The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform
Richard H Heist - One of the best experts on this subject based on the ideXlab platform.
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Nucleation of 1-Pentanol Using a Thermal Diffusion Cloud Chamber
Aerosol Science and Technology, 1998Co-Authors: Anne Bertelsmann, Richard H HeistAbstract:ABSTRACT We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas obtained from constant pressure critical supersaturation measurements and from constant temperature critical supersaturation experiments utilizing the high-pressure diffusion Cloud chamber. We continue to observe significant background gas effects upon nucleation that we have reported previously; and we briefly discuss the important issue of stability (the absence of buoyancy-driven convective motion of the gas-vapor mixture) within the Cloud chamber. We apply our previously determined criteria for establishing the upper limit of total pressure to be used during nucleation investigations involving thermal diffusion Cloud Chambers to the experiments described in this report.
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Recent experiments concerning the role of non-condensable background gases on nucleation
Nucleation and Atmospheric Aerosols 1996, 1996Co-Authors: Richard H Heist, Anne BertelsmannAbstract:Publisher Summary This chapter determines the nature and origin of the effects of background gases on nucleation. It emphasizes on the critical role of the thermal diffusion Cloud Chambers (TDCC) aspect ratio in carrying out quantitative nucleation rate measurements. The results of the investigations appear to suggest that all nucleation data obtained using diffusion Cloud Chambers must be organized according to total pressure and kind of background gas used in addition to the temperature of the experiment and the type of condensable used. These results may also suggest that total pressure and the kind of background gas present during nucleation are important components of any reasonable description of the nucleation process itself. Reports of instability during low pressure TDCC nucleation experiments in conjunction with the special construction aspects of the high pressure diffusion Cloud chamber (HPCC) have led to reasonable questions regarding stability in the HPCC.
Joseph L. Katz - One of the best experts on this subject based on the ideXlab platform.
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Homogeneous nucleation rates of n-pentanol measured in an upward thermal diffusion Cloud chamber
The Journal of Chemical Physics, 1999Co-Authors: Markus M. Rudek, Joseph L. Katz, Igor V. Vidensky, Vladimír Ždímal, Jiri SmolikAbstract:Homogeneous nucleation rates of n-pentanol as functions of both supersaturation and temperature were measured in two different upward thermal diffusion Cloud Chambers, by research groups in Prague and Baltimore. The measurements were made at temperatures between 280 K and 320 K. The nucleation rates obtained are compared to the rates measured by Luijten et al. [J. Chem. Phys. 106, 4152 (1997)], by Hrubý et al. [J. Chem. Phys. 104, 5181 (1996)], and by Strey et al. [J. Chem. Phys. 84, 2325 (1986)]. Fair agreement between our data and the data obtained by the other authors also was found.
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CONDENSATION OF SUPERSATURATED VAPORS. X. PRESSURE AND NONIDEAL GAS EFFECTS
The Journal of Chemical Physics, 1996Co-Authors: Jeffery A. Fisk, Joseph L. KatzAbstract:Calculations of temperatures and supersaturations in nucleation experiments often include the assumption that all gases are ideal and they ignore the increase in vapor pressure due to the presence of noncondensible gases. Regardless of experimental technique, such assumptions can lead to substantial errors when comparing experiment to theory, especially when included in only one or the other. To demonstrate these effects, the procedures for calculating the temperatures and supersaturations in thermal diffusion Cloud Chambers are examined in detail. Nonideal gas effects do alter them; however, these effects also alter the rates calculated by nucleation theory and the effect is larger on nucleation theory than on the analysis of the experimental data. Due to the presence of noncondensible gases there also is a Poynting type effect, but it very nearly cancels in thermal diffusion Cloud Chambers when included consistently in both theory and experiment. An additional effect which arises only in nucleation theo...
Jiří Smolík - One of the best experts on this subject based on the ideXlab platform.
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2-D Model for the Description of Thermal Diffusion Cloud Chambers: Description and First Results†
The Journal of Physical Chemistry B, 2001Co-Authors: Frank Stratmann And, Martin Wilck, Vladimír Ždímal And, Jiří SmolíkAbstract:In thermal diffusion Cloud Chambers (TDCCs), a decrease of nucleation rate with increasing total pressure was observed repeatedly, both near atmospheric pressures and at elevated pressures. Because this pressure effect was observed almost only using TDCCs, there have been some concerns inside the nucleation community whether it is not an experimental artifact. One questionable point in this context is that, to calculate the profiles of temperature and saturation ratio in TDCCs it is assumed that if the chamber is sufficiently “flat”, a 1-d model can be used for the description of the transport processes in the central part of the chamber. The major concern in this context is that the heated chamber wall may cause a buoyancy driven convection that can propagate toward the center of the chamber and cause a slow motion of the gas mixture. To investigate this effect, a 2-d model of coupled mass, heat, and momentum transport in TDCCs has been developed. In the paper this model is described, and its predictive ...
Jiri Smolik - One of the best experts on this subject based on the ideXlab platform.
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Homogeneous nucleation rates of n-pentanol measured in an upward thermal diffusion Cloud chamber
The Journal of Chemical Physics, 1999Co-Authors: Markus M. Rudek, Joseph L. Katz, Igor V. Vidensky, Vladimír Ždímal, Jiri SmolikAbstract:Homogeneous nucleation rates of n-pentanol as functions of both supersaturation and temperature were measured in two different upward thermal diffusion Cloud Chambers, by research groups in Prague and Baltimore. The measurements were made at temperatures between 280 K and 320 K. The nucleation rates obtained are compared to the rates measured by Luijten et al. [J. Chem. Phys. 106, 4152 (1997)], by Hrubý et al. [J. Chem. Phys. 104, 5181 (1996)], and by Strey et al. [J. Chem. Phys. 84, 2325 (1986)]. Fair agreement between our data and the data obtained by the other authors also was found.
Anne Bertelsmann - One of the best experts on this subject based on the ideXlab platform.
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Nucleation of 1-Pentanol Using a Thermal Diffusion Cloud Chamber
Aerosol Science and Technology, 1998Co-Authors: Anne Bertelsmann, Richard H HeistAbstract:ABSTRACT We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas obtained from constant pressure critical supersaturation measurements and from constant temperature critical supersaturation experiments utilizing the high-pressure diffusion Cloud chamber. We continue to observe significant background gas effects upon nucleation that we have reported previously; and we briefly discuss the important issue of stability (the absence of buoyancy-driven convective motion of the gas-vapor mixture) within the Cloud chamber. We apply our previously determined criteria for establishing the upper limit of total pressure to be used during nucleation investigations involving thermal diffusion Cloud Chambers to the experiments described in this report.
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Recent experiments concerning the role of non-condensable background gases on nucleation
Nucleation and Atmospheric Aerosols 1996, 1996Co-Authors: Richard H Heist, Anne BertelsmannAbstract:Publisher Summary This chapter determines the nature and origin of the effects of background gases on nucleation. It emphasizes on the critical role of the thermal diffusion Cloud Chambers (TDCC) aspect ratio in carrying out quantitative nucleation rate measurements. The results of the investigations appear to suggest that all nucleation data obtained using diffusion Cloud Chambers must be organized according to total pressure and kind of background gas used in addition to the temperature of the experiment and the type of condensable used. These results may also suggest that total pressure and the kind of background gas present during nucleation are important components of any reasonable description of the nucleation process itself. Reports of instability during low pressure TDCC nucleation experiments in conjunction with the special construction aspects of the high pressure diffusion Cloud chamber (HPCC) have led to reasonable questions regarding stability in the HPCC.