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Hironori Minoshima - One of the best experts on this subject based on the ideXlab platform.

  • Reply to the Comment by K. Jorgensen et al. to “Analysis of Constant Rate Period of spray drying of slurry”
    Chemical Engineering Science, 2006
    Co-Authors: Hironori Minoshima
    Abstract:

    Abstract Previously developed model for spray drying of slurry droplets with high solid content (Liang, 2001) was revised to describe correctly a boundary condition on the outer surface of droplet on basis of the Rate of liquid evaporation.

  • Analysis of Constant Rate Period of spray drying of slurry
    Chemical Engineering Science, 2001
    Co-Authors: Hua Liang, Kunio Shinohara, Hironori Minoshima, Keiichiro Matsushima
    Abstract:

    A model has been developed for spray drying of slurry droplets with proper high solid content during the Constant-Rate Period. The equations governing mass and heat transfer phenomena were numerically solved using the finite element method. The model is able to predict the crust formation as a function of slurry properties and operating parameters. For water-based suspension droplets of monodisperse silica particles, the effects of these parameters on granule morphology were simulated and the results were compared with the experimental data. Good agreement is reported between theory and experiment. The simulations demonstRated that the large primary-particle yields dense solid granules. The solid content of granules increases with slurry concentration when primary particles are smaller than a certain value. On the other hand, the preferred manner to obtain solid product granules for a given precursor slurry concentration is to start with initial droplets as small as possible at relatively low ambient temperature.

Peter A. Munro - One of the best experts on this subject based on the ideXlab platform.

  • mathematical modelling of hot air drying of sweet potato slices
    International Journal of Food Science and Technology, 2007
    Co-Authors: Lm Diamante, Peter A. Munro
    Abstract:

    Summary The effect of air dry bulb temperature, air relative humidity, air velocity and sample thickness on the thin-layer air drying of sweet potato slices was investigated. The drying Rate curves consisted of two approximately linear falling Rate Periods and contained no Constant Rate Period. Several mathematical models were fitted to the drying Rates of sweet potato slices under a range of drying conditions. It was found that the modified Page equation best described the thin-layer air drying of sweet potato slices down to a moisture content of 10% dry basis. Correlations were also determined for the slope and intercept of the modified Page equation in terms of the experimental variables.

  • mathematical modelling of the thin layer solar drying of sweet potato slices
    Solar Energy, 1993
    Co-Authors: Lm Diamante, Peter A. Munro
    Abstract:

    Abstract An indirect solar dryer was used to study the drying of sweet potato slices. The solar drying Rates of sweet potato slices were affected by the fluctuating chamber temperature over the drying Period. Solar drying Rate curves exhibited a Constant Rate Period and one linear falling Rate Period. A mathematical model for solar drying of sweet potato slices was derived based on the simplified form of the Fick's diffusion equation. The mathematical model could satisfactorily describe the solar drying of sweet potato slices to a moisture content below 20% dry basis. The mean effective drying chamber temperature and sample thickness were the main factors that affected the solar drying process for sweet potato slices.

  • Moisture Desorption Isotherms and Drying Rates of Mineral Acid Casein
    1990
    Co-Authors: Lm Diamante, Peter A. Munro, Michael G. Weeks
    Abstract:

    The equilibrium moisture desorption isotherms of mineral acid casein were determined at three different temperatures. The desorption isotherms were sigmoid in shape and of type II according to the BET classification. A three-Constant modified Henderson equation described the isotherms satisfactorily as a function of temperature. As the precipitation pH of casein curd samples was increased, their drying Rates during the falling Rate Period in a tunnel drier decreased. The drying Rate curve of casein in a fluidised bed drier had a long Constant Rate Period, a low critical moisture content and one falling Rate Period whereas only a short Constant Rate Period and a high critical moisture content were observed in the tunnel drier. A logarithmic model satisfactorily described drying Rates during the falling Rate Period in both types of drier.

  • Moisture Desorption Isotherms and Drying Rates of Mineral Acid Casein
    1990
    Co-Authors: Lm Diamante, Peter A. Munro, Michael G. Weeks
    Abstract:

    The equilibrium moisture desorption isotherms of mineral acid casein were determined at three different temperatures. The desorption isotherms were sigmoid in shape and of type II according to the BET classification. A three-Constant modified Henderson equation described the isotherms satisfactorily as a function of temperature. As the precipitation pH of casein curd samples was increased, their drying Rates during the falling Rate Period in a tunnel drier decreased. The drying Rate curve of casein in a fluidised bed drier had a long Constant Rate Period, a low critical moisture content and one falling Rate Period whereas only a short Constant Rate Period and a high critical moisture content were observed in the tunnel drier. A logarithmic model satisfactorily described drying Rates during the falling Rate Period in both types of drier.

Hiromichi Shibata - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Segment Scale in a Pore Network of Porous Materials on Drying Periods
    Drying Technology, 2013
    Co-Authors: Hiromichi Shibata, Yumiko Hirohashi
    Abstract:

    Drying Periods of porous glass disks of nonhygroscopic MPG glass and hygroscopic Vycor glass were investigated. A simple model of dimensionless segment sizes is proposed where a dimensionless segment size is equal to the value of the tortuosity factor of gas diffusion. This model was applied to the estimation of the segment size and the drying Periods of a porous Vycor glass disk. The drying Rate curve of the Vycor glass disk showed that the first falling Rate Period appeared to be included in the Constant Rate Period and that the second falling Rate Period started right after the Constant Rate Period ended, whereas the drying Rate curve of the MPG glass disk estimated from previous models showed that the first falling Rate Period and the second falling Rate Period were clearly distinguished. The difference in drying Periods between two porous glass disks was caused by a large difference in the respective segment sizes.

  • The Differences in Drying Rate Curves of Sintered Glass Beads at Subatmospheric and Atmospheric Pressures and at Lower Pressures in Steam
    Developments in Chemical Engineering and Mineral Processing, 2008
    Co-Authors: Hiromichi Shibata, Mitsuharu Ide
    Abstract:

    Steam drying of sintered glass beads under vacuum was investigated. The drying Rates were predicted from an evaporation zone model for the Constant Rate Period, and from a receding evaporation front model for the falling Rate Period in which the data of moisture contents in the pendular state were estimated from those in air under vacuum. The predicted, as well as observed, normalized drying Rate curves including the critical moisture contents in steam under vacuum were different from those in steam at subatmospheric and atmospheric pressures. However, they were similar to those in air under vacuum in the corresponding pressure range. This was because the moisture content in the pendular state under vacuum was larger than that at subatmospheric and atmospheric pressures, and heat transfer was a Rate-controlling step both in steam and in air under vacuum.

  • Comparison of Drying Rate Curves of Porous Solids in Superheated Steam to Those in Air
    Drying Technology, 2005
    Co-Authors: Hiromichi Shibata
    Abstract:

    ABSTRACT Drying of porous solids was experimentally investigated in superheated steam as well as in air. Drying Rate curves, including critical moisture contents, in steam at subatmospheric pressure, were compared to those for air at atmospheric pressure; moreover, they were compared to those for steam at atmospheric pressure as well. The former comparison was carried out under conditions of sample temperatures of 41.8–42.5°C (which were nearly equal to saturation temperatures of 42.1–42.2°C at pressures of 8.23–8.30 kPa) for the Constant Rate Period in steam and the corresponding sample temperatures of 42.0–45.0°C (which were close to the wet-bulb temperatures) for the Constant Rate Period in air. There were distinct differences between normalized drying Rate curves, including critical moisture contents in steam and in air at the above similar sample temperatures for materials of baked clay, firebrick, and cemented glass balloons over the minimum value of 8.3 × 10−3 µm and up to the maximum value of 1.2 ...

  • Prediction of drying Rate curves on sintered spheres of glass beads in superheated steam under vacuum
    Industrial & Engineering Chemistry Research, 1990
    Co-Authors: Hiromichi Shibata, Jiro Mada, Kazumori Funatsu
    Abstract:

    The superheated steam drying of sintered spheres of coarse glass beads was investigated under vacuum. The drying Rate curves for the Constant-Rate Period and the critical moisture contents were estimated on the basis of an evaporation zone model for superheated steam drying at atmospheric pressure, and the drying Rate curves for the falling Rate Period were estimated from an evaporation front model

Kazumori Funatsu - One of the best experts on this subject based on the ideXlab platform.

Y T Puyate - One of the best experts on this subject based on the ideXlab platform.

  • Models for predicting drying stresses and strains in a film cast on a substRate: An alternative approach
    Chemical Engineering Science, 2009
    Co-Authors: Y T Puyate, Christopher J. Lawrence
    Abstract:

    Models based on Biot's theory for the deformation of a satuRated porous body are presented for the stress and strain produced during drying of film cast on a substRate. A two-stage drying process is considered, where a Constant-Rate Period is followed by a falling-Rate Period. The compressive stress that develops in the body is proportional to the evaporation Rate and increases as the permeability of the body decreases. The maximum stress occurs at the drying surface at the end of the Constant-Rate Period. During the falling-Rate Period, the receding drying front divides the material into satuRated and unsatuRated regions; the satuRated region is subjected to compressive stress while the stress in the unsatuRated region would be released if the solid network is elastic as assumed in the analysis. The receding drying front is accounted for in the models.

  • Performance Evaluation Of Mass-Transfer Coefficients For Constant-Rate Period Of Drying During Tape Casting
    Global Journal of Engineering Research, 2008
    Co-Authors: Y T Puyate
    Abstract:

    Temperature-dependent mass-transfer coefficient is presented for the Constant-Rate Period during non-convective drying of water-based alumina suspension for tape casting. Predicted drying Rates based on the temperature-dependent mass-transfer coefficient and Constant value of the mass-transfer coefficient are compared with experimental data in a range of ambient temperature from 298K to 328K and a range of relative humidity from 40% to 90%. It is shown that the temperature-dependent mass-transfer coefficient is adequate with maximum error of about 9% in predicted drying Rates. The Constant mass-transfer coefficient is also adequate, but with errors in predicted drying Rates of about 18% and 16% at 40%RH(328K) and 65%RH(328K) respectively, and maximum error of about 9% at all other data points. A model based on drying parameters of the suspension in the Constant-Rate Period is also presented for estimating wet-bulb temperature within the specified ranges of ambient temperature and relative humidity. Model-estimated wet-bulb temperatures are compared with those estimated from a humidity-temperature chart for air-water vapour system at atmospheric pressure and good agreement is obtained. Keywords : Drying; Suspension; Ceramics; Wet-bulb temperature; Tape casting. Global Journal of Engineering Research Vol. 7 (1) 2008: pp. 47-50

  • Performance evaluation of heat-transfer co-efficients for Constant-Rate Period of drying during tape casting
    Journal of Modeling Design and Management of Engineering Systems, 2007
    Co-Authors: Y T Puyate
    Abstract:

    Ceramic suspensions for tape casting are known to dry in two stages; the first stage is called the Constant-Rate Period, and the second stage is the falling-Rate Period. The drying Rate in the Constant-Rate Period can be characterized by mass-transfer coefficient or heat-transfer coefficient. A general model is presented that predicts the heat-transfer coefficient at a given temperature and different ambient humidity in the Constant-Rate Period. An average value of the heat-transfer coefficient for a temperature range from 298K to 328K, and a range of relative humidity from 40% to 90%, during drying of water-based alumina suspension for tape casting is calculated using this model to be. A model developed for the water-based suspension is also presented that predicts the heat-transfer coefficient as a function of temperature. Predicted drying Rates based on heat-transfer coefficients obtained from the two models are compared with experimental data and good agreement is obtained. The average value of the coefficient for the suspension is shown to be inadequate. Keywords : Modelling; Drying; Tape casting; Suspension; Ceramics; Heattransfer Coefficient Journal of Modeling, Design and Management of Engineering Systems, Vol. 3 (1) 2005: pp. 25-37

  • sherwood s models for the falling Rate Period a missing link at modeRate drying intensity
    Chemical Engineering Science, 2006
    Co-Authors: Y T Puyate, C J Lawrence
    Abstract:

    Abstract An exact model is presented for the falling-Rate Period of drying of solids based on Sherwood's diffusion theory, where an external evaporation-controlled Constant-Rate Period is followed by an internal diffusion-controlled falling-Rate Period. Both the Constant-Rate Period and the falling-Rate Period are characterized by a Constant diffusion coefficient. The exact model is compared with two existing models by Sherwood for the falling-Rate Period, and with experimental data on water-based alumina suspension for tape casting and on wood. Good agreement is obtained between predictions of the exact model and the experimental data in both cases. It is shown that Sherwood's two models for the falling-Rate Period are adequate at low drying Rates ( μ 1.5 ) , and high drying Rates ( μ > 9 ) , where μ is the drying intensity. The exact model is valid for all values of μ and hence provides a missing link between Sherwood's models at modeRate drying intensity.

  • DETERMINATION OF THE Constant-Rate MASS-TRANSFER COEFFICIENT FOR DRYING DURING TAPE CASTING
    Journal of Modeling Design and Management of Engineering Systems, 2004
    Co-Authors: Y T Puyate
    Abstract:

    Ceramic suspensions for tape casting are known to dry in two stages; the first stage is called the Constant-Rate Period, and the second stage is the falling-Rate Period. During the Constant-Rate Period, the drying Rate of a material is Constant. During the falling-Rate Period, the drying Rate gradually decreases as the moisture content of the material falls. A mass-transfer coefficient is estimated for the Constant–Rate Period of drying of water-based alumina suspensions for tape casting. A model based on the mass-transfer coefficient is also presented for the drying Rate in the Constant-Rate Period. The model is compared with experimental data and good agreement is obtained if the mass-transfer coefficient is taken to be 7.55 x 10 -9 kg/m 2 s Pa. JMDMES Vol.2(1) 2003: 83-88