Comparative analysis of drying coffee beans using microwave and conventional oven

This article reports a comparative study of experimental results obtained during the drying of Castilla-variety coffee beans from Santander, Colombia. They were performed by two means: thermal and electromagnetic radiation. Twenty experiments were carried out, ten tests in a microwave cavity at 2,450 MHz-1,080W, and ten tests using a conventional electric oven with temperature controlled at 50±2oC. Experiments were made using samples of coffee beans with parchment, without parchment, and of the only-parchment. For each sample, dimensionless moisture ratio and diffusion coefficients were determined, according to the second law of Fick. We found that the diffusion coefficient of the samples dried in a microwave cavity was twenty-two times higher than the diffusion coefficient of samples dried with thermal radiation. Likewise, it was observed that samples in conventional oven showed a uniform temperature, in contrast with those heated by microwave radiation. Such results are useful for designing hybrid systems for drying coffee beans.

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Diffusion Coefficients from Capillary Flow

Society of Petroleum Engineers Journal ◽

10.2118/302-pa ◽

1963 ◽

Vol 3 (03) ◽

pp. 256-266 ◽

Cited By ~ 1

Author(s):

H.R. Bailey ◽

W.B. Gogarty

Keyword(s):

Differential Equation ◽

Diffusion Coefficient ◽

Numerical Solution ◽

Diffusion Coefficients ◽

Molecular Diffusion ◽

Capillary Flow ◽

Molecular Diffusion Coefficient ◽

Flow Method ◽

And Diffusion ◽

Flow Experiments

Abstract Methods are presented for determining molecular diffusion coefficients by using data from capillary flow experiments. These methods are based on a numerical solution (presented in a previous paper) of the partial differential equation describing the combined mechanisms of flow and diffusion. Results from this numerical solution are given and compared with the approximate analytical solution of G. I. Taylor. The numerical solution is valid over a much larger time range. These methods are applied to experimental results for the fluid pairs water-potassium permanganate solution and amyl acetateorthoxylene. Both of these fluid pairs have approximately equal densities and viscosities. Graphical and numerical techniques are presented for deters mining diffusion coefficients from the flow data. Values obtained by these techniques are compared with values obtained by other methods. Introduction The molecular diffusion coefficient is known to be a variable in determining the amount of mixing in a miscible displacement process. The effect of molecular diffusion on dispersion in longitudinal flow through porous media has been examined by different investigators. These investigators concluded that at low velocities of flow, the amount of dispersion is approximately proportional to the molecular diffusion coefficient. The influence of diffusion on fingering, channeling, and overriding has been mentioned by other investigators. Recent studies have been made on the effects of molecular diffusion in connection with the problem of gravity segregation. Many different methods have been developed for the experimental determination of molecular diffusion coefficients. These methods differ mainly according to boundary conditions selected and analytical procedures used. Nevertheless, all of these methods have the condition in common that the bulk fluids in which diffusion is occurring are stationary with respect to each other. In connection with a series of papers on mixing in capillary flow, Taylor suggested the use of a flow method for determining molecular diffusion coefficients. Additional studies have been conducted on miscible displacements in capillary tubes, but the data from these studies were not used for the specific purpose of determining diffusion coefficients. The flow method proposed by Taylor results in a single value of the diffusion coefficient for the fluid pair used in the displacement experiments. This single value represents the true value for the fluid pair when the diffusion coefficient is independent of concentration. If the diffusion coefficient is a function of concentration, the single value obtained by the flow method gives an average value for the coefficient of the fluid pair. These average values are based on diffusion taking place over the entire range of concentration, i.e., from 0 per cent of one fluid to 100 per cent of that same fluid. In field applications of the miscible displacement process, gradients occur over the same range of concentration as are found in the displacements in capillary tubes. Molecular diffusion coefficients obtained from the capillary flow method should, therefore, be especially relevant to field operations. This investigation was undertaken to evaluate the feasibility of obtaining molecular diffusion coefficients from capillary flow experiments. In making this evaluation, diffusion coefficients were first determined for two systems from data obtained in capillary flow experiments. These values of the diffusion coefficient were then compared to values obtained by other methods. MIXING IN CAPILLARY FLOW-THEORETICAL The theoretical basis for determining molecular diffusion coefficients from capillary flow experiments is the partial differential equation relating the mechanisms of flow and diffusion. SPEJ P. 256^

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Simulation and Computation of Diffusion in Solids

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.182-183.933 ◽

2012 ◽

Vol 182-183 ◽

pp. 933-936

Author(s):

Zhi Hong Hou ◽

Shi Yong Luo

Keyword(s):

Diffusion Coefficient ◽

Diffusion Process ◽

Diffusion Coefficients ◽

Database Management ◽

Concentration Distribution ◽

Database Management System ◽

Critical Conditions ◽

Second Law ◽

Diffusion In Solids ◽

Diffusion Computation

A computation software on diffusion computation in solids was developed. The software includes two sub-modules of “database management system (DBMS)” and "Evaluation & prediction". The “DBMS” deals with the diffusion coefficients gathered from reported documents and the data evaluated according to some rules, besides, it can provide users with retrieval of diffusion coefficients. Based on the solutions to the Fick’s first law and the Fick’s second law in the four typical critical conditions, the "Evaluation & prediction" sub-module gives the predication of concentration distribution after diffusion process in solids or computation for diffusion coefficient.

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ENDOCARP ANALYSIS OF A TRADITIONAL VARIETY OF COLOMBIAN COFFEE

Coffee Science ◽

10.25186/cs.v14i2.1572 ◽

2019 ◽

Vol 14 (2) ◽

pp. 206

Author(s):

MILTON MUÑOZ ◽

MANUEL ROA ◽

RODRIGO CORREA

Keyword(s):

Mass Loss ◽

Diffusion Coefficients ◽

Optimization Methods ◽

Second Law ◽

Infrared Analysis ◽

Coffee Bean ◽

Dehydration Process ◽

Traditional Variety ◽

Coffee Beans ◽

Hemicellulose Degradation

<p> This article presents the main results of thermal analytical and drying tests applied to the endocarp of coffee bean samples, in order to analyze their influence on the coffee dehydration process. An infrared analysis, as well as TGA, DTGA and DSC tests, were applied to the parchment of a sample of Castilla variety coffee beans and later compared with similar tests performed on coffee beans of the same variety, upon parchment removal. For analytical tests, the main thermogravimetric transitions are reported up to a temperature of 1000 °C. From thermograms, four temperature range were identified for parchment, with their respective mass loss: 33-33.7°C, 9.48%; 33.7-251.2°C, 16.23%; 251.2-358°C, 47.48%; and 358-800°C, 15.52%. The greatest mass loss was due to cellulose and hemicellulose degradation. The study was complemented by drying experiments on samples of beans with and without parchment. The diffusion coefficients were found using Fick’s second law and metaheuristic optimization methods (global optimization). On average, the diffusion coefficient of grains without endocarp is 46% greater than that of beans dried with the parchment. Coffee beans with parchment took, on average, 50% more time to reaching moisture levels of 12% (on dry basis). The results are considered important for the projection and design of new coffee drying systems and their automatic control. </p>

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Studies on Transformations of Hemophilus influenzae

The Journal of General Physiology ◽

10.1085/jgp.44.6.1229 ◽

1961 ◽

Vol 44 (6) ◽

pp. 1229-1239 ◽

Cited By ~ 7

Author(s):

Sol H. Goodgal ◽

Roger M. Herriott

Keyword(s):

Diffusion Coefficient ◽

Diffusion Coefficients ◽

Sedimentation Coefficient ◽

Close Correlation ◽

Erythromycin Resistance ◽

Hemophilus Influenzae ◽

A Value ◽

Transforming Activity ◽

Separation Cell ◽

And Diffusion

The sedimentation and diffusion coefficients have been determined for Hemophilus influenzae transforming activity and DNA using P32-labeled DNA. The methods employed the Spinco fixed boundary separation cell for measurements of the sedimentation coefficient and the Northrop-Anson diffusion cell to determine the diffusion coefficient. There was a very close correlation between the amount of DNA and transforming activity sedimented or diffused. The sedimentation coefficient (s20°), for both biological activity and DNA was 27 and the diffusion coefficient (D20°) 1 x 10-8 cm2/sec. The molecular weight calculated from these coefficients gave a value of 16 million. There was no difference in the sedimentation coefficients for the two unlinked markers, streptomycin and erythromycin resistance, and the diffusion coefficients for single markers or the linked markers, streptomycin and cathomycin, were the same.

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Dependence of Viscosity and Diffusion on β-Cyclodextrin and Chloroquine Diphosphate Interactions

Processes ◽

10.3390/pr9081433 ◽

2021 ◽

Vol 9 (8) ◽

pp. 1433

Author(s):

Lenka Musilová ◽

Aleš Mráček ◽

Eduarda F. G. Azevedo ◽

M. Melia Rodrigo ◽

Artur J. M. Valente ◽

...

Keyword(s):

Diffusion Coefficient ◽

Diffusion Coefficients ◽

Mutual Diffusion ◽

Binary Diffusion Coefficient ◽

Concentration Gradients ◽

Cross Diffusion ◽

Taylor Dispersion Technique ◽

Dispersion Technique ◽

And Diffusion ◽

Chloroquine Diphosphate

Mutual diffusion coefficients of chloroquine diphosphate (CDP) in aqueous solutions both without and with β-cyclodextrin (β-CD) were measured at concentrations from (0.0000 to 0.0100) mol dm−3 and 298.15 K, using the Taylor dispersion technique. Ternary mutual diffusion coefficients (Dik) measured by the same technique are reported for aqueous CDP + β-CD solutions at 298.15 K. The presence of β CD led to relevant changes in the diffusion process, as showed by nonzero values of the cross-diffusion coefficients, D12 and D21. β-CD concentration gradients produced significant co-current coupled flows of CDP. In addition, the effects of β-CD on the transport of CDP are assessed by comparing the binary diffusion coefficient of aqueous CDP solutions with the main diffusion coefficient (D11) measured for ternary {CDP(1) + β-CD(2)} solutions. These observations are supported by viscosity analysis. All data allow to have a better interpretation on the effect of cyclodextrin on the transport behavior of CDP.

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Energetics of mixing and transport phenomena in Cd-X (X=Pb, Sn) melts

BIBECHANA ◽

10.3126/bibechana.v15i0.18751 ◽

2017 ◽

Vol 15 ◽

pp. 113-120

Author(s):

R P Koirala ◽

I Koirala ◽

D Adhikari

Keyword(s):

Diffusion Coefficient ◽

Interaction Energy ◽

Liquid Alloy ◽

Diffusion Coefficients ◽

Chemical Study ◽

The Other ◽

And Diffusion ◽

Good Agreement ◽

Mixing And Transport ◽

Linear Concentration

We report a quasi-chemical study of the thermodynamic and transport properties of mixing of liquid Cd-Pb and Cd-Sn alloys at 773K. The interaction energy in the alloys is found to be positive which suggests homo-coordination of atoms in the alloys. The viscosities of the alloys at 773K computed from two different approaches exhibit non-linear concentration dependence with the results for Cd-Sn alloy being in very good agreement and satisfactory agreement for Cd-Pb alloy. In lower concentrations of Cd-component, Cd-Pb alloy has larger viscosity and on the other side of concentration, Cd-Sn alloy has larger value. The calculations of inter-diffusion coefficients result in concave diffusion isotherms for the alloys. The higher values of inter-diffusion coefficients for Cd-Sn suggest that Cd and Sn metals tend to mix more readily than Cd and Pb metals do in Cd-Pb alloy. The correlation between viscosity and diffusion implies that the inter-diffusion coefficient is large for low viscous liquid alloy and vice-versa.BIBECHANA 15 (2018) 113-120

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The Effect of Particle Drag and Wall Absorption on Mass Transfer in Concentric Annulus Flows

Mapana Journal of Sciences ◽

10.12723/mjs.18.1 ◽

2011 ◽

Vol 10 (1) ◽

pp. 1-13

Author(s):

B. Umadevi ◽

Dinesh P.A. ◽

Indira R. Rao ◽

Vinay C.V.

Keyword(s):

Mass Transfer ◽

Diffusion Coefficient ◽

Diffusion Coefficients ◽

Dispersion Model ◽

Transport Coefficients ◽

Time Dependent ◽

Exchange Coefficient ◽

Concentric Annulus ◽

Annular Gap ◽

And Diffusion

The effects of the irreversible boundary reaction and the particle drag on mass transfer are studied analytically in concentric annulus flows. The solution of mathematical model, based on the generalized dispersion model brings out the mass transport following by the insertion of catheter on an artery in terms of the three effective transport coefficients, viz., the exchange, convection and diffusion coefficient. A general expression is derived which shows clearly the time dependent nature of the coefficients in the dispersive model. The complete time dependent expression for the exchange coefficient is obtained explicitly and independent of velocity distribution in the flow; however it does depend on the initial solute distribution. Because of the complexity of the problem only asymptotic large time evaluations are made for the convective and diffusion coefficients, but these are sufficient to give the physical insight into the nature of the problem of the effects of drag and absorption parameters. It is found that as absorption parameter increases exchange and convection coefficients will be enhanced, but diffusion coefficient will be reduced. After certain period of time exchange coefficient will be constant for different values annular gap. As the drag parameter increases convection and diffusion coefficients will be reduced. With the enhancement of catheter radius i.e., the annular gap will be reduced then the convection and diffusion coefficients will be decreased.

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The Impact of Equilibrium Gas Pressure and Coal Particle Size on Gas Dynamic Diffusion in Coal

Processes ◽

10.3390/pr7090571 ◽

2019 ◽

Vol 7 (9) ◽

pp. 571

Author(s):

Li ◽

Nie ◽

Tian ◽

Zhao ◽

Zhang

Keyword(s):

Particle Size ◽

Diffusion Coefficient ◽

Diffusion Coefficients ◽

Effective Diffusion ◽

Gas Pressure ◽

Particle Sizes ◽

Gas Desorption ◽

The Impact ◽

And Diffusion ◽

Dynamic Diffusion

The diffusion coefficient of gases in coal varies with time. This study aims to develop an unsteady dynamic diffusion (UDD) model based on the decay of diffusion coefficient with time and the change of integral. This study conducted a series of gas desorption and diffusion experiments with three different combinations of particle sizes and gas pressures and compared the diffusion coefficients of the three models. The UDD model exhibited good fitting results, and both the UDD and bidisperse models fitted the experimental data better than the unipore model. In addition, the dynamic diffusion coefficient (DDe) decreased rapidly in the initial stage but gradually decreased to a stable level in the later stage. All the effective diffusion coefficients of the three models negatively correlated with the particle size. In the unipore model, the diffusion coefficient of coal samples with three particle sizes increased with gas pressure. In the bidisperse and UDD models, the diffusion coefficients (Dae, Die, and DDe) of 0.25–0.5 mm and 0.5–1.0 mm coal samples increased with gas pressure. However, DDe and Dae of 1.0–1.25 mm coal samples increased first and then decreased. Furthermore, Die decreased first and then increased, with no sign of significant pressure dependence. Finally, the correlation and significance between the constant and diffusion coefficient in the UDD model was investigated.

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The Influence of Sorption Pressure on Gas Diffusion in Coal Particles: An Experimental Study

Processes ◽

10.3390/pr7040219 ◽

2019 ◽

Vol 7 (4) ◽

pp. 219 ◽

Cited By ~ 5

Author(s):

Yang ◽

Wang ◽

Zhang ◽

Ren

Keyword(s):

Diffusion Coefficient ◽

Diffusion Coefficients ◽

Gas Diffusion ◽

Gas Pressure ◽

Fast Diffusion ◽

Pore Characteristic ◽

Coal Particles ◽

Pore Size Distributions ◽

Coal Ranks ◽

And Diffusion

Gas pressure changes during the process of coal mine gas drainage and CBM recovery. It is of great importance to understand the influence of sorption pressure on gas diffusion; however, the topic remains controversial in past studies. In this study, four samples with different coal ranks were collected and diffusion experiments were conducted under different pressures through the adsorption and desorption processes. Three widely used models, i.e., the unipore diffusion (UD) model, the bidisperse diffusion (BD) model and the dispersive diffusion (DD) model, were adopted to compare the applicability and to calculate the diffusion coefficients. Results show that for all coal ranks, the BD model and DD model can match the experimental results better than the UD model. Concerning the fast diffusion coefficient Dae of the BD model, three samples display a decreasing trend with increasing gas pressure while the other sample shows a V-type trend. The slow diffusion coefficient Die of BD model increases with gas pressure for all samples, while the ratio β is an intrinsic character of coal and remains constant. For the DD model, the characteristic rate parameter kΦ does not change sharply and the stretching parameter α increases with gas pressure. Both Dae and Die are in proportion to kΦ, which reflect the diffusion rate of gas in the coal. The impacts of pore characteristic on gas diffusion were also analyzed. Although pore size distributions and specific surface areas are different in the four coal samples, correlations are not apparent between pore characteristic and diffusion coefficients.

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3D trajectories and diffusion of single ceria particles near a glass surface and their removal

Journal of Materials Research ◽

10.1557/s43578-020-00067-4 ◽

2021 ◽

Author(s):

Jihoon Seo ◽

Akshay Gowda ◽

Panart Khajornrungruang ◽

Satomi Hamada ◽

S.V. Babu

Keyword(s):

Diffusion Coefficient ◽

Diffusion Coefficients ◽

Glass Surface ◽

Evanescent Wave ◽

Three Dimensional ◽

Separation Distance ◽

Dimensional Diffusion ◽

Mean Squared Displacement ◽

Glass Surfaces ◽

And Diffusion

AbstractWe extend our recent 2D trajectory (x–y plane) and diffusion coefficient data of ceria particles near a glass surface obtained at pH 3, 5, and 7 using evanescent wave microscopy and video imaging to 3D trajectories by analyzing the separation distance between the particles and the glass surface in the vertical z‐direction. Mean squared displacement (MSD3D) of ceria particles was calculated to quantify 3D trajectories. Three‐dimensional diffusion coefficients were obtained from the MSD3D curves and were compared with two‐dimensional diffusion coefficients. By analyzing the MSD curves, we found that ceria particles exhibited only confined motion at pH 3 and 5, while both confined and Brownian motion were showed at pH 7. We also evaluated the cleaning ability of DI water adjusted to pH 10 and 12 to remove ceria particles from glass surfaces and related the results to the calculated trajectory, diffusion coefficient, and interaction potential data.

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