Experimental Determination of Polymers and Polymer-Based Composite Materials Diffusion Properties

2019 ◽  
Vol 945 ◽  
pp. 401-406
Author(s):  
V. Dmitriev ◽  
G. Baronin ◽  
E. Sergeeva
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Composite Materials ◽  
Effective Diffusion ◽  
Mass Transfer Process ◽  
Polymer Materials ◽  
Zonal Method ◽  
Kinetic Problem ◽  
Humidity Dependence ◽  
Diffusion Properties

The widespread use of polymer composite materials makes it necessary to study their physical properties. Particular attention is given to polymers reacted with water and other low molecular weight compounds in their preparation as well as during operation. Most studies have been devoted in the diffusion properties of materials in the form of films, while operating materials often have a different shape, for example pellets. Well at small sizes of granules is impossible to use stationary methods. In this paper, the diffusion coefficient is determined by the zonal method based on the integration of the diffusion equation. A significant increase in the effective diffusion coefficient with an increase in the diffusant concentration associated with the plasticizing action of water was detected. Temperature-humidity dependence of diffusion effective coefficient is approximated by the refined formula which helps to calculate mass transfer process kinetics and carry out theoretical analysis of water diffuse properties in polymer matrix. With the movement of individual particles of polymer materials in real dryers, it is expedient to break the kinetic problem of mass transfer into external and internal one. The validity of the two-level consideration of the kinetic problem of granular polymer materials deep drying and the applicability of the data obtained for their diffusion properties are shown. The microkinetics of a single particle drying is considered, it is the determining condition for the accuracy of the kinetic calculation.

scholarly journals Исследование коэффициента диффузии в тонких изделиях из пористых материалов

2019 ◽  
Vol 89 (10) ◽  
pp. 1630
Author(s):  
В.П. Беляев ◽  
С.В. Мищенко ◽  
П.С. Беляев
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Diffusion Coefficient ◽  
Transfer Process ◽  
Noise Immunity ◽  
Measurement Accuracy ◽  
High Sensitivity ◽  
Mass Transfer Process ◽  
Static Characteristic ◽  
Rapid Diffusion

A new method for studying mass transfer process in porous media has been considered, which allows the rapid diffusion coefficient control in thin products without destroying them and without the preliminary calibration of the diffuser concentration meter. The method provides an increase in the measurement accuracy due to the possibility of choosing the measured parameters included in the design expression. Parameters are taking from the segments of converter static characteristic. The converter has high sensitivity and noise immunity.

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.

Study on the diffusion coefficients for ammonia nitrogen and nitrite and nitrate in PVA gels

2016 ◽  
Vol 74 (8) ◽  
pp. 1773-1779 ◽  
Author(s):  
Hong Yang ◽  
Qingkun Guan
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Polynomial Equation ◽  
Ammonia Nitrogen ◽  
Test Device ◽  
Surface Method ◽  
Cubic Polynomial ◽  
Addition Amount

In order to quantify the proliferation of polyvinyl alcohol (PVA) gels in a matrix and optimize the performance of mass transfer, activated carbon (AC) and CaCO3 were selected as adding materials in this experiment. For the performance of mass transfer, the optimal conditions were analyzed using response surface method (RSM) considering the inter-correlated effects of the amount of AC and CaCO3. For RSM, 13 trials resulted in a partial cubic polynomial equation, which best predicted the amount of residual debris after homogenization. The results of the study show that the effective diffusion coefficient test device can analysis the diffusion rate nitrogen, nitrite and nitrate within the PVA gels quantitatively; adding appropriate amounts of AC and CaCO3 in the biological active filter can improve the performance of mass transfer effectively; the maximum effective diffusion coefficient of nitrogen and nitrite and nitrate in the packing were 1.3637 × 10−9 and 1.0850 × 10−9 and 1.0199 × 10−9 m2/s, respectively, at optimal addition amount.

scholarly journals A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry snow

2015 ◽  
Vol 9 (5) ◽  
pp. 1857-1878 ◽  
Author(s):  
A. C. Hansen ◽  
W. E. Foslien
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Effective Thermal Conductivity ◽  
Heat And Mass Transfer ◽  
Effective Diffusion ◽  
Mixture Theory ◽  
Temperature Gradients ◽  
Snow Metamorphism ◽  
Sublimation Rates

Abstract. The microstructure of a dry alpine snowpack is a dynamic environment where microstructural evolution is driven by seasonal density profiles and weather conditions. Notably, temperature gradients on the order of 10–20 K m−1, or larger, are known to produce a faceted snow microstructure exhibiting little strength. However, while strong temperature gradients are widely accepted as the primary driver for kinetic growth, they do not fully account for the range of experimental observations. An additional factor influencing snow metamorphism is believed to be the rate of mass transfer at the macroscale. We develop a mixture theory capable of predicting macroscale deposition and/or sublimation in a snow cover under temperature gradient conditions. Temperature gradients and mass exchange are tracked over periods ranging from 1 to 10 days. Interesting heat and mass transfer behavior is observed near the ground, near the surface, as well as immediately above and below dense ice crusts. Information about deposition (condensation) and sublimation rates may help explain snow metamorphism phenomena that cannot be accounted for by temperature gradients alone. The macroscale heat and mass transfer analysis requires accurate representations of the effective thermal conductivity and the effective mass diffusion coefficient for snow. We develop analytical models for these parameters based on first principles at the microscale. The expressions derived contain no empirical adjustments, and further, provide self consistent values for effective thermal conductivity and the effective diffusion coefficient for the limiting cases of air and solid ice. The predicted values for these macroscale material parameters are also in excellent agreement with numerical results based on microscale finite element analyses of representative volume elements generated from X-ray tomography.

scholarly journals A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in snow

2015 ◽  
Vol 9 (2) ◽  
pp. 1503-1554
Author(s):  
A. C. Hansen ◽  
W. E. Foslien
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Heat And Mass Transfer ◽  
Effective Diffusion ◽  
Mixture Theory ◽  
Temperature Gradients ◽  
Analytical Models ◽  
Snow Metamorphism ◽  
Sublimation Rates

Abstract. The microstructure of a dry alpine snowpack is a dynamic environment where microstructural evolution is driven by seasonal density profiles and weather conditions. Notably, temperature gradients on the order of 10–20 K m−1, or larger, are known to produce a faceted snow microstructure exhibiting little strength. However, while strong temperature gradients are widely accepted as the primary driver for kinetic growth, they do not fully account for the range of experimental observations. An additional factor influencing snow metamorphism is believed to be the rate of mass transfer at the macroscale. We develop a mixture theory capable of predicting macroscale deposition and/or sublimation in a snow cover under temperature gradient conditions. Temperature gradients and mass exchange are tracked over periods ranging from 1 to 10 days. Interesting heat and mass transfer behavior is observed near the ground, near the surface, as well as immediately above and below dense ice crusts. Information about deposition (condensation) and sublimation rates may help explain snow metamorphism phenomena that cannot be accounted for by temperature gradients alone. The macroscale heat and mass transfer analysis requires accurate representations of the thermal conductivity and the effective mass diffusion coefficient for snow. We develop analytical models for these parameters based on first principles at the microscale. The expressions derived contain no empirical adjustments, and further, provide self consistent values for thermal conductivity and the effective diffusion coefficient for the limiting cases of air and solid ice. The predicted values for these macroscale material parameters are also in excellent agreement with numerical results based on microscale finite element analyses of representative volume elements generated from X-ray tomography.

scholarly journals Numerical Calculation of the Diffusion Process in Multicomponent Hydrocarbon Gas Mixtures

2021 ◽  
Vol 15 ◽  
pp. 61-68
Author(s):  
Beketayeva Meruyert
Keyword(s):  
Mass Transfer ◽  
Diffusion Processes ◽  
Effective Diffusion ◽  
Mass Transfer Process ◽  
Multicomponent Diffusion ◽  
Gas Mixtures ◽  
Production Operation ◽  
Gaseous Fuels ◽  
Effective Coefficients ◽  
Hydrocarbon Gas

Knowledge of the laws of diffusion is necessary in the description, design and calculation of the mass transfer process in the production, operation and transportation of gaseous fuels. In this article, the calculation of diffusion processes for five natural hydrocarbon gas mixtures into the air was carried out. The effective diffusion coefficients and matrix coefficients of multicomponent diffusion were determined. Also the advantages of using effective coefficients in the description of mass transfer were shown.

The Influence of Grain Form on Effective Diffusion Coefficient of Polycrystalline

2015 ◽  
Vol 756 ◽  
pp. 529-533
Author(s):  
Marija V. Chepak-Gizbrekht ◽  
Anna G. Knyazeva
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Grain Boundary ◽  
Effective Diffusion Coefficient ◽  
Effective Properties ◽  
Mass Transfer Rate ◽  
Effective Diffusion ◽  
High Mass ◽  
Know How ◽  
Nonlinear Character

To study the behavior of materials with special properties, such as micro and nanograin structure, it is necessary to know how the size and the form of grain influences on the effective properties of the material. In particular, for materials with fine-dispersed structure characterized by high mass transfer rate, which could be due to several reasons. To study this kind of materials is necessary to build mathematical models taking into account the peculiarities that arise from the transition to the micro structure of the macrostructure. This paper presents a method of calculating the effective diffusion coefficient, which takes into account the influence of the size and form of grains. This method could be useful for the construction of multilayer models of mass transfer. On the example of hexagonal polycrystalline material shown that the dependence of the effective diffusion coefficient of the angle at the grain boundary acquires nonlinear character with the increase of grain boundary layer.

Sign in / Sign up

Export Citation Format

Share Document