scholarly journals Moisture potental theory application for modelling of enclosing structure unsteady-state moisture regime

Vestnik MGSU ◽  
2019 ◽  
pp. 484-495 ◽  
Author(s):  
About the authors: Vladimir G. Gagarin ◽  
Kirill P. Zubarev
Keyword(s):  
Moisture Transfer ◽  
Single Layer ◽  
Mineral Wool ◽  
Expanded Polystyrene ◽  
Moisture Regime ◽  
Unsteady State ◽  
Concrete Masonry ◽  
Aerated Concrete ◽  
Moisture Potential ◽  
Maximum Moisture Content

Introduction. Known calculation methods for enclosing structure unsteady-state moisture regime proposed by K.F. Fokin, are examined. The first one describes moisture transfer in a sorption zone, and another allows calculation in oversorption zone also. “Thermodynamic moisture potential” of enclosing structure materials introduced by V.N. Bogoslovsky is described. Moisture potential F developed by V.G. Gagarin and V.V. Kozlov is shown. The moisture potential F allows describing water vapor and liquid moisture movement in material in a consistent way. The scientific novelty of the study is the development of calculation method based on moisture potential F. Practical relevance of the study is the possibility to obtain performance humidity values of enclosing structure materials by means of calculations for engineering practice. Materials and methods. A moisture transfer equation is derived on the basis of process physical interpretation, A mathematical model, consisting of heat conductivity equation, derived moisture transfer equation, spatial-time domain, boundary and initial conditions, is formulated. Moisture potential in single-layer and multilayer enclosing structures is determined using finite difference method. Results. Calculations for four types of enclosing structures are made on the basis of the proposed mathematical model: single-layer aerated concrete wall; a wall made of aerated concrete masonry base and clay brick cladding; a wall made of aerated concrete masonry base and mineral wool insulation with thin plaster layer; a wall made of aerated concrete masonry base and expanded polystyrene insulation with thin plaster layer. Conclusions. Calculated performance humidity values of enclosing structure materials were lower than values stated in regulatory documents. The presented results allow to define building heat loss definition and heating system design more accurately. Specification data on maximum wetting plane position obtained earlier were proved within the framework of the developed theory: in enclosing structures with aerated concrete base and mineral wool insulation maximum moisture content is located at the joint of plaster and insulation layers; in enclosing structures with aerated concrete base and expanded polystyrene insulation maximum moisture content is located in the insulation layer. Acknowledgements. Authors are deeply indebted to V.V. Kozlov, PhD in Technical Sciences, and V.K. Akhmetov, Doctor of Engineering Science, Professor, for discussion and useful comment in the course of study.

scholarly journals USING DISCRETE-CONTINUOUS APPROACH FOR THE SOLUTION OF UNSTEADY-STATE MOISTURE TRANSFER EQUATION FOR MULTILAYER BUILDING WALLS

2021 ◽  
Vol 17 (2) ◽  
pp. 50-57
Author(s):  
Kirill Zubarev
Keyword(s):  
Building Materials ◽  
Moisture Transfer ◽  
State Equation ◽  
Climate Impact ◽  
Mineral Wool ◽  
Moisture Regime ◽  
Unsteady State ◽  
Continuous Approach ◽  
Aerated Concrete ◽  
Building Walls

Moisture regime of enclosing structures is one of the most complicated and controversial directions in construction industry. Temporary climate impact on enclosing structures and low moisture inertia of building materials lead to the situation in which it is impossible to calculate the steady-state moisture regime. Numerical methods are usually used to assess the moisture behaviour of the enclosing structures. In the current paper, a differential equation of moisture transfer is formulated. The solution of the unsteady-state equation of moisture transfer was obtained using the discrete-continuous approach. Thus, a formula which allows scientists to calculate unsteady-state moisture transfer in multilayer walls of buildings was obtained. A two-layer building enclosing structure with aerated concrete base and mineral wool insulation was calculated.

scholarly journals MOISTURE REGIME CALCULATION FOR SINGLE-LAYER ENCLOSING STRUCTURES USING DISCRETE-CONTINUAL MATHEMATICAL MODEL

2018 ◽  
Vol 14 (3) ◽  
pp. 42-49
Author(s):  
Vladimir G. Gagarin ◽  
Kirill P. Zubarev
Keyword(s):  
Mathematical Model ◽  
Temperature Distribution ◽  
Single Layer ◽  
Moisture Regime ◽  
Continuous Control ◽  
Unsteady State ◽  
Calculation Results ◽  
Aerated Concrete ◽  
State Method ◽  
Moisture Potential

The paper describes moisture regime calculation for single-layer enclosing structures using discrete-continual method. A formula for calculation of moisture potential dependence on time in any enclosing structure section, at any time, under continuous control for temperature distribution, has been derived. Moisture regime calculation results under the proposed method have been compared to results obtained by well-known methods by V.G. Gagarin and V.V. Kozlov for aerated concrete single-layer enclosing structure. It has been found out that the proposed method gives quantitative and qualitative results similar to results obtained using Gagarin’s unsteady-state method.

scholarly journals Assessment of enclosing structure moisture regime using moisture potential theory

2018 ◽  
Vol 193 ◽  
pp. 03053 ◽  
Author(s):  
Vladimir Gagarin ◽  
Vadim Akhmetov ◽  
Kirill Zubarev
Keyword(s):  
Mathematical Models ◽  
Potential Theory ◽  
Single Layer ◽  
Moisture Distribution ◽  
Moisture Regime ◽  
Continuous Control ◽  
Unsteady State ◽  
Steady State Method ◽  
State Method ◽  
Moisture Potential

The paper describes principal development directions of mathematical models of enclosing structure moisture regime. Benefits of mathematical models based on moisture potential theory are demonstrated. Moisture regime calculation by means of moisture potential, taking liquid and vapor moisture transfer into consideration, and using discrete-continual approach is proposed. New formulas for single-layer and multi-layer enclosing structures allowing for numerical analytic determination of moisture potential value in any enclosing structure section, at any moment of time, under continuous control of temperature distribution, have been derived. Moisture distribution has been studied for a number of enclosing structures using different methods of moisture potential theory: unsteady-state method, quasi-stationary method, the proposed discrete-continual method. Moisture regime has been determined for single-layer enclosing structure with ceramic brick basement and lime brick cladding in Moscow. It is shown that the greatest moisture value is achieved in enclosing structure calculation by means of steady-state method. Unsteady-state method gives more accurate moisture distribution. The proposed discrete-continual method gives quantitative and qualitative result of moisture distribution similar to results obtained by unsteady-state method. The benefit of discrete-continual method is a distribution obtained analytically, which allows to use solution results without numerical method application.

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%.

USING THE UNIVERSITY'S ENERGY EFFICIENCY KNOWLEDGE HUB FOR ENERGY RENOVATION AND ENERGY MODERNIZATION OF UNIVERSITY BUILDINGS

Management ◽  
2022 ◽  
Vol 34 (2) ◽  
pp. 35-44
Author(s):  
Valeriia Shcherbak
Keyword(s):  
Energy Efficiency ◽  
Moisture Transfer ◽  
Full Range ◽  
Potential Temperature ◽  
Theory And Practice ◽  
Moisture Regime ◽  
Mathematical Methods ◽  
Energy Reconstruction ◽  
Wide Range ◽  
Moisture Potential

BACKGROUND AND OBJECTIVES. The most important socio-economic task in the current period is to transfer Ukraine's economy to an intensive way of development in order to improve the level and quality of life of the population and solve the full range of social problems. Implementation of such a policy dictates the need to solve problems of reconstruction and modernization of buildings and structures, primarily related to the public sphere (including higher education institutions), in order to eliminate the existing inconsistency of the technical condition and functional and consumer qualities of public buildings to current standards and consumer requirements. Therefore, one of the most urgent directions of development of higher educational institutions is the task of providing effective overhaul and reconstruction of buildings, increasing their energy efficiency.METHODS. The theoretical and methodological basis of the study were the fundamental and applied developments of leading domestic and foreign scientists in the theory and practice of management of energy modernization and energy reconstruction of buildings, increasing energy efficiency of buildings. The factual basis of research were the legislative acts of Ukraine in the field of energy efficiency, normative and methodical documents on the modernization and reconstruction of buildings, Directive 2010/31/EC in the field of energy saving. When solving specific tasks the methods of system and comparative analysis, economic-mathematical methods of efficiency evaluation of energy reconstruction and energy modernization projects were used.FINDINGS. The method of calculation of the reduced resistance to heat transfer of the enclosing structures and the shell of the 4th building of Kyiv National University of Technology and Design as a whole taking into account the temperature and humidity conditions in the fencing marginal zones. It is shown that in the enclosure edge zones the heat protective properties decrease resulting in a deterioration of the heat protection of the whole building. Practical recommendations for the design of fencing structures of modern buildings taking into account the temperature-moisture regime are proposed.CONCLUSION. For the analysis of complex processes of moisture transfer in enclosures, a mathematical model based on the moisture potential is most convenient. A certain difference from the thermal potential (temperature) to the definition of the moisture potential allows to diagnose the most general assessment of the moisture regime of exterior and interior fences on the basis of HUB knowledge on energy efficiency. At use of this model it is possible to consider process of moisture exchange in a wide range of humidity and temperature taking into account movement of a moisture as a basis of carrying out energy reconstruction and energy modernization of operating buildings of the university.

scholarly journals Moisture behavior calculation of single-layer enclosing structure by means of discrete-continuous method

2018 ◽  
Vol 170 ◽  
pp. 03014 ◽  
Author(s):  
Vladimir Gagarin ◽  
Vadim Akhmetov ◽  
Kirill Zubarev
Keyword(s):  
Temperature Distribution ◽  
Single Layer ◽  
Ambient Air ◽  
Continuous Method ◽  
Moisture Distribution ◽  
Engineering Practice ◽  
Unsteady State ◽  
Calculation Results ◽  
State Method ◽  
Moisture Potential

The paper proposes mathematical model for unsteady-state moisture behaviour calculation of single-layer enclosing structures by means of moisture potential and discrete-continuous method. A formula for moisture potential value calculation for single-layer enclosing structure in any enclosing structure section, at any moment of time, under continuous control for temperature distribution, has been derived. Moisture transfer between the enclosing structure and ambient air is taken into account by means of third-kind boundary conditions. Temperature distribution is taken as constant during a month. The proposed method allows for moisture potential determination according to the proposed formula for every month. Calculation results obtained by the proposed method, well-known unsteady-state method and engineering method developed by V.G. Gagarin and V.V.Kozlov have been compared for single-layer enclosing structure made of aerated concrete. It was shown that average value calculation results disagreement does not exceed 7% for the proposed method and unsteady-state method. However, the proposed approach allows for moisture distribution determination using analytical expression, which is convenient for use in engineering practice.

scholarly journals DERIVATION OF THE EQUATION OF UNSTEADY-STATE MOISTURE BEHAVIOUR IN THE ENCLOSING STRUCTURES OF BUILDINGS USING A DISCRETE-CONTINUOUS APPROACH

2021 ◽  
Vol 17 (4) ◽  
pp. 83-90
Author(s):  
Kirill Zubarev
Keyword(s):  
Boundary Conditions ◽  
Moisture Transfer ◽  
High Accuracy ◽  
Continuous Method ◽  
Engineering Practice ◽  
Unsteady State ◽  
Liquid Phases ◽  
Continuous Approach ◽  
Moisture Potential ◽  
Transfer Mechanisms

Two differential equations of moisture transfer based on the theory of moisture potential have been considered. The first equation includes the record of moisture transfer mechanisms of  vapor and liquid phases and their relationship. The second equation is a simplified form of the first equation which makes it possible to apply a discrete-continuous approach. The peculiar properties of the boundary conditions setting of the outside air for temperature and humidity fields have been presented. It is proved that the use of the discrete-continuous method provides high accuracy of calculations and can be used in engineering practice to assess the unsteady humidity regime of enclosing structures.

scholarly journals Resistance of ETICS with Fire Barriers to Cyclic Hygrothermal Impact

2021 ◽  
Vol 13 (16) ◽  
pp. 9220
Author(s):  
Rosita Norvaišienė ◽  
Paweł Krause ◽  
Vincent Buhagiar ◽  
Arūnas Burlingis
Keyword(s):  
Physical And Mechanical Properties ◽  
Mineral Wool ◽  
Expanded Polystyrene ◽  
Test Rig ◽  
Horizontal Strip ◽  
Climate Chamber ◽  
Expanded Polystyrene Foam ◽  
Hygrothermal Performance ◽  
Thermal Data ◽  
Chamber Temperature

The article presents the results of a set of hygrothermal experiments of an external wall insulated with an ETICS. As an add-on to previous studies, thermal insulation in the form of polystyrene with an additional horizontal strip of mineral wool was used. Laboratory tests were carried out in accordance with ETAG 004. The ETICS test rig was composed of combustible expanded polystyrene foam (EPS) and horizontal strips of noncombustible mineral wool (MW) fire barriers over windows. The physical and mechanical properties of four types of finishing renders (without an additional reinforcement mesh in base coat of the fire barriers) were analyzed across full hygrothermal cycles in a climate chamber. Temperature sensors were mounted onto different ETICS layers to collect thermal data during the weathering. The testing of ETICS regarding their hygrothermal performance revealed that there were no visible defects on any renderings and over the junctions depending on the type of used insulation materials. Results also showed that the joints of EPS and MW have approximately half of their bond strength from polystyrene strength.

Performance Study on Masonries of Different Aerated Concrete Blocks

2014 ◽  
Vol 633 ◽  
pp. 299-302 ◽  
Author(s):  
Peng Fei Peng ◽  
Xian Ming Qin ◽  
Yu Sheng Wu
Keyword(s):  
Water Absorption ◽  
Natural Condition ◽  
Crack Width ◽  
Concrete Block ◽  
Performance Study ◽  
Shrinkage Cracking ◽  
Concrete Cracking ◽  
Concrete Masonry ◽  
Concrete Blocks ◽  
Aerated Concrete

The masonries with a square of 2m×3m of 3 different aerated concrete blocks were built respectively, and plastered with plastering mortar. The shrinkage-cracking property and other performances of different aerated concrete masonries were studied in natural condition. The results showed that, there were less cracks and smaller crack width in the masonry of aerated concrete with low water absorption, the condition of aerated concrete cracking can be improved by plastering with plastering mortar; the shrinkage of aerated concrete block masonry with low water absorption is smaller, the shrinkage of aerated concrete masonry plastered by special plastering mortar is smaller.

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