Heat Conductivity Coefficient Research Articles

Preparation of Ultrafine Fly Ash-Based Superhydrophobic Composite Coating and Its Application to Foam Concrete

The waterproof and thermal insulation property of foamed concrete is very important. In this study, the ultrafine fly ash (UFA)-based superhydrophobic composite coating was applied onto foam concrete. The UFA-based base coating that closely adhered to the concrete initially improved the waterproofness of the test block, and the silane coupling agent-modified UFA-based surface coating further achieved superhydrophobicity. The UFA on the coating surface and the asperities on the surface jointly formed a lotus leaf-like rough micro–nanostructure. The 154.34° water drop contact angle and 2.41° sliding angle on No. 5 coating were reached, indicating that it was a superhydrophobic surface. The water absorption ratios of the composite coating block were 1.87% and 16.6% at 4 h and 7 days, which were reduced by 97% and 75% in comparison with the original foam concrete. The compressive strength and heat conductivity coefficient after soaking for 4 h of the composite coating block were higher than 4.0 MPa and 0.225 W·m−1·K−1, respectively. The UFA-based superhydrophobic composite coating proposed in this study and applied onto foam concrete is simple and cheap, requires no precise instrument, and can be applied in a large area.

Computer Simulation of Thermal Processing of Steel

The review of the numerical modelling of casting and welding of steel workpieces was studied. The contemporary industry needs tools to optimize and control parameters of processes by considering the favourite chemical composition of steel. In recent time, very efficient tool for optimizing and controlling of the process parameters is numerical modelling of engineering processes. At casting and welding numerical modelling is focused on optimization of distribution of microstructure contents, mechanical and physical properties distribution and tolerated distortions and residual stresses. Mechanical properties and prevention of distortion and cracking can be accomplished by prediction and control of residual stresses and microstructure distribution. The numerical modelling of thermal processing of metals consists of the research of multi-scale processes and multi-physics processes, such as phase transformations, heat transfer and mechanics of materials, and research of numerical methods for computer interpretation of the problem. By means of the numerical modelling and computer simulation of thermal processing should calculate the transient temperature field, melting and solidification processes, as well as, to calculate distribution of mechanical and physical properties and microstructure composition. In this work, the numerical models of studied thermal processes are based on the finite volume method. Values of surface heat transfer coefficient, heat capacity and heat conductivity coefficient were obtained by the inversion method. The microstructures composition has been predicted by CCT diagrams and additionally improved by the kinetic equations. The mathematical model has accomplished to solve thermal processing of 3-D axially symmetric specimens.

Development and Characterization of Thermal Insulation Geopolymer Foams Based on Fly Ash

The main purpose of the article is to present the differences in the parameters of geopolymer foams obtained in the same way, which is associated with difficulties in controlling the foaming process. Difficulties in controlling the foaming process of geopolymers are the direct reason for the lack of implementation of such materials nowadays. The article shows the results for experimental research, especially research into insulation, physical, and mechanical properties for the designated foamed materials. Microspheres (75%), sand (5%) and fly ash (20%) were used to produce foamed geopolymers. Hydrogen peroxide was the foaming agent. Heat conduction coefficients of 0.08-0.07 W/mK were obtained. The material density was obtained at the level of 363-375 [kg/m3] and the compressive strength was 520-683 [kPa]. The results showed that geopolymers can be a good alternative to conventional insulation materials, but the foaming technology should be developed so that it is stable and allows for reproducible material parameters.

Heat dissipation investigation of the power lithium-ion battery module based on orthogonal experiment design and fuzzy grey relation analysis

In this work, the physical and mathematical models for a battery module with sixteen lithium-ion batteries are established under different arrangement modes based on the climate in the central and southern region, the heat dissipation characteristics are investigated under different ventilation schemes, and the best cell arrangement structure and ventilation scheme are obtained. Then, the influence of four parameters (inlet airflow velocity, air inlet radius, inlet and outlet eccentricity, and air vent area ratio) of selected optimal forced air-cooled model on heat dissipation performance of battery module is analyzed based on the combination of orthogonal experiment design method and fuzzy grey relation theory. The results show that 4 × 4 battery arrangement is superior to 2 × 8 arrangement, straight arrangement is better than staggered arrangement, and ventilation scheme (air inlet is on the upper surface and air outlet is on the lower surface) is of the best heat dissipation performance among all ventilation schemes. Moreover, air vent area ratio, eccentricity and the inlet airflow velocity have the most significant effect on average temperature, temperature difference and heat conduction coefficient of power lithium-ion battery pack, respectively. This work will provide great reference values for cooling performance enhancement of the power lithium-ion battery pack.

Research of Fireproof Capability of Coating for Metal Constructions Using Calculation-Experimental Method

Determination of characteristic of fireproof capability of examined fire-retardant coating by experiment-calculated method solving the inverse heat conduction problems based on the firing tests data. With the aim of determining the fire-resistance time of metal sheets with fire-retardant coating there are used experimental research methods of patterns behavior during heating according to the requirements of National Standards of Ukraine B.V. 1.1.-4-98 are used; mathematical and computer modelling of processes of unsteady heat transfer in the system “metal sheet – fire-retardant coating”; determination of thermal characteristics and characteristic of coating fireproof capability. Firing tests of metal sheets covered by the flame retardant “Amotherm Steel Wb” are carried out. Based on the obtained data (temperature from the unheated sheet surface) there are determined the thermal characteristics of formed coating depending on temperature and the characteristic of fireproof capability of examined coating for 30 minutes fire-resistance time. The effectiveness of intumescent coating “Amotherm Steel Wb” is proved and the dependence between its heat conduction coefficient and temperature during heating in experimental stove of metal sheet with this coating in standard temperature conditions is specified. The co-relation between the thickness of intumescent coating “Amotherm Steel Wb” and fire-retarding quality of metal constructions is identified. Besides the necessary minimum thicknesses of such coating from the thickness of metal sheet for importance of 30 minutes fire-resistance time are calculated.

Thermal effects of nonlinear acoustic-gravity waves propagating at thermospheric temperatures matching high and low solar activity

Numerical high-resolution modeling of nonlinear acoustic-gravity waves (AGWs) generated at the Earth's surface and propagating to the thermosphere shows that wave characteristics are depending on modifications in the mean density, temperature, molecular dissipation and composition due to variations of solar activity (SA). Amplitudes of temperature wave perturbations are generally larger at high SA at altitudes above 150 km, due to larger mean temperature and smaller molecular heat conductivity. Increasing kinematic coefficients of molecular heat conduction and viscosity result in stronger decreasing AGW amplitudes at altitudes larger 150 km at low SA. Dissipating AGWs generally produce heating at altitudes below 120 km. At larger heights, AGWs generally heat the thermosphere at low SA and cool it at high SA. Wave enthalpy fluxes are mainly upwards below 120 km altitude and downwards above 150 km at high SA, where they may have directions opposite to the upward wave energy fluxes. Downward wave enthalpy fluxes correspond to AGW cooling the upper atmosphere at high SA. Nonlinear dissipating AGWs may produce upward and downward transport of atmospheric mass. These mass flows may produce adiabatic heat influxes in the upper atmosphere. Mainly positive residual wave-induced mass flows at altitudes higher 150 km may contribute to the wave cooling of the upper atmosphere. Wave breaking and interactions between waves and the mean flow in the nonlinear model are stronger at higher amplitudes of AGW excitation at the ground, which lead to bigger energy losses for larger-amplitude waves. At high SA, resulting effects in the thermosphere depend on the balance between, on one hand, increases in wave amplitudes, caused by weaker molecular dissipation and smaller transfer of the wave energy to the wave-induced jet flows, and, on the other hand, decreases in the amplitudes due to higher density and larger AGW reflection. The thermal effects of waves in the upper atmosphere may depend on competitions between heating due to dissipation of the upward wave energy flux and cooling due to divergence of the downward wave entropy (or potential enthalpy) flux. At high SA, larger mean temperatures and larger temperature perturbations might increase magnitudes of downward wave entropy fluxes, which may result in more frequent downward wave enthalpy fluxes and wave cooling of the upper atmosphere.

Оценка эксплуатационных характеристик коротковолокнистой базальтовой теплоизоляции при криогенных температурах

This work shows the potential of highly porous thermal insulation made of short basalt super-thin fibers chopped using liquid technology for insulating cryogenic piping. The effective heat conductivity coefficient, maximum-permissible porosity and insulation density were determined for short basalt fibers with a mean diameter of 1.88 mcm and a length of 1.0–1.5 mm, taking into account radiation heat transfer. The results of compression tests are presented for highly porous flat insulation samples made of short basalt fibers without binding agents and those reinforced with Al2O3. It is established that the thermal insulation material containing a binding agent has the strength, elasticity modulus and elastic compression deformation two times higher than samples without a mineral binding agent.

Technique for Determination of Thermal Properties of Iron Ore Materials

Methods for determination of thermal properties of various materials, including iron ore, are adequately covered in the relevant literature. They rely, as a rule, on certain solutions to the problem of heat conductivity without consideration of internal heat sources that occur in the body of sample under study if the heating (cooling) process is accompanied by various thermochemical and phase transformations, which is typical of iron ore materials. Therefore, such methods allow determination of only effective or apparent values of thermal properties, which adequately reflect properties of the material only in specific heat treatment conditions. The point is that in the presence of internal heat sources, parameters to find substantially depend on the heating rate and sample shape and size. This paper considers a new technique, which allows finding (at known calculated values of heat capacity and material density) how five thermal parameters (temperature and heat conductivity coefficients, power of internal heat sources, as well as effective values of heat and temperature conductivity) depend on the heating (cooling) temperature. Improvement of methods of processing iron ore materials at elevated temperatures in various heat aggregates requires knowledge of thermal properties of the materials and variation of these parameters during heat treatment in a wide temperature range. This is due to the fact that heating of such materials is usually accompanied by development of complex physical and chemical processes such as oxidation and reduction of iron oxides, decomposition of carbonates, porosity and strength change, formation of new chemical compounds, and others, many accompanied by release or absorption of heat [1–12]. The degree of completion of these processes depends on the temperature conditions and composition of the material and coolant. Consideration of the effect of these conditions on the temperature distribution in the treated layer of material and consequently on the duration of the heat treatment it is possible only having reliable data on the thermal constants [13]. Methods of determination of thermal properties of iron ore materials are widely discussed in the literature [14–20]. However, all they address the heat conductivity problem without consideration of internal heat sources, and thus can determine only the effective values of thermal parameters, valid for specific conditions of heating. The effect of internal heat sources on thermal properties to find can be taken into account only by using respective solutions to the heat conductivity problem. The below method to determine the complex of thermal properties of iron ore materials relies on the solution to the heat conductivity problem with internal heat sources under symmetric heating conditions of the first kind, which is valid for objects of simplest shape (infinite plate, infinite cylinder, ball).

ОСОБЕННОСТИ ОПТИМИЗАЦИОННОЙ ЗАДАЧИ НА ПОДБОР МАТЕРИАЛОВ ДЛЯ МИНИМИЗАЦИИ ПОТЕРИ ТЕПЛА ЧЕРЕЗ ПЛОСКУЮ СТЕНКУ

Актуальность. Хранение тепла и его эффективное использование связано с подбором материалов для тепловой изоляции стенок. Такие материалы представлены широким спектром теплофизических свойств и стоимости на рынке. Тогда возникает задача оптимизации, ее решение должно обеспечивать наименьшие потери тепла через стенку при ограниченном выборе материалов с заданными коэффициентами теплопроводности. Вместе с тем при решении оптимизационной задачи могут возникнуть сложности в оценке правильности полученных результатов. Поэтому этот вопрос нуждается в детальном обсуждении. Цель: математическое моделирование стационарных режимов переноса тепла, формулировка минимаксной задачи о потере тепла через стенку, построение области решения минимаксной задачи, анализ полученных результатов и формулировка выводов. Объект: стенка, теплоизоляционные материалы, потоки тепла, условия минимальности, оптимальные решения. Методы: решение минимаксной задачи с применением аналитических методов. Результаты. Сформулирована простая минимаксная задача: дана двухслойная плоская стенка с произвольными коэффициентами теплопроводности и фиксированными толщинами. На правой и левой границах стенки задана постоянная и различная температура. Также задан максимальный тепловой поток через стенку и область возможных значений коэффициентов теплопроводности (т. е. возможные материалы) для каждого слоя стенки. Требуется из этой области найти коэффициенты теплопроводности, обеспечивающие тепловой поток ниже заданного максимального значения. На этом примере показано, что решение поставленной минимаксной задачи может приводить к неверному результату: можно получить или не весь спектр допустимых решений, или задача может не иметь решения. Это означает необходимость строгого отношения к формулировке и методу решения оптимизационных задач для процессов переноса тепла.

On the Analytical and Numerical Study of a Two-Dimensional Nonlinear Heat Equation with a Source Term

The paper deals with two-dimensional boundary-value problems for the degenerate nonlinear parabolic equation with a source term, which describes the process of heat conduction in the case of the power-law temperature dependence of the heat conductivity coefficient. We consider a heat wave propagation problem with a specified zero front in the case of two spatial variables. The solution existence and uniqueness theorem is proved in the class of analytic functions. The solution is constructed as a power series with coefficients to be calculated by a proposed constructive recurrent procedure. An algorithm based on the boundary element method using the dual reciprocity method is developed to solve the problem numerically. The efficiency of the application of the dual reciprocity method for various systems of radial basis functions is analyzed. An approach to constructing invariant solutions of the problem in the case of central symmetry is proposed. The constructed solutions are used to verify the developed numerical algorithm. The test calculations have shown the high efficiency of the algorithm.

Zero dissipation limit to rarefaction wave with vacuum for the one-dimensional non-isentropic micropolar equations

The zero dissipation limit of the one-dimensional non-isentropic micropolar equations is studied in this paper. If the given rarefaction wave which connects to vacuum at one side, a sequence of solution to the micropolar equations can be constructed which converge to the above rarefaction wave with vacuum as the viscosity and the heat conduction coefficient tend to zero. Moreover, the uniform convergence rate is obtained. The key point in our analysis is how to control the degeneracies in the vacuum region in the zero dissipation limit process.

Analysis of crack problems in functionally graded materials under thermomechanical loading using graded finite elements

This paper represents a comprehensive study of the fracture behaviour of linear elastic isotropic functionally graded materials (FGMs) subjected to mechanical and thermal loading. For this purpose, an improved graded 9-node quadrilateral finite element which includes the variation of elastic (Young's modulus and Poisson's ratio) and thermal properties (coefficient of thermal expansion and heat conductivity) at the element level is developed. The performance of the new element in conducting thermomechanical fracture analysis is evaluated by conducting a set of simulations to compare the fracture parameters in FGMs with sharp material and temperature gradients against those with mild material and temperature gradients. The reliability of the proposed element is verified by comparing with existing solutions. The thermomechanical coupling and its influence on the coupled modes of fracture which originates from the material gradient in FGMs are investigated. The influence of the steady-state temperature distribution, as well as the material gradient on the crack tip local fields and fracture parameters, such as stress intensity factors, mode mixity, and energy release rate, are studied. More importantly, it was found that compared with conventional homogeneous finite elements the current model is more reliable for modelling crack problems in FGMs.

Synthesis and characterization of high-temperature resistant and thermally conductive magnetic PBI/Fe3O4nanofibers

In the present study, magnetite nanoparticles were added to an electrospinning solution of polyvinylidene fluoride (PVDF)/polybenzimidazole (PBI) polymers to prepare PBI/Fe3O4nanofibers (NFs). The operating voltage of the electrospinning device was set to 15 kV, the distance between the needle and the plate was 10 cm, and the feed rate was set to 0.3 mL h−1. The microstructures of the as-prepared NFs were investigated by Fourier transform infrared spectrophotometry, atomic force microscopy, thermogravimetric analysis, and vibration sample magnetometry. Magnetite-doped PVDF/PBI NFs exhibited superior magnetism and saturation magnetization in the range of 1.5–5 emu g−1. It was observed that the thermal resistance of the fibers increased with the increasing amount of magnetic particles and nanocomposite fiber (NCF) 1 and NCF2 exhibited excellent thermal resistance up to 415°C and 450°C, respectively. The heat conduction coefficient of the fibers was measured at 4, 6, and 8 W. The thermal conductivity of the NFs increased with the increasing amount of magnetite nanoparticles, and the highest thermal conductivity coefficient for NCF2 (1.83 W mK−1) was measured at 4 W.

THEORETICAL STUDY OF HEAT CONDUCTION IN MULTI-LAYER SPHERICAL BODY WITH PHASE TRANSFORMATION IN LAYERS

The objective of the study is to build a simple yet informative mathematical model that describes the heat conduction in a spherical multi-layer body with phase transformation in the layers. The numerical scheme based on the theory of Markov chains is proposed to solve this problem numerically. The radial sector of the body is divided into finite number of spherical perfectly mixed cells of different volume, which form a chain of cells. The heat exchange between the cells is described with the heat conduction matrix, the entries of which depend on the local thermo-physical properties of material in the cells (heat conduction coefficient, density, specific heat capacity). These properties can vary from one cell to another and with time. The outer cell of the chain can exchange with heat with outside environment, the temperature of which can vary with time. The state of the process is observed in discrete moments of time separated by small but finite transition duration. If the temperature of a cell reaches the value, the phase transformation begins at which, the evolution of the cell thermal and phase state is described with the corresponding kinetic equation of the phase transformation. The process of melting and solidification is used as the example to verify the qualitative predictability of the model. The graphs of temperature distribution evolution and diagrams of phase content distribution in a multi-layer spherical body are presented. The obtained results on the evolution of the thermal and phase state of the ball have no contradiction to the physical sense of the process. The proposed algorithm has very low computational time (1-3 min for one regime). The other processes of the phase transformation can be easily implemented in the model, for instance, drying, exothermic and endothermic chemical reactions, etc.

Numerical Modeling of Heat and Mass Transport with Inner Heat Exchange in Unsaturated Porous Media

We are focused to the numerical modelling of heat, contaminant and water transport in unsaturated porous media in 3D. The heat exchange between water and porous media matrix is taken into the account. The determination of heat energy transmission coefficient and matrix heat conductivity is solved by means of inverse problem methods. The mathematical model represents the conservation of heat, contaminant and water mass balance. It is expressed by coupled non-linear system of parabolic-elliptic equations. Mathematical model for water transport in unsaturated porous media is represented by Richard's type equation. Heat transport by water includes water flux, molecular diffusion and dispersion. A successful experiment scenario is suggested to determine the required parameters including heat transmission and matrix heat conductivity coefficients. Additionally we investigate contaminant transport with heat transmission and contaminant adsorption. The obtained experiments support our method suitable for solution of direct and inverse problems. This problem we have discussed previously in 1D model, but preferential streamlines in 1D thin tubes shadow accurate results in determination of required parameters. In our presented setting we consider a cylindrical sample which is suitable in laboratory experiments for inverse problems.

Thermal behavior analysis of hollow bricks filled with phase-change material (PCM)

Light-weight materials are comprehensively used to reduce the building weight in high-rise or super high-rise buildings, but they will reduce building thermal inertia remarkably, which can increase the air-conditioning load fluctuation and reduce indoor thermal comfortable. According to this condition, phase-change material (PCM) is filled to hollow bricks to improve thermal behavior by latent thermal storage. A numerical model with the heat transfer process of melting-solidifying was built, and a full-scale experiment was done to verify this model. Due to the filled PCM, the thermal performance of hollow bricks was improved obviously from experimental and numerical results. Under suitable phase-change temperature, the filled PCM can reduce the attenuation rate from 13.07% to 0.92%–1.93% and increase the delay time from 3.83 h to 8.83h–9.83 h. Meanwhile, the filled PCM can reduce the peak heat flux from 45.26 W/m2 to 19.19 W/m2-21.4 W/m2, but cannot reduce the average value. In addition, inner cavities were the better choice for PCM and there was an extra phase-change extent of close to 90% in favor of the different outdoor thermal environment. Finally, influence rules of latent heat and thermal conductivity coefficient of PCM were analyzed on temperature and heat flux in inner surfaces.

TAKING INTO ACCOUNT DEPENDENCE OF VISCOSITY COEFFICIENT ON TEMPERATURE DURING VAPOR CONDENSATION ON A VERTICAL WALL

In the present study, the problem of vapor condensation on a flat vertical surface is investigated in the case of an arbitrary dependence of the dynamic viscosity coefficient on temperature according to a fairly general law. At a constant value of this coefficient and other characteristics of a condensing liquid (heat conductivity coefficient, density) this task was considered by Nusselt in a constant gravitational field. The results obtained by Nusselt formed the basis (with certain modifications) for the computational practice of heat exchange equipment of chemical technology in the presence of steam condensation of any heat carrier. Formation of a condensate film occurs due to heat transfer through the liquid film, vapor condensation at the outer edge of the film and the flow of liquid along the surface. The article generalizes the Nusselt theory for the heat transfer coefficient under the indicated conditions, and as a result, convenient calculation formulas for the heat transfer coefficient, which are necessary to describe the operation of heat and mass exchange equipment. Approximate relations are proposed for calculating the dynamic viscosity coefficient, which are useful for calculating film flow on a flat surface. A comparison is made with the previously used ratios in an approximate manner taking into account the dependence of viscosity coefficient on temperature. When in technical applications one wants to determine the average value of two parameters, which are then used to calculate certain characteristics of a process, then, traditionally, the average of these parameters is considered. This article shows that by simplifying the dependence of the effective dynamic viscosity coefficient, more accurate results are obtained by dividing the interval of the width of the current film in the ratio of three to one, where three fourths refer to the wall temperature, and one fourth to the condensation temperature. The analytical dependencies presented in this paper can be used for practical calculations of the heat exchange equipment.

Morphology and the Thermoelectric Properties of γ-GdxDy1 – xS1.5 – y Solid Solution Ceramics

The temperature dependences of the Seebeck coefficient, the electrical conductivity (T = 300–873 K) and also the heat conductivity coefficient, and the thermoelectric figure of merit (T = 300–770 K) of polycrystalline samples of solid solutions based on gadolinium and dysprosium sulfides of compositions γ‑GdxDy1 – xS1.49 (x = 0.1, 0.2, 0.3, 0.4) have been studied. It is found that the morphological features of the samples, namely, specifically of the crystallite surface that causes a change in the number of the deformation centers, determines the thermal conductivity of γ-GdxDy1 – xS1.49 solid solutions; the thermal conductivity of the composition with x = 0.2 is found to decrease anomalously. For this composition, the lowest values of the Seebeck coefficient –371 μV/K at 873 K, resistivity 880 μΩ m at 873 K, and the thermal conductivity coefficient 0.68 ± 0.03 W/m K at 770 K have been obtained; in this case, the thermoelectric figure of merit achieves the value ZT = 0.23.

Effects of Feedstocks and Laser Remelting on Microstructural Characteristics of ZrO<sub>2</sub>-7wt.%Y<sub>2</sub>O<sub>3</sub> Thermal Barrier Coatings Prepared by Plasma Spraying

Conventional and nanometer aggregate ZrO2-7wt.%Y2O3 ceramic powders taken as raw materials, plasma spraying and plasma spraying-laser remelting compound technology was used to prepare conventional and nanostructured thermal barrier coatings on the TiAl alloy surface. Effects of powder structure (feedstock) and laser remelting on organizational structure and phase of the coatings were analyzed using scanning electron microscope (SEM) and X-ray diffractometer (XRD). Results indicate that: conventional plasma sprayed ceramic coating presents typical lamellar stacking features; plasma sprayed nanostructured coating consists of fully melted region and partially melted region, presenting a two-phase structure. Under the comprehensive impacts of laser power, energy density, temperature field distribution in the laser action region, ceramic heat conductivity coefficient and coating thickness and other factors, the coating presents obvious lamellar structural features after laser remelting; the upper part is compact columnar crystal remelting region and the lower part is residual plasma spraying region. Due to toughening effect of residual nanoparticles in the remelting region of laser remelted nanostructured coating, grain-boundary strength is high and there are a considerable number of transgranular fractures, but the fractures in the remelting region of laser remelted conventional coating are basically intergranular fractures. Conventional plasma sprayed ceramic coating is mainly of tetragonal phase together with a small quantity of monoclinic phases, but nanometer plasma sprayed ceramic coating only has non-equilibrium tetragonal phases. After laser remelting, both conventional coating and nanometer coating mainly have non-equilibrium tetragonal phases with a small quantity of cubic phases.

ANALYTICAL MODEL OF WETTING THE POROUS MEDIUM

The purpose of this article is to develop an analytical model for determining the weakening of the thermal insulation capacity of porous materials - mineral wool and polystyrene because of increased water content. In the dry state, it was assumed that the sample consists of a skeleton and air-filled pores without process moisture content. In the second shot, however, dry material skeleton and pores with dry air and moisture content were taken into account. In addition, the results of tests involving the process of absorbing moisture in different moisturizing environments for both types of materials were presented. Based on the adopted calculation model, the value of the heat conduction coefficient in the dry state was determined based on the sum of the products of the volume shares of individual components of the material sample, i.e. the apparent volume of the sample material skeleton and the volume of air pores contained. The results of the thermal conductivity coefficient λ obtained in this way are consistent with those obtained from measurements during the experiment. This allowed to determine the validation of the adopted calculation model.
 Key words: humidity in porous materials, heat transfer coefficient, moisturizing