A modelling study for moisture diffusivities and moisture transfer coefficients in drying of solid objects

Abstract

SUMMARYThis article presents an effective analytical model for determining the moisture diffusivities and moisture transfer coefficients for solid objects (namely, infinite slab, infinite cylinder, sphere; and also for irregularly shaped objects, by using a shape factor) subject to drying applications in a medium. The unsteady-state moisture diffusion analysis is used on the basis of two important criteria: 0 1 < Bi < 100 and Bi > 100. The drying coefficients and lag factors were employed. The analytical models are then verified using available experimental data taken from the literature. The results show that the method presented here can be used to determine the moisture diffusion coefficients and moisture transfer coefficients for such solid objects in a simple and accurate manner for a variety of drying applications.KEY WORDS: drying applications solid objects drylng coefficient lag factor moisture diffusivity moisture transfer coefficient moisture loss analysis

Applicability of moisture transfer Bi–Di correlation for convective drying of broccoli

“…The lag factor did not depend on drying conditions (p > 0.05 for both temperature and air velocity) and G values were negligibly over 1. This leads to the Biot number in the range 0.1 and 100 (as it was obtained by further calculations) indicating the presence of the external and internal resistance to mass diffusivity (Dincer & Dost, 1996). The lag factor proved to be a system specific mass transfer property varying for different drying systems and for different drying beds (McMinn, 2004).…”

Applicability of moisture transfer Bi–Di correlation for convective drying of broccoli

“…The lag factor did not depend on drying conditions (p > 0.05 for both temperature and air velocity) and G values were negligibly over 1. This leads to the Biot number in the range 0.1 and 100 (as it was obtained by further calculations) indicating the presence of the external and internal resistance to mass diffusivity (Dincer & Dost, 1996). The lag factor proved to be a system specific mass transfer property varying for different drying systems and for different drying beds (McMinn, 2004).…”

Prediction of drying times for irregular shaped multi-dimensional moist solids

“…This case is valid for food products as clearly shown earlier with a large amount of experimental data (Dincer & Dost, 1996;Dincer et al, 2000). Of course, the value of Biot number is particularly a function of moisture diffusivity, moisture transfer coefficient, dimensions of the product.…”

A Modeling Study for Moisture Diffusivities and Moisture Transfer Coefficients in Drying of “&lt;i&gt;Violet de Galmi&lt;/i&gt;” Onion Drying

“…The results of this study indicate that the model developed by Dincer and Dost [19] can be used with reasonable accuracy and confidence to calculate the moisture diffusivity and mass transfer coefficient values for convective drying of "Violet de Galmi" onion for temperature range of 40˚C -70˚C and a relative humidity of 20%. Through this model, effective diffusion coefficient values are obtained between 0.2578 × 10 −9 m 2 ·s −1 and 0.5460 × 10 −9 m 2 ·s −1 .…”

Applicability of moisture transfer Bi–Di correlation for convective drying of broccoli

“…The lag factor did not depend on drying conditions (p > 0.05 for both temperature and air velocity) and G values were negligibly over 1. This leads to the Biot number in the range 0.1 and 100 (as it was obtained by further calculations) indicating the presence of the external and internal resistance to mass diffusivity (Dincer & Dost, 1996). The lag factor proved to be a system specific mass transfer property varying for different drying systems and for different drying beds (McMinn, 2004).…”

Prediction of drying times for irregular shaped multi-dimensional moist solids

“…This case is valid for food products as clearly shown earlier with a large amount of experimental data (Dincer & Dost, 1996;Dincer et al, 2000). Of course, the value of Biot number is particularly a function of moisture diffusivity, moisture transfer coefficient, dimensions of the product.…”

A Modeling Study for Moisture Diffusivities and Moisture Transfer Coefficients in Drying of “&lt;i&gt;Violet de Galmi&lt;/i&gt;” Onion Drying

“…The results of this study indicate that the model developed by Dincer and Dost [19] can be used with reasonable accuracy and confidence to calculate the moisture diffusivity and mass transfer coefficient values for convective drying of "Violet de Galmi" onion for temperature range of 40˚C -70˚C and a relative humidity of 20%. Through this model, effective diffusion coefficient values are obtained between 0.2578 × 10 −9 m 2 ·s −1 and 0.5460 × 10 −9 m 2 ·s −1 .…”

Applicability of moisture transfer Bi–Di correlation for convective drying of broccoli

“…The lag factor did not depend on drying conditions (p > 0.05 for both temperature and air velocity) and G values were negligibly over 1. This leads to the Biot number in the range 0.1 and 100 (as it was obtained by further calculations) indicating the presence of the external and internal resistance to mass diffusivity (Dincer & Dost, 1996). The lag factor proved to be a system specific mass transfer property varying for different drying systems and for different drying beds (McMinn, 2004).…”

Prediction of drying times for irregular shaped multi-dimensional moist solids

“…This case is valid for food products as clearly shown earlier with a large amount of experimental data (Dincer & Dost, 1996;Dincer et al, 2000). Of course, the value of Biot number is particularly a function of moisture diffusivity, moisture transfer coefficient, dimensions of the product.…”

A Modeling Study for Moisture Diffusivities and Moisture Transfer Coefficients in Drying of “&lt;i&gt;Violet de Galmi&lt;/i&gt;” Onion Drying

“…The results of this study indicate that the model developed by Dincer and Dost [19] can be used with reasonable accuracy and confidence to calculate the moisture diffusivity and mass transfer coefficient values for convective drying of "Violet de Galmi" onion for temperature range of 40˚C -70˚C and a relative humidity of 20%. Through this model, effective diffusion coefficient values are obtained between 0.2578 × 10 −9 m 2 ·s −1 and 0.5460 × 10 −9 m 2 ·s −1 .…”