scholarly journals Nonequilibrium Thermal Dynamic Modeling of Porous Medium Vacuum Drying Process

2012 ◽  
Vol 2012 ◽  
pp. 1-22 ◽  
Author(s):  
Zhijun Zhang ◽  
Ninghua Kong
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Heat And Mass Transfer ◽  
Water Saturation ◽  
Coupled Model ◽  
Water Evaporation ◽  
Vacuum Drying ◽  
Vapor Pressures ◽  
Drying Process ◽  
Medium Vacuum

Porous medium vacuum drying is a complicated heat and mass transfer process. Based on the theory of heat and mass transfer, a coupled model for the porous medium vacuum drying process is constructed. The model is implemented and solved using COMSOL software. The water evaporation rate is determined using a nonequilibrium method with the rate constant parameterKr.  Krvalues of 1, 10, 1000, and 10000 are simulated. The effects of vapor pressures of 1000, 5000, and 9000 Pa; initial moistures of 0.6, 0.5, and 0.4 water saturation; heat temperatures of 323, 333, and 343 K; and intrinsic permeability of 10−13, 10−14, and 10−15 m2are studied. The results facilitate a better understanding of the porous medium vacuum drying process.

scholarly journals Cortex Effect on Vacuum Drying Process of Porous Medium

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Zhijun Zhang ◽  
Shiwei Zhang ◽  
Tianyi Su ◽  
Shuangshuang Zhao
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Fruits And Vegetables ◽  
Water Saturation ◽  
Coupled Model ◽  
Water Evaporation ◽  
Vacuum Drying ◽  
Vapor Pressures ◽  
Drying Process ◽  
Medium Vacuum

Corns, fruits, and vegetables are usually used as porous medium in drying process. But in fact, it must be considered as the cortex effect on mass transfer because the mass transfer of cortex is very difficult than inner medium. Based on the theory of heat and mass transfer, a coupled model for the porous medium vacuum drying process with cortex effect is constructed. The model is implemented and solved using COMSOL software. The water evaporation rate is determined using a nonequilibrium method with the rate constant parameterKrthat has been studied. The effects of different vapor pressures (1000, 5000, and 9000 Pa), initial moisture contents (0.3, 0.4, and 0.5 water saturation), drying temperatures (323, 333, and 343 K), and intrinsic permeability for cortex part (10−13, 10−14, 10−15 m2) on vacuum drying process were studied. The results facilitate a better understanding of the porous medium vacuum drying process that nearer to the reality.

scholarly journals Numerical Comparison of Triangular and Sinusoidal External Vibration Effects on the 3D Porous Drying Process

2020 ◽  
Vol 10 (2) ◽  
pp. 5554-5560
Author(s):  
N. Ben Khedher ◽  
R. Ramzi ◽  
I. A. Alatawi
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Heat And Mass Transfer ◽  
Control Volume ◽  
Saturation Pressure ◽  
Three Dimensional ◽  
Mass Transfer Process ◽  
Numerical Comparison ◽  
Drying Process ◽  
External Vibration

Drying is one of the most energy-intensive industrial processes. One of the techniques aiming to reduce energy consumption is the vibration technique which is generally employed to intensify the heat and mass transfer process. In this respect, this paper presents a three-dimensional numerical model to study the external vibration effects on the drying process of a porous medium. The model is based on a comparison of heat and mass transfer phenomena that arise during vibrating drying of unsaturated porous medium for two cases: triangular and sinusoidal external vibrations. The three-dimensional unstructured Control Volume Finite Element Method (CVFEM) is employed to simulate the vibrating drying. Numerical results of the time evolution of temperature, liquid saturation, pressure, and water content are compared and analyzed for the two cases.

A numerical model of the open-width coupling drying process for cotton fabrics based on the theory of heat and mass transfer in porous media

2019 ◽  
Vol 90 (13-14) ◽  
pp. 1639-1657
Author(s):  
Shuangqing Wang ◽  
Huile Zhang ◽  
Huimin Chen ◽  
Yi Zhong ◽  
Xiaoli Yue
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Surface Temperature ◽  
Water Content ◽  
Heat And Mass Transfer ◽  
Absolute Error ◽  
Cotton Fabrics ◽  
Water Evaporation ◽  
Drying Process ◽  
Fabric Surface

In order to reveal the physical drying characteristics of various kinds of cotton fabrics and further provide theoretical guides for designing drying equipment and improving drying technologies, a finite element model is built that is able to describe coupling of the drying process between fabrics and environment. Specifically, three kinds of cotton fabrics mesoscopic structures parameters and mechanical properties are firstly measured and then these fabrics are equivalent to porous media, and the equivalent media can characterize the fabrics precisely. Then, the formulas for calculating the convection heat transfer and thermodynamic properties of fabrics are also improved and verified by corresponding experiments. The results shows that the improved formulas can calculate the properties more accurately. Next, we apply this model to analyze the regular change of surface temperature and water content with time during the drying process of three kinds of fabrics under different technologies. The results indicates that the coupled heat and mass transfer of drying processes are obviously affected by liquid phase transition. In addition, with higher wind temperature, the velocity of water evaporation inside fabrics is faster and, when water content inside fabric becomes lower in the drying process, the velocity of water evaporation decreases. The numerical values agrees well with the corresponding experimental values: The mean absolute error of water content inside fabric in the drying process is less than 1.51 g, while the average absolute error of fabric surface temperature is about 1.63℃, which means this model can precisely capture the coupling drying process of various kinds of cotton fabrics inside the oven. It is expected that the model can be applied for providing theoretical guidance for designing structures of drying equipment and improving drying technologies.

Free Convective Heat and Mass Transfer in a Doubly Stratified Porous Medium Saturated with a Power-Law Fluid

2009 ◽  
Vol 36 (6) ◽  
pp. 524-537 ◽  
Author(s):  
P. A. Lakshmi Narayana ◽  
P. V. S. N. Murthy ◽  
P. V. S. S. S. R. Krishna ◽  
Adrian Postelnicu
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Power Law ◽  
Power Law Fluid

Simulation of volumetric heating of a moist medium with allowance for fluid mobility

2012 ◽  
Vol 9 (1) ◽  
pp. 91-93
Author(s):  
U.R. Ilyasov ◽  
A.V. Dolgushev
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Numerical Solution ◽  
Heat And Mass Transfer ◽  
Transfer Process ◽  
Thermal Action ◽  
Mass Transfer Process ◽  
Low Permeability ◽  
Volumetric Heating ◽  
Drying Regime

The problem of volumetric thermal action on a moist porous medium is considered. Numerical solution, the influence of fluid mobility on the dynamics of the heat and mass transfer process is analyzed. It is established that fluid mobility leads to a softer drying regime. It is shown that in low-permeability media, the fluid can be assumed to be stationary.

scholarly journals Modeling and simulation of heat and mass transfer in an Ethiopian fresh injera drying process

Heliyon ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. e06201
Author(s):  
Alamrew B. Solomon ◽  
Solomon W. Fanta ◽  
Mulugeta A. Delele ◽  
Maarten Vanierschot
Keyword(s):  
Mass Transfer ◽  
Modeling And Simulation ◽  
Heat And Mass Transfer ◽  
Drying Process
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