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Denis Flick - One of the best experts on this subject based on the ideXlab platform.

  • coupling population balance and residence time distribution for the ice crystallization modeling in a scraped surface heat exchanger
    Chemical Engineering Science, 2013
    Co-Authors: Marcela Arellano, Hayat Benkhelifa, Graciela Alvarez, Denis Flick
    Abstract:

    Abstract This paper presents the mathematical modeling of the ice crystallization process occurring during the freezing of sorbet in a continuous scraped surface heat exchanger (SSHE). Two different modeling approaches have been used, both of which include the nucleation, growth and breakage phenomena of the ice crystals. For both models, the rate of ice crystal nucleation and growth were determined by the subcooling degree. The first model combines heat transfer and population balance equations (PBE), assuming plug flow. The evolution of the values of product temperature, Mean Chord length, ice volume fraction and apparent viscosity were determined as a function of the residence time. The second model is a coupled model of heat transfer and PBE combined with an empirical model of residence time distribution (RTD), which makes it possible to take into account the fact that the fluid fractions flowing throughout the SSHE do not have the same time–temperature history. The values of the variables (product temperature and Mean Chord length) were determined for each fraction of fluid exiting the SSHE, and the bulk values were then calculated using the RTD. Simulation results were compared to a set of experimental data obtained during the ice crystallization process of sorbet in a continuous SSHE at the laboratory pilot scale. With a first estimated set of model parameters, it has been shown that the experimental tendencies are represented very satisfactorily by the two models within a 10% error limit. These modeling approaches can then be considered as a promising tool for the understanding and the prediction of the ice crystallization process in SSHEs so as to identify new ways to improve the performance of the process.

  • Coupling population balance and residence time distribution for the ice crystallization modeling in a scraped surface heat exchanger
    Chemical Engineering Science, 2013
    Co-Authors: Marcela Arellano Salazar, Hayat Benkhelifa, Graciela Alvarez, Denis Flick
    Abstract:

    This paper presents the mathematical modeling of the ice crystallization process occurring during the freezing of sorbet in a continuous scraped surface heat exchanger (SSHE). Two different modeling approaches have been used, both of which include the nucleation, growth and breakage phenomena of the ice crystals. For both models, the rate of ice crystal nucleation and growth were determined by the subcooling degree. The first model combines heat transfer and population balance equations (PBE), assuming plug flow. The evolution of the values of product temperature, Mean Chord length, ice volume fraction and apparent viscosity were determined as a function of the residence time. The second model is a coupled model of heat transfer and PBE combined with an empirical model of residence time distribution (RTD), which makes it possible to take into account the fact that the fluid fractions flowing throughout the SSHE do not have the same time-temperature history. The values of the variables (product temperature and Mean Chord length) were determined for each fraction of fluid exiting the SSHE, and the bulk values were then calculated using the RTD. Simulation results were compared to a set of experimental data obtained during the ice crystallization process of sorbet in a continuous SSHE at the laboratory pilot scale. With a first estimated set of model parameters, it has been shown that the experimental tendencies are represented very satisfactorily by the two models within a 10% error limit. These modeling approaches can then be considered as a promising tool for the understanding and the prediction of the ice crystallization process in SSHEs so as to identify new ways to improve the performance of the process. (C) 2013 Elsevier Ltd. All rights reserved,

Hayat Benkhelifa - One of the best experts on this subject based on the ideXlab platform.

  • coupling population balance and residence time distribution for the ice crystallization modeling in a scraped surface heat exchanger
    Chemical Engineering Science, 2013
    Co-Authors: Marcela Arellano, Hayat Benkhelifa, Graciela Alvarez, Denis Flick
    Abstract:

    Abstract This paper presents the mathematical modeling of the ice crystallization process occurring during the freezing of sorbet in a continuous scraped surface heat exchanger (SSHE). Two different modeling approaches have been used, both of which include the nucleation, growth and breakage phenomena of the ice crystals. For both models, the rate of ice crystal nucleation and growth were determined by the subcooling degree. The first model combines heat transfer and population balance equations (PBE), assuming plug flow. The evolution of the values of product temperature, Mean Chord length, ice volume fraction and apparent viscosity were determined as a function of the residence time. The second model is a coupled model of heat transfer and PBE combined with an empirical model of residence time distribution (RTD), which makes it possible to take into account the fact that the fluid fractions flowing throughout the SSHE do not have the same time–temperature history. The values of the variables (product temperature and Mean Chord length) were determined for each fraction of fluid exiting the SSHE, and the bulk values were then calculated using the RTD. Simulation results were compared to a set of experimental data obtained during the ice crystallization process of sorbet in a continuous SSHE at the laboratory pilot scale. With a first estimated set of model parameters, it has been shown that the experimental tendencies are represented very satisfactorily by the two models within a 10% error limit. These modeling approaches can then be considered as a promising tool for the understanding and the prediction of the ice crystallization process in SSHEs so as to identify new ways to improve the performance of the process.

  • Coupling population balance and residence time distribution for the ice crystallization modeling in a scraped surface heat exchanger
    Chemical Engineering Science, 2013
    Co-Authors: Marcela Arellano Salazar, Hayat Benkhelifa, Graciela Alvarez, Denis Flick
    Abstract:

    This paper presents the mathematical modeling of the ice crystallization process occurring during the freezing of sorbet in a continuous scraped surface heat exchanger (SSHE). Two different modeling approaches have been used, both of which include the nucleation, growth and breakage phenomena of the ice crystals. For both models, the rate of ice crystal nucleation and growth were determined by the subcooling degree. The first model combines heat transfer and population balance equations (PBE), assuming plug flow. The evolution of the values of product temperature, Mean Chord length, ice volume fraction and apparent viscosity were determined as a function of the residence time. The second model is a coupled model of heat transfer and PBE combined with an empirical model of residence time distribution (RTD), which makes it possible to take into account the fact that the fluid fractions flowing throughout the SSHE do not have the same time-temperature history. The values of the variables (product temperature and Mean Chord length) were determined for each fraction of fluid exiting the SSHE, and the bulk values were then calculated using the RTD. Simulation results were compared to a set of experimental data obtained during the ice crystallization process of sorbet in a continuous SSHE at the laboratory pilot scale. With a first estimated set of model parameters, it has been shown that the experimental tendencies are represented very satisfactorily by the two models within a 10% error limit. These modeling approaches can then be considered as a promising tool for the understanding and the prediction of the ice crystallization process in SSHEs so as to identify new ways to improve the performance of the process. (C) 2013 Elsevier Ltd. All rights reserved,

Diana Thongjaomayum - One of the best experts on this subject based on the ideXlab platform.

  • surprising variants of cauchy s formula for Mean Chord length
    Physical Review E, 2019
    Co-Authors: Prabodh Shukla, Diana Thongjaomayum
    Abstract:

    : We examine isotropic and anisotropic random walks which begin on the surface of linear (N), square (N×N), or cubic (N×N×N) lattices and end upon encountering the surface again. The Mean length of walks is equal to N and the distribution of lengths n generally scales as n^{-1.5} for large n. Our results are interesting in the context of an old formula due to Cauchy that the Mean length of a Chord through a convex body of volume V and surface S is proportional to V/S. It has been realized in recent years that Cauchy's formula holds surprisingly even if Chords are replaced by irregular insect paths or trajectories of colliding gas molecules. The random walk on a lattice offers a simple and transparent understanding of this result in comparison to other formulations based on Boltzmann's transport equation in continuum.

  • Surprising variants of Cauchy’s formula for Mean Chord length
    'American Physical Society (APS)', 2019
    Co-Authors: Prabodh Shukla, Diana Thongjaomayum
    Abstract:

    We examine isotropic and anisotropic random walks which begin on the surface of linear (N ), square (N × N ), or cubic (N × N × N) lattices and end upon encountering the surface again. The Mean length of walks is equal to N and the distribution of lengths n generally scales as n−1.5 for large n. Our results are interesting in the context of an old formula due to Cauchy that the Mean length of a Chord through a convex body of volume V and surface S is proportional to V/S. It has been realized in recent years that Cauchy’s formula holds surprisingly even if Chords are replaced by irregular insect paths or trajectories of colliding gas molecules. The random walk on a lattice offers a simple and transparent understanding of this result in comparison to other formulations based on Boltzmann’s transport equation in continuum. ©2019 American Physical Societ

Graciela Alvarez - One of the best experts on this subject based on the ideXlab platform.

  • coupling population balance and residence time distribution for the ice crystallization modeling in a scraped surface heat exchanger
    Chemical Engineering Science, 2013
    Co-Authors: Marcela Arellano, Hayat Benkhelifa, Graciela Alvarez, Denis Flick
    Abstract:

    Abstract This paper presents the mathematical modeling of the ice crystallization process occurring during the freezing of sorbet in a continuous scraped surface heat exchanger (SSHE). Two different modeling approaches have been used, both of which include the nucleation, growth and breakage phenomena of the ice crystals. For both models, the rate of ice crystal nucleation and growth were determined by the subcooling degree. The first model combines heat transfer and population balance equations (PBE), assuming plug flow. The evolution of the values of product temperature, Mean Chord length, ice volume fraction and apparent viscosity were determined as a function of the residence time. The second model is a coupled model of heat transfer and PBE combined with an empirical model of residence time distribution (RTD), which makes it possible to take into account the fact that the fluid fractions flowing throughout the SSHE do not have the same time–temperature history. The values of the variables (product temperature and Mean Chord length) were determined for each fraction of fluid exiting the SSHE, and the bulk values were then calculated using the RTD. Simulation results were compared to a set of experimental data obtained during the ice crystallization process of sorbet in a continuous SSHE at the laboratory pilot scale. With a first estimated set of model parameters, it has been shown that the experimental tendencies are represented very satisfactorily by the two models within a 10% error limit. These modeling approaches can then be considered as a promising tool for the understanding and the prediction of the ice crystallization process in SSHEs so as to identify new ways to improve the performance of the process.

  • Coupling population balance and residence time distribution for the ice crystallization modeling in a scraped surface heat exchanger
    Chemical Engineering Science, 2013
    Co-Authors: Marcela Arellano Salazar, Hayat Benkhelifa, Graciela Alvarez, Denis Flick
    Abstract:

    This paper presents the mathematical modeling of the ice crystallization process occurring during the freezing of sorbet in a continuous scraped surface heat exchanger (SSHE). Two different modeling approaches have been used, both of which include the nucleation, growth and breakage phenomena of the ice crystals. For both models, the rate of ice crystal nucleation and growth were determined by the subcooling degree. The first model combines heat transfer and population balance equations (PBE), assuming plug flow. The evolution of the values of product temperature, Mean Chord length, ice volume fraction and apparent viscosity were determined as a function of the residence time. The second model is a coupled model of heat transfer and PBE combined with an empirical model of residence time distribution (RTD), which makes it possible to take into account the fact that the fluid fractions flowing throughout the SSHE do not have the same time-temperature history. The values of the variables (product temperature and Mean Chord length) were determined for each fraction of fluid exiting the SSHE, and the bulk values were then calculated using the RTD. Simulation results were compared to a set of experimental data obtained during the ice crystallization process of sorbet in a continuous SSHE at the laboratory pilot scale. With a first estimated set of model parameters, it has been shown that the experimental tendencies are represented very satisfactorily by the two models within a 10% error limit. These modeling approaches can then be considered as a promising tool for the understanding and the prediction of the ice crystallization process in SSHEs so as to identify new ways to improve the performance of the process. (C) 2013 Elsevier Ltd. All rights reserved,

F. Tommasino - One of the best experts on this subject based on the ideXlab platform.

  • A Novel Hybrid Microdosimeter for Radiation Field Characterization Based on the Tissue Equivalent Proportional Counter Detector and Low Gain Avalanche Detectors Tracker: A Feasibility Study
    Frontiers in Physics, 2021
    Co-Authors: M. Missiaggia, E. Pierobon, M. Castelluzzo, A. Perinelli, F. Cordoni, M. Centis Vignali, G. Borghi, E. V. Bellinzona, E. Scifoni, F. Tommasino
    Abstract:

    In microdosimetry, lineal energies y are calculated from energy depositions ϵ inside the microdosimeter divided by the Mean Chord length, whose value is based on geometrical assumptions on both the detector and the radiation field. This work presents an innovative two-stages hybrid detector (HDM: hybrid detector for microdosimetry) composed by a tissue equivalent proportional counter and a silicon tracker made of 4 low gain avalanche diode. This design provides a direct measurement of energy deposition in tissue as well as particles tracking with a submillimeter lateral spatial resolution. The data collected by the detector allow to obtain the real track length traversed by each particle in the tissue equivalent proportional counter and thus estimates microdosimetry spectra without the Mean Chord length approximation. Using Geant4 toolkit, we investigated HDM performances in terms of detection and tracking efficiencies when placed in water and exposed to protons and carbon ions in the therapeutic energy range. The results indicate that the Mean Chord length approximation underestimate particles with short track, which often are characterized by a high energy deposition and thus can be biologically relevant. Tracking efficiency depends on the low gain avalanche diode configurations: 34 strips sensors have a higher detection efficiency but lower spatial resolution than 71 strips sensors. Further studies will be performed both with Geant4 and experimentally to optimize the detector design on the bases of the radiation field of interest.The main purpose of HDM is to improve the assessment of the radiation biological effectiveness via microdosimetric measurements, exploiting a new definition of the lineal energy (yT), defined as the energy deposition ϵ inside the microdosimeter divided by the real track length of the particle.