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 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.

scholarly journals Energy in buildings: A review of models on hygrothermal transfer through the porous materials for building envelop

2021 ◽  
Author(s):  
Macmanus Chinenye Ndukwu ◽  
Merlin Simo-Tagne ◽  
Ifiok Edem Ekop ◽  
Mathew I. Ibeh ◽  
Maureen A. Allen ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Building Materials ◽  
Mass Conservation ◽  
Building Envelope ◽  
Different Boundary Conditions ◽  
Building Envelop ◽  
Hygroscopic Nature ◽  
Model Equations ◽  
Building Walls ◽  
Heat And Moisture

The hygrothermal transfer is very important for the design of a building envelope for thermal comfort and economic and energy analysis of the building envelope. The applications of various materials in building envelope have been studied extensively. The study presents several models for the hygrothermal transfer for various building walls. Several energy and mass conservation equations with different boundary conditions and input considerations were presented in this paper for concrete, bricks and wooden walls. The effect of hysteresis was ignored in developing most model equations, while few considered flow pattern of fluid through the wall surfaces. Due to the flexibility of Luikov models, it formed the basis for modelling the coupled heat and mass transfer for porous material independent of hygroscopic nature with different boundary conditions defined according to the geometry and orientations. The influence of type of wall, orientation, thickness, the density of the material and climatic variations on the temperature and moisture evolutions within the building materials was more pronounced. Literature, presenting imaging models using imagery software like COMSOL multi-physics, CFD etc. were scarce considering that microscopic imagery is now deployed to measure the heat and moisture evolution in materials. Future models should include shrinkage or expansion influence on the fibrous material like wood due to their behaviour under environmental condition.

scholarly journals Application Method of a Simplified Heat and Moisture Transfer Model of Building Construction in Residential Buildings

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4180
Author(s):  
Joowook Kim ◽  
Michael Brandemuehl
Keyword(s):  
Latent Heat ◽  
Moisture Transfer ◽  
Residential Buildings ◽  
Building Energy ◽  
The United States ◽  
Building Envelope ◽  
Outdoor Environment ◽  
Transfer Model ◽  
Heat And Moisture Transfer ◽  
Heat And Moisture

Several building energy simulation programs have been developed to evaluate the indoor conditions and energy performance of buildings. As a fundamental component of heating, ventilating, and air conditioning loads, each building energy modeling tool calculates the heat and moisture exchange among the outdoor environment, building envelope, and indoor environments. This paper presents a simplified heat and moisture transfer model of the building envelope, and case studies for building performance obtained by different heat and moisture transfer models are conducted to investigate the contribution of the proposed steady-state moisture flux (SSMF) method. For the analysis, three representative humid locations in the United States are considered: Miami, Atlanta, and Chicago. The results show that the SSMF model effectively complements the latent heat transfer calculation in conduction transfer function (CTF) and effective moisture penetration depth (EMPD) models during the cooling season. In addition, it is found that the ceiling part of a building largely constitutes the latent heat generated by the SSMF model.

scholarly journals Numerical Network Modeling of Heat and Moisture Transfer through Capillary-Porous Building Materials

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1819
Author(s):  
Borys Basok ◽  
Borys Davydenko ◽  
Anatoliy M. Pavlenko
Keyword(s):  
Building Materials ◽  
Moisture Transfer ◽  
Three Dimensional ◽  
Total Pore Volume ◽  
Equivalent Diameter ◽  
Average Pore ◽  
The Difference ◽  
Three Dimensional Coordinate ◽  
Solid Liquid ◽  
Heat And Moisture

The article presents the modeling of the dynamics of the vapor-gas mixture and heat and mass transfer (sorption-desorption) in the capillary structure of the porous medium. This approach is underpinned by the fact that the porous structure is represented by a system of linear microchannels oriented along the axes of a three-dimensional coordinate system. The equivalent diameter of these channels corresponds to the average pore diameter, and the ratio of the total pore volume to the volume of the entire porous material corresponds to its porosity. The entire channel area is modeled by a set of cubic elements with a certain humidity, moisture content, pressure and temperature. A simulation is carried out taking into account the difference in temperatures of each of the phases: solid, liquid and gas.

Development of a numerical approach to assess the effect of coupled heat and moisture transfer on energy consumption of residential buildings in Moroccan context

2021 ◽  
pp. 174425912110560
Author(s):  
Yassine Chbani Idrissi ◽  
Rafik Belarbi ◽  
Mohammed Yacine Ferroukhi ◽  
M’barek Feddaoui ◽  
Driss Agliz
Keyword(s):  
Energy Consumption ◽  
Building Materials ◽  
Moisture Transfer ◽  
Residential Buildings ◽  
Building Design ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Heat And Moisture Transfer ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture

Hygrothermal properties of building materials, climatic conditions and energy performance are interrelated and have to be considered simultaneously as part of an optimised building design. In this paper, a new approach to evaluate the energy consumption of residential buildings in Morocco is presented. This approach is based on the effect of coupled heat and moisture transfer in typical residential buildings and on their responses to the varied climatic conditions encountered in the country. This approach allows us to evaluate with better accuracy the response of building energy performance and the indoor comfort of building occupants. Annual energy consumption, cooling and heating energy requirements were estimated considering the six climatic zones of Morocco. Based on the results, terms related to coupled heat and moisture transfer can effectively correct the existing energy consumption calculations of the six zones of Morocco, which currently do not consider energy consumption due to coupled heat and moisture transfer.

Positive pressure effect on moisture performance in a school building

2019 ◽  
Vol 43 (2) ◽  
pp. 121-142
Author(s):  
Andrea Ferrantelli ◽  
Camilla Vornanen-Winqvist ◽  
Milla Mattila ◽  
Heidi Salonen ◽  
Jarek Kurnitski
Keyword(s):  
Air Quality ◽  
Moisture Content ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Moisture Transfer ◽  
Building Envelope ◽  
Positive Pressure ◽  
School Building ◽  
Negative Effects ◽  
Moisture Performance

Moisture excess in buildings constitutes a complex problem affecting indoor air quality, energy consumption and the lifetime of the building envelope. We investigate the effect on moisture transfer in structures as a positive pressure is applied inside the enclosure. It is found that, contrary to established belief, the positive pressure does not induce any negative effects on the structures’ moisture content in normally ventilated classrooms, even with high occupancy. Our case study consists of a school building in Finland, subject to temperature and relative humidity measurements after a small (5–7 Pa) positive pressure was realized through ventilation control. We first address analytically the moisture excess generated inside the classrooms for 14 days, using dynamical balance equations that account for both ventilation effects and occupants’ moisture release in the environment. It is found that the average moisture excess is very small, largely below 1 g/m3, even for ventilation rates that are half the design value. We also examine the moisture performance of the envelope, by addressing the moisture migration at upper and lower joints of the external walls for both measured and design values of the indoor absolute humidity (AH). A coupled numerical model of diffusion and convection shows that moisture accumulation in the envelope and the according stresses are negligible for any realistic AH values. This result is in agreement with field measurements at the school. In conclusion, it seems that applying a small overpressure in a well-ventilated school building during a standard service period resulted in no accumulation inside the external walls, even at high occupancy and with low ventilation. Remarkably, it slightly dried out the moisture content in structures under actual occupancy conditions. The positive pressure has accordingly no negative effects on moisture performance, and is capable to guarantee a good indoor air quality as well.

scholarly journals Numerical modelling of a hemp concrete wall

2019 ◽  
Vol 85 ◽  
pp. 08003 ◽  
Author(s):  
Georges Costantine ◽  
Chadi Maalouf ◽  
Tala Moussa ◽  
Guillaume Polidori ◽  
Elias Kinab
Keyword(s):  
Building Materials ◽  
Moisture Transfer ◽  
Numerical Study ◽  
Object Oriented ◽  
Hysteresis Phenomenon ◽  
Energy Costs ◽  
Concrete Wall ◽  
Heat And Moisture ◽  
Account Heat ◽  
Indoor And Outdoor

In a global warming context associated to the abuse of energy consumption, actual researches focus more and more on reducing energy costs in the building sector. This target could be achieved by using innovative building materials, such as hemp concrete, due to its positive impacts on thermal and environmental levels. The aim of this work is to carry out a numerical study of a hemp concrete wall subjected to several indoor and outdoor conditions of temperature and relative humidity using the program object oriented SPARK. The hygrothermal behaviour of the wall is investigated taking into account heat and moisture transfer within the wall as well as hysteresis phenomenon between the sorption and desorption curves and their temperature dependency.

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