Assessment of Efficiency of Drying Grain Materials Using Microwave Heating

We present results of experimental work on studying the drying of a dense layer of grain using microwave heating. We investigated a series of techniques to supply heat to grain to assess energy efficiency of a microwave field. We studied the following ways of drying: a microwave method, a pulsating microwave method, a microwave-convective cyclic method with blow of a layer with heated air flow and air without preheating, simultaneous microwave-convective drying method.Studying the kinetics of drying in a microwave field showed that we can divide the process into heating periods (zero drying rate), constant (first drying rate) and falling (second drying rate). These periods are characteristic for drying of colloidal capillary-porous bodies at other methods of heat supply. We obtained empirical relationships for the drying rate and the average temperature of grain in the first period based on the generalization of experimental data on the study on drying of grain of buckwheat, barley, oats, and wheat. We presented kinetic dependences in a dimensionless form. They summarize data on the studied grains. The aim of comprehensive studies of various methods of heat supply during drying was determination of the optimal method and rational operational parameters, which ensure high intensity of the process and the required quality of the finished product with minimal energy consumption.All studies took place under identical conditions and for the same grain (oats) to ensure the accuracy of the comparison. We determined that the most preferable method is a simultaneous microwave-convective energy supply without air preheating, which minimizes specific energy consumption. Experimental studies on drying using a microwave field made possible to select the required process parameters: power, heating rate, mass, and form of loading. We plan to develop a technology for drying of grain using microwave energy based on the study dat

PENGARUH LAMA WAKTU PERENDAMAN DAN SUHU KONDISI OPERASI PADA GABAH DENGAN MENGGUNAKAN ROTARY DRYER FIREBRICK (The Effect of Immersion Time and Temperature condition in operation on the Rate Drying of Unhulled Rice on Rotary Dryer Firebrick )

Drying is a process-water discharge of materials using thermal energy so that the level of the water content of the material menurun.Proses drying is usually accompanied by the evaporation of water contained in the material. In this lab used a rotary kiln dryer to dry the grain. Rotary dryer consists of a horizontal cylindrical shell mounted on a roller bearing, so the cylinder can rotate and tilt angle position a little shaping. Feed entered at the high end of the cylinder, and will come out as a dry product on the other end. As the heater can be used hot air or exhaust gases of combustion are still having a high temperature. On grain drying using the rotary dryer can be concluded that the greater the temperature used for drying the evaporative H2O will further increase. The greater the temperature used to dry the less time for drying. The higher the temperature the higher the rate of drying is used and the more material used, the lower the rate of drying pengeringannya.Laju will decrease if the water layer that covers the material has a thin, water in uapkan the less, so it needs a bit of heat as well. On grain drying with variable temperature 55oC, 60 oC, 65 oC, 70 oC, 75 oC obtained% H2O evaporated with 6.67% of data, 7.74%, 8.91%, 9.76%, 10.65% and Data obtained for the drying rate 0.098 lb.ft2 / h, 0.187 lb.ft2 / h, 0.197 lb.ft2 / h, 0.212 lb.ft2 / h, 0.237 lb.ft2 / h. Optimum temperature is 65 ° C, not too low and not too high for the heating temperature. At the time variable immersion 24 hours, 27 hours, 30 hours, 33 hours, 36 hours obtained obtained with the data teruapkan% H2O 4.26%, 9.46%, 10.92%, 11.49%, 16.63% and Data obtained for the drying rate of 0.049 lb.ft2 / h, 0.101 lb.ft2 / h, 0.132 lb.ft2 / h, 0.142 lb.ft2 / h, 0.196 lb.ft2 / h. From the experiment it can be concluded that the longer the immersion time, the greater the drying rate

Metallic salt deposition on porous particles by dry impregnation in fluidized bed: Effect of drying conditions on metallic nanoparticles distribution

In this paper, the fluidized bed dry impregnation of coarse alumina porous particles by a metallic salt, manganese nitrate, is investigated. In this technique the penetration of each drop of metallic solution in the porous solid particle and solvent evaporation takes place at the same time, then liquid diffusion phenomenon is negligible. So, the metal loading is directly related to the operating time and liquid flow rate and concentration. It is found that the competition between two phenomena, drying and capillary flow, controls the deposit location. In order to determine the importance of the solvent evaporation process compared to the solution penetration by capillarity, an impregnation module, IM, was defined as the ratio between the drying characteristic time and a capillary penetration time. The adequate choice of the operating conditions (bed temperature, liquid and fluidization gas flow rate) allows a uniform deposition of the metallic precursor inside the porous matrix or on the support surface. The impregnation under slow drying conditions (IM ≥ 10 and solvent content in the bed atmosphere τs ≥ 0.2) leads to a homogeneous deposition inside the pores. Under fast drying conditions (IM < 5 and τs < 0.2), the deposit is located at the particle external surface.In the case of slow drying, the impregnation kinetics can be represented by a “shrinking core” model. The critical impregnation rate is controlled by the competition between dissolution and recrystallization at the elementary grain scale. The size of the metal crystallites depends on the pore mean size and size distribution and on the drying rate

Assessment of Efficiency of Drying Grain Materials Using Microwave Heating

We present results of experimental work on studying the drying of a dense layer of grain using microwave heating. We investigated a series of techniques to supply heat to grain to assess energy efficiency of a microwave field. We studied the following ways of drying: a microwave method, a pulsating microwave method, a microwave-convective cyclic method with blow of a layer with heated air flow and air without preheating, simultaneous microwave-convective drying method.Studying the kinetics of drying in a microwave field showed that we can divide the process into heating periods (zero drying rate), constant (first drying rate) and falling (second drying rate). These periods are characteristic for drying of colloidal capillary-porous bodies at other methods of heat supply. We obtained empirical relationships for the drying rate and the average temperature of grain in the first period based on the generalization of experimental data on the study on drying of grain of buckwheat, barley, oats, and wheat. We presented kinetic dependences in a dimensionless form. They summarize data on the studied grains. The aim of comprehensive studies of various methods of heat supply during drying was determination of the optimal method and rational operational parameters, which ensure high intensity of the process and the required quality of the finished product with minimal energy consumption.All studies took place under identical conditions and for the same grain (oats) to ensure the accuracy of the comparison. We determined that the most preferable method is a simultaneous microwave-convective energy supply without air preheating, which minimizes specific energy consumption. Experimental studies on drying using a microwave field made possible to select the required process parameters: power, heating rate, mass, and form of loading. We plan to develop a technology for drying of grain using microwave energy based on the study dat

Adaptive Speckle Imaging Interferometry: a new technique for the analysis of microstructure dynamics, drying processes and coating formation

We describe an extension of multi-speckle diffusing wave spectroscopy adapted to follow the non-stationary microscopic dynamics in drying films and coatings in a very reactive way and with a high dynamic range. We call this technique "Adaptive Speckle Imaging Interferometry". We introduce an efficient tool, the inter-image distance, to evaluate the speckle dynamics, and the concept of "speckle rate" (SR, in Hz) to quantify this dynamics. The adaptive algorithm plots a simple kinetics, the time evolution of the SR, providing a non-invasive characterization of drying phenomena. A new commercial instrument, called HORUS(R), based on ASII and specialized in the analysis of film formation and drying processes is presented.Comment: 11 pages, 4 figure

Validation of a coupled heat, vapour and liquid moisture transport model for porous materials implemented in CFD

Moisture-related damage is an important issue when looking at the performance of building envelopes. In order to accurately predict the moisture behaviour of building components, building designers can resort to Heat, Air and Moisture (HAM) models. In this paper a newly developed heat and mass transfer model that is implemented in a 3D finite volume solver, Fluent®, is presented. This allows a simultaneous modelling approach of both the convective conditions surrounding a porous material and the heat and moisture transport in the porous material governed by diffusion. Unlike most HAM models that often confine to constant convective transport coefficients it is now possible to better predict these convective boundary conditions. An important application of the model is the convective drying of porous building materials. Especially during the first drying stage, the drying rate is determined by the convective boundary conditions. The model was validated against a convective drying experiment from literature, in which a saturated ceramic brick sample is dried by flowing dry air over one side of the sample surface. Temperature and relative humidity measurements at different depths in the sample, moisture distribution profiles and mass loss measurements were compared with simulation results. An overall good agreement between the coupled model and the experiments was found, however, the model predicted the constant drying rate period better than the falling rate period. This was improved by adjusting the material properties. The adjustment of the material properties was supported by neutron radiography measurements.publisher: Elsevier articletitle: Validation of a coupled heat, vapour and liquid moisture transport model for porous materials implemented in CFD journaltitle: Building and Environment articlelink: http://dx.doi.org/10.1016/j.buildenv.2014.06.024 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved.status: publishe

Humidity-insensitive water evaporation from molecular complex fluids

We investigated theoretically water evaporation from concentrated supramolecular mixtures, such as solutions of polymers or amphiphilic molecules, using numerical resolutions of a one dimensional model based on mass transport equations. Solvent evaporation leads to the formation of a concentrated solute layer at the drying interface, which slows down evaporation in a long-time scale regime. In this regime, often referred to as the falling rate period, evaporation is dominated by diffusive mass transport within the solution, as already known. However, we demonstrate that, in this regime, the rate of evaporation does not also depend on the ambient humidity for many molecular complex fluids. Using analytical solutions in some limiting cases, we first demonstrate that a sharp decrease of the water chemical activity at high solute concentration, leads to evaporation rates which depend weakly on the humidity, as the solute concentration at the drying interface slightly depends on the humidity. However, we also show that a strong decrease of the mutual diffusion coefficient of the solution enhances considerably this effect, leading to nearly independent evaporation rates over a wide range of humidity. The decrease of the mutual diffusion coefficient indeed induces strong concentration gradients at the drying interface, which shield the concentration profiles from humidity variations, except in a very thin region close to the drying interface.Comment: 13 pages, 10 figure