Minimum Fluidization Velocity of Food Materials: Effect of Moisture and Shape (original) (raw)
Related papers
Fluidization Behaviour of Food Materials: Effect of Moisture and Shape
Changes in fluidization behaviour of three geometrical shaped food particulates, cylindrical (beans), parallelepiped (potato) and spherical (green peas) with change in moisture content during drying were investigated using a fluidized bed dryer. Fluidization behaviour was characterised for cylindrical shape particles with three length diameter-ratios; 1:1, 2:1 and 3:1, parallelepiped particles with three aspect ratios, 1:1, 2:1 and 3:1 and spherical particles. All drying experiments were conducted at 500C and 15 % RH using a heat pump dehumidifier system. Fluidization experiments were undertaken for the bed heights of 100, 80, 60 and 40 mm and at 10 moisture content levels. An empirical relationship of the form Umf = A + B e -Cm was developed for change of minimum fluidization velocity with moisture content for cylindrical shapes and for spherical shapes a linear model of Umf = A + B m. Due to irregularities in shape minimum fluidisation velocity of parallelepiped particulates (pota...
Density Variation of Different Shaped Food Particulates in Fluid Bed Drying: Empirical Models
Journal of Agricultural and Marine Sciences [JAMS], 2009
Three particular geometrical shapes, parallelepiped, cylindrical and spherical, were selected from potatoes (aspect ratio = 1:1, 2:1, 3:1), cut beans (length:diameter = 1:1, 2:1, 3:1) and peas respectively. The density variation of food particulates was studied in a batch fluidised bed dryer connected to a heat pump dehumidifier system. Apparent density and bulk density were evaluated with non-dimensional moisture at three different drying temperatures of 30, 40 and 50 oC. Relative humidity of hot air was kept at 15% in all drying temperatures. Several empirical relationships were developed for the determination of changes in densities with the moisture content. Simple mathematical models were obtained to relate apparent density and bulk density with moisture content.
2009
Changes in fluidization behaviour behaviour was characterised for parallelepiped particles with three aspect ratios, 1:1, 2:1 and 3:1 and spherical particles. All drying experiments were conducted at 50 0 C and 15 % RH using a heat pump dehumidifier system. Fluidization experiments were undertaken for the bed heights of 100, 80, 60 and 40 mm and at 10 moisture content levels. Due to irregularities in shape minimum fluidisation velocity of parallelepiped particulates (potato) could not fitted to any empirical model. Also a generalized equation was used to predict minimum fluidization velocity. The modified quasi-stationary method (MQSM) has been proposed to describe drying kinetics of parallelepiped particulates at 30 o C, 40 o C and 50 o C that dry mostly in the falling rate period in a batch type fluid bed dryer.
Fluidization Characteristics of Moist Food Particles
International Journal of Food Engineering, 2006
Changes in fluidization behaviour of green peas particulates with change in moisture content during drying were investigated using a fluidized bed dryer. All drying experiments were conducted at 50 + 2 0C and 13 + 2 % RH using a heat pump dehumidifier system. Fluidization experiments were undertaken for the bedheights of 100, 80, 60 and 40 mm and at 10 moisture content levels.
Influence of shapes of selected vegetable materials on drying kinetics during fluidized bed drying
Journal of Food Engineering, 2003
Three different particular geometrical shapes of parallelepiped, cylinder and sphere were taken from cut green beans (length:diameter=1:1, 2:1 and 3:1) and potatoes (aspect ratio=1:1, 2:1 and 3:1) and peas, respectively. Their drying behaviour in a fluidised bed was studied at three different drying temperatures of 30, 40 and 50 °C (RH=15%). Drying curves were constructed using non-dimensional moisture ratio (MR) and time and their behaviour was modelled using exponential (MR=exp(−kt)) and Page (MR=exp(−ktn)) models.The effective diffusion coefficient of moisture transfer was determined by Fickian method using uni- and three-dimensional moisture movements. The diffusion coefficient was least affected by the size when the moisture movement was considered three-dimensional, whereas the drying temperature had a significative effect on diffusivity as expected. The drying constant and diffusivity coefficients were on the descending order for potato, beans and peas. The Arrhenius activation energy for the peas was also highest, indicating a strong barrier to moisture movement in peas as compared to beans and skinless cut potato pieces.
Fluidisation behaviour of cylindrical green bean particulates in drying
Tropical Agricultural Research, 1998
ABSTRACT. Changes in fluidization behaviour of green bean particulates with change in moisture content during drying were investigated using a fluidized bed dryer. Fluidization behaviour was characterised for cylindrical shape particles with three length diameter-ratios; 1: 1, 2: 1 and 3: 1.
Journal of Food Engineering, 2003
Drying behavior of maize and green peas investigated in a pilot scale fluidized bed dryer with inert energy carriers. The variations of drying material density, size and mass diffusivity with change of moisture content were investigated. It was found that, air temperature, inert material, and air velocity had no significant effect on physical properties and therefore, shrinkage and density are only functions of moisture content, but diffusivity is a function of temperature and moisture content. Based on the experimental data obtained, some correlations were developed for variation of shrinkage, density and diffusivity of green peas and maize during drying in a fluidized bed with inert particles. The shrinkage, density and moisture diffusivity of green peas and maize could be predicted by an average accuracy of 98% by use of proposed correlations.
MODELING DIMENSIONAL SHRINKAGE OF SHAPED FOODS IN FLUIDIZED BED DRYING
Journal of Food Processing and Preservation, 2005
Three particular geometrical shapes of parallelepiped, cylinder and sphere were selected from cut beans (length : diameter = 1:1, 2:1, 3:1), potatoes (aspect ratio = 1:1, 2:1, 3:1) and peas, respectively. The dimensional shrinkage behavior was studied in a batch fluidized bed at three drying temperatures of 30, 40 and 50C. Relative humidity of hot air was kept at 15%. Dimensional shrinkage was plotted using a nondimensional moisture ratio and the shrinkage behavior of the selected foods was modeled with simple mathematical models.
[2011]Evaluation Kinetic Parameters for Drying of Granular Material in Fluidized
An experimental investigation on drying black pepper in the temperature range of 55 to 80°C is attempted in a fluidized bed to estimate the drying kinetics. The drying kinetics is modeled using several simple semi empirical models to estimate the kinetic parameters. Among the semi empirical model tested with the experimental data the Page model followed by Approximate Diffusion model are identified to predict the drying kinetics with lesser error. The kinetic parameter (k) is found to increase with the temperature for all the models. The activation energy (E) estimated using Arrhenius equation is found to be 32.48kJ/mol. The effective diffusivity coefficient is evaluated using Fick's diffusion equation which is found increase with increase in temperature of the heating medium and to vary in the range of 0.42x10 -11 to 1.0x10 -11 m 2 /s. The effective diffusivity in comparison with other food grains such as Ragi, Millet and Corn in fluidized beds are found to be higher than the effective diffusivity for the black pepper.
Thermal analysis in fluidized bed drying of moist particles
Applied Thermal Engineering, 2002
This paper deals with thermal modeling of the fluidized bed drying of wet particles to study heat and mass transfer aspects and drying thermal efficiencies. The model is then validated with the literature experimental data obtained for corn. A parametric investigation is undertaken to study the effects of the inlet air temperature, the air velocity and the initial moisture content of the material (i.e. corn) on the process thermal efficiency. The results show that the thermal efficiencies of the fluidized bed drying decrease sharply with decreasing moisture content of corn and hence increasing drying time, and apparently become the lowest at the end of the drying process. This clearly indicates that the moisture transfer from the material depends strongly on the air temperature, air velocity and the moisture content of material. A good agreement is obtained between the model predictions and the available experimental results.