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This study describes the development and utilization of a novel setup for measuring the thermal conductivity of polyurethane composites with various nanoparticle contents. Measurements were conducted using both an experimental setup and a professional instrument, the TPS 2500 S, with results demonstrating high agreement with the precision of the measurements. The setup was further validated using a standard reference material with a thermal conductivity of 0.200 W/m/K. Additionally, the reliability of the setup was confirmed by its stability against ambient temperature variations between 20 and 30 degrees Celsius. This research presents a cost-effective method for measuring the thermal conductivity of polyurethane composites. Data processing involves noise reduction and smoothing techniques to ensure reliable results. The setup offers 5% accuracy and proves to be versatile for both research and educational applications. [ABSTRACT FROM AUTHOR]

These days, the use of natural materials is required for sustainable and consequently plus-, zero- and low-energy construction. One of the main objectives of this research was to demonstrate that pelite concrete block masonry can be a structural and thermal insulation material. In order to determine the actual thermal insulation parameters of the building partition, in situ experimental research was carried out in real conditions, taking into account the temperature distribution at different heights of the partition. Empirical measurements were made at five designated heights of the partition with temperature and humidity parameters varying over time. The described experiment was intended to verify the technical parameters of perlite concrete in terms of its thermal insulation properties as a construction material used for vertical partitions. It was shown on the basis of the results obtained that the masonry made of perlite concrete blocks with dimensions of 24 × 24.5 × 37.5 cm laid on the mounting foam can be treated as a building element that meets both the structural and thermal insulation requirements of vertical single-layer partitions. However, it is important for the material to work in a dry environment, since, as shown, a wet perlite block has twice the thermal conductivity coefficient. The results of the measurements were confirmed, for they were known from the physics of buildings, the general principles of the formation of heat and the moisture flow in the analysed masonry of a perlite block. Illustrating this regularity is shown from the course of temperature and moisture in the walls. The proposed new building material is an alternative to walls with a layer of thermal insulation made of materials such as polystyrene or wool and fits into the concept of sustainable construction, acting against climate change, reducing building operating costs, improving living and working conditions as well as fulfilling international obligations regarding environmental goals. [ABSTRACT FROM AUTHOR]

An automated system for measuring the thermal conductivity of functional and structural materials was developed. The main building blocks of the setup are the following: heating unit and cooling unit creating a heat flux gradient in the test sample; thermal resistances for temperature registration and control; and thermal pads for better contact between parts of the setup and the sample. The effect of the thermal conductivity of thermal pads and thermal resistances on the distribution of thermal fields in the developed setup was studied by computer modelling. A control software for the measuring setup was developed based on the hardware implementation of the steady-state Fourier's law-based method for the determination of thermal conductivity. The stopping criterion for the setup control software is the equality of heat fluxes in the heating and cooling units, as well as the stability of the thermal conductivity coefficient readings. The testing and calibration of the device were carried out using a sample of pure aluminum (99.999 wt.% Al). It was found that the experimental value of the thermal conductivity coefficient of the aluminum sample at room temperature (T = 22 °C) is <λ> = 243 ± 3 W/m·K. This value of the thermal conductivity coefficient is consistent with the literature data and experimental values obtained by the laser flash method, which ranges within λ = 210–260 W/m·K. [ABSTRACT FROM AUTHOR]

Introduction. The article presents the results of studies of structural and heat-insulating cement-based foam concrete for monolithic individual housing construction using porous aggregates sand and superplasticizers. The relevance of the study is to improve the technological properties of foam concrete mixtures to enhance their transportation and laying in formwork, as well as to increase the strength and thermal insulation parameters of wall materials used in individual housing construction. A synergistic effect is ensured and increased stability of the foam concrete mixture is achieved, resulting in an increase in the grade of compressive strength of foam concrete and a decrease in thermal conductivity by partially replacing quartz sand with expanded clay or slag sand in the amount of 25% by volume and introducing the superplasticizer “Steinberg MP-4”. Materials and methods. The study of foam concrete mixture and foam concrete was carried out in the accredited laboratory of TSUAB in accordance with the requirements of national standards. Results. The use of combined additives, including a superplasticizer and a mineral porous aggregate, leads to increase the grade of compressive strength of foam concrete from B1 to B2 while maintaining the average density grade D600, and also allows reducing the thermal conductivity coefficient of foam concrete to 17% compared to the basic composition. Conclusion. The developed compositions for the production of monolithic structural and heat-insulating foam concrete of natural hardening with a combined additive, including mineral porous aggregate and current plasticizers, are recommended for individual housing construction of low-rise buildings.

Foam concrete, a type of lightweight concrete, is highly preferred due to its lightness and ease of application. In addition, substitute materials are used in the foam concrete mixture in order to further improve the properties of foam concrete. In this study, the engineering properties of foam concrete produced using liquid latex were analyzed. For this purpose, liquid latex was added to the mixing water. The amount of latex is fixed at 25% of the cement weight. Additionally, the amount of liquid latex added to the mixture was reduced from the amount of mixing water. According to the results, it was determined that liquid latex made positive contributions to the engineering properties of the produced foam concrete. It was found that the water absorption value of latex-added samples decreased significantly compared to the reference sample. In addition, the thermal conductivity coefficient of the samples with latex added was lower than the reference sample. In the microstructural analysis, it was seen that the pores were more homogeneous than the reference sample and no cracks occurred. Finally, the long chain bonds formed by liquid latex in concrete were detected for the first time by SEM image analysis in this study. [ABSTRACT FROM AUTHOR]

3D braided composites reinforced with graphene nanoplatelets (GNPs) contribute to improving the thermal conductivity coefficients of the composites. However, the microstructures of 3D braided composites are so complicated that the interior and surface unit cells have different thermal conductivity. Meanwhile, the synergistic reaction of GNPs further improves the challenge of predicting the thermal conductivity of the composites. This paper investigates the thermal conductivity of 3D braided composites reinforced with GNPs by finite element modeling based on multi-unit cell models. Firstly, the thermal conductivity of epoxy resin modified by GNPs is analyzed by 2D periodical unit cell models. Then a detailed multi-unit cell model is introduced to establish the finite element model for predicting the thermal conductivity. Meanwhile, the periodical thermal boundary conditions are also applied to the finite element models. Finally, the effectiveness of the multi-unit cell modeling is validated through two typical cases. The thermal conductivity for the interior, surface and integral unit cell models are analyzed, respectively. The results indicate the thermal conductivity of 3D braided composites is improved obviously with increasing GNPs mass fraction. With the braiding angle increasing, the transverse thermal conductivity of 3D braided composites gradually increases and the longitudinal thermal conductivity decreases almost linearly. Meanwhile, the thermal conductivity of the composites gradually increases with fiber volume fraction increasing. The results provide important theoretical basis for the design of the thermal conductivity of 3D braided composites reinforced with GNPs. [ABSTRACT FROM AUTHOR]

Significant portion of the energy consumed in our country is used for heating and cooling processes in buildings. To reduce this energy consumption, proper energy utilization and effective insulation are essential. This study was conducted with the aim of minimizing heat loss through windows and enhancing thermal insulation. Two types of calculations were performed: experimental and numerical. Various glass samples were used for these calculations. Numerical calculations were conducted using Comsol Multiphysics 5.4 and the Heat Transfer Module, while experimental measurements of thermal conductivity coefficients were carried out in accordance with TS EN 12667 standards using the HFM Fox-314 measurement device. Based on the measurements and comparisons conducted for Isparta province, it was determined that the three-layered 16 mm gas-filled argon gas Solar Low-e coated glass with a thermal conductivity coefficient of 0.113 W/mK, a thermal transmittance coefficient of 0.388 m2K/W, and a thermal transmittance coefficient of 1.1 W/m2K is the most ideal application. Furthermore, it was observed that 10 samples outperformed the TS 825 standards. [ABSTRACT FROM AUTHOR]

Abstract The thermal conductivity of engobed building ceramics was studied as a function of their microstructure. The following thermal conductivity coefficients of the samples were determined: clinker bricks with 5% water absorption - 1.04 W/(m·K) and facing bricks (ordinary) with 12% water absorption - 0.48 W/(m·K) (ignoring the voids in the samples). A comparison of the thermal conductivity of brick samples of uniform thickness without engobe and with engobe showed that the latter had a slight increase in thermal conductivity of 0.3% due to forming a denser outer layer on its surface with 2.0-0.3% water absorption. However, as the engobe coating is applied as an additional layer on the top of the ceramic bricks and the product has a greater thickness, the heat flow through the engobed bricks is 0.1-0.2 % lower. The results can be applied to technologies for achieving energy-efficient decorative and protective coatings for building ceramics.

Recycling crushed clay bricks (CCB) in concrete is a sustainable and cost-effective process. Huge quantities of crushed clay bricks waste cause many serious environmental problems around the world. To deal with this problem, crushed bricks were recycled in the concrete industry as an alternative to natural resources, and the brick powder was reused as a partial replacement for cement. The objective of this paper is to study the effect of crushed clay bricks on the characteristics of concrete. 7 concrete mixtures containing coarse crushed brick aggregate (CCBA) and fine crushed brick aggregate (FCBA) were prepared as a complete substitute for sand and dolomite, respectively. Clay brick powder (CBP) and silica fume were used as a partial substitute for cement by 5%, 10%, and 15% of its weight. The water-to-cement ratio was 0.35. For comparison, a control mixture was prepared. Various tests were conducted to evaluate the performance of concrete. The results showed that the workability of the different mixtures containing CCB decreased compared to that of the reference mixture. The compressive strength values of mixtures containing CCBA had a clear decrease compared to the reference mix at 7, 28, and 56 days of curing. The modulus of rupture results had the same path as compressive strength results. The thermal conductivity coefficient for mixtures including CCBA decreased compared to the control mix. Scanning Electron Microscope images indicated crystals of calcium silicate hydrate because of the pozzolanic interaction between the brick powder and the fine crushed clay bricks with calcium hydroxide.

The DSC method revealed endothermic effects (–613.9 J/g) during gypsum dihydrate heating associated with the heat absorption during the release of crystalline hydrate water in the range of 100–250°C during the heating process. Mass losses during water evaporation were determined by TGA and amount of up to 20%. The thermal conductivity coefficient of gypsum samples is 0.288 W/m K. The influence of mineral additives—glass spheres, wollastonite, and chopped basalt fiber—on changes in the properties of gypsum samples at curing times of 2 h and 1, 3, 7, and 14 days was studied. An addition of glass spheres up to 10 wt % reduces gypsum strength by 10–13% and density, by 16%, additive up to 20 wt % reduces strength by two times and density by 36–40%, and additive up to 50 wt % reduces strength by from five to six times and density by 80–85%, with the thermal conductivity coefficient decreasing to 0.236 W/m K. An addition of wollastonite 10–20 wt % increases the strength of gypsum samples by 13–16%, and addition of 50 wt % reduces the strength by two times. An addition of 0.5–1.5 wt % chopped basalt fibers increases strength by 10–16%, as well as the strength gain rate. Additions of wollastonite and basalt fibers practically do not change the density of gypsum samples, but increase the thermal conductivity coefficient to 0.320–0.373 W/m K. [ABSTRACT FROM AUTHOR]

The results are presented of research on the mechanical and thermophysical characteristics of a composite material—paper mass. The work determined the thermal conductivity coefficient, density, sound speed at surface sounding, and destructive force for the first layer, which was 2 mm thick, and for the composite as a whole. In total, six samples of different geometrical shapes were researched. [ABSTRACT FROM AUTHOR]

During the transition from liquid to solid, the thermal conductivity coefficient λ of concrete decreases. Although λ of hardened concrete is well investigated, there is limited research on the transition from liquid to solid and how it depends on hydration. Currently, only simplified qualitative approaches exist for the liquid state and the transient process. An experimental method is not available. For this purpose, a test rig is designed to experimentally capture the evolution of λ for fine-grain concretes during transition. The performance of the test setup is evaluated on a characteristic high-performance concrete (HPC). The results are compared to theoretical predictions from the literature. The developed test rig is mapped in a digital twin to investigate extended boundary conditions, such as different heat sources and temperatures of the experimental setup. It allows the experiment to be repeated and optimized for different setups with little effort. The test principle is as follows: A liquid concrete sample is heated through a controlled external source, while the transient temperature distribution over the height is measured with a fiber optic sensor. The thermal conductivity is derived from the heat flux induced and the temperature distribution over an evaluation length. Experiments show that λ in the liquid state is approximately 1.4 times greater than in the solid state and exponentially decreases for the transient process. Numerical results on the digital twin indicate that the robustness of the results increases with the temperature of the heat source. Moreover, the derivation in λ turns out to be strongly dependent on the evaluation length. A length of three times the maximum grain diameter is recommended. [ABSTRACT FROM AUTHOR]

Recycling crushed clay bricks (CCB) in concrete is a sustainable and cost-effective process. Huge quantities of crushed clay bricks waste cause many serious environmental problems around the world. To deal with this problem, crushed bricks were recycled in the concrete industry as an alternative to natural resources, and the brick powder was reused as a partial replacement for cement. The objective of this paper is to study the effect of crushed clay bricks on the characteristics of concrete. 7 concrete mixtures containing coarse crushed brick aggregate (CCBA) and fine crushed brick aggregate (FCBA) were prepared as a complete substitute for sand and dolomite, respectively. Clay brick powder (CBP) and silica fume were used as a partial substitute for cement by 5%, 10%, and 15% of its weight. The water-to-cement ratio was 0.35. For comparison, a control mixture was prepared. Various tests were conducted to evaluate the performance of concrete. The results showed that the workability of the different mixtures containing CCB decreased compared to that of the reference mixture. The compressive strength values of mixtures containing CCBA had a clear decrease compared to the reference mix at 7, 28, and 56 days of curing. The modulus of rupture results had the same path as compressive strength results. The thermal conductivity coefficient for mixtures including CCBA decreased compared to the control mix. Scanning Electron Microscope images indicated crystals of calcium silicate hydrate because of the pozzolanic interaction between the brick powder and the fine crushed clay bricks with calcium hydroxide. [ABSTRACT FROM AUTHOR]

New composites made of natural fiber polymers such as wasted date palm surface fiber (DPSF) and pineapple leaf fibers (PALFs) are developed in an attempt to lower the environmental impact worldwide and, at the same time, produce eco-friendly insulation materials. Composite samples of different compositions are obtained using wood adhesive as a binder. Seven samples are prepared: two for the loose natural polymers of PALF and DPSF, two for the composites bound by single materials of PALF and DPSF using wood adhesive as a binder, and three composites of both materials and the binder with different compositions. Sound absorption coefficients (SACs) are obtained for bound and hybrid composite samples for a wide range of frequencies. Flexural moment tests are determined for these composites. A thermogravimetric analysis test (TGA) and the moisture content are obtained for the natural polymers and composites. The results show that the average range of thermal conductivity coefficient is 0.042–0.06 W/(m K), 0.052–0.075 W/(m K), and 0.054–0.07 W/(m K) for the loose fiber polymers, bound composites, and hybrid composites, respectively. The bound composites of DPSF have a very good sound absorption coefficient (>0.5) for almost all frequencies greater than 300 Hz, followed by the hybrid composite ones for frequencies greater than 1000 Hz (SAC > 0.5). The loose fiber polymers of PALF are thermally stable up to 218 °C. Most bound and hybrid composites have a good flexure modulus (6.47–64.16 MPa) and flexure stress (0.43–1.67 Mpa). The loose fiber polymers and bound and hybrid composites have a low moisture content below 4%. These characteristics of the newly developed sustainable and biodegradable fiber polymers and their composites are considered promising thermal insulation and sound absorption materials in replacing synthetic and petrochemical insulation materials in buildings and other engineering applications. [ABSTRACT FROM AUTHOR]

Relevance. Polymer composite materials with carbon components have not only good functional characteristics as resistors, but also low price, low specific gravity, and relatively simple industrial manufacturing technology. This determines the expansion of the scope of their application, including in material-intensive oil and gas equipment, in high-voltage electrical and electrophisikal installations. Expanding the areas of application of such materials requires research into thermophysical characteristics and methods for controlling them to optimize thermal conditions during continuous operation of equipment containing components made of polymer composite materials with carbon fillers. Thermophysical characteristics can be formed using a wide range of parameters; the main ones are the type of electrically conductive and connecting components. However, changing the binder requires a radical change in technology, which is not always acceptable for a number of reasons. Aim. To study the effect of the electrically conductive component (carbon black) on the thermophysical characteristics of rubbers filled with carbon black; establish the dependence of the thermophysical characteristics of the composite on the type of carbon black. Object. Thermophysical characteristics of the composite material, largely determined by the electrically conductive component. Methods. Instrumental measurements of thermophysical and electrical characteristics of materials, statistical and correlation analysis. Results. The authors have experimentally established that the thermophysical characteristics of rubbers filled with carbon black (heat capacity, thermal conductivity, and thermal diffusivity) depend on the type of carbon black. They identified the patterns of changes in these characteristics. The paper analyzes their relationship with the properties of carbon black and the characteristics of the macrostructure of the composite material. Based on the conducted research, the authors developed the recommendations for selecting the grade of carbon black for composites used in such areas as: electric heating systems operating on the principles of self-regulating heaters, devices operating in non-stationary thermal conditions, etc.

Numerical analysis of time-dependent conductive heat transfer in three-dimensional solid bodies with a heat source is important in their use in various industries. In this article, an attempt has been made to investigate this issue for a cylinder consisting of four equal pieces with different thermal conductivity coefficients and heat sources, and conclusions have been drawn. The geometry of the cylinder consists of two lower (first) and upper (second) layers. In the lower layer of two solid bodies, one is a piece of rubber with a thermal conductivity coefficient of K1=0.16 w/m○k and the other is a piece of walnut wood with a thermal conductivity coefficient of K2=0.077 w/m○k and two solid objects are used in the upper layer. One is a piece of polyurethane with a thermal conductivity coefficient of K3=0.02 w/m○k and the other is a piece of cork with a thermal conductivity coefficient of K4=0.04 w/m○k. There are four heat source mechanisms: constant value, linear, quadratic, and sinusoidal or periodic heat source with a certain frequency. All the surfaces of the cylinder walls in the time interval 0 ≤ t ≤ 10 s10, T = 0 are assumed. The obtained results show that the temperature distribution when the value of the heat source is constant affects a larger area, and the highest increase in temperature in the direction of the z-axis belongs to the constant, quadratic, sinusoidal and linear heat source, respectively.

Recent years have seen a growing demand from both researchers and industry for reliable models that can predict human thermophysiological responses. This article outlines scenarios concerning the impact of the environment on human thermal comfort, taking into account the properties of special protective clothing and the functioning of the human thermoregulation system. It provides the overview of the concept of thermal comfort and the thermoregulation system of the human body. The mathematical model should consider the complex behavior of thermophysical processes within the “person – clothing – environment” system. The heat flow between human skin and the inner surface of protective clothing is represented by a system of partial differential equations. The system is nonlinear due to the nature of human thermoregulation. The modeling encompasses both thermal and aerodynamic effects of the environment (such as temperature, air humidity, etc.), the thermal and moisture resistance of clothing, as well as heat and moisture flows to the surface of the human body resulting from internal thermoregulation. A particular challenge lies in the fact that all these processes must be modeled in an interconnected manner. Thus, the task is to move, based on mathematical models and a compartmental approach, to a quantitative assessment of the processes of mass transfer and heat of both individual parts and the human body as a whole. This problem is resolved in the work under consideration. Finite difference methods are applied to approximate spatial partial derivatives, which simplifies the problem to solving a system of nonlinear ordinary differential equations. To solve the problem, a high-precision approximation in the time dimension is used. The model is applied to predict the reaction of a clothed person to various changes in environmental conditions.

This study describes the development and utilization of a novel setup for measuring the thermal conductivity of polyurethane composites with various nanoparticle contents. Measurements were conducted using both an experimental setup and a professional instrument, the TPS 2500 S, with results demonstrating high agreement with the precision of the measurements. The setup was further validated using a standard reference material with a thermal conductivity of 0.200 W/m/K. Additionally, the reliability of the setup was confirmed by its stability against ambient temperature variations between 20 and 30 degrees Celsius. This research presents a cost-effective method for measuring the thermal conductivity of polyurethane composites. Data processing involves noise reduction and smoothing techniques to ensure reliable results. The setup offers 5% accuracy and proves to be versatile for both research and educational applications.

The article discusses the effect of additives of waste mineral wool fibers on geopolymer binder. This is an important study in terms of the possibility of recycling mineral wool waste. The paper describes an effective method for pulverizing the wool and the methodology for forming geopolymer samples, labeled G1 for glass-wool-based geopolymer and G2 for stone-wool-based geopolymer. The compressive and flexural strengths and thermal conductivity coefficient of the geopolymer with the addition of mineral fibers were determined. The key element of the article is to verify whether the addition of mineral wool fibers positively affects the properties of the geopolymer. The results obtained prove that the addition of fibers significantly improves the flexural strength. For the G1 formulation, the ratio of compressive strength to flexural strength is 18.7%. However, for G2 samples, an even better ratio of compressive strength to flexural strength values of 26.3% was obtained. The average thermal conductivity coefficient obtained was 1.053 W/(m·K) for the G1 series samples and 0.953 W/(m·K) for the G2 series samples. The conclusions obtained show a correlation between the porosity and compressive strength and thermal conductivity coefficient. The higher the porosity, the better the thermal insulation of the material and the weaker the compressive strength. [ABSTRACT FROM AUTHOR]

ABSTACT: Introduction. Research to improve the quality of foam concrete products through targeted control of technological processes of structure formation of cement-based compositions is relevant. The strength of foam concrete is significantly influenced by the adhesion strength of the hardened cement paste to the aggregate. This article discusses methods of chemical and mechanochemical activation of foam concrete filler with glyoxal-containing additives, interaction with hydration products of binders and increasing the strength of the contact zone. The quality of foam concrete can be improved by controlling the properties of the contact zone. Materials and methods. The study was conducted using standard test procedures specified in national standards. Results. With preliminary chemical and mechano-chemical exposure of the sand surface to glyoxal-containing additives and its subsequent introduction into the foam concrete mixture the grade of strength of foam concrete increases to B1 while maintaining the average density grade D500 in comparison with foam concrete of the control composition, while the shrinkage value decreases by 20–38.5% and thermal conductivity coefficient by 37%. Conclusion. The use of glyoxal-based additives in foam concrete mixtures by pre-activating the sand surface can improve the quality of cement foam concrete.

In the paper, a theoretical calculation of the coefficient of thermal conductivity of solid solutions of PbSnTe was carried out. The contribution of phonon scattering on substitution atoms to the effect of reducing thermal conductivity has been established. The composition of the PbSnTe solid solution, characterized by the lowest values of the lattice component of the thermal conductivity coefficient klat, was determined. The concentration of intrinsic charge carriers in solid solutions is calculated and their influence on the thermoelectric parameters of the material is shown.

Recent studies for nanofluids, did not pay enough attention to the effect of the nanoparticle size and nanofluid stability on the heat transfer rate. In this study, the thermal conductivity (TC) coefficient of silica/deionized water (DW) nanofluid with various sizes of nanoparticles and various rates of nanofluid stability was investigated. Validation experiments, including X-Ray diffraction analysis (XRD), FE-Scanning Electron Microscopy (FE-SEM), Dynamic Light Scattering (DLS), and Zeta Potential (Zp), were carried out to examine the particle sizes and the nanofluid stability. The results illustrated that increasing the temperature leads to the augmentation of the TC coefficient of the SiO2/deionized water in all nanoparticle sizes and all volume concentrations. Also, increasing the volume concentration of the nanofluid leads to the augmentation of the TC coefficient of the nanofluid in all nanoparticle sizes and all temperatures. Eventually, increasing the nanoparticle sizes causes the TC coefficient of the nanofluid to be decreased in all volume concentrations. For the 11 nm nanoparticle size, the amount of the Relative TC (RTC) coefficient enhancement by increasing the temperature was 1.2%, 2.5%, 4.7%, and 6.8% for concentrations of 0.0.1%, 0.1%, 0.5%, and 1%, respectively. For the 50 nm nanoparticle size, this enhancement was from 0.7% to 6.5%, and for the 70 nm nanoparticle size, it was from 0.5% to 5.7%. Finally, Artificial Intelligence (AI) optimization was done to find the optimized size and stability.

Introduction. The authors present the results of an experimental study of the thermal insulation properties of vacuum panels using a digital copy of the test bench. The subject of the study is a vacuum insulation panel in the form of a sealed parallelepiped with internal stiffeners. When the air pressure inside the body is reduced, the specific thermal resistance of such vacuum insulation panels becomes higher than that of modern insulation materials. The use of such panels as thermal insulation for land means of transport, particularly passenger carriages and refrigerator wagons, significantly reduces energy costs for heating or air conditioning the interior. Experimental determination of the thermal properties of vacuum insulation panels is time consuming and requires expensive equipment due to their considerable heterogeneity. The aim of the study is to develop a method for determining the thermal resistance of insulating materials with internal heterogeneity in the shortest possible time with acceptable accuracy.Materials and methods. The research methods combine physical experiments on three vacuum insulation panel prototypes and numerical experiments on 3D models of these samples. Specifically, the test stand was calibrated using its digital counterpart — a virtual test bench created as a 3D model using SolidWorks software.Results. The study of the transient thermal process on the stand model in SolidWorks Simulation allowed us to reduce the time of the physical experiment to 40 minutes and to determine the values of the effective thermal conductivity coefficient of the three vacuum insulation panel prototypes.Discussion and conclusion. The study of the steady-state thermal process of 3D models of vacuum insulation panel prototypes in SolidWorks Simulation showed that the discrepancy between the experimental and calculated values of the effective thermal conductivity coefficient is less than 5%. The proposed method for determining the effective thermal conductivity coefficient of materials is suitable for use in the incoming and outgoing inspection of car insulation during overhaul.

Ensuring flow in an oil field is one of the most costly problems in oil production and transportation. The fight against the formation of paraffin deposits consists both in the application of methods for the prevention and removal of deposits, and in the modeling of this process. An important parameter for the application of some technologies for preventing the formation of deposits and modeling the temperature regime of the pipeline is the coefficient of thermal conductivity of these deposits. The paper presents a study of the influence of the thermal conductivity of organic deposits on the rate of their formation, measured for 5 hours at the Cold Rod installation. According to the research results, it was found that over time, the thermal conductivity of organic deposits increases, while the rate of deposit formation decreases significantly. This process is explained by an increase in temperature on the surface of deposits due to their compaction and displacement from the volume of the liquid phase. The results obtained are extremely important in modeling the process of deposit formation and modeling a number of technologies to combat them. [ABSTRACT FROM AUTHOR]

A technique for the experimental determination of the thermophysical characteristics of inactive aluminophosphate and borosilicate glasses by differential scanning calorimetry (DSC) is proposed and tested. The advantages of this measurement technique are shown. For glassy matrices of various compositions, the specific heat capacity and thermal conductivity coefficient are determined. The obtained experimental values make it possible to calculate the thermal conductivity values. The applicability of this method is proved by working with real samples of vitrified high-level waste to study their properties and form a database based on them. [ABSTRACT FROM AUTHOR]

The demand for 3D printer technology and products, one of the additive manufacturing methods, is increasing daily in the sectoral and academic fields. Many types of polymer-based filaments are used in 3D printers, pure or filled/reinforcement. Utilizing these specialized materials in places suitable for their mechanical and thermal properties will help efficiently use resources. Using 3D printers, it is possible to manufacture products that provide thermal insulation or good heat conduction in heating and cooling areas. Especially due to the energy requirements for heating and cooling, it is very important to know the thermal performance of materials to ensure and maintain energy efficiency. This study experimentally investigated the mechanical properties and heat conduction coefficients of 3D printed parts. The experiments were conducted with seven different filament materials (PLA, PLA+, PLA-CF, PLA Wood, Tough PLA, ABS+, TPU) and three layer thicknesses (0.1, 0.2, and 0.3 mm). Samples for tensile testing, hardness, and thermal conductivity coefficient measurements were produced, and measurements were performed. In the experiments, the highest tensile strength was obtained in PLA-CF with 0.3 mm layer thickness, and the lowest tensile strength was obtained in PLA Wood with 0.3 mm layer thickness. Tensile strength decreased with an increasing layer thickness in PLA, PLA Wood, ABS+, and TPU, while it increased in PLA-CF. The highest tensile strength of PLA+ was determined to be 0.2 mm and 0.1 mm layer thickness in Tough PLA. Hardness results showed minimal change in hardness values with increasing layer thickness. The thermal conductivity values of the samples varied according to the additives and layer thicknesses. The highest thermal conductivity increase was measured in PLA-CF with 11.84%, and the lowest thermal conductivity decrease was measured in Tough PLA with 9.44%. [ABSTRACT FROM AUTHOR]

Pineapple leaf fiber (PALF), striped sunflower seed fiber (SFSF), and watermelon seed (WMS) are considered natural waste polymer materials, which are biodegradable and sustainable. This study presents new novel thermal insulation and sound absorption materials using such waste as raw materials. PALF, SFSF, and WMS were used as loose, bound, and hybrid samples with different compositions to develop promising thermal insulation and sound-absorbing materials. Eleven sample boards were prepared: three were loose, three were bound, and five were hybrid between PALF with either SFSF or WMS. Wood adhesive was used as a binder for both the bound and hybrid sample boards. Laboratory scale sample boards of size 30 cm × 30 cm with variable thicknesses were prepared. The results show that the average thermal conductivity coefficient for the loose samples at the temperature range 20–80 °C is 0.04694 W/(m.K), 0.05611 W/(m.K), and 0.05976 W/m.K for PALF, SFSF, and WMS, respectively. Those for bound sample boards are 0.06344 W/(m.K), 0.07113 W/(m.K), and 0.08344 W/m.K for PALF, SFSF, and WMS, respectively. The hybrid ones between PALF and SFSF have 0.05921 W/m.K and 0.06845 W/(m.K) for two different compositions. The other hybrid between PALF and WMS has 0.06577 W/(m.K) and 0.07007 for two different compassions. The sound absorption coefficient for most of the bound and hybrid boards is above 0.5 and reaches higher values at some different frequencies. The thermogravimetric analysis for both SFSF and WMS shows that they are thermally stable up to 261 °C and 270 °C, respectively. The three-point bending moment test was also performed to test the mechanical properties of the bound and hybrid sample boards. It should be mentioned that using such waste materials as new sources of thermal insulation and sound absorption materials in buildings and other applications would lead the world to utilize the waste until zero agrowaste is reached, which will lower the environmental impact. [ABSTRACT FROM AUTHOR]

An analytical dependence between the dimensionless coefficients of added mass and thermal conductivity was obtained in a suspension of spherical particles. The dependence is confirmed by comparison with the theoretical data of other authors, including at elevated concentrations of dispersed particles, taking into account their hydrodynamic interaction. [ABSTRACT FROM AUTHOR]

The aim of this article is to address the influence of air humidity and testing temperature on the thermal conductivity coefficient (λ) of various thermal insulation materials. This group includes wood-based materials, rock wools, heat-insulating renders, climate boards, and lightweight cellular concretes. These materials are used both indoors and outdoors in buildings. Over the course of several years, data were collected from laboratory tests to determine the thermal conductivity coefficient (λ) in relation to increases in temperature and humidity. The obtained results were compared with values provided by the manufacturers of the insulation materials. The aforementioned research was carried out due to the rather high sorption of most materials and thus the possibility of them becoming humid at high air humidity. Because of the very large difference in the thermal conductivity coefficient of water and air, a relatively small increase in the mass moisture content of the materials results in a loss of insulation. [ABSTRACT FROM AUTHOR]

Currently, it is estimated that the construction sector consumes over 40% of the energy produced and about 50% of the mass of processed materials. As a consequence, there is a challenge to look for alternative material solutions allowing for the storage and conversion of energy. Phase change materials give us such opportunities. Their introduction leads to additional benefits related to thermal parameters. The work presents a short overview of PCMs along with the possibility of their application. Then, as part of the research, the selected phase change material was applied to the internal plaster layer of an external wall to check its activity. The obtained results were compared to the values of reference samples (without PCM). The proposed solution leads to the improvement of the analyzed partitions' thermal parameters. [ABSTRACT FROM AUTHOR]

The article attempts to assess the possibility of using non-woven fabrics made of waste fibers in cladding panels. For this purpose, woolen and polypropylene nonwovens were tested for mass per unit area, characteristic opening size, and lengthwise and crosswise elongation at maximum strength. Non-woven fabrics were placed in the middle of the thickness of cement and gypsum boards and subjected to tests of density, thermal conductivity coefficient λ, and bending strength. The influence of individual nonwoven fabrics with different properties on the properties of the finished composite was determined. It was found that wool nonwoven fabrics had the best effect on the thermal conductivity coefficient. A better affinity for nonwoven fabrics was shown by gypsum mortar. The best influence on the bending strength of the panels had polyester non-woven fabrics with the lowest mass per unit area and the largest characteristic opening size.

Objective. The purpose of the work is the practical approbation of a nondestructive thermal imaging method to identify hidden (invisible) defects and qualitative analysis of the thermal protection of a complex of construction objects in the city of Vologda, as well as the study of some physical (thermophysical) indicators (coefficients of thermal conductivity, thermal resistance (thermal insulation) and heat transfer) of structural building material in the form of silicate brick.Method. The fundamental laws of the theory of heat transfer, thermal nondestructive testing, infrared and technical diagnostics, the current domestic regulatory and technical and regulatory documentation, field experiments on real objects and laboratory samples.Result. The results of the practical determination of hidden defects in the thermal shells of the complex of civil and industrial buildings functioning in the urban environment, thermophysical properties (coefficients of thermal conductivity, thermal resistance (thermal insulation), heat transfer) of modern building materials by methods of thermal non-destructive testing are presented. The locations of identified invisible defects of thermal protection of the surveyed construction objects are determined and recommendations for their elimination are proposed. The obtained values of thermophysical characteristics for the studied structural building material are consistent with the data of current regulatory documents.Conclusion. The features of the nondestructive method of infrared thermography in determining the hidden defects of the heatshielding shells of operated buildings of various functional purposes and the complex of thermophysical parameters of modern structural building materials are shown. The demand for thermal imaging during energy and technical surveys of construction objects, their individual structural elements, life support engineering systems, as well as studies on the refinement, quantification and prediction of various thermal properties of building materials and products has been experimentally confirmed.

The absorption of heat by rocks is accompanied by an increase in the kinetic energy of molecules and atoms and is recorded by a change in rock temperature. The thermal properties of rocks characterize the ability to transfer and absorb heat and change their size when the temperature rises. The main thermal properties of rocks are thermal conductivity, heat capacity, linear thermal expansion, and thermal volumetric expansion. In this paper, the influence of temperature effects on the thermal properties of reservoirs – the coefficient of temperature conductivity, specific heat capacity, and thermal conductivity is studied using the samples of oil-saturated reservoirs from the good number 19Bp of the Upper Uplift of Sotnikovsky deposit. The dependence of the thermal properties of the core material on temperature was revealed using a number of laboratory experiments. The results of these studies contribute to improving the reliability of data on the relationship of thermal properties with other physical properties of oil-saturated reservoirs and can be used to improve the efficiency of the development of fields of super-viscous oil.

The aim of this study was to develop a simple algebraic equation to calculate the effective thermal conductivities of porous solid materials, particularly concrete with porous aggregates. The components of the equation consisted of material porosity and density, and thermal conductivity coefficients of the matrix and pore gas. The equation was applied to ten samples of organic sediment stones, volcanic rocks and porous aggregates, including concrete with expanded clay, expanded polystyrene and pumice aggregates. The thermal conductivity coefficients given by the equation were higher than those measured experimentally (6.62–16.89%). The proposed equation was also compared with six algebraic equations. The results suggest that the proposed algebraic equation can be used to calculate the thermal conductivity coefficients of solid materials containing complex geometrical pores. The newly produced porous samples can be used as light concrete in building. [ABSTRACT FROM AUTHOR]

The purpose of this work is to simulate the processes of gaseous swelling in SiC ceramics as well as the associated changes in strength and thermophysical properties under high-temperature irradiation with helium ions. The choices of irradiation conditions (irradiation temperatures of 700 and 1000 K) and irradiation fluences (1015–1018 ion/cm2) are based on the possibilities of modeling the processes of destructive changes in the near-surface layer as a result of the accumulation of gas-filled inclusions during high-dose irradiation. During this study, it was found that an increase in the irradiation temperature of the samples from 700 to 1000 K leads to a decrease in the resistance to gas swelling, since with the temperature increase, the mobility of implanted helium in the near-surface layer grows, which results in an increase in the size of gas-filled bubbles and, as a result, accelerated destruction of the damaged layer. It has been established that in the case of irradiation at 700 K, the critical fluence for swelling associated with the formation of visible gas-filled bubbles on the surface is 5 × 1017 ion/cm2, while for samples irradiated at a temperature of 1000 K, the formation of gas-filled bubbles is observed at a fluence of 1017 ion/cm2. Measurements of the thermal conductivity coefficient showed that the formation of gas-filled bubbles leads to a sharp deterioration in heat transfer processes, which indicates that the created defective inclusions prevent phonon heat transfer. Changes in the strength characteristics showed that a decrease in hardness occurs throughout the entire depth of the damaged ceramic layer. However, with a rise in the irradiation fluence above 1017 ion/cm2, a slight damaged layer thickness growth associated with diffusion processes of helium implantation into the near-surface layer is observed. The relevance of this study consists in obtaining new data on the stability of the strength and thermophysical parameters of SiC ceramics in the case of helium accumulation and its subsequent radiation-induced evolution in the case of irradiation at temperatures of 700 and 1000 K. The data obtained during the experimental work on changes in the properties of ceramics will make it possible to determine the potential limits of their applicability in the case of operation under extreme conditions at elevated temperatures in the future. [ABSTRACT FROM AUTHOR]

Carbonation is a natural process in all materials based on burnt lime and cement. Many publications treat the influence of carbonation on the properties of Autoclaved Aerated Concrete (AAC), especially on compressive strength. The influence of carbonation on compressive strength, dry density, shrinkage, and thermal conductivity on AAC in different density classes (350–600) was a subject of this research program. AAC specimens were subjected to accelerated carbonation in a climate chamber at a temperature of 20°C, 65% RH of a period of 14 days with a CO2 concentration of 0.5%. The different moisture content of specimens was used in the research program. All tests were conducted in accordance with EN 771‐4:2011+A1:2015. To determine the phase content and microstructure change the XRD analysis was used. [ABSTRACT FROM AUTHOR]

Autoclaved aerated concrete (AAC) is a very popular and porous material, which is foamed in a production process by using aluminum powder. The research program explores the influence of different particle size distributions for properties of AAC with different densities. The compressive strength, thermal conductivity, and shrinkage can be improved by changing the pore size. The research program focused on different density classes of AAC. The pore sizes were changed by using different aluminum powder, different water‐to‐solid ratio, and different starting temperature of the concrete mix. All tests were made on a technological scale and all properties were tested according to EN 771‐4:2011+A1:2015 standard. All samples were tested for dry density, compressive strength, thermal conductivity, shrinkage, and phase composition. The change in pore size can influence not only the AAC properties but also the amounts of raw materials used in the production process and CO2 consumption in its cycle life. [ABSTRACT FROM AUTHOR]

Autoclaved aerated concrete (AAC) is a construction material with very good thermal properties. In many countries, the majority of masonry structures are developed using a single wall from low‐density AAC. In some countries, like Poland, the most popular solution is an AAC construction wall with covering insulation material. In the house construction process, several challenging spots can be observed where thermal bridges can develop. One of them will be the place of installation of external window roller blinds on a reinforced concrete lintel or an aerated concrete lintel. In fact, there are several solutions to this problem, but there is no clear answer in the literature about which of those will be optimal in terms of reducing the loss of thermal energy, the cost of which is growing year by year. The research program includes tests of the thermal conductivity of a wall unit built of AAC of various density classes, with the most popular thermal insulation materials available on the market, such as: EPS polystyrene, XPS polystyrene, or aluminum mats. [ABSTRACT FROM AUTHOR]

In this study, thermal conductivity, mechanical properties, and thermal degradation of pumice-added epoxy materials were investigated. 2%, 4%, 6%, 8%, and 10% of pumice was added to the epoxy resin (EP) % by weight. Various types of analyses and tests were conducted to determine the thermal conductivity, mechanical properties, and thermal degradation of these epoxy materials. The tests and analyses proved that the addition of pumice leads to a decrease in the thermal conductivity coefficient and density of the pure EP material. It also increases the degree of hardness. The addition of pumice had a positive effect on mechanical properties. Compared to pure EP, it increased the tensile strength, Young’s modulus, bending strength, and flexural modulus. As a result of TGA analysis it was determined that with the incorporation of pumice into the EP, its decomposition rate progressed more slowly. At 800°C, the carbon residue improved as a result of the addition of pumice. [ABSTRACT FROM AUTHOR]

Modern construction market is experiencing a shortage of highly efficient thermal insulation materials. Alkali-silicate raw mixtures in combination with high-performance fillers currently make it possible to create porous heat-insulating materials with unique properties: rigid cellular structure, specified geometric dimensions and shape, low thermal conductivity, incombustibility, high processability, environmental friendliness, etc. at a relatively low cost. The use of such heat-insulating materials in construction allows solving the problems of energy saving, accessibility and cost-effectiveness. The article considers possibility of obtaining heat-insulating material based on sodium silicate (silicate glue “Polipax”) and natural material – flasks from Taskalinsky deposit of West Kazakhstan region. Technical characteristics of Polypax glue are given. Using a scanning electron microscope, elemental, chemical, and oxide compositions of the flask were studied. A recipe for a heat-insulating composite material (HCM) has been compiled.To assess the quality of the obtained HCM, its physical and mechanical characteristics were determined: density, water resistance, thermal conductivity, strength. Samples I-II in terms of density and strength showed the best results, and samples III-IV differ slightly from the technical conditions in terms of the studied indicators. It has been determined that the obtained HCM using flask as filler has a positive effect on the performance properties of the heat-insulating material, and is also economically viable, because local raw materials are used. Thus, it is possible to use flask from Taskalinsky deposit of West Kazakhstan region as filler for heat-insulating material. [ABSTRACT FROM AUTHOR]

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In this research, an attempt was made to investigate effects of expanded perlite aggregate grain size on consistency, density, compressive strength, thermal conductivity and microstructure of 15 different composite mixes with silica aerogel. As for the samples preparation, expanded perlite aggregate of 5 different groups based on grain size, were used for sample preparation, then partially replaced by volume for 20% and 40% of hydrophobic silica aerogel particles. The results showed, that density of the samples varied between 0.35 g/cm3 and 1.5 g/cm3, flexural strength varied between 3.4 MPa and 7.4 MPa, compressive strength was in the range between 12.3 MPa and 55 MPa, thermal conductivity coefficient was in the range between 0.130 W/mK and 0.190 W/mK. Scanning electron microscopy showed that expanded perlite aggregates and silica aerogel particles are capable of being mixed and formed homogenous mixture. Nevertheless, microscope images indicated weaker adhesion of silica aerogel particles at interfacial zone as compared with expanded perlite aggregate particles. Results revealed, that both of the factors: grain size of expanded perlite aggregate particles silica aerogel content influenced the density, compressive strength and thermal conductivity. The study also indicated feasibility of expanded perlite aggregate and silica aerogel for achieving homogeneous mixture of the lightweight cementitious composites. Study demonstrated that using different size fractions of expanded perlite aggregate affects differently physical, mechanical and thermal characteristics of the lightweight cementitious composite with silica aerogel. [ABSTRACT FROM AUTHOR]

In engineering, the phenomenon of heat transfer through cylindrical walls and various shells formed by the rotation of flat figures around a fixed axis is often used. Such structural elements are widely used in condensers of steam turbine installations, in the details of the flow part of gas turbines, rocket and aircraft engines. The article describes the solution of the problem of rational choice of thermal insulation material and its geometric characteristics when using thermal insulation to reduce heat losses from cylindrical surfaces. The results of the calculation of the thermal insulation of the pipe are presented graphically. The performed analysis allows us to formulate a generalized conclusion: a rational choice of insulation is possible only if an increase in its thickness is accompanied by an increase in the thermal resistance of the entire model.

In this study, Ficus elastica leaves have been reinforced into an epoxy composite and some physical and chemical characterization of the obtained composite is made. Ficus elastica leaves are ground between 297 and 149 microns. The biomass (Ficus elastica) prepared as a filler material is kept in sodium hydroxide (% 7 NaOH) solution for 24 hours for alkali activation. It is then washed three times with distilled water and dried in an oven at 75 °C for 3 hours. Composite production is carried out by reinforcing the prepared filler to the epoxy resin in certain proportions by mass. The effect of the biomass filler added at the rate of 0 wt.%, 1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% on the density, Shore D hardness, thermal conductivity coefficient, and activation energy of the epoxy composite is determined. According to the results obtained, the density of the epoxy composite decreases as the filler ratio in the mixture increases. Shore D hardness of epoxy composite decreases with the addition of biomass filler. The epoxy composite produced with biomass reinforcement reduces both the thermal conductivity coefficient and the activation energy. Besides, when the chemical bond structure of the obtained polyester composite is analyzed by Fourier transform infrared spectrometer (FTIR), it is seen that there is a physical interaction. According to scanning electron microscopy (SEM) images, 5 wt.% and 7 wt.% reinforcement of Ficus elastica leaves negatively affects the surface morphology of the epoxy composite.