Enthalpy-driven optimization of intermittent drying of Mangifera indica L

Effects of intermittent radio frequency drying on structure and gelatinization properties of native potato flour

Radio frequency (RF) treatment technology has now been studied and used for kinds of food products as its rapid and volumetric heating effects. It is meaningful to study the characteristics of potato drying with a new RF treatment method. In this study, intermitted RF combined treatments were used to get high-efficiency dehydration effects for potato drying, but the impact and mechanism of RF radiation on drying efficiency or quality is still unknown. To explore the drying characteristics, the effects of different RF radiation and the associated intermittent periods on the characterization of color, crystalline, thermal, pasting, rheology, and structural properties of potato flour were systematically studied. Longer RF radiation period (7 min) has a positive effect on drying efficiency and quality. The effect of intermittent period was not as significant as that of RF radiation, but a slightly increasing trend of the quality properties with intermittent period also indicated the tempering effect. The combined action of RF intermittent treatment on potato drying was found and investigated in this study, which may support RF drying processing improvement.

System modelling of non-stationary drying processes

The kinetics of the drying process in continuous drum dryers differs from the drying of single objects in a batch mode. Drying process is affected by too many factors; hence, it is practically impossible to obtain an analyt- ical solution from the initial equations of heat and mass transfer, since the duration of drying depends on the opera- ting parameters. Therefore, it is of high theoretical and practical importance to create a highly efficient rotary drum dryer. Its design should be based on an integrated research of non-stationary processes of heat and mass transfer, hydrodynamics of fluidized beds, and drying kinetics in the convective heat supply. The experiment described in the present paper featured sunflower seeds. It was based on a systematic approach to modelling rotary convective drying processes. The approach allowed the authors to link together separate idealized models. Each model characterized a process of heat and mass transfer in a fluidized bed of wet solids that moved on a cylindrical surface. The experiment provided the following theoretical results: 1) a multimodel system for the continuous drying process of bulky mate- rials in a fluidized bed; 2) an effective coefficient of continuous drying, based on the mechanics of the fluidized bed and its continuous dehydration. The multimodel system makes it possible to optimize the drying process according to its material, heat-exchanger, and technological parameters, as well as to the technical and economic characteristics of the dryer.

Convective drying of onion: modeling of drying kinetics parameters

Drying is a simultaneous heat and mass transfer processes. Drying kinetics is determined by both internal properties and external drying conditions. In this study, two important drying kinetics parameters of onions i.e. effective water diffusivity and relative activation energy of reaction engineering approach (REA) are determined. The generated parameters are used to model thin layer drying of onion at different temperatures (40, 50, 60, and 70 °C) and relative humidity of 20%. The effective water diffusivity is in the range of 2.8 × 10^-10 m² s^-1 and 8.1 × 10^-10 m² s^-1. Unlike the diffusivity, the relative activation energy of the REA is independent on drying conditions and thus the latter approach requires less effort in generating the transport properties. The transport parameters can be applied for assisting in designing dryer units and evaluating the performance of existing dryer units.

The effect of intermittent drying on the cracking ratio of soybeans (Glycine max) at different relative humidity using reaction engineering approach modeling

Intermittent drying (ID) was applied to reduce soybean cracking because of the low moisture gradient and little thermal stress on soybeans during their tempering period. The drying temperature and relative humidity (RH) for the drying and tempering periods were 35°C and 20% and 25°C and 43%, respectively. The intermittency (α) of the drying was defined as the ratio of the drying period to the duration of the drying and tempering periods, and it varied at α = 1, 0.5, 0.4, and 0.25 to evaluate the drying characteristics and the soybeans' quality. Intermittency processes redistributed the moisture in the soybean so that the low thermal stress was applied to the soybeans. The percentage of cracked grains increased with increasing the duration of drying period and decreasing tempering period. The moisture content and temperature changes during drying of soybeans were well fitted by reaction engineering approach (REA) modeling. Additionally, the physics that describe the soybeans' drying behavior during ID were explained by the model parameters obtained from the REA modeling, such as the surface relative humidity and the surface water vapor concentration. ID showed the highest drying efficiency at α = 0.25 regarding the total drying time (13,800 s, i.e., the shortest drying time) and the lowest cracking ratio (<2.18%).

Tempering-Drying Simulation and Experimental Analysis of Corn Kernel

In order to study the effect of corn kernel composition and physical structure on moisture distribution and transfer process and obtain the optimal tempering-drying parameters of corn kernel, a physical model was constructed with four different components as follows: seed coat, horny endosperm, farinaceous endosperm and embryo. The drying model was established based on the assumption of different diffusion coefficients and same thermal conductivity for the four components. The software of COMSOL Multiphysics was used to simulate the heat and mass transfer process inside the corn kernel during the thin-layer drying. The results showed that the least total drying time and the best drying quality were achieved under the multistage circulating drying of 10 min hot air drying and 60 min tempering, and the tempering degree was up to 0.9207.

Modeling of high-temperature treatment of wood using the reaction engineering approach (REA)

A simple and accurate model of high-temperature treatment of wood can assist in the process design and the evaluation of performance of equipment. The high-temperature treatment of wood is essentially a drying process under linearly-increased gas temperature up to final temperature of 220-230°C which is a challenging process to model. This study is aimed to assess the applicability and accuracy of the reaction engineering approach (REA) to model the heat treatment of wood. In order to describe the process using the REA, the maximum activation energy (ΔE(v,b)) is evaluated according to the corresponding external conditions during the heat treatment. Results indicate that the REA coupled with the heat balance describes both moisture content and temperature profiles during the heat treatment very well. A good agreement towards the experimental data is indicated. It has also been shown that the current model is highly comparable in accuracy with the complex models.