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Richard H Heist - One of the best experts on this subject based on the ideXlab platform.

  • Thermal diffusion Cloud Chamber: new criteria for proper operation
    Atmospheric Research, 2003
    Co-Authors: Richard H Heist, Anne Bertelsmann, Daniel M. Martinez, Yuk Fung Chan
    Abstract:

    Abstract We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas obtained from constant temperature critical supersaturation experiments utilizing the high-pressure diffusion Cloud Chamber. We have observed significant background gas effects on vapor nucleation that differ somewhat from that we have reported previously. In this paper, we discuss the important issue of stability (the absence of buoyancy-driven convective motion of the gas–vapor mixture) and Cloud Chamber operation; and we focus now on the lower total pressure limit required for stable Chamber operation. We describe how violating this limit is manifested by the experimental data, and we show actual results for the nucleation of 1-pentanol with hydrogen as a background gas which illustrates the importance of considering these stability issues. For the first time, we identify three regions of operation for the diffusion Cloud Chamber. Region I corresponds to the range of total pressures below this lower total pressure limit; Region III corresponds to the range of total pressures above the upper total pressure limit (described earlier); and, Region II corresponds to the range of total pressures that permit “proper” operation of the diffusion Cloud Chamber. Here we define proper operation as operation under conditions that are believed to be well represented by a one-dimensional model of diffusion in a stagnant gas. We provide, for the first time, an empirical procedure for determining the lower total pressure limit. We also argue against the commonly used pressure ratio as a predictor for “proper” Cloud Chamber operation.

  • Thermal diffusion Cloud Chamber—new criteria for proper operation
    AIP Conference Proceedings, 2000
    Co-Authors: Richard H Heist, Daniel M. Martinez, Yuk Fung Chan, Anne Bertelsmann
    Abstract:

    We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas utilizing the high-pressure diffusion Cloud Chamber (HPCC). We discuss the important issue of buoyancy-driven convective motion and Cloud Chamber operation, and we focus on the lower total pressure limit required for stable Chamber operation. We provide, for the first time, an empirical procedure for determining the lower total pressure limit.

  • diffusion Cloud Chamber operation and the background gas effect
    Atmospheric Research, 1998
    Co-Authors: Anne Bertelsmann, Richard H Heist
    Abstract:

    Key design and operational aspects for thermal diffusion Cloud Chamber (TDCC) applications are discussed in the context of a two-dimensional solution to the mass and energy balances describing diffusion through a stagnant background gas. The important issue of buoyancy-driven convective disturbances and their impact upon nucleation measurements made using a diffusion Cloud Chamber are discussed. A new derivation of the relation that predicts the upper limit of total pressure allowed for stable (the absence of buoyancy-driven convective disturbances) operation of the diffusion Cloud Chamber is presented. For the first time, this limit of stable operation can be predicted prior to making experimental measurements. Nucleation data obtained in our laboratory are examined in the context of this predicted limit of stable operation. New nucleation data are presented for 1-pentanol using helium as a background gas. Only data corresponding to stable operation in the Cloud Chamber is used in the analysis. The effect of background gas on nucleation we have reported previously is confirmed for 1-pentanol, as well as for all the other alcohols that have been investigated in our laboratory.

  • Nucleation of 1-Pentanol Using a Thermal Diffusion Cloud Chamber
    Aerosol Science and Technology, 1998
    Co-Authors: Anne Bertelsmann, Richard H Heist
    Abstract:

    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.

  • Two-dimensional transport and wall effects in the thermal diffusion Cloud Chamber. II. Stability of operation
    The Journal of Chemical Physics, 1997
    Co-Authors: Anne Bertelsmann, Richard H Heist
    Abstract:

    In this paper, the second of a series of two presenting a detailed description of thermal diffusion Cloud Chamber operation, we address the operational stability of the vapor–gas mixture in a diffusion Cloud Chamber with respect to density profile extrema and the accompanying possibility of buoyancy-driven convective flow disturbances. We examine conditions for stable operation (no convective flow disturbances) in the central portion of the Cloud Chamber, as well as conditions necessary for stable operation in the vicinity of the Cloud Chamber wall. We find that the total density profile in the central portion of the Cloud Chamber can pass through a density minimum even though the density at the upper plate surface is less than the density at the lower plate surface. This local density profile inversion can result in unstable (convective) behavior that propagates through the Cloud Chamber. Furthermore, we find that local extrema in the total density profile near the Chamber wall can lead to subtle, convec...

Anne Bertelsmann - One of the best experts on this subject based on the ideXlab platform.

  • Thermal diffusion Cloud Chamber: new criteria for proper operation
    Atmospheric Research, 2003
    Co-Authors: Richard H Heist, Anne Bertelsmann, Daniel M. Martinez, Yuk Fung Chan
    Abstract:

    Abstract We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas obtained from constant temperature critical supersaturation experiments utilizing the high-pressure diffusion Cloud Chamber. We have observed significant background gas effects on vapor nucleation that differ somewhat from that we have reported previously. In this paper, we discuss the important issue of stability (the absence of buoyancy-driven convective motion of the gas–vapor mixture) and Cloud Chamber operation; and we focus now on the lower total pressure limit required for stable Chamber operation. We describe how violating this limit is manifested by the experimental data, and we show actual results for the nucleation of 1-pentanol with hydrogen as a background gas which illustrates the importance of considering these stability issues. For the first time, we identify three regions of operation for the diffusion Cloud Chamber. Region I corresponds to the range of total pressures below this lower total pressure limit; Region III corresponds to the range of total pressures above the upper total pressure limit (described earlier); and, Region II corresponds to the range of total pressures that permit “proper” operation of the diffusion Cloud Chamber. Here we define proper operation as operation under conditions that are believed to be well represented by a one-dimensional model of diffusion in a stagnant gas. We provide, for the first time, an empirical procedure for determining the lower total pressure limit. We also argue against the commonly used pressure ratio as a predictor for “proper” Cloud Chamber operation.

  • Thermal diffusion Cloud Chamber—new criteria for proper operation
    AIP Conference Proceedings, 2000
    Co-Authors: Richard H Heist, Daniel M. Martinez, Yuk Fung Chan, Anne Bertelsmann
    Abstract:

    We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas utilizing the high-pressure diffusion Cloud Chamber (HPCC). We discuss the important issue of buoyancy-driven convective motion and Cloud Chamber operation, and we focus on the lower total pressure limit required for stable Chamber operation. We provide, for the first time, an empirical procedure for determining the lower total pressure limit.

  • diffusion Cloud Chamber operation and the background gas effect
    Atmospheric Research, 1998
    Co-Authors: Anne Bertelsmann, Richard H Heist
    Abstract:

    Key design and operational aspects for thermal diffusion Cloud Chamber (TDCC) applications are discussed in the context of a two-dimensional solution to the mass and energy balances describing diffusion through a stagnant background gas. The important issue of buoyancy-driven convective disturbances and their impact upon nucleation measurements made using a diffusion Cloud Chamber are discussed. A new derivation of the relation that predicts the upper limit of total pressure allowed for stable (the absence of buoyancy-driven convective disturbances) operation of the diffusion Cloud Chamber is presented. For the first time, this limit of stable operation can be predicted prior to making experimental measurements. Nucleation data obtained in our laboratory are examined in the context of this predicted limit of stable operation. New nucleation data are presented for 1-pentanol using helium as a background gas. Only data corresponding to stable operation in the Cloud Chamber is used in the analysis. The effect of background gas on nucleation we have reported previously is confirmed for 1-pentanol, as well as for all the other alcohols that have been investigated in our laboratory.

  • Nucleation of 1-Pentanol Using a Thermal Diffusion Cloud Chamber
    Aerosol Science and Technology, 1998
    Co-Authors: Anne Bertelsmann, Richard H Heist
    Abstract:

    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.

  • Two-dimensional transport and wall effects in the thermal diffusion Cloud Chamber. II. Stability of operation
    The Journal of Chemical Physics, 1997
    Co-Authors: Anne Bertelsmann, Richard H Heist
    Abstract:

    In this paper, the second of a series of two presenting a detailed description of thermal diffusion Cloud Chamber operation, we address the operational stability of the vapor–gas mixture in a diffusion Cloud Chamber with respect to density profile extrema and the accompanying possibility of buoyancy-driven convective flow disturbances. We examine conditions for stable operation (no convective flow disturbances) in the central portion of the Cloud Chamber, as well as conditions necessary for stable operation in the vicinity of the Cloud Chamber wall. We find that the total density profile in the central portion of the Cloud Chamber can pass through a density minimum even though the density at the upper plate surface is less than the density at the lower plate surface. This local density profile inversion can result in unstable (convective) behavior that propagates through the Cloud Chamber. Furthermore, we find that local extrema in the total density profile near the Chamber wall can lead to subtle, convec...

G. Jay Doster - One of the best experts on this subject based on the ideXlab platform.

  • Homogeneous nucleation of n-pentanol measured in an expansion Cloud Chamber
    The Journal of Chemical Physics, 2002
    Co-Authors: John L. Schmitt, G. Jay Doster
    Abstract:

    An expansion Cloud Chamber was used to measure homogeneous nucleation rates for n-pentanol in argon carrier gas at four nucleation temperatures 292, 282, 272, and 252 K. The nucleation rates range from about 15000 to 400 drops/cm3 s. The data exhibits changes with time that are attributed to the removal of trace impurities by self-cleaning action in the Cloud Chamber. Data at the highest supersaturation ratio for a given number of drops observed is considered to be closest to true homogeneous nucleation. A comparison of these measurements with data in the literature at similar temperatures and nucleation rates shows the data from this study to be approximately three orders of magnitude lower in nucleation rate at a given supersaturation ratio.

Yuk Fung Chan - One of the best experts on this subject based on the ideXlab platform.

  • Thermal diffusion Cloud Chamber: new criteria for proper operation
    Atmospheric Research, 2003
    Co-Authors: Richard H Heist, Anne Bertelsmann, Daniel M. Martinez, Yuk Fung Chan
    Abstract:

    Abstract We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas obtained from constant temperature critical supersaturation experiments utilizing the high-pressure diffusion Cloud Chamber. We have observed significant background gas effects on vapor nucleation that differ somewhat from that we have reported previously. In this paper, we discuss the important issue of stability (the absence of buoyancy-driven convective motion of the gas–vapor mixture) and Cloud Chamber operation; and we focus now on the lower total pressure limit required for stable Chamber operation. We describe how violating this limit is manifested by the experimental data, and we show actual results for the nucleation of 1-pentanol with hydrogen as a background gas which illustrates the importance of considering these stability issues. For the first time, we identify three regions of operation for the diffusion Cloud Chamber. Region I corresponds to the range of total pressures below this lower total pressure limit; Region III corresponds to the range of total pressures above the upper total pressure limit (described earlier); and, Region II corresponds to the range of total pressures that permit “proper” operation of the diffusion Cloud Chamber. Here we define proper operation as operation under conditions that are believed to be well represented by a one-dimensional model of diffusion in a stagnant gas. We provide, for the first time, an empirical procedure for determining the lower total pressure limit. We also argue against the commonly used pressure ratio as a predictor for “proper” Cloud Chamber operation.

  • Thermal diffusion Cloud Chamber—new criteria for proper operation
    AIP Conference Proceedings, 2000
    Co-Authors: Richard H Heist, Daniel M. Martinez, Yuk Fung Chan, Anne Bertelsmann
    Abstract:

    We report results of new nucleation experiments involving 1-pentanol with hydrogen as the background gas utilizing the high-pressure diffusion Cloud Chamber (HPCC). We discuss the important issue of buoyancy-driven convective motion and Cloud Chamber operation, and we focus on the lower total pressure limit required for stable Chamber operation. We provide, for the first time, an empirical procedure for determining the lower total pressure limit.

John L. Schmitt - One of the best experts on this subject based on the ideXlab platform.

  • Homogeneous nucleation of n-pentanol measured in an expansion Cloud Chamber
    The Journal of Chemical Physics, 2002
    Co-Authors: John L. Schmitt, G. Jay Doster
    Abstract:

    An expansion Cloud Chamber was used to measure homogeneous nucleation rates for n-pentanol in argon carrier gas at four nucleation temperatures 292, 282, 272, and 252 K. The nucleation rates range from about 15000 to 400 drops/cm3 s. The data exhibits changes with time that are attributed to the removal of trace impurities by self-cleaning action in the Cloud Chamber. Data at the highest supersaturation ratio for a given number of drops observed is considered to be closest to true homogeneous nucleation. A comparison of these measurements with data in the literature at similar temperatures and nucleation rates shows the data from this study to be approximately three orders of magnitude lower in nucleation rate at a given supersaturation ratio.