Research on Condensation in Porous Wall Exposed to Hot Humid Climate

2012 ◽  
Vol 174-177 ◽  
pp. 2006-2011
Author(s):  
Zhen Hua Zhuo ◽  
Xing Guo Guo
Keyword(s):  
Moisture Content ◽  
Moisture Transfer ◽  
Strong Dependence ◽  
Porous Wall ◽  
Water Source ◽  
Vapor Condensation ◽  
Condensation Rate ◽  
Humid Climate ◽  
Heat And Moisture ◽  
Wet Zone

According to the work of Motakef and EI-Masri, the wall is divided into dry-wet-dry zones. Based on the heat and moisture transfer through porous media, considered the vapor condensation as a vapor sink, water source and heat source, coupled heat and moisture equations for wet zone were established. Closed-form analytical expressions for the condensation rate, moisture content and the time at which critical moisture content value is reached are obtained. The analysis has indicated that the condensation rate exhibits a strong dependence on the ratio of temperature drops across the wet zone to the square of that zone width and the maximum condensation rate value is reached at the boundary of wet zone close to lower temperature.

scholarly journals Identification of heat and mass transfer processes in bread during baking

2005 ◽  
Vol 9 (2) ◽  
pp. 73-86 ◽  
Author(s):  
Ivanka Zheleva ◽  
Vesselka Kambourova
Keyword(s):  
Partial Differential Equations ◽  
Moisture Content ◽  
Differential Equations ◽  
Moisture Transfer ◽  
Partial Differential ◽  
Linear Partial Differential Equations ◽  
Mass Transfer Processes ◽  
Model Equations ◽  
Heat And Moisture ◽  
Simultaneous Heat

A mathematical model representing temperature and moisture content in bread during baking is developed. The model employs the coupled partial differential equations proposed by Luikov. Dependences of mass and thermal properties of dough on temperature and moisture content are included in the model. Resulting system of non-linear partial differential equations in time and one space dimension is reduced to algebraic system by applying a finite difference numerical method. A numerical solution of the model equations is obtained and simultaneous heat and moisture transfer in dough during baking is predicted. The changes of temperature and moisture content during the time of the process are graphically presented and commented.

Effects of Moisture on Temperature During Drying of Consolidated Porous Materials

1993 ◽  
Vol 115 (3) ◽  
pp. 724-733 ◽  
Author(s):  
F. Kallel ◽  
N. Galanis ◽  
B. Perrin ◽  
R. Javelas
Keyword(s):  
Moisture Content ◽  
Porous Materials ◽  
Moisture Transfer ◽  
Initial Moisture Content ◽  
Transfer Coefficients ◽  
One Dimensional ◽  
Excess Water ◽  
Brick And Mortar ◽  
Heat And Moisture ◽  
Simultaneous Heat

A one-dimensional model for simultaneous heat and moisture transfer in consolidated porous materials is solved for homogeneous brick and mortar slabs. It is validated by comparing numerically predicted moisture content and temperature evolutions with corresponding measured values. It correctly predicts that initially saturated slabs at 20°C which are suddenly placed in contact with air at 20°C and a relative humidity of 50 percent undergo a rapid transient reduction of their temperature down to 13°C due to the evaporation of excess water content. The model is used to study the effets of the initial moisture content and convection transfer coefficients on the minimum temperature of the slabs and on the duration of the transient.

A hybrid analytical–numerical method for computing coupled temperature and moisture content fields in porous soils

2017 ◽  
Vol 42 (1) ◽  
pp. 68-94 ◽  
Author(s):  
Suelen Gasparin ◽  
Marx Chhay ◽  
Julien Berger ◽  
Nathan Mendes
Keyword(s):  
Moisture Content ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Moisture Transfer ◽  
Physical Phenomenon ◽  
Computational Cost ◽  
Analytical Models ◽  
Heat And Moisture Transfer ◽  
Porous Soils ◽  
Heat And Moisture

This work is devoted to proposing a hybrid numerical–analytical method to address the problem of heat and moisture transfer in porous soils. Several numerical and analytical models have been used to study heat and moisture transfer. The complexity of the coupled transfer in soils is such that analytical solutions exist only for limited problems, while numerical solutions can deal with more realistic ones but at a higher computational cost. Therefore, we propose to implement analytical solutions where variations of temperature and moisture content are known to be almost nonvarying, while the numerical solution is implemented in the remaining region, near the boundaries. The coupling between solutions is performed assuming the continuity of both fields and fluxes at each interface. This strategy allows assuring the physical phenomenon occurring at the interface. Numerical experiments are performed, showing the accuracy, the efficiency, and the great potential of the method regarding applications in nonlinear soil problems.

Heat and moisture transfer performance of thin cotton fabric under impingement drying

2018 ◽  
Vol 89 (15) ◽  
pp. 3089-3097
Author(s):  
Miao Qian ◽  
Jinghan Wang ◽  
Zhong Xiang ◽  
Zhewei Zhao ◽  
Xudong Hu
Keyword(s):  
Moisture Content ◽  
Cotton Fabric ◽  
Moisture Transfer ◽  
Transfer Model ◽  
Transfer Performance ◽  
Heat And Moisture Transfer ◽  
Drying Time ◽  
Uniform Distributions ◽  
Heat And Moisture ◽  
Over Time

To investigate the drying characteristics of thin cotton fabric for reducing the energy consumption during the heat setting process, a two-dimensional heat and moisture transfer model considering lateral heat and moisture transmission under the impingement drying condition was developed in this study. The curves of the variation in fabric temperature and moisture content over time were obtained and the results indicate that the drying rate increases with the decrease in the moisture content in the fabric. In addition, non-uniform distributions of temperature and moisture on the fabric over time were obtained. The drying time per unit area on the fabric was found to increase with time. Further, experiments were conducted to test the heat and moisture transfer performance of the fabric, and the experimental results agree reasonably well with the calculations.

scholarly journals Modeling of Coupled Heat and Mass Transfers in a Stabilized Earthen Building Envelope with Thatched Fibers

Fibers ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 75
Author(s):  
Madeleine Nitcheu ◽  
Donatien Njomo ◽  
Pierre Meukam ◽  
Cyrille Fotsing Talla
Keyword(s):  
Moisture Content ◽  
Building Materials ◽  
Numerical Solutions ◽  
Moisture Transfer ◽  
Building Envelope ◽  
One Dimensional ◽  
Composites Materials ◽  
Model Equations ◽  
Mass Transfers ◽  
Heat And Moisture

In order to reduce the heat and mass transfers in buildings, which increase energy bills, the development of composites materials such as earth bricks stabilized with thatch fibers is important for their construction. This paper aims to study a one-dimensional model of heat and moisture transfer through porous building materials. The coupled phenomena of heat and mass transfer are described by the Luikov model. Equations and boundary conditions are discretized using the finite difference method. The results obtained illustrate the temporal evolutions of the temperature and the moisture content, as well as the distributions of the temperature and moisture content inside the wall. The profile of the temperature and water content that are obtained are compared with the other numerical solutions that are available in the literature.

scholarly journals The use of cellular automata in modeling the processes of wood drying in a stack

2021 ◽  
Vol 3 (2) ◽  
pp. 39-44
Author(s):  
Ya. I. Sokolovskyy ◽  
◽  
O. V. Sinkevych ◽  
Keyword(s):  
Cellular Automata ◽  
Moisture Content ◽  
Relative Error ◽  
Moisture Transfer ◽  
Physical Characteristics ◽  
Cad Model ◽  
Wood Drying ◽  
Heat And Moisture Transfer ◽  
Heat And Moisture ◽  
Drying Chamber

In this work, we investigated the possibilities of using a model of cellular automata in solving the problem of heat and moisture transfer in a periodic wood drying chamber. Thus, in this work are investigating the processes of heat and moisture transfer between the wood and its drying agent. Studies are carried out by using CAD model of stack of dried wood. To use cellular automata, it is proposed to present the CAD model as an array of cubes, each of which has six faces (cells). In this work also proposes to use the different research zones, each of which allows us to calculate the values of temperature and moisture content in different places of the CAD model. In particular, these zones can be placed inside the wood, on its boundary or in the agent of its drying. The proposed cell-automata model contains local relationships between cells that describe their general behavior. In addition to describing the general behavior of cells, the model provides the possibility of setting the physical characteristics of the material. This allows us to approximate processes and determine new values of the physical characteristics of the material, including temperature and moisture content. The proposed algorithm for the use of cellular automata makes it possible to obtain a reliable result unnecessarily to conduct complex and expensive practical experiments. To speed up the calculation process, propose to use multilayered, which consists in obtaining numerical values of the physical characteristics of the material from several adjacent cells, which are located in the same direction of interaction. The work also provides graphs of changes in temperature and relative humidity of the wood drying agent. In this work is also given graphs of changes in temperature and moisture content of wood inside and on its boundary. To check the adequacy and reliability, all results are compared with the results of another experiment. To check the adequacy and reliability, we compared the obtained results with the results of another experiment. For this comparison in work it is calculated the relative error between the temperature and moisture content values of both experiments. The value of this relative error makes it possible to determine the prospects for the use of cellular automata in the simulation of heat and moisture transfer processes in wood drying chambers. Keywords: сellular automata; CAD model; algorithm of work; transition rules; wood drying chamber.

scholarly journals Influence of Initial Moisture Content on Heat and Moisture Transfer in Firefighters’ Protective Clothing

2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Dongmei Huang ◽  
Song He
Keyword(s):  
Moisture Content ◽  
Protective Clothing ◽  
Moisture Transfer ◽  
Burn Injury ◽  
Initial Moisture Content ◽  
Water Evaporation ◽  
Vapor Density ◽  
Degree Burn ◽  
Heat And Moisture ◽  
Second Degree

This paper presents a model for heat and moisture transfer through firefighters’ protective clothing (FPC) during radiation exposure. The model, which accounts for air gaps in the FPC as well as heat transfer through human skin, investigates the effect of different initial moisture contents on the thermal insulation performance of FPC. Temperature, water vapor density, and the volume fraction of liquid water profiles were monitored during the simulation, and the heat quantity absorbed by water evaporation was calculated. Then the maximum durations of heat before the wearer acquires first- and second-degree burns were calculated based on the bioheat transfer equation and the Henriques equation. The results show that both the moisture weight in each layer and the total moisture weight increase linearly within a given environmental humidity level. The initial moisture content in FPC samples significantly influenced the maximum water vapor density. The first- and second-degree burn injury time increase 16 sec and 18 sec when the RH increases from 0% to 90%. The total quantity of heat accounted for by water evaporation was about 10% when the relative humidity (RH) is 80%. Finally, a linear relationship was identified between initial moisture content and the human skin burn injury time before suffering first- and second-degree burn injuries.

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