Shrinkage, effective diffusion coefficient, surface transfer coefficients and their factors during solar drying of food products – A review

Solar Energy ◽  
2021 ◽  
Author(s):  
Vishnuvardhan Reddy Mugi ◽  
V.P. Chandramohan
Keyword(s):  
Diffusion Coefficient ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Food Products ◽  
Solar Drying ◽  
Transfer Coefficients

scholarly journals Heat and mass transfer coefficients and modeling of infrared drying of banana slices

Revista CERES ◽  
2017 ◽  
Vol 64 (5) ◽  
pp. 457-464 ◽  
Author(s):  
Fernanda Machado Baptestini ◽  
Paulo Cesar Corrêa ◽  
Gabriel Henrique Horta de Oliveira ◽  
Fernando Mendes Botelho ◽  
Ana Paula Lelis Rodrigues de Oliveira
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Shelf Life ◽  
Heat And Mass Transfer ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Infrared Drying ◽  
Ripening Stages

ABSTRACT Banana is one of the most consumed fruits in the world, having a large part of its production performed in tropical countries. This product possesses a wide range of vitamins and minerals, being an important component of the alimentation worldwide. However, the shelf life of bananas is short, thus requiring procedures to prevent the quality loss and increase the shelf life. One of these procedures widely used is drying. This work aimed to study the infrared drying process of banana slices (cv. Prata) and determine the heat and mass transfer coefficients of this process. In addition, effective diffusion coefficient and relationship between ripening stages of banana and drying were obtained. Banana slices at four different ripening stages were dried using a dryer with infrared heating source with four different temperatures (65, 75, 85, and 95 ºC). Midilli model was the one that best represented infrared drying of banana slices. Heat and mass transfer coefficients varied, respectively, between 46.84 and 70.54 W m-2 K-1 and 0.040 to 0.0632 m s-1 for temperature range, at the different ripening stages. Effective diffusion coefficient ranged from 1.96 to 3.59 × 10-15 m² s-1. Activation energy encountered were 16.392, 29.531, 23.194, and 25.206 kJ mol-1 for 2nd, 3rd, 5th, and 7th ripening stages, respectively. Ripening stages did not affect the infrared drying of bananas.

scholarly journals Dehydration of infrared ginger slices: heat and mass transfer coefficient and modeling

2019 ◽  
Vol 43 ◽  
Author(s):  
Paulo Cesar Corrêa ◽  
Fernanda Machado Baptestini ◽  
Juliana Soares Zeymer ◽  
Marcos Eduardo Viana de Araujo ◽  
Rita Cristina Pereira de Freitas ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Heat And Mass Transfer ◽  
Effective Diffusion Coefficient ◽  
Diffusion Theory ◽  
Effective Diffusion ◽  
Heat Transfer Process ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
And Storage

ABSTRACT Dehydration of plant products extends its shelf life and reduces its mass and volume, which increases transport and storage efficiency and adds value to food. However, it is an intensive process in energy and time, making necessary the search for more efficient technologies, Thus, this study aimed to investigate the infrared ginger dehydration process by approaching the constant period of dehydration to the theory of mass and heat transfer process to the wet bulb thermometer and the decreasing period of dehydration to liquid diffusion theory. We submitted 5.0 mm thickness and 2.0 cm diameter slices to a dryer with infrared radiation at 50, 60, 70, 80, 90 and 100 °C until constant mass. Heat and mass transfer coefficients, and effective diffusion coefficient increased linearly with temperature increasing, resulting in values ranging from 69.40 to 92.23 W m-2 °C-1, 0.062 to 0.089 m s-1 and 3.81 x 10-9 to 1.13 x 10-8 m2 s-1. Variation of heat and mass transfer coefficients was described by a linear model and the variation of effective diffusion coefficient with the temperature was described with the Arrhenius relation, whose activation energy was 22.07 kJ mol-1. The modified Henderson and Pabis model was able to satisfactorily describe the period of decreasing drying rate.

The Effective Diffusion Coefficient and Mass Transfer Coefficient of Nordic Softwoods as Calculated from Direct Drying Experiments

Holzforschung ◽  
1999 ◽  
Vol 53 (5) ◽  
pp. 534-540 ◽  
Author(s):  
Antti Hukka
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Transfer Coefficients ◽  
Medium Temperature ◽  
Whole Process ◽  
Moisture Profiles

Summary The effective diffusion coefficient and mass transfer coefficient of Scot's pine and Norway spruce heartwood are calculated from the measured development of the internal moisture profiles of sawn timber during drying. Measurement is made using the oven-dry method. Calculation of both coefficients is based on using an existing timber drying simulation model to iteratively optimise the parameter values for the diffusion and mass transfer coefficients of prescribed functional form. The results show that the procedure employed is a feasible method to obtain numerical values for the internal and external transfer coefficients as functions of wood moisture content and temperature. The resulting diffusion coefficient and mass transfer coefficient are applicable in the whole moisture range between green and dry states in temperatures 20–80°C thus covering the whole process of medium-temperature wood drying.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

scholarly journals Restricted diffusion of model sulfides over a NiMo/BK catalyst under hydrodesulfurization reaction conditions

RSC Advances ◽  
2017 ◽  
Vol 7 (70) ◽  
pp. 44340-44347 ◽  
Author(s):  
Huadong Wu ◽  
Aijun Duan ◽  
Zhen Zhao ◽  
Chunming Xu ◽  
Guiyuan Jiang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Molecular Size ◽  
Restricted Diffusion ◽  
Reaction Conditions ◽  
Effective Factors

The effective factors (η) of a NiMo/BK catalyst are greater than that of the traditional NiMo/Al2O3; the effective diffusion coefficient (De) decreases with the increasing molecular size of the model sulfides.

scholarly journals Characterization of Effective Diffusion within Viscoelastic Fluids with Elastic Instabilities

Fluids ◽  
2022 ◽  
Vol 7 (1) ◽  
pp. 33
Author(s):  
Valerie Hietsch ◽  
Phil Ligrani ◽  
Mengying Su
Keyword(s):  
Diffusion Coefficient ◽  
Couette Flow ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Flow Shear ◽  
Shear Rates ◽  
Flow Environment ◽  
Disk Rotation ◽  
Elastic Instabilities ◽  
Fluorescein Dye

We considered effective diffusion, characterized by magnitudes of effective diffusion coefficients, in order to quantify mass transport due to the onset and development of elastic instabilities. Effective diffusion coefficient magnitudes were determined using different analytic approaches, as they were applied to tracked visualizations of fluorescein dye front variations, as circumferential advection was imposed upon a flow environment produced using a rotating Couette flow arrangement. Effective diffusion coefficient results were provided for a range of flow shear rates, which were produced using different Couette flow rotation speeds and two different flow environment fluid depths. To visualize the flow behavior within the rotating Couette flow environment, minute amounts of fluorescein dye were injected into the center of the flow container using a syringe pump. This dye was then redistributed within the flow by radial diffusion only when no disk rotation was used, and by radial diffusion and by circumferential advection when disk rotation was present. Associated effective diffusion coefficient values, for the latter arrangement, were compared to coefficients values with no disk rotation, which were due to molecular diffusion alone, in order to quantify enhancements due to elastic instabilities. Experiments were conducted using viscoelastic fluids, which were based on a 65% sucrose solution, with different polymer concentrations ranging from 0 ppm to 300 ppm. Associated Reynolds numbers based on the fluid depth and radially averaged maximum flow velocity ranged from 0.00 to 0.5. The resulting effective diffusion coefficient values for different flow shear rates and polymer concentrations quantified the onset of elastic instabilities, as well as significant and dramatic changes to local mass transport magnitudes, which are associated with the further development of elastic instabilities.

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