Development of a model and methods for calculating the humidity regime in enclosing structures

Kuz'menko Yuliya Evgen'evna ORCID: 0000-0002-6892-1055 Researcher, Siberian Federal University 660041, Russia, Krasnoyarskii krai, g. Krasnoyarsk, ul. Pr. Svobodnyi, 79 yul.kuzmenko@mail.ru

Introduction (relevance, study, goals)

The study of the issue of waterlogging of materials in Russia has been relevant for a century. The topic of moisture transfer in materials and structures has been studied since the 20s of the last century, and the emergence of interest in it was preceded by the need to predict the humidity regime using multilayer enclosing structures.

It is impossible to ignore the issue of waterlogging of enclosing structures. An increase in the humidity of materials significantly affects the properties of enclosing structures: material fatigue increases (degradation of mechanical properties), corrosion processes increase, thermal conductivity increases, as a result of which heat losses and energy consumption for heating buildings increase. These changes reduce the durability and service life of capital construction projects. Also, as a result of the accumulation of moisture on the inner surface of the enclosing structures, the risk of the development of moldy fungi increases, subsequently having a negative impact on human health and the microclimate of the room. All these factors are reflected in one way or another in the emergence of the study of the humidity regime of enclosing structures and in the rationing of protection against waterlogging.

 A lot of theoretical and experimental works have been devoted to this issue, at the moment various calculation methods and mathematical models of moisture transfer have been developed. However, there are no systematic historical data on the development and emergence of the model and methods of accounting for the humidity regime.

The purpose of the study is a historical review of the emergence of the model and methods for calculating moisture transfer, the study of the formation of norms for protection against waterlogging, as well as the identification of the periodization of the study of this issue in the review of thematic innovative scientific publications. The main objectives of the study are:

- to study the main early works in the field of humidity regime of enclosing structures and regulatory documentation;

 - analyze the results of scientific research on this topic;

 - to identify and analyze the chronology of the appearance of the model, methods of moisture transfer and rationing of protection against waterlogging of structures;

- to investigate the parameters of the main concepts of the periodization of the formation of the methodology for calculating moisture transfer in Russia since the early 20s of the last century.

Scientific novelty of the study

The scientific novelty of this study lies in the formation of a conceptual innovative approach to the periodization of the development of methodological foundations for the study of stationary and non-stationary methods of calculating moisture transfer systems in Russia over the past century and up to the present time.

Materials and methods of research

The results of scientific research on this topic and the content of regulatory legal acts are used as material for this scientific work. General scientific methods are used in the work: analysis and synthesis of literature, study and generalization of information, comparative analysis.

The main part

            The creation and development of methods and models of the humidity regime of fences has been noted for the last 100 years. When analyzing the first structures with insulating layers, the possibility of moisture diffusion inside the structure was ignored. V.D. Machinsky, K.F. Fokin, O.E. Vlasov, A.N. Borshchevsky, R.E. Briling, E.H. Odelsky, F.V. Ushkov, V.N. Bogoslavsky, A.U. Franchuk, S.V. Alexandrovsky, V.I. Lukyanov, V.I. Lukyanov made a significant contribution to the development and study of methods for calculating the humidity regime of enclosing structures.Gagarin and many other scientists.

            The primary reason for studying the issue of the humidity regime of enclosing structures was the need to moisten the walls indoors. When dampness occurs in the premises, attention was paid primarily to measures to combat it, so A. Tretyakov ^[1] in his work of 1916 considers dampness in dwellings, absolutely without touching on the issue of moisture diffusion in the wall material. This problem began to be solved in the 1920s and 30s, in the works of professors V.D. Machinsky V. D. and K.F. Fokin.

            V. D. Machinsky was the first to draw attention to the identification of the role of diffusion and condensation of air moisture and the need to take into account the humidity regime of fences in his work "On the condensation of air vapor in building fences" ^[2]. He found that in heated buildings, the enclosing structures are moistened from the inside. He also concluded that water vapor condenses on cold surfaces inside the fence, moving due to partial pressure differences. Machinsky V. D. proposed the main recommendations that improve the humidity regime of the premises: the device of vapor barrier from the warm side of the enclosing structure, the sequence of layers in multilayer walls. A.N. Borshchevsky described in more detail the mechanism of moisture transfer in enclosing structures in 1932 ^[3].

Fig. 1. Classification of methods for calculating moisture transfer in the time periodization of their occurrence.

            In 1935, based on his own conclusions, Machinsky V. D. continues to work and offers a primary calculation method ^[4], which consists in comparing the vapor permeability resistances of the outer and inner parts of the fence. This technique was used at the initial stages of design as a primary assessment of the structure, but there was no possibility of quantifying the condensing moisture in the fence at that time.

            The discoverer of the method for determining the humidity regime is K.F. Fokin, who in 1935 ^[5] developed a qualitative stationary calculation method. This technique is based on a model of water vapor transfer in the structure under the influence of boundary conditions, which makes it possible to designate a condensation zone in the underlying structure of the enclosing structure and calculate the process of moisture accumulation in stationary conditions.  This method was improved in the works of F.V. Ushkov, E.H. Odelsky, A.U. Franchuk, A.M. Shklover. V.M. Ilyinsky and has been used in regulatory documentation since the 60s.  In 1955, SNiP II-B.3 "Construction heat engineering" was included in the design standards ^[6], where for the first time there was mention of the need to calculate enclosing structures for compliance with the requirements of the normal humidity regime with respect to vapor permeability resistance. In SNiP II-A.7-62 "Construction equipment" ^[7] of 1962, the section "Norms of the humidity regime of external fences" was already introduced directly, including a stationary calculation method that has not changed to date and is included in SP 50.13330.2012 "Thermal protection of buildings" ^[8].

The emergence and development of models and methods for calculating the humidity regime in foreign countries occurred in a similar way, but later for various reasons. Stationary calculation methods close to the method of K.F. Fokin appeared in the USA in 1938-39, the work of A.V. Lykov had a great influence on the development of the moisture transfer model and were adopted as a basis by many foreign specialists. In Germany, the stationary calculation method was developed in the 50s thanks to the work of N. Glaser.

Fig. 2. Scientific contribution of scientists to the methods of calculating the humidity regime.

Non–stationary calculation methods were developed due to the shortcomings of the stationary method identified by V.D. Machinsky, the main reason is the variable temperature and humidity of the external environment, which does not allow the stationary mode to be established inside the fence. A.S. Epstein was the first to identify the possibility and necessity of calculating a non-stationary humidity regime in his 1936 work "Calculation of condensation dampening of structures" ^[12] and proposed a calculation method. The method was considered quite time-consuming.

In 1941, K.F. Fokin developed a non-stationary method for calculating the humidity regime of enclosing structures ^[13]. The method excluded the specified disadvantages of the A.S. Epstein method, in addition, a new parameter was introduced – the specific relative vapor capacity of the material. In 1953-55, K.F. Fokin improved the calculation method ^[14,15], in the final version, the method allowed calculating the humidity regime of multilayer structures. In the future, F.V. Ushkov proposed the possibility of graphical calculation and techniques that simplify the "method of sequential humidification" proposed by K.F. Fokin. The works of A.U. Franchuk, A.V. Lykov, M.A. Gurevich, A.I. Folomin made a great contribution to the study of mathematical models of moisture transfer in non-standard calculation methods in the 50s. Also, a major role in the development of the non-stationary calculation method was played by the work of V.N. Bogoslavsky, who proposed the theory of the humidity potential ^[16] and a calculation method similar to the calculation of the equations of thermal conductivity. The idea of humidity potential was realized in the works of B.V. Abramov, A.G. Peregozhentsev.

Fig. 3. Evolution of the basic concepts and methodology of moisture transfer systems in the context of periodization.

The methods of non-stationary calculation of the humidity regime are time-consuming and require deep knowledge, they are quite difficult to apply without the participation of computers. For these purposes, a hydrointegrator was used for the first time, further calculations were carried out on electric AVMs. For the first time in our country, V.I. Lukyanov used a computer to calculate moisture transfer in 1966. He created a program that allows calculations of two-dimensional and three-dimensional humidity fields.

Fig. 4. Software for visualization of calculations of the humidity regime at the present time.

 In the modern world of advanced technologies, there are many programs that allow you to perform calculations of the humidity regime of enclosing structures, with the possibility of modeling and analyzing the processes of moisture transfer in structures, visualizing the results: COMSOL Multiphysics, TEMPERATURE-3D, LIT THERMO ENGINEER and others.

Conclusions

The results of the review indicate the great contribution of Russian scientists to the creation of theoretical foundations and the development of methods for calculating the humidity regime of fences. The occurrence of rationing of the humidity regime of external fences has been identified and analyzed. The chronology of the appearance of the model and methods of moisture transfer and rationing of protection against waterlogging of structures is analyzed. The parameters of the basic concepts of the periodization of the formation of the methodology for calculating moisture transfer in Russia since the early 20s of the last century have been investigated. In particular, three main time periods were identified: 1920-30, 1940-50 and 1960-70. In the first chronological segment, the problem of dampness in the premises and the main aspects of moisture diffusion within the framework of the use of innovative construction technologies were considered. The second time period is marked by the first stages of the development of a non-stationary method for calculating moisture transfer and studying the issues of moisture distribution in materials and structures. The study of the third chronological period is associated with the first use of a computer to produce the corresponding mathematical calculations. In general, the work contains up-to-date information about innovative ways of visualizing stationary and non-stationary methods of calculating moisture transfer by means of software.