Thermal Insulation Capacity Research Articles

Thermal Insulation Capacity of a 3D Printed Material

AbstractThe 3D printing process allows obtaining parts with different interior structures and made of different materials. Such parts can be used to avoid overheating of various objects under the action of thermal radiation. The existence of different internal structures of the parts, as well as the 3D printing conditions and the distinct physical properties of the materials used, determine a different behavior of the parts in terms of their thermal insulation capacity. To obtain an image of the thermal conductivity of thin parallelepiped‐shaped parts achieved by 3D printing, experimental research is conceived and materialized. The experiments involve the use of an infrared heat source, respectively, measurement of temperature on the surface opposite to that exposed to thermal radiation. The obtained results are mathematically processed to obtain empirical mathematical models that would highlight 3D printed parts' ability to be used as thermal insulating materials.

An analytical model for predicting residual stress in TBC-film cooling system considering non-uniform temperature field

Residual stress is an important parameter to evaluate and predict the interfacial peeling and failure of a thermal barrier coating (TBC) system in the thermal cycle. Considering a non-uniform temperature field, an analytical model for predicting residual stress of the TBC-film cooling system was established. Based on the double-layer TBC-film cooling system, the analytical solutions were validated by comparing with the previous results. Then, the four-layer system, including the superalloy substrate (SUB), the metallic bond coat (BC), the thermally grown oxide (TGO), and the ceramic top coat (TC), was analyzed. The distribution of residual stress was discontinuous at the interface among the layers. The maximum peeling moment occurred at the BC/SUB interface, and the maximum shear stress occurred at the TGO/BC interface. Therefore, the probabilities, of which opening edge cracks (mode I) appeared at the BC/SUB interface and shearing edge cracks (mode II) appeared at the TGO/BC interface, were higher than that at other interfaces. The deflection and bending direction of the system were affected by the temperature difference and coefficient of thermal expansions. The large thickness of the coating could effectively improve the thermal insulation capacity of the system, but the peeling moment and shear stress also increased. Therefore, preventing the thermal growth of the TGO layer and reducing the thickness of the TC layer can improve the stability of the system and extend service lifetime of the system while ensuring that the cooling requirements for hot section components are met.

Impact of phase change materials on lightened earth hygroscopic, thermal and mechanical properties

Climate change is leading construction engineers and building stakeholders to improve materials thermal insulation and heat storage capacity. The development of energy efficient building materials with a low environmental impact is a real challenge. In this sense, earth-based materials are known worldwide and have been used since thousands of years. These materials present many advantages but their deployment on a large scale, while respecting the operative standards, is still limited.Considering lightened earth, present work aims to improve their thermal properties by using phase change materials (PCM). The incorporation of PCM in construction materials has aroused great interest due to their capacity to store thermal energy.In present study, mechanical, hygrometric and thermal experimental studies were carried out on soil-fiber-PCM mixtures. The PCM incorporation showed an interesting improvement of the lightened earth thermal properties and a deterioration of the hygrometric properties while keeping their mechanical properties relatively unchanged.

Performance of particleboards based on annual plant byproducts bound with bio-adhesives

Because the timber market is more and more competitive, the particleboard manufacturers are looking for new sources of plant raw material. In the same time, the use of healthier, safer and more environmentally friendly materials becomes a priority in the building sector. In this context, using bio-based adhesives to bond the particles instead of the synthetic ones is an interesting alternative. In the same time agricultural byproducts as annual plant stems can be a sustainable alternative raw material. These resources are abundant, renewable and safe raw material. Moreover, their porous structure gives them interesting properties for building materials such as lightness and thermal insulation capacity. Two agricultural byproducts abundant in France have been studied: flax shives and sunflower bark. Particleboards were made at laboratory scale by thermocompression of the plant raw particles to a target density of 500 kg m−3. The plant particles were bond by different methods:- * without addition of any adhesive. In that case water was sprayed on the plant particles before the forming process and was evaporated during the thermocompression. It leads to extraction of soluble and lignocellulosic compounds from the agroresources that can act as adhesives.- * with addition of a biobased adhesive based on casein, the protein from bovine milk, or based on a commercial caseinate, added at different ratios to the plant particles.- The effect of the type of agroresources, the particle size, the formulation of the biosourced adhesive, and its application are evaluated testing the physico-chemical properties of the particleboards: mechanical properties (bending test and internal bond), thermal properties, and behavior towards water and fire. Using a biobased adhesive improves the mechanical properties of the particleboards significantly compared to the version without added adhesive. Panels made with flax shives generally showed better properties than with sunflower bark, so flax shives seem more suitable for particleboard manufacturing. But after optimization of the formulation and the process, both raw materials could be used with casein-based adhesive yielding efficient and fully biobased particleboards for applications such as furniture or door panels.

Assessment of Mechanical and Thermal Properties of Hemp-Lime Mortar.

The use of renewable and natural materials characterized by the low environmental impact is nowadays a key issue for the sustainable development of the construction industry. For this reason, the interest for natural fibers, to be used as reinforcement in composites as an alternative to other fibers, is continuously growing. In this paper, the use of hemp for reinforcing lime mortar used as plaster is considered with a multidisciplinary approach, taking into consideration the structural and thermal performance. Natural fibers have several advantages compared to industrial ones, such as low cost, low environmental impact, biodegradability, renewable nature. Moreover, these can show remarkable mechanical performance in relation to specific weight, and sometimes, as in the case of hemp fibers, these can improve the thermal insulation capacity of the plaster. However, the experimental results on the mechanical features are still lacking, especially to assess their durability, and the variability of thermal parameters with the mechanical characteristics. Therefore, this paper proposes an experimental program, developed at Laboratory of Materials and Structures (LAMAS) of the University of Sannio (Italy), aimed at investigating the main mechanical properties (compression strength, flexural strength) of lime mortar reinforced by hemp fibers and subjected to various environmental exposures and aging processes. The characterization is completed with the measurement for the produced samples of the thermal conductivity by means of the standardized guarded hot plate technique.

Preparation of the novel B4C–SiC composite aerogel with high compressive strength and low thermal conductivity

A novel B4C–SiC composite aerogel is synthesized using nano boron carbide suspension, 3-aminopropyltriethoxysilane (APTES), and resorcinol–formaldehyde (RF) as precursors through the sol–gel route and carbothermal reduction process. The effects of different B/Si molar ratios and calcination temperatures on the physical chemistry properties of B4C–SiC composite aerogels are investigated. The addition of the B4C phase is beneficial for improving the comprehensive properties of composite aerogel. The results show that the compressive strength of B4C–SiC composite aerogel is as high as 3.05 MPa. The specific surface area can reach 692.81 m2/g, which ensures that it has a thermal insulation capacity under elevated temperatures. After heat-treated at 1650 °C for 3 h, the thermal conductivity of carbon fiber mat reinforced composite aerogel is 0.058 W/m K (25 °C). This composite aerogel material has great application prospects in the field of high temperature insulation.

Heat transfer simulation across a building insulated with foam concrete wall cladding

Foam concrete is a light-weight concrete. It has high flowability, porosity, fire resistance, airborne sound insulation, good heat insulation, and a desirable compressive strength. The goal of this study is to produce thermal insulation foamed concrete cladding using cement, fly ash, and rice straw. Rice straw and fly ash were used to improve the thermal properties of foamed concrete. The present study analyses the thermal and strength properties of foam concrete. Numerical study to investigate the thermal insulation capacity using COMSOL software is also done. The w/s ratio of 0.55, fly ash cement ratio of 1:1 is fixed for all the specimens. The result shows that the mix with 1% rice straw (by weight of cement), 20% foam volume, is found to be optimum in terms of strength, thermal conductivity.

Mosses reduce soil nitrogen availability in a subarctic birch forest via effects on soil thermal regime and sequestration of deposited nitrogen.

In high‐latitude ecosystems bryophytes are important drivers of ecosystem functions. Alterations in abundance of mosses due to global change may thus strongly influence carbon (C) and nitrogen (N) cycling and hence cause feedback on climate. The effects of mosses on soil microbial activity are, however, still poorly understood. Our study aims at elucidating how and by which mechanisms bryophytes influence microbial decomposition processes of soil organic matter and thus soil nutrient availability.We present results from a field experiment in a subarctic birch forest in northern Sweden, where we partly removed the moss cover and replaced it with an artificial soil cover for simulating moss effects on soil temperature and moisture. We combined this with a fertilization experiment with 15N‐labelled N for analysing the effects of moss N sequestration on soil processes.Our results demonstrate the capacity of mosses to reduce soil N availability and retard N cycling. The comparison with artificial soil cover plots suggests that the effect of mosses on N cycling is linked to the thermal insulation capacity of mosses causing low average soil temperature in summer and strongly reduced soil temperature fluctuations, the latter also leading to a decreased frequency of freeze‐thaw events in autumn and spring. Our results also showed, however, that the negative temperature effect of mosses on soil microbial activity was in part compensated by stimulatory effects of the moss layer, possibly linked to leaching of labile substrates from the moss. Furthermore, our results revealed that bryophytes efficiently sequester added N from wet deposition and thus prevent effects of increased atmospheric N deposition on soil N availability and soil processes. Synthesis. Our study emphasizes the important role of mosses in carbon and nutrient cycling in high‐latitude ecosystems and the potential strong impacts of reductions in moss abundance on microbial decomposition processes and nutrient availability in subarctic and boreal forests.

Design feasibility of a net-zero energy neighborhood in Qazvin

Fossil fuel combustion to supply energy demand has significant effects on air pollution and global warming through an increase in environmental pollutants and greenhouse gases resulting in climate change, environmental deterioration, and spread of different diseases. In Iran, the high growth of annual consumption of various fossil fuels has triggered many environmental and socioeconomic problems, and the building sector with a share of 40% in energy consumption plays a significant role in energy consumption levels. The main aim of this study is to investigate how to decrease residential buildings’ energy demand through passive methods and substitute renewable energy for fossil fuel to supply energy for buildings in a framework of a net-zero energy neighborhood unit in Qazvin. The methods applied in this study were based on analytical method, causal study method, and simulation. In this study, DesignBuilder thermal simulation software is used to estimate the energy consumption decrease through the passive strategies. In addition, the buildings’ energy demand is supplied using renewable energy sources. Results show that improving the thermal insulation and heat capacity of housing materials can reduce energy demand by 31.5%. In addition, appropriate window shading and natural ventilation decrease the buildings’ annual energy consumption levels (32 residential units) at a rate of 2 and 17.5%, respectively. Furthermore, achieving the net-zero energy definition required 902 units of PV modules with nominal power of 256 W, as well as 24 solar collectors and their assimilation with the energy grid.

Behavior of a hemp-based concrete wall under dynamic thermal and hygric solicitations

Here we document the behavior at wall scale of a hemp-based hygroscopic material under various temperature and moisture dynamic conditions. The wall was made of precast hemp concrete (HC) blocks with air cavities. It was tested within a bi-climatic chamber and monitored thanks to hygrothermal sensors in the wall and in the chambers. The results from an in-house heat and moisture transfer model were compared to the experimental data, using the actual thermal and hygric characteristics of the hemp-based material determined in a previous study. The experiments allowed to demonstrate how the heat and moisture transport phenomena within the wall are coupled, particularly how a temperature difference can be a sufficient driving force for the release of moisture. The work points out the impact of moisture adsorption on heat release and on the temperature changes within the wall. Finally the numerical model served also to the modelling of an equivalent wall made of concrete to help highlighting the moisture dumping capability of the bio-based material, together with its thermal insulation capacity.

FIRE RESISTANCE OF STEEL AIR DUCTS WITH COMBINED FIRE PROTECTION SYSTEM

The results of research of fire resistance of steel air ducts with the combined system of fire protection in the conditions of fire influence according to the standard temperature regime according to DSTU B V.1.1-4 are resulted. Steel air ducts were investigated, in the design of which two fire protection systems were used, in which passive fire protection material material (fiberglass "IPS-T-1000") and reactive fire protection material materials ("Endotherm HT-150" and "Endotherm 250103") were used. The research method is applied, which is based on the provisions of DSTU B V.1.1-16. The essence of this technique is that the samples of steel ducts are installed in the vertical support structure of the furnace and exposed to fire. According to the obtained experimental data, the integrity and thermal insulation capacity of air ducts are evaluated. According to the results of the research, the peculiarities of temperature distribution on the unheated surface of air ducts in the conditions of fire influence and characteristics of fire resistance of steel air ducts with the combined fire protection system are determined. It is shown that the temperature is most important on the unheated surface of the duct near the place of its compaction in the vertical enclosingstructure. The temperature on the surface of the duct at a distance of 325 mm from the enclosing structure is several tens of degrees lower than the temperature on the surface of the duct at a distance of 25 mm from it. The period of time to achieve the loss of thermal insulation capacity of air ducts and the class of their fire resistance, which is EI 45. The direction of further researches which are focused on revealing of dependencesbetween a time interval before achievement of loss of thermal insulation capacity and thickness of layers of the combined system of fire protection for steel air ducts is defined. This detection will determine the optimalparameters of the combined fire protection system for steel air ducts, acceptable to ensure their fire resistance for a wide range of duration of fire exposure at a standard temperature.

Model-based design, synthesis and use of thermally insulating mortar formulations for energy conservation in buildings

Internally structured porous calcium-silicate-hydrate (CSH) particles were made by a sol-gel process using natural rubber as template. These particles were formulated in cement to produce mortar with excellent thermal insulation properties. The synthesis of CSH and its formulation in cement were comparatively optimized using response surface models based on central composite design (CCD) of experiments and artificial neural networks (ANN). CSH samples produced using a range of rubber/silica mass ratios (0.2–2.0) and hydrothermal processing temperatures (120–210 °C) were used to make CSH–mortars with various CSH/cement mass ratios (0.0–2.0). Thermal insulation capability of the different CSH–mortars was determined. Models based on CCD and ANN both achieved similar accuracy in predicting the insulating response. This notwithstanding, the ANN model identified optimal conditions for making a CSH–mortar that was cheaper and had nearly the same thermal insulation capacity as the optimal product predicted by the CCD-based model. The novel internally structured CSH particles were confirmed to greatly (∼3.4-fold) improve the thermal insulation performance of the CSH–mortars relative to controls.

Improvements in the thermal behavior in the manufacture of the H10 block using coffee husks as an alternative industrial additive

Industrial organic waste reuse in product manufacturing processes is a strategy that strengthens the circular economy. Thanks to materials science, the coffee husk is considered a sustainable alternative that promotes industrial processes optimization in the ceramic industry and contributes to the energy efficiency of buildings. This paper summarizes the behavior of H10 blocks on a laboratory scale in 2 mixtures of clay and coffee husk fired in 3 different temperatures: 900 °C, 1000 °C, and 1100 °C, at the “Centro de Investigación en Materiales Cerámicos, Universidad Francisco de Paula Santander”, Colombia; and evaluates the relationship of physical and mechanical properties with thermal behavior by heat transfer and heat fluxes, simulated in the analysis system software through the finite element method. The results support the improvement of thermal insulation capacity. Due to this, coffee husk combustion generates internal air chambers that increase the porosity of the product. In spite of, physical and mechanical properties contrast thermal benefits with increasing water absorption percentages and thus decreasing the compressive strength of samples. In conclusion, new materials development is a technological advance that expands possibilities to create new solutions for buildings and even improves standardized designs in the ceramic industry.

Towards the Use of Novel Materials in Shipbuilding: Assessing Thermal Performances of Fire-Doors by Self-Consistent Numerical Modelling

Nowadays, fire-doors optimization is approached by using consolidated design guidelines and traditional materials, such as rock wool. Then, selected solution is directly tested in a mandatory fire-test. Unfortunately, few pieces of information could be retrieved either if the test succeeds or fails, which makes both improvements in the design and use of innovative materials difficult. Thus, in this work, a self-consistent finite element method (FEM) analysis is developed and assessed against experimental fire-test results, highlighting the critical parameters affecting the numerical simulations. Using this tool, a new fiberglass-containing foam, with improved acoustic and mechanical properties, as compared to the rock-wool, is studied as a potential insulating material for on-board fire-doors. The assessment of the performance of the new material demonstrates that, contrary to common believe, the effective thermal insulation capacity is not necessarily the critical factor in determining the fire-resistance of a fire-door. Using the validated FEM analysis, it has been proven that the reduction of the thermal bridges originated at the door edges allows, firstly, for the attainment of a fire-door 37% thinner and 61% lighter with respect to a traditional one, and, secondly, the use of new material as insulator in fire-doors that, even if less thermally capable, could improve other properties of the door, as an example its soundproofing.

Thermal barrier coatings formed by flame-spray with metal–EDTA

Nowadays, the selection of a suitable spray method to design the coating microstructure such as its porosity, is key to effectively improving the properties of the base materials. In this study, the microstructures and thermal insulation capability of chelate flame-sprayed erbium oxide (Er2O3) and yttrium oxide (Y2O3) coatings directly deposited on aluminum alloy (A5052) substrates were investigated. A rotation apparatus and cooling agent (liquid nitrogen) were used during the synthesis to cool the substrate and control the deposited particles’ shape or form during film deposition. The results show that the Y2O3 coatings had higher thermal insulation capability than the Er2O3 coatings. It is worth noting that the thermal insulation capacity of the Y2O3 and Er2O3 coatings synthesized by cooling the substrate with liquid nitrogen was improved. For thicknesses of 90–128 μm and cross-sectional porosities of 12%–33% of the Y2O3 coatings, a temperature drop (ΔTf = 37 °C) of the porous structure Y2O3 coating at 440 °C and an increase from 0.10 to 0.32 of ΔTf per unit micron (°C μm–1) were observed. This was due to the coating having a more undulated layer surface and more complicated microstructures. Therefore, it is a new idea with the chelate flame-spray method to synthesize thermal barrier coatings on low-melting-point-metal materials.

The variations on thermal conductivity and structures of silty clay modified by waste fly ash and oil shale ash after freeze–thaw cycles

This study was to present changes on the thermal conductivity and structures of silty clay (SC) modified by waste fly ash (FA) and oil shale ash (OSA) after freeze–thaw (F-T) cycles, and discuss the thermal insulation capacity of modified silty clay (MC) and its main influencing factors. Firstly, the thermal conductivity of SC and MC at different moisture contents and dry density was measured after different numbers of F-T cycles. Secondly, the experimental study was conducted to analyze variations on the structure of MC after different numbers of F-T cycles. The test results of thermal conductivity show that: 1) the thermal conductivity of SC and MC decreases with the number of F-T cycles, and they would be constant after 20 F-T cycles; 2) the thermal conductivity of MC ranging from 0.765 to 1.134 W/m/K is lower than that of SC ranging from 1.277 to 1.747 W/m/K, indicating that MC possesses a certain thermal insulation characteristic. The structure analysis shows that: 1) during F-T cycles, the change trends on the micro-structure parameters, macropores and particle size of MC are different; 2) among the many factors which could cause variations on the thermal conductivity of MC during F-T cycles, the variation on macropores could be the main factor.

Isolation systems based on energy efficient basalt fiber wares

The article analyzes the properties of wares based on continuous and staple basalt fiber which offers high fire-resistance, thermal insulation capacity, vibrancy resistance, noiseproofing, as well as chemical durability including durability to arctic atmosphere and marine climate effects. That sort of fiber is a core for construction fabric, canvas and special-purpose products.The research findings of usage of modifying mineral additions as part of basalt working mass are reported. Modifiers’ introduction allows to decrease temperature interval of working mass’ melting by 80-100 ‘C. Herewith optimal melt’s amorphy degree is reached within the temperature range of working mass melting of 1400-1520 ‘C. It causes energy intensity’s reduction while manufacturing fabrics and the ability of using more technological smelting units and ways to rework the melt into a fiber.Fabrication of special buildings’ engineering structures isolation systems using basalt fiber fabrics, canvas and fire-resistant rolled materials which guarantees standard value of thermal resistance is proposed.

FEM-based evaluation of friction and initial imperfections effects on sandwich pipes local buckling

Sandwich pipes have been studied as one option to overcome the high pressure problems in deep and ultra-deep waters. They have become a possible alternative solution for submarine infrastructure due to its thermal insulation capacity. This contribute to preventing the pipeline from clogging due to the difference in temperature between reservoir fluids and water at the bottom of the sea. The pipelines in ultra-deepwater are continually exposed to severe operating conditions, such as the effect of high levels of external pressure that can cause local deformation or even collapse of the pipe. Thus, a greater understanding of the mechanical behavior of sandwich pipes is required. This paper presents a FEM-based evaluation of friction and initial imperfection effects on sandwich pipes local buckling. The non-linear evaluation was carried out in FEM of local buckling of two sandwich pipes, with polypropylene and cement as filled annular material. The influence of initial imperfections and the degree of friction, between the annular material and the steel pipes, as well as geometric variations of the pipe were considered. The numerical simulations results indicate a capacity to withstand ultra-deep waters collapsing pressures, around 3000 m, either for polypropylene or cement filled annular material model. In addition, the results indicate that the collapse pressure is inversely proportional to the increase in annular thickness and directly proportional to the decrease in friction which have an impact and contribution on the carrying capacity of the sandwich pipe. Further research will consider a design of experiments analysis of reported effects for different diameter-to-thickness ratios.

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

ДОСЛІДЖЕННЯ ВОГНЕСТІЙКОСТІ КАБЕЛЬНИХ ПРОХОДОК ІЗ ЗАСТОСУВАННЯМ РЕАКТИВНОГО ВОГНЕЗАХИСНОГО МАТЕРІАЛУ «ЕНДОТЕРМ ХТ-150»

Наведено результати дослідження вогнестійкості кабельних проходок, у конструкції яких застосовано реактивний вогнезахисний матеріал «Ендотерм ХТ-150». Використано методику дослідження, яка ґрунтується на положеннях ДСТУ Б В.1.1-8, ДСТУ-Н Б EN 1991-1-2, ДСТУ-Н Б EN 1992-1-2. Сутність цієї методики полягає у тому, що зразки кабельних проходок встановлюють у вертикальну опорну конструкцію печі й піддають вогневому впливу. За отриманими експериментальними даними оцінюють цілісність і теплоізолювальну здатність кабельних проходок. За результатами дослідження визначено характеристики вогнестійкості кабельних проходок, у конструкції яких застосовано реактивний вогнезахисний матеріал «Ендотерм ХТ-150». Встановлено, що конструктивні параметри цих кабельних проходок суттєво впливають на їхню вогнестійкість. Так, кабельні проходки, в яких кабелі прокладено у сталевих коробах з вогнезахисним покриттям реактивним матеріалом, відповідають класу вогнестійкості EI 150. Кабельна проходка, в якій кабелі з вогнезахисним покриттям реактивним матеріалом безпосередньо проходять через огороджувальну конструкцію, відповідає класу вогнестійкості EI 90. Визначено напрям подальших досліджень, які орієнтовані на виявлення впливу параметрів сталевого кабельного короба, огороджувальної конструкції, вогнезахисного облицювання із застосуванням реактивного вогнезахисного матеріалу і марок кабелів на вогнестійкість кабельних проходок.