Thermotechnical analysis of the structuresby using numerical methods

Вестник МГСУ 11/2013
  • Tusnina Olga Alexandrovna - Moscow State University of Civil Engineering (MGSU) postgraduate student, Department of Metal and Timber Structures, Moscow State University of Civil Engineering (MGSU), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation; Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript .

Страницы 91-99

In the paper the features of a structural thermotechnical analysis with the use of numerical methods are considered. Characteristics of heat transfer processes can be obtained using experimental or theoretical analysis. A theoretical investigation works with mathematical model, not with real physical phenomenon. The mathematical model for heat transfer processes consists of a set of differential equations. If the methods of classical mathematics are used for solving these equations, many phenomena of practical interest will be predicted. That’s why in order to solve these problems it is advisable to apply numerical methods. In this paper an algorithm of numerical calculation of threedimensional temperature fields is considered.The numerical algorithm for solving the differential equation of steady three-dimensional thermal conductivity is represented. Discretization of this equation was performed by control-volume method. A solution of a set of discretized equations can be obtained by using a convenient combination of the direct method TDMA (Tri-diagonal matrix algorithm) for one-dimensional situation and the Gauss-Seidel method. The described approach allows us taking into consideration thermal inhomogeneity, such as thermal bridges, and the features of the geometry of the structure. The computing program TEPL was developed on the basis of the described algorithms. As a result of the calculation made by TEPL three-dimensional temperature field was obtained. On the basis of this field thermal resistance and temperature distribution in the structure were calculated.The examples of using the program for solving real practical problems are shown in the paper. Roofing consisted of sandwich panels supported by purlins with the use of screws in one case and rivets as fasteners in the other. The main difference between these two structures is that screws are installed through the insulation layer of a panel and violate its integrity, while rivets are connected to the lowest sheet of a panel and purlin flange and do not make any changes in insulation. The results of the numerical analysis in TEPL show that screws are thermal bridges and must be taken into account in the process of calculating thermal resistance of roofs.

DOI: 10.22227/1997-0935.2013.11.91-99

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Investigation of rational types of light concrete for external walls in conditions of hot climate

Вестник МГСУ 10/2018 Том 13
  • Hoshim R. Ruziev - Bukhara Engineering Technology Institute , Bukhara Engineering Technology Institute, 15 K. Murtazaev st., Bukhara, 200100, Uzbekistan.

Страницы 1211-1219

Introduction. The paper presents theoretical and experimental studies of the improvement of the structure of lightweight concrete, which provides the maximum value of the attenuation of the amplitude of external air temperature fluctuations during the passage of heat flow through the walls and the reduction of thermal conductivity, the results of the 3-factor experiment on determining the rational structure of claydite concrete and the methods for their processing. To determine the purposeful structure of the composition of lightweight concrete and its thermal conductivity, a complex of research works was carried out at the Central Research Institute for Housing, applied to lightweight concrete for exterior walls. The main optimization criterion was the maximum reduction in thermal conductivity while providing the necessary strength, durability and waterproofness. The purpose of this work is theoretical research and experimental substantiation of methods for improving the structure of lightweight concrete used for a hot climate with improved functional performance. Materials and methods. As material a claydite gravel with bulk density p = 400 kg/m3 of Lianozovsky plant (Moscow) was used, at a ratio of 40 % of the fraction 5-10 mm and 60 % of the fraction 10-20 mm and a Portland cement of the brand “400” of the Voskresensky plant, not plasticized. The water flow rate was varied for 10 seconds, to ensure the mixture to be vibropacked.As a foam generating agent and plasticizer, the “Saponified wood resin” (SDO) was used in a 5 % aqueous solution. The methods were adopted in accordance with the Recommendation on the technology of factory production and quality control of lightweight concrete and large-panel constructions of residential buildings. M. CNIIEP dwelling, 1980. In the department of the lightweight concrete application at CNIIEP of dwelling, a method for the purposeful formation of the structure and composition of lightweight concrete, which provides a set of physic-technical, technological and technical-economic requirements, was developed. Results. Calculations are reduced to obtaining mathematical models of dependence of strength R, density ρ, thermai conductivity λ and other indicators of concrete characteristics from initial factors in the form of regression equations. Based on the equations obtained, it was possible to determine the expedient composition of lightweight concrete, which, in combination with the operational characteristics, provides comparable results of the technical and economic characteristics of a single-layer structure from the projected type of lightweight concrete. Conclusions. 1. An improved composition of the structural and heat insulating lightweight concrete for the load-bearing part of the structure, providing its high thermal stability by chemical additives and low consumption of porous sand, was developed. An algorithm for selecting its composition on computer is made. 2. The conducted researches in the field of design of external enclosing structures for hot climate conditions have shown that: single-layer exterior wall constructions with massiveness of D ≤ 4 provide minimum allowable values of heat flux attenuation and temperature fluctuation amplitude on the inner wall surface.

DOI: 10.22227/1997-0935.2018.10.1211-1219

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