scholarly journals The use of sorption and excess sorption isotherm in the mathematical modeling of the unsteady-state heat and humidity regime of the building envelope

2021 ◽  
Vol 2131 (5) ◽  
pp. 052072
Author(s):  
Z Zhou ◽  
K P Zubarev
Keyword(s):  
Water Vapor ◽  
Sorption Isotherm ◽  
Moisture Transfer ◽  
Sorption Isotherms ◽  
Building Envelope ◽  
Vapor Transfer ◽  
Potential Capacity ◽  
Partial Transfer ◽  
Relative Potential ◽  
Moisture Potential

Abstract In the given article the development of the moisture transfer equation based on the theory of moisture potential is considered. The task of combined heat and moisture transfer is one of the most complicated tasks in the building thermal physics field. The classical equations of moisture transfer by K.F. Fokin representing the transfer of moisture under the action of partial transfer potentials - the gradient of the partial pressure of water vapor and the gradient of humidity F - are listed. The possibility of uniform accounting of the combined water vapor transfer on the basis of the moisture potential F is described. The sorption isotherm for aerated concrete is constructed in accordance with the experiment carried out in a desiccator with an aqueous solution of sulfuric acid. A new equation of moisture transfer which takes into account moistening with vaporous moisture in the sorption zone of moisture and liquid moisture in the excess sorption zone of moisture is derived. In order to simplify the work with the obtained equation a new value of the relative potential capacity is introduced. A graph construction of sorption and excess sorption isotherms which are obtained using an analytical expression for the relative potential capacity is proposed. In the sorption zone of humidification the sorption and excess sorption isotherms coincide with the classical sorption isotherm. Meanwhile, in the excess sorption zone of humidification the sorption and excess sorption isotherms depend on temperature.

scholarly journals The comparison of a discrete-continuous approach and a method of finite differences in solving the problem of unsteady-state heat and moisture transfer in the building envelope

2021 ◽  
Vol 2131 (5) ◽  
pp. 052073
Author(s):  
Z Zhou ◽  
K P Zubarev
Keyword(s):  
Thermal Conductivity ◽  
Boundary Conditions ◽  
Finite Differences ◽  
Transfer Equation ◽  
Moisture Transfer ◽  
Building Envelope ◽  
Unsteady State ◽  
State Heat ◽  
Continuous Approach ◽  
Moisture Potential

Abstract This article is devoted to the development of methods for calculating heat and humidity regime in the building envelope. The equation of steady-state thermal conductivity with boundary conditions of the third kind and the formula for calculating heat losses of a building based on the heat transfer equation have been considered. The equation of unsteady-state thermal conductivity as well as its solution using the discrete-continual approach has also been studied. The solution of the unsteady-state heat conductivity problem with invariable over time boundary conditions using the discrete-continuous approach was proposed by A.B. Zolotov and P.A. Akimov. The subsequent modernization of the solution was conducted by V.N. Sidorov and S.M. Matskevich. The unsteady-state equation of moisture transfer based on Fick’s second law using the theory of moisture potential is derived. The solution of the unsteady-state moisture transfer equation using the finite difference method according to an explicit difference scheme as well as the solution of the unsteady-state moisture transfer equation using the discrete-continuous approach is demonstrated. To prove the effectiveness of using the discrete-continuous approach in the area of the unsteady-state humidity conditions we compared the calculation results of the distribution of moisture in a single-layer enclosing structure made of aerated concrete using two methods of moisture potential theory. It was found that the difference in the results of calculation by the discrete-continual formula and by the method of finite differences does not exceed 3.2%.

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 Effect of hot calendering on physical properties and water vapor transfer resistance of bacterial cellulose films

2016 ◽  
Vol 51 (21) ◽  
pp. 9562-9572 ◽  
Author(s):  
V. L. D. Costa ◽  
A. P. Costa ◽  
M. E. Amaral ◽  
C. Oliveira ◽  
M. Gama ◽  
...  
Keyword(s):  
Water Vapor ◽  
Physical Properties ◽  
Bacterial Cellulose ◽  
Transfer Resistance ◽  
Cellulose Films ◽  
Vapor Transfer ◽  
Water Vapor Transfer

scholarly journals Characteristics of Knitted Structures Produced by Engineered Polyester Yarns and Their Blends in Terms of Thermal Comfort

2015 ◽  
Vol 10 (1) ◽  
pp. 155892501501000 ◽  
Author(s):  
Nida Oğlakcioğlu ◽  
Ahmet Çay ◽  
Arzu Marmarali ◽  
Emel Mert
Keyword(s):  
Water Vapor ◽  
Thermal Comfort ◽  
Moisture Transfer ◽  
Water Vapor Permeability ◽  
Air Permeability ◽  
Vapor Permeability ◽  
Moisture Management ◽  
Thermal Comfort Properties ◽  
Knitted Structure ◽  
Drying Properties

Engineered yarns are used to provide better clothing comfort for summer garments because of their high levels of moisture and water vapor management. The aim of this study was to investigate the characteristics of knitted structures that were produced using different types of polyester yarns in order to achieve better thermal comfort properties for summer clothing. However they are relatively expensive. Therefore, in this study engineered polyester yarns were combined with cotton and lyocell yarns by plying. This way, the pronounced characteristics of these yarns were added to the knitted structure as well. Channeled polyester, hollow polyester, channeled/hollow blended polyester, cotton, and lyocell yarns were plied with each other and themselves. Then, single jersey structures were knitted using these ply yarn combinations and air permeability, thermal resistance, thermal absorptivity, water vapor permeability, moisture management, and drying properties were tested. The results indicate that channeled PES fabrics are advantageous for hot climates and high physical activities with regards to high permeability and moisture transfer and also to fast drying properties. Besides, air permeability and thermal properties improved through the combination of lyocell yarn with engineered polyester yarns. However, the use of lyocell or cotton with engineered yarns resulted in a to a decrease in moisture management properties and an increase in drying times

Dynamic Moisture Vapor Transfer through Textiles

1988 ◽  
Vol 58 (12) ◽  
pp. 697-706 ◽  
Author(s):  
K. Hong ◽  
N. R. S. Hollies ◽  
S. M. Spivak
Keyword(s):  
Moisture Transfer ◽  
Polyester Fabric ◽  
Rate Of Change ◽  
Vapor Concentration ◽  
Dynamic Surface ◽  
Time Dynamic ◽  
Surface Wetness ◽  
Vapor Transfer ◽  
Moisture Vapor ◽  
Fabric Surface

Cotton, polyester, and a blend in plain woven, pure finish fabrics were studied to determine their influence on dynamic surface wetness and moisture transfer through textiles. A simulated sweating skin was used, over which were placed test fabrics incorporating a clothing hygrometer to continuously measure dynamic surface wetness. Moisture vapor concentration and its rate of change at both inner and outer fabric surfaces was determined. At the inner fabric surface facing the sweating skin, all-cotton fabric exhibited the slowest buildup of moisture vapor concentration, followed by the cotton/polyester blend. The all-polyester fabric showed the highest rate of change in moisture vapor concentration. These dynamic moisture changes differ from reports of little or no fiber effect when tested at equilibrium moisture transfer conditions. Indeed the equilibrium moisture vapor transfer also showed no significant fiber differences in this work. It is the short time, dynamic moisture vapor transfer that is believed to hold most promise for explaining wetness and moisture-related subjective sensations in human comfort of worn clothing. The newly modified clothing hygrometer provides a sensitive method for ascertaining dynamic surface wetness on both fabrics and clothing as worn.

scholarly journals A brief compendium of water entry results derived from laboratory tests of various types of wall assemblies

2019 ◽  
Vol 282 ◽  
pp. 02050
Author(s):  
Michael A. Lacasse ◽  
Nathan Van Den Bossche ◽  
Stephanie Van Linden ◽  
Travis V. Moore
Keyword(s):  
Numerical Simulation ◽  
Performance Evaluation ◽  
Laboratory Tests ◽  
Moisture Transfer ◽  
Control Design ◽  
Water Entry ◽  
Building Envelope ◽  
Test Results ◽  
Different Types ◽  
Wood Frame

There is an increase in the use of hygrothermal models to complete the performance evaluation of walls assemblies, either in respect to design of new assembles or the retrofit of existing wall assemblies. To this end there are guides available in which is provided information on moisture loads to wall assemblies. This includes, for example, Criteria for Moisture-Control Design Analysis in Buildings given in ASHRAE 160, Assessment of moisture transfer by numerical simulation provided in EN 15026, and NRC’s “Guidelines for Design for Durability of the Building Envelope”. The designer of a new assembly or evaluator of an existing wall is tasked with having to determine what moisture loads to apply to the wall and where to apply this load within the assembly. Typically there is little or no information that is readily available regarding moisture loads to walls and thus the suggested hourly moisture load, as given in ASHRAE 160, is 1% by weight of the total driving rain load to the wall (i.e. kg/m2-hr). In this paper, a brief compendium of water entry test results derived from laboratory tests of various types of wall assemblies is provided from which estimates of moisture loads to different types of wall can be developed. Water entry test results are given of wood frame walls typically used in housing, but also metal-glass curtain walls and other commercial wall assemblies, where possible, in terms of driving loads to the wall.

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