous condensation. The condensation nuclei with nitrogen as a carrier gas are passed through a bubbler containing DOP, producing a nuclei-vapor mixture. The mixture is condensed producing the aerosols of narrow size distribution. A heater section previous to the condenser section provides complete evaporation across the tube diameter, while the condenser walls in free convection create a low temperature gradient, both of which enhance aerosol monodispersity. The results show that controlling the nuclei number concentration as well as vapor source can produce aerosols with sufficient monodispersity. © 2007 WIT Press.Item Particle deposition in human respiratory system: Deposition of concentrated hygroscopic aerosols(2009) Varghese, S.K.; Gangamma, S.In the nearly saturated human respiratory tract, the presence of water-soluble substances in the inhaled aerosols can cause change in the size distribution of the particles. This consequently alters the lung deposition profiles of the inhaled airborne particles. Similarly, the presence of high concentration of hygroscopic aerosols also affects the water vapor and temperature profiles in the respiratory tract. A model is presented to analyze these effects in human respiratory system. The model solves simultaneously the heat and mass transfer equations to determine the size evolution of respirable particles and gas-phase properties within human respiratory tract. First, the model predictions for nonhygroscopic aerosols are compared with experimental results. The model results are compared with experimental results of sodium chloride particles. The model reproduces the major features of the experimental data. The water vapor profile is significantly modified only when a high concentration of particles is present. The model is used to study the effect of equilibrium assumptions on particle deposition. Simulations show that an infinite dilution solution assumption to calculate the saturation equilibrium over droplet could induce errors in estimating particle growth. This error is significant in the case of particles of size greater than 1 ?m and at number concentrations higher than 105/cm3. 2009 Informa UK Ltd.Item Particle deposition in human respiratory system: Deposition of concentrated hygroscopic aerosols(2009) Varghese, S.K.; Gangamma, S.In the nearly saturated human respiratory tract, the presence of water-soluble substances in the inhaled aerosols can cause change in the size distribution of the particles. This consequently alters the lung deposition profiles of the inhaled airborne particles. Similarly, the presence of high concentration of hygroscopic aerosols also affects the water vapor and temperature profiles in the respiratory tract. A model is presented to analyze these effects in human respiratory system. The model solves simultaneously the heat and mass transfer equations to determine the size evolution of respirable particles and gas-phase properties within human respiratory tract. First, the model predictions for nonhygroscopic aerosols are compared with experimental results. The model results are compared with experimental results of sodium chloride particles. The model reproduces the major features of the experimental data. The water vapor profile is significantly modified only when a high concentration of particles is present. The model is used to study the effect of equilibrium assumptions on particle deposition. Simulations show that an infinite dilution solution assumption to calculate the saturation equilibrium over droplet could induce errors in estimating particle growth. This error is significant in the case of particles of size greater than 1 ?m and at number concentrations higher than 105/cm3. © 2009 Informa UK Ltd.Item Particulate respiratory dose to Indian women from domestic cooking(2005) Varghese, S.K.; Gangamma, S.; Patil, R.S.; Sethi, V.Particulate mass size distributions were measured during cooking and non-cooking periods in three Indian urban household kitchens with Liquefied Petroleum Gas as fuel. Based on the measured mass size distributions, fraction of particulate deposition in the respiratory system were calculated for a healthy Indian female using a deterministic lung deposition model. Respiratory physiological data of Indian women were collected from the published data. These physiological parameters were incorporated in the model to determine the particulate deposition in the respiratory system. The cooking generated very high concentration of particles 4 to 5 times more than the non-cooking background periods. Particulate size distributions in both cooking and non-cooking periods showed bimodal characteristics. Cooking process generated particles predominantly in accumulation mode (0.1-0.3 ?m) whereas during non-cooking periods particulates are found in coarse mode (1.0-2.0 ?m). Also, during frying process, the particulates were found to have a predominant coarser/droplet mode 0.7-1.0 ?m. The highest deposition was observed in pulmonary region during cooking periods. The study shows that the daily particulate dose to the urban Indian women from domestic cooking is comparable with the dose resulting from outdoor particulate exposure. Copyright American Association for Aerosol Research.