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Housing in Algeria is experiencing a multi-dimensional crisis: crisis in design (standardization of housing), construction, financing, management, etc., which has a negative impact on user comfort, poor housing quality and high energy consumption.This article focuses on the study of the impact of different thermal insulation str ategies on energy consumption (heating and cooling) of a residential building situated in semi arid climate (Constantine northeast of Algeria) using thermal dynamic simulation tool (TRNSYS 16)

The aim of this work is to study the effect of the incorporation of wood ash from the combustion ofbiomass waste on the thermal properties of compressed earth bricks (BWA). These bricks were obtained as apartial substitution of the soil with different contents (0, 5, 10, 15 and 20% wt). The specimens manufacturedwere compacted with a compaction stress at 10 MPa, conserved in the laboratory at a temperature of 20 ± 2 °C,then allowed to harden for 7 and 28 days. The results showed that the partial substitution of the soil leads to adecrease in thermal properties.Thermal conductivity values were decreased to different soil substitutionproportions and with curing time. Minimum values were achieved for specimens containing 20% by weight ofWA, with better thermal insulation, at thermal conductivity values ranging from 0.78 W/mK in BWA at 28 daysand 1 W/mK in BWA at 7 days. This decrease was attributed firstly to the quantity of water consumed during thepozzolanic reaction that occurs between the soil components and the lime of the WA, secondly to themicrostructure of this soil used.

Recently, low-emissivity paint has gained more importance than commercial paints. Low emissivity (Low-E) Paint also termed as a coating for radiation control, in which the emissivity of radiations of longer waves are reduced dramatically (i.e., the emissivity of commercially available paint is 0.9) by imparting low emissivity particles in the base paint but not suitable to reduce near-infrared radiation. Commercially available paints as of today have minimum of 0.7 emissivity and it does not give any significant energy saving. The low emissivity property of paint makes it particularly suitable for reducing the radiative heat exchange in many domestic applications i.e., home electronics, building construction components, roof surfaces, heat storage tanks, and pipes, etc in result, low power required to heat or cool the building in respective whether conditions. In this work, different samples of white paint were prepared in the lab by using a low shear mixer (mechanical stirrer) under very controlled conditions and studied the results of dry paint films to reduce the thermal emissivity then commercially available paint. Then we investigate the drying time of the wet paint films and analyze thermal heat into visible light through thermal imaging camera, Crosshatch, and IR transmission. We also studied the emissivity through ET-100 and aging stability through a weather-o-meter instrument, which investigated that emissivity value achieved in the range of 0.4–0.6 than commercial paints. The results showed that paint exhibits an acceptable aesthetic emissivity value of ∼0.60. It was calculated theoretically that by the use of this novel Low-E paint, annually about 20%–25% less energy will be consumed in building for cooling or heating. The Open Access funding is provided by the Qatar National Library, Al Rayyan Doha Qatar . We are also thankful to everyone who supported and assisted us in completing this work. Our appreciations and thanks also go to our colleagues and laboratory engineers at National Textile University, Faisalabad, Pakistan and also Northwestern Polytechnical University, Xi’an, China.

This study numerically simulated and investigated the flow field characteristics of a typical dual-pulse solid rocket motor with a soft pulse separation device through thermal insulation ablation under high-temperature dual-pulse erosion. The ablation rate of ethylene -propylene-diene monomer (EPDM) insulator was measured after the experiment. Experimental results were analyzed through scanning electron microscopy and microcomputed tomography. The ablation mechanism of the EPDM insulator under the operation conditions of a dual-pulse solid rocket motor was evaluated by analyzing the results. The results reveal that the internal flow field of the motor with a soft pulse separation device is uniform. The original charred layer existing on the EPDM insulator surface in the first pulse combustor is the decisive factor affecting the final ablation rate of the dual-pulse motor during the second pulse operation, and the ablation characteristic region is easily formed with the exfoliation of the charred layer. The ablation rate difference of the insulator increases with gas velocity.

Global warming has become one of the major environmental problems facing mankind in the 21st century. The existing refrigeration technology of buildings, like air conditioning, consumes a lot of energy. Passive daytime radiative cooling technology works without consuming energy, nor emitting carbon dioxide and other greenhouse gases. This review summarizes the development of daytime passive radiative cooling technology from the basic principles, structure and materials of radiative coolers; analyses and evaluates the various existing radiative coolers. The core of radiative cooling lies in the combination of multi-scale micro/nano structures. The cooler reflects sunlight thus preventing the building from being heated up; while allows the building to radiate its own heat out thus being cooled down; meanwhile maintains the temperature difference by the heat insulation effect of the porous structure in the film. The common challenges and potential solutions for the commercialization of radiative cooling technologies are analyzed, which may promote the applications of the technology in the near future.

The building sector accounts for nearly 40% of global energy consumption. In Nigeria, more than two-thirds of the consumption comes from residential buildings. Energy efficiency measures through the adoption of insulation materials are tools that could crash the peak demand of energy in buildings while improving its thermal comfort and aerogel is considered as the most effective material for insulation, owing to its unique thermal properties. In this paper, we present the performance of aerogel as a thermal insulation material towards a sustainable design of residential buildings for tropical climates in Nigeria. First, a typical residential building in the tropical region was modeled with conventional materials utilized in the region and was later modified through the application of aerogel material on various surfaces of the model. A whole building energy simulation was then carried out in each variation and the outcome was compared to effectively conclude on the significance of aerogel in terms of thermal comfort improvement and energy consumption reduction. Results show that aerogel had the highest influence when inserted in the attic and floor slabs of the designed model. A reduction of more than 6% was attained in the recorded indoor mean air and operative temperatures while still maintaining an acceptable humidity range. Concerning energy consumption, a reduction of more than 15% was achieved. However, the high price of aerogel may hinder its application on the studied building but could be a good investment where climate change and sustainability are of high importance and less concern is given to expenditure. Aerogel demonstrated significant potential with respect to both thermal comfort improvement and energy consumption reduction on the designed model. The outcome of the study is hoped to serve as a base reference for the insulation of residential buildings with similar climate and characteristics to the adopted case building.

Natural gas hydrate (NGH) holds great promise as a source of clean energy. It is critical for acquiring the largest possible in situ NGH core for NGH eigen features and resource assessment. However, the existing NGH coring technology has limitations, such as temperature increments, limited coring diameters, low coring rates, and complex coring structures. Therefore, this study designs and proposes an NGH freezing coring (NGHFC) method and verifies the freezing and coring capacities of the NGHFC method in laboratories and experimental wells. Results suggest that NGHFC shows good freezing and heat-retention properties. A freezing core heat transfer model is developed. According to the actual air temperature and operating time, the optimum initial temperature of the cold source can be determined using this model. The average coring rate of NGHFC can reach 77.86 %. The research results will provide a new idea of coring gas hydrates.

Eco-friendly materials with superior thermal insulation and mechanical properties are desirable for improved energy- and space-efficiency in buildings. Cellulose aerogels with structural anisotropy could fulfill these requirements, but complex processing and high energy demand are challenges for scaling up. Here we propose a scalable, nonadditive, top-down fabrication of strong anisotropic aerogels directly from wood with excellent, near isotropic thermal insulation functions. The aerogel was obtained through cell wall dissolution and controlled precipitation in lumen, using an ionic liquid (IL) mixture comprising DMSO and a guanidinium phosphorus-based IL [MTBD][MMP]. The wood aerogel shows a unique structure with lumen filled with nanofibrils network. In situ formation of a cellulosic nanofibril network in the lumen results in specific surface areas up to 280 m2/g and high yield strengths >1.2 MPa. The highly mesoporous structure (average pore diameter ∼20 nm) of freeze-dried wood aerogels leads to low thermal conductivities in both the radial (0.037 W/mK) and axial (0.057 W/mK) directions, showing great potential as scalable thermal insulators. This synthesis route is energy efficient with high nanostructural controllability. The unique nanostructure and rare combination of strength and thermal properties set the material apart from comparable bottom-up aerogels. This nonadditive synthesis approach is believed to contribute significantly toward large-scale design and structure control of biobased aerogels. QC 20221019

The materials with thermal insulating and fire-retardant properties are highly demanded for architectures to improve the energy efficiency. The applications of conventional inorganic insulating materials such as silica aerogels are restricted by their mechanical fragility and organic insulating materials are either easily ignitable or exhibit unsatisfactory thermal insulation performance. Here, we report an organic/inorganic composite aerogel with integrated double network structure, in which silica constituent homogeneously distribute in the anisotropic polyimide nanofiber aerogel matrix and strong interfacial effect is formed between two components. The integrated binary network endows the polyimide/silica composite aerogels with outstanding compressibility and flexibility even with a high inorganic content of 60%, which can withstand 500 cyclic fatigue tests at a compressive strain of 50% in the radial direction. The resulting composite aerogel exhibits a combination of outstanding insulating performance with a low thermal conductivity (21.2 mW m−1 K−1) and excellent resistance to a 1200°C flame without disintegration. The high-performance polyimide/silica aerogels can decrease the risk brought by the collapse of reinforced concrete structures in a fire, demonstrating great potential as efficient building materials.

According to the few researches on Nearly zero energy residential buildings (NZERB) in hot-summer and cold-winter zone, although it could reduce the cooling load of buildings due to its high thermal insulation and air tightness, it still needed for certain cooling in summer. This paper studied indoor environment of NZERB under three kinds of air-conditioners (split-type air-conditioner, multi-line air-conditioner and ceiling radiant air-conditioner). Firstly, a simulation model of NZERB was established based on Nanjing, a typical city in hot-summer and cold-winter zone. Secondly, variation of indoor air temperature and building load characteristics with outdoor air temperature were studied. Thirdly, indoor environment and energy consumption under three selected conventional air-conditioners in summer were simulated. Finally, the discussion was given, and an air-conditioner combining with convective and radiant cooling were proposed. The results indicated that the air-conditioner needed to be turned on in NZERB in hot-summer and cold-winter zone due to the room air temperature in off-air condition ranged from 32 °C to 36 °C, which was higher than designed indoor environment temperature in summer, but the indoor environment of NZERB under three selected conventional air-conditioners could not meet the requirements of energy saving and comfort at the same time, and a proposed convective-radiant air-conditioner could be fast, stable, and energy saving. The findings can provide a reference for conducting active technology in NZERB.

Both obsidian and perlite belong to acid volcanic rock and have a similar structure and chemical composition, but the insulation material prepared from expanded obsidian cannot reach the performance level of that prepared from expanded perlite. To date, obsidian cannot be used in large quantities, although its resource is abundant. In order to comprehensively utilise this resource, in the present work the authors developed a new type of lightweight thermal insulation material by using obsidian as a main raw material which is energy-efficient and environmentally friendly. The effects of raw materials such as obsidian, sodium silicate, hydrogen peroxide and cetyltrimethylammonium bromide on physical properties including thermal conductivity, porosity, density and compressive strength were studied in detail. The optimised thermal insulation material exhibits low thermal conductivity (0.051–0.86 W m−1 K−1), low density (0.1–0.24 g/cm3) and adjustable compressive strength (0.09–1.52 MPa). Compared to other inorganic insulation materials, this new thermal insulation material is very light and has a better thermal insulation performance. Therefore, this work proposes a new energy-efficient way to prepare a promising noncombustible thermal insulation material, and also provides a way to use obsidian resources in large quantities.

This work demonstrates the substantially improved thermal radiation blocking capability of polymer foams with the utilization of carbonaceous nanoparticles to overcome the limitation of the nanocellular foam's thermal insulation capability to achieve superinsulation. Without carbon, the radiation heat transfer becomes extremely high through thin and transparent cell walls and struts of the low-density nanocellular foams. However, this high radiative heat transfer can be successfully reduced by incorporating multi-walled carbon nanotubes (MWCNTs). The effect of carbon on heat transfer in foams was mathematically modelled and experimentally verified. The model includes contributions of thermal transport through conduction and radiation, while convection is negligible. The effects of MWCNTs on thermal conductivity, refractive index, absorption index, dielectric permittivity and dielectric loss of the solid were studied using two examples of polystyrene/MWCNT and PMMA/MWCNT nanocomposite foams. It was found that, with carbon, the radiation blocking capability is significantly improved and nanocellular foams could achieve superinsulation level through the Knudsen effect. The optimal cellular structure at which heat transfer is minimized was investigated with the aim of manufacturing superinsulation. The foam's total heat transfer decreased while the optimal expansion ratio increased with the filler content, which is preferable for manufacturing high performance insulation with less polymer.

Polystyrene (PS) is rich in plastic materials, but it produces a large amount of waste every year, causing a huge burden on the environment. Although PS plastic is the source of a common "white pollution" in daily life, it still has a high utilization value. At the same time, the flammability of PS material determines that it cannot be applicated in places where fire accidents occur frequently. As a result, its application has been greatly limited. In order to realize the efficient utilization of waste PS and broaden its scope of application, PS was modified by hyper-crosslinking in order to improve its fire-retardant performance. In this method, the PS solution with high purity was obtained by dissolving waste PS foam with 1,2-dichloroethane (DCE), and then the hyper-crosslinked polymer with high specific surface area was prepared by adding cross-linking agent formaldehyde dimethyl acetal (FDA) and a Lewis-acid catalyst ferric chloride (FeCl3). Further studies showed that the effects of the amount of cross-linking agent FDA, catalyst FeCl3 and PS on the reaction products were different. In addition, compared the as-prepared fire-retardant materials with PS foam from the aspects of flame retardancy and thermal insulation, it can be concluded that the fire-retardant performance of the materials prepared by this method has been significantly enhanced. And it is proved that this method is feasible towards the preparation of a large number of fire-retardant composite materials by using a scale-up experiment.

Carbon aerogels with nanoporous structure are attractive for thermal insulation under extreme conditions, but their practical applications are usually plagued by the inherent brittleness and easy-oxidation characteristic at high temperature. Herein, silica-modified carbon aerogels (SCAs) with extraordinarily high strength are prepared via a facile sol-gel polymerization of phenolic resin and siloxane, followed by ambient pressure drying and carbonization. The resulting SCAs possess medium-high density of ∼ 0.5 g·cm-3 and mesoporous structure with the mean pore size of 33 nm. During carbonization process, the siloxane could be gradually transformed into the amorphous SiO2 particles and crystalline SiC particles, which are coated on the surface of carbon nanoparticle and consequently improve the oxidation-resistance of carbon aerogels. Due to the density-porosity trade-off, the SCAs have high compressive strength of 10.0 MPa and satisfied thermal conductivities of 0.118 W·m-1·K-1 at 25 °C and 0.263 W·m-1·K-1 at 1000 °C. Furthermore, needled carbon fiber-reinforced SCAs (CF-SCAs) with ultrahigh compressive strength of 210.5 MPa are prepared, which exhibit good thermal conductivities of 0.207 W·m-1·K-1 at 25 °C and 0.407 W·m-1·K-1 at 1000 °C. The ultrahigh mechanical strength, good oxidation-resistance, good thermal insulation as well as the facile preparation make the SACs great promising in high-temperature insulations especially under harsh conditions.

Inorganic fibers and opacifiers are indispensable for improving the strength and high temperature insulation performance of the fumed silica-based thermal insulation material. However, zirconia fiber enhances the strength of the fumed silica-based thermal insulation material and reduces the radiative heat transfer to replace the opacifier. The sample of fumed SiO2/Al2O3 doped with 7% zirconia fiber (FZ7) has a lower density of 0.70 g/cm3 and a high porosity of 75.0%. In addition, the thermal conductivity of FZ7 at 800 °C is 0.077 W/(m·K), which is lower than the sample of fumed SiO2/Al2O3 doped with 7% glass fiber (FG7) and 0.089 W/(m·K) at 800 °C. The effective extinction coefficient of the thermal insulation material containing zirconia fiber is larger than that of the glass fiber by Fourier transform infrared spectroscopy analysis and calculation, indicating that the zirconia fiber has a distinct absorption and scattering effect on infrared radiation to reduce the radiative heat transfer. Therefore, zirconia fiber enhances the strength and decreases the high temperature thermal conductivity of the composites with the dual effect on the insulation and mechanical performance of the fumed silica-based thermal insulation material.

Porous mullite ceramics are potential advanced thermal insulating materials. Pore structure and purity are the main factors that affect properties of these ceramics. In this study, high performance porous mullite ceramics were prepared via aqueous gel-casting using mullite fibers and kaolin as the raw materials and ρ-Al2O3 as the gelling agent. Effects of addition of mullite fibers on the pore structure and properties were examined. The results indicated that mullite phase in situ formed by kaolin, and ρ-Al2O3 ensured the purity of mullite samples and mullite fibers bonded together to form a nest-like structure, greatly improving the properties of ceramic samples. In particular, the apparent porosity of mullite samples reached 73.6%. In the presence of 75% of mullite fibers, the thermal conductivity was only 0.289 W/m K at room temperature. Moreover, the mullite samples possessed relatively high cold compressive strength in the range of 4.9–9.6 MPa. Therefore, porous mullite ceramics prepared via aqueous gel-casting could be used for wide applications in thermal insulation materials, attributing to the excellent properties such as high cold compressive strength and low thermal conductivity.

The consequences of extreme energy consumption are seen both in the energy and environmental crisis. Subsequently, researchers are attempting to find methods to address this issue. Building envelopes and insulation materials are elements that can effectively influence consumption through their passive effect on thermal comfort levels. Strategies pertaining to this that rely on both, advanced and traditional materials, have been able to show good potential. However, the technical complexity of using such strategies can be impeded from the perspective of developing countries. With the aim of creating effective low-cost feasible insulations through using methods of minimal intricacies, the potentials of simple amalgamation of materials are empirically investigated in this study. In this context, closed-cell rigid Polyurethane (PU) foam is used as a base to hold phase change materials (PCMs) to create two PU/PCM panels, of different PCM content. The thermal performance of the panels is experimentally examined and compared, with hot-arid climates prevailing in developing countries in mind. Results revealed that panels containing PCMs were able to perform more effectively in comparison with regular PU foam panels, and, that increasing the amount of PCM has also shown to be advantageous in this regard.

Growing interest in liquefied natural gas (LNG) as a rocket fuel demands reliable prediction and an improved understanding of the changes in its composition arising from the preferential boil-off of lighter components during long duration storage. Unfortunately, current methods of predicting boil-off gas (BOG) evolution from cryogenic liquids are based on limited experimental data. This work reports a series of new experiments which measure the temporal change in BOG production, composition, and pressure at industrially relevant conditions for both ternary mixtures of methane, ethane, and nitrogen and an LNG mixture used as rocket fuel. Faster pressure build-up rates are consistently observed with decreasing initial liquid volume fraction, whilst a decline of 8% in the LNG higher heating value was observed after thirty-three days of weathering. The data is compared with a robust and efficient superheated vapor (SHV) model, implemented in the software package BoilFAST, which allows for reliable calculations of self-pressurisation and boil-off losses for different tank geometries and thermal insulation systems. The model exhibits good agreement with the experimental data across all conditions explored. Finally, the potential effect of LNG composition and heating value changes on rocket engine performance was assessed by examining changes in the adiabatic flame temperature and burnt gas volume ratio. While our data suggest that the rocket engine performance would improve as a result of weathering, the effectiveness of the weathered LNG as a coolant in a regeneratively cooled rocket engine decreases.

Improving the mechanical property of the silicon aerogel while maintaining its excellent thermal insulation performance is still a big challenge in developing the next-generation thermal insulation materials. To solve this problem, the optically active polyurethane aerogel composite is developed via the sol-gel method to combine the advantages of the thermal insulation performance of the silicon aerogel and the mechanical property of the end-capped siloxane optically-active polyurethane. The prepared composite is characterized by the scanning electron microscopy, the Fourier transform infrared spectroscopy, the absorption-desorption curve, the thermal analysis, and the mechanical property. Results show that the composite has intact pores with high surface area and pore volume, leading to excellent thermal insulation and mechanical performance. Moreover, its thermal insulation performance is greatly enhanced due to the better distributed small pores and the thermal reflective effect of binaphthyl groups which collaboratively block heat loss from thermal conduction and thermal radiation. The thermal stability is similar to silicon aerogel and its heat resistance temperature is 445℃. The addition of macromolecular polymers increases the contact points between particles, the contact areas between particles of the network skeletons, and the supporting effect of the skeleton material, which ensures the stability of the material structure. The compressive modulus of prepared composite is up to 2.465 MPa, which is 600 times more than that of the pure SiO2 aerogels.

The dimensions 0.3 × 0.3 × 0.1 m, composed by the reinforced concrete (RC), prestressed concrete (PC), and Polypropylene reinforced concrete (PRC) and 28 days the strength & precise temperatures measured along surfaces. Mathematical models were planned to forecast concrete strengths when acquainted with thermal flare because numerous mechanical tests like compressive, tensile, flexural strengths and density are performed. Mechanical properties of various mixes of concrete beneath the effect of fireplace flame exposure are presented. Three distinct concrete mixes are prepared. The Bi-material concrete parts were subjected to fireplace flame temperatures travel from room temperature (27 °C) at completely different ages of thirty, sixty and ninety days. At numerous heat levels of 400 °C, 600 °C and 850 °C were elected to exposure length of 2.0 h. When the hearth performance, concrete specimens were quenched in an exceedingly water tank to supply the most tremor because of sharp freezing. The experiment demarcates that the PC explosive ¼ hour after test start spalling begins. The panels with Polypropylene and RC panels maintained their integrity and structural stability for 4 h, failing in the thermal insulation criteria at 3¾ hours and 2¼ hours, respectively. The polypropylene panels depict no spalling of concrete, compared to control concrete for a more extended period and thermal insulation because of suitable properties.

Core-shell ceramics fibers with multiple composition are ideal candidates for thermal insulation application at high temperature. Herein, ultrathin C–SiC/ZrSixOyCz core-shell fibers were successfully fabricated by coaxial electrospinning and high temperature pyrolysis with polycarbosilane (PCS) as core precursor and Zirconium butoxide as shell precursor, respectively. The ceramics fibers revealed distinct core-shell partition. The average diameter was about 3 μm and the shell thickness increased to 500 nm with increasing pyrolysis temperature. Thermogravimetry analysis (TGA) results showed that the weight of the fibers reduced to 60% in Ar atmosphere and rose to 108% in O2 atmosphere, which confirmed the excellent thermal stability and anti-oxidation properties due to the protection effect of shell layer and the self-healing mechanism. Moreover, the ceramics fibers maintained good flexibility and deformability. Such optimized anti-oxidation and mechanical performance indicates that the prepared core-shell fibers could be an excellent thermal insulation material for high temperature application.

The thermal performance of the building depends on the design and construction characteristics of the walls that interact with the external climate factors and that play a role in creating the thermal environment. Therefore, the current study aims to improve the thermal performance of the building walls by building hollow (double) walls and finding the optimal thickness of the air gap between the walls used as thermal insulation to improve or reduce heat gain, and thus reduce cooling loads. Experiments were carried out on different days in the summer on a model room of sandwich panel with dimensions of 2 m length, 2 m width, 2.4 m height (32.5 latitude) kut city, Iraq. In the southwest wall, two holes were made, the dimensions of these two holes (1 m length, 0.3 m width). Six models of hollow (double) walls were built in these two openings with air gap of 1,2,3,4,5,6 cm thickness . Each model of these walls contains three air gap separated from each other by a layer of cork. The experimental results showed that the greater the thick of the air gap gave the smaller amount of heat gain, therefore, the optimum thickness of the air gap was 6 cm, which gave 19.45 % heat gain reduction more than that of 1 cm thickness.

Solar ponds are systems that store solar energy in salt water as heat energy. In order to store heat energy for a long time in solar pond, the heat insulation should be done well. In this study, the effect of phase change materials was investigated to improve the insulation of the pond and to store the heat energy for a longer time. The melting temperature is a key parameter in the selection of phase change materials. The temperature distribution of the solar pond was examined and phase change materials with melting temperatures in the range of the pond average temperature ?10?C were selected. Three different phase change materials were used in the walls of the solar pond for insulation. The temperature and enthalpy changes of the system were calculated numerically for a year. The heat storage ratio of the solar pond was determined by using the obtained enthalpy and solar radiation data. Consequently, the heat storage ratio of the pond with glass-wool is maximum 20.95% in July and minimum 7.92% in January. The heat storage ratio of the solar pond which paraffin C18, capric acid and paraffin 44 are used as phase change materials is maximum 32.22%, 34.85%, and 47.81% in December, respectively. It is observed that the appropriate selection of phase change materials is provided a longer storage time for solar ponds.

Thermal energy has been considered to propagate by wave-like phonons with well-defined wave vectors in crystalline materials. In this work, we demonstrate a completely different thermal conduction scenario in crystalline rare earth niobates, RE3NbO7 (RE=La, Nd, Sm, Eu, Gd), having ultralow thermal conductivities of 1.0–1.5 Wm-1K-1. Especially, the rare earth niobates exhibit glass-like temperature dependence of thermal conductivity from room temperature to 1273 K, indicating significant suppression of both phonon and radiation heat transfer. According to Cahill model based on amorphous theory, minimum thermal conductivity of rare earth niobate was calculated. It is shown that the glass-like thermal conductivity result from a wide range of amorphous solids due to phonon scattering by multiple lattice imperfections. Furthermore, phonon mean free path of RE3NbO7 is comparable to the atomic spacing of crystal indicating that energy carried by phonons can only transmission between a few atomic spacings leading to the ultralow thermal conductivity. The mechanical properties of rare earth niobates are also discussed.

Thermal protection materials with excellent thermal insulation properties and high reliability are crucial for aerospace vehicle. Mullite fiber insulation tiles coated with MoSi2-borosilicate glass (MFIT@MoSi2) were prepared by a simple slurry method. Results shown that the surface temperature rapidly reached 1043.1 °C under the heat flux of 450 kW/m2, while the cold-surface remained at room temperature. The adjusting effects of MoSi2-based coating on the thermal response and transfer properties of MFIT were investigated systematically. Compared with MFIT, the surface and internal temperatures of MFIT@MoSi2 were obviously suppressed, due to the existence of MoSi2-based coating with high emissivity, which effectively enhanced the thermal radiation of the surfaces. Finally, the structural reliability under coupled environment of heating (q0 = 450 kW/m2) and random vibration with high magnitude (20–2000 Hz, Grms = 20 g) was also investigated. Destructive cracking and peeling of the coating were not observed, due to the excellent bonding strength between the coating and the substrate. The results provided an important basis for the potential application of insulation tiles with mullite fibers in aerospace vehicles and the design of lightweight thermal protection systems.

Pore structure is one of the major factors influencing the failure mechanisms of thermal barrier coatings (TBCs) during high-temperature service. Powders exhibiting different pore structures have been produced using the plasma spheroidization technique. To improve the strain tolerance of an aircraft engine's hot sections, the preparation method of the TBCs material—8-wt% yttria-stabilized zirconia powders—has been continuously optimized. In this paper, the constrained effects of pores on the ceramic top coating of plasma-sprayed lamellar TBCs were investigated. Furthermore, the crystal phase structures, thermophysical properties, porosity, microstructures, and synthesis mechanism of powders and coatings were analyzed. Results revealed that the top ceramic coating, which was made from powders cooled by air and distilled water, can influence the coating porosity. Moreover, thermal insulation was substantiated by the finite element analysis method. Consequently, dense powders cooled by water can be used on the top surface in direct contact with high temperature flame flow to resist the diffusion of oxides, and the porous powder cooled by air can be applied in the middle coating to decrease the thermal conductivity. Hence, TBCs with various layers of different porosities can prolong the service life of thermal barrier coatings.

In this study, a new type of highly porous ceramic was successfully fabricated from α-Al2O3 whiskers and nano-sized Al2O3 particle slurry by vacuum infiltration with the subsequent annealing in air. It was found that with an increase in the alumina slurry amount or sintering temperature, the porosity of the foam ceramic decreased while its compressive strength increased. The optimal alumina slurry content and sintering temperature were equal to 4 g, and 1350 °C, respectively. The as-synthesised porous foam ceramic exhibited a low density of 0.65 g/cm3, high porosity of 83.51%, high compressive strength of 3.84 MPa, and low thermal conductivity of 1.37 W/m⋅K at room temperature, suggesting its potential applications in high-temperature gas filtration and thermal insulation materials.

Perlite is one of the major constituents of the radioactive thermal insulation waste (RTIW) originating from nuclear power plants and, for proper waste management, a significant reduction in its volume is required prior to disposal. In this work, the volume reduction of perlite is studied by high-temperature treatment method with using K2CO3 as a flux. The perlite is ground with 0–30 wt% K2CO3, and differential thermal analysis/thermogravimetric analysis is used to monitor the glass transition temperature (Tg) and weight loss. The Tg varied between ~772.2 and 837.1 °C with the minima at ~643.5 °C with the addition of ~10 wt% K2CO3. It is observed that compared to the pure perlite the volume reduction ratio (VRR) increases with the addition of K2CO3. The VRR of 11.20 is observed with 5 wt% K2CO3 at 700 °C, as compared to VRR of 5.56 without K2CO3 at 700 °C. The X-ray photoelectron spectroscopy and scanning electron microscopy are used to characterize perlite samples heat-treated without/with 5 wt% K2CO3 at 700 °C. Moreover, the atomic absorption spectroscopy indicates that the proposed heat-treatment procedure is able to completely retain the radionuclides present in the perlite RTIW.

An updated method of heating calculation of buildings operated in the conditions of intermitt ent heating is considered. On the basis of the conducted studies, analytical dependences were obtained for determining energy consumption during heating of building enclosing structures, taking into account the infl uence of the order of location of thermal insulation and structural layers, as well as temperature changes during heating of each layer. Formulas for fi nding the change in the temperature of the internal air during the heating of the premises and the internal surface of the enclosing structures are obtained. On the basis of the proposed refi ned methodology, the calculation of the heating of the living room of a country cott age located on the territory of the Samara region was performed.

Актуальность исследования обусловлена необходимостью рудников решать новые проблемы нормализации микроклимата, возникающие при проходке все более глубоких и нагретых породных массивов протяженными тупиковыми выработками. Цель: определить эффективность различных способов нормализации микроклимата в забое разведочной выработки-2 ПАО «ГМК "Норильский никель"». Объекты: геологоразведочная выработка-2 ПАО «ГМК "Норильский никель"». Методы: численное моделирование тепломассопереноса в атмосфере горной выработки, проведение сравнительного анализа результатов моделирования. Результаты. Рассмотрены способы нормализации микроклимата в глубоких протяженных тупиковых выработках, их особенности, преимущества и недостатки. Представлена математическая модель тепломассопереноса в атмосфере горной выработки с вентиляционным трубопроводом, учитывающая конвективный и лучистый теплообмен. Представлены результаты расчета различных способов снижения температуры воздуха, подаваемого в забой геологоразведочной выработки, строящейся на медно-никелевом руднике компании ПАО «ГМК "Норильский никель"». Проведен сравнительный анализ различных горнотехнических и теплотехнических мероприятий по снижению температуры воздуха в забое выработки до значений, допустимых согласно Правилам безопасности. Выявлено, что увеличение объема подачи воздуха не позволяет значительно снизить температуру в забое. Применение теплоизолированного вентиляционного трубопровода существенно снижает температуру подаваемого в забой воздуха, но её значение по-прежнему остается выше допустимых значений. Показано, что использование камеры орошения позволяет обеспечить допустимую температуру воздуха в зимний период, но не позволяет обеспечить её в летний период. Наиболее универсальным, эффективным, но дорогостоящим способом снижения температуры воздуха является применение подземных систем кондиционирования воздуха на базе парокомпрессионных машин. The relevance of the research is provided by the complexity of microclimate normalization in long blind drifts which are driven deeply through geothermally heated rocks. The aim of the research is the evaluation of usability of different ways for microclimate normalization in the working section of the exploration drift-2 in the mine of PJSC «MMC "Norilsk Nickel"». Objects: the exploration mine exploration drift-2 of PJSC «MMC "Norilsk Nickel"». Methods: the numerical simulation of heat and mass transfer in the atmosphere of the long exploration drift, the comparative analysis of simulation results. Results. The paper reviews ways, comparing their features, advantages, and disadvantages, for microclimate normalization in deep blind drifts. The presented mathematical model describes the heat and mass transfer in the working section of the blind drift with ventilation through the air duct. The model considers convective and radiant heat transfers. The results of the numerical simulation are given for different air-cooling methods which are applicable in the case of the deep copper-nickel mine of PJSC «MMC "Norilsk Nickel"». Drawing on this, different mining and thermal engineering operations for normalization of air temperatures in the working section regarding safety requirements are compared. It is defined that increasing the intake air flowrate could not decrease the air temperature near the face. The use of thermally insulated duct significantly decreases the air temperature in the working section but does not reduce it to the permitted value. It is shown, that the air irrigation could normalize temperatures in winter and not during the summer months. Underground air conditioning is the most universal and effective way for this purpose but highly expensive.

Now a days, the global warming has increased the temperature in the environment that forced the building occupant to get assisting from the air condition to reduce the heat tension inside the building, this could increase the electricity bill amount. The aim of this study is to measure the optimum thickness of Rockwool insulation to experimentally and numerically to reduce the heating load inside the buildings. Two devices have been used through this research, Infrared Thermometer to measure profile temperature of the walls along with VELOCICALC to measure the air temperature and air velocity. Three different layers of Rockwool insulation have been applied on the roof of wooden room. The data present the two layers thickness of Rockwool is the best selection to reduce the heating load inside the room, the differential between outside and inside is 0.9 °C, the Rockwool of one layer reduced only 0.5 °C and the maximum thickness with three layers reduced only 1 °C, which is not much effective compared to the two layers but even more costly. CFD analysis shows agreement with the experimental result. The results shows if the dimensions of a UCSI lecture room is to be considered, then applying Rockwool insulation with a thickness of 100 mm would cost around RM 1520 as a UCSI lecture room is of 8 m width and 9 m length. However, two layers of Rock wool insulation could save around 29.30% of ROI per annum.

In recent years, prefabricated structures have been widely constructed to reduce construction costs and time. In this study, a new type of prefabricated structure, lightweight concrete-filled steel tubular (CFST)-framed building assembled with microcrystalline foam boards (MFBs), was developed. The MFBs exhibited high strength, heat insulation, soundproof, light weight, fireproof, and ecofriendly characteristics. The MFBs were combined with light steel keels and connected to the CFST frame with flexible and rigid connections. Shaking table tests on a full-scale, two-story, single-span lightweight CFST-framed building assembled with MFBs as exterior wallboards were performed to assess its dynamic properties and seismic response under the earthquake. The input waves used for the shaking table tests were the El-Centro, Taft, and Zhangjiakou artificial waves with seismic ground motion intensities of 8°–9°. The results indicated that the CFST-framed building exhibited satisfactory seismic performance. The main damage behavior was the cracking and spalling of the MFBs, however, the MFBs used as exterior wallboards were easy to repair and replace. No wallboard collapse occurred, and the lightweight CFST frame was in the elastic deformation stage. The flexible connections absorbed a large amount of energy, resulting in a reduction in the displacement of the structure and little damage to the wallboards under the earthquake. Finally, a nonlinear distribution model of acceleration amplification factors for calculating the seismic force on MFBs was established.

With increasing global warming, the skiing season is shortened to different degrees all over the world. As a crucial way to ensure the sustainable development of the ski industry, snow storage has been gradually studied and applied in Europe. Covering thermal insulation materials is a key engineering measure for the success of snow storage. This study used numerical methods rather than an experimental method to evaluate the thermal insulation performance of nine snow storage coverage schemes in Harbin, Beijing, and Altay, China. We investigated the thermal insulation performance of nine snow storage coverage schemes (three natural materials and six artificial ones) using a solar radiation method and an implicit finite difference method. Sensitivity analyses were conducted, and the cost performance of schemes 5–9 were analyzed. Based on the cost and thermal insulation performance, we used schemes 4 (geotextile, straw bale), 5 (geotextile, extruded polystyrene foam), and 7 (geotextile, polyurethane foam) to evaluate the snow storage effects in Harbin, Beijing, and Altay. Results showed that among schemes 1–9, scheme 7 has the best thermal insulation performance. If natural materials are used, then scheme 3 gives the best thermal insulation performance. Among schemes 5–9, scheme 5 is the most economical. The heat transfer in Beijing is higher than that in Harbin and Altay, while the latter two show similar heat transfers. The combination of meteorological conditions and coverage schemes influence the melting rate of snowpacks. The melting rate of snowpacks can be reduced with an optimized coverage scheme. The proposed methods can serve the selection of coverage schemes for snow storage.

It has generally been believed that the lattice thermal conductivity (κL) is mainly contributed by acoustic phonons and the contribution of optical phonons can be neglected in crystalline materials. However, in this work, we demonstrate that the contribution of optical phonons play an important role in the complex structural low- κ L oxides. The mode-wised κL of three representative oxides, MgO, BaHfO3 and La2Zr2O7, with different structural complexity was calculated using first-principles phonon Boltzmann transport equation (BTE) method. It is found that the contribution of optical phonons become significant as the structural complexity increases. Especially, for La2Zr2O7, the κL is dominated by optical phonons due to the large density of states. Optical phonons exhibit amorphous-like phonon-phonon scattering characteristics that are different from those of acoustic phonons. Furthermore, calculations for materials other than the three representative oxides were conducted and the results confirmed the validity of our conclusions.

Wheat straw, in the form of compacted bales, is increasingly used as thermal insulation in the external walls of buildings. Common practice is to use a render finish, applied directly to surface of the straw bales, to protect them from decay, and enhance structural performance and fire resistance. Coatings are typically made of water vapour permeable materials, such as lime or earth-based renders. Such coatings should allow water vapour to diffuse through, minimising the risk of liquid moisture build up within the thickness of the wall, reducing likelihood of decay. However, to date there has been very limited scientific study of this behaviour in rendered straw bale walls. The aim of the work presented in this paper was to develop understanding of the hygrothermal performance of lime rendered wheat straw bales. A test panel was subjected to varying environmental conditions, including a thermal shock, dynamic freeze–thaw exposure and hot humid conditions. Key scientific contributions of this work include data on the dynamic and steady-state hygrothermal characteristics wheat straw bale walls, combined with the application of heat and moisture modelling. This work will further support uptake of straw bale construction by designers and their wider use in energy-efficient construction projects.

It remains urgent challenges to adopt suitable strategies to consume unwanted microwave pollution emitted by high-tech electronic devices satisfactorily. Confronted with narrow effective absorption bandwidth (EAB) and high filler loading bottlenecks of MXene-Based microwave absorber, herein, we employ Lewis molten salt etching approach to both exfoliate Ti3AlCN powders into Ti3CNCl2 suspension and intercalate ferromagnetic composition into interlamination simultaneously. By utilizing the crosslinking effect of dopamine, the Ti3CNCl2 are anchored on the surfaces of graphene oxide (GO) nanosheets, constructing interconnecting microstructure. Both the 3D conductive network and the modification of MXene manifest crucial impacts on enhancing microwave absorption performance of the resulting ultra-lightweight reduced GO (RGO)-based aerogel. The minimum intensity of reflection loss achieves −62.62 dB with the absorber mass loading of 0.7 wt%. Remarkably, more than 90% of the incident microwave is qualified to be absorbed over the whole Ku band. The EAB is broadened while tailoring the thickness to 3 mm, ranging from 10.2 to 18 GHz. Besides, the aerogel presents valuable thermal insulation properties. Our methodology of synthesizing MXene/RGO aerogel not only provides promising insights into microstructural construction but also endows the possibility for integrating thermal insulation property towards next-generation high-performance microwave absorption devices.

This paper aimed to design and optimize the structure of a thick thermal barrier coating by adding graded layers to achieve a balance between high thermal insulation capacity and durability. To this end, conventional TBC, conventional TTBC, and functionally graded TTBCs were deposited on the superalloy substrate by air plasma spraying. To determine the quality of the bond strength of the coatings, the bonding strength was measured. The durability of coatings was evaluated by isothermal oxidation and thermal shock tests. Then, at a temperature of 1000 °C, the thermal insulation capacity of the coatings was carried out. The microstructure of the coatings was characterized by a scanning electron microscope. The results showed that the thickness of the TGO layer formed on the bond coat in the conventional TBC and TTBC under the oxidation test at 1000 °C after 150 h was 2.79 and 2.11 μm, respectively, whereas, in the functionally graded TTBC samples, no continuous TGO layer was observed as a result of internal oxidation. The functionally graded TTBC presented higher durability than conventional TTBC due to improved bonding strength, thermal shock resistance, and the lack of a TGO layer at the bond/top coat interface. Also, the thermal insulation capacity of the functionally graded TTBC (with 1000 μm thickness of YSZ coating) was better than TTBC.

Single-phase (Ce0.2Zr0.2Ti0.2Sn0.2Ca0.2)O2-δ porous high-entropy ceramics have been in-situ fabricated by foam-gelcasting-freeze drying method at different temperatures. The microstructure, phase composition, and properties of the obtained ceramics were investigated. The results indicate that compared with other porous ceramics reported in the literatures, this type of ceramics exhibits excellent performance. The sample prepared at 1350 °C shows high porosity (88.6 %), low thermal conductivity (0.023 W m-1 K-1), and high compressive strength (1.48 MPa). The current study suggests that porous (Ce0.2Zr0.2Ti0.2Sn0.2Ca0.2)O2-δ high entropy ceramics are promising candidates for thermal insulation applications.

In this study, a high-entropy approach was employed to design a new single-phase A2B2O7 oxide for thermal insulation applications. Multicomponent high-entropy oxides, containing up to seven different cations, were successfully synthesized in a single defective fluorite structure. We observed that the incorporation of the functional cation, Zn2+, effectively blocked the heat radiation phenomenon by reducing the photon mean free path, and further reduced the high-temperature thermal conductivity owing to the larger free carrier concentration originated from the large number of oxygen vacancies. Although a large concentration of Zn2+ caused a slight reduction in thermal expansion, this study suggests that functional cations can be easily incorporated; thus, expanding the material diversity beyond the typical doping levels to develop new thermal barrier materials.

In this study, a fully biodegradable ultra-light poly(lactic acid)/silicon dioxide (PLA/SiO2) aerogel nanocomposite with ultra-low thermal conductivity was successfully fabricated. PLA used was a produced from lactic acid, where the lactic acid has been produced from carbohydrates. The rheological properties of PLA were enhanced by diphenylmethane diisocyanate (MDI). The foaming properties, cell density, cell size uniformity, mechanical properties and thermal conductivity and thermal diffusivity of PLA were further improved by SiO2 aerogel, and finally the ultra-low density foamed material was prepared by supercritical CO2. The density of PLA foam can be as low as 0.02 g/cm3 and the thermal conductivity as low as 0.02628 W/m·K. The PLA-based composites can be used in many fields such as thermal insulation, vibration damping and packaging, and can be fully biodegradable and sustainable throughout their life cycle, which meets the global trend of energy saving and emission reduction.

Cellular concrete is a lightweight solid cementitious foam that is used mainly for thermal insulation and sound absorption. Either partially or wholly, when the Portland cement in the binder is replaced with ash, the environmental impact of the material is reduced. However, the resulting changes in the cell structure and their subsequent impact upon the physical properties of the material have not been well examined. In this study, cellular concrete was prepared from alkali activated fly ash binders and separately, from Portland cement binders blended with wood ash. The cell structure was photographed using laser confocal microscopy and the images were analyzed to quantify the cellular network in terms of the porosity and the fractal dimension of the porous phase. Alongside, the cellular concrete specimens were tested for their thermal constants and sound absorption. The results show that there was an increase in the fractal dimension and an associated drop in thermal conductivity for an increase in the porosity.

Pipelines in the offshore sector make common use of polypropylene (and other polymer) coating systems to protect the infrastructure and provide thermal insulation. High pressure high temperature pipelines are subject to large axial loads due to restraint by seafloor soils of thermal strains in the pipe wall. Friction between pipe coating material and seafloor soil plays a defining role in the build-up of axial stress and the formation of lateral buckling. Accurate quantification of pipe–soil interface friction is key to robust pipeline stability design and possibilities to enhance or manipulate the friction coefficient may be attractive to designers. An extensive campaign of soil and interface tests using a range of granular materials and polypropylene surface specimens engineered to achieve varying surface textures was carried out. The results show that interface friction primarily depends on stress level and the magnitude of the surface texture in relation to the particle size. Herein, a new relative texture parameter, Ta, is developed that, unlike alternative relative roughness parameters, can be obtained using conventional profilometry measurement techniques. An expression for estimating the friction coefficient in relation to texture and stress level is proposed that can serve as a useful predictor of pipe–soil interface friction.

Weak thermal stability and low-burning resistance of the rigid polyurethane foams are the classic problems in the usage of them. Therefore, it is required to improve these problems of the foams while reducing the cost of production. This study investigated the effects of dolomite (DOL) and intumescent flame retardant (IFR) system on thermal and combustion behaviors of rigid polyurethane foams (RPUFs). For this purpose, DOL (5, 10, and 15 wt%) and DOL/IFR (5/5, 10/5, and 5/10 wt%) combinations were added into RPUFs. Thermogravimetric analyses were performed to investigate the thermal decompositions of the foams and the thermal conductivity measurements were performed to examine the effects of DOL and DOL/IFR additions on the thermal insulation properties of the foams. Cone calorimeter and UL 94 tests were performed to investigate the fire resistances of the foams. The test results showed that up to 15 wt% DOL could be incorporated into the rigid polyurethane foams as filler without any problems in the foam productions, and the thermal and the combustion behaviors of the foams were slightly enhanced. In addition, it was determined that IFR should be used to improve the thermal stability and the fire resistance of the DOL added foams. Among DOL/IFR combinations, 5 wt% DOL and 10 wt% IFR addition satisfied the best performance in terms of the thermal stability and the fire resistance with reducing the smoke, CO, CO2 and NO emissions. In general, the additions of DOL and IFR slightly increased the thermal conductivity coefficients of the foams. © 2023 Wiley Periodicals LLC.

Fibre panels for thermal building insulation, Basajaun Results in Brief

Progress in Applied Science and Technology, 13, 1, 26-32

The literature showed many studies that evaluated a single or multiple Phase change materials (PCMs) layers in passive, active or in hybrid configurations for building applications. However, little attention has been given to evaluate the energy performance of buildings when PCMs are used together with other passive design strategies. In this work, the energy performance of an office building in a typical arid Saharan climate is simulated using EnergyPlus when phase change materials (PCMs)-embedded envelope is implemented. The office building was analyzed without/with PCMs using various thicknesses. Results indicated that the annual electrical energy for heating, ventilation and air conditioning (HVAC) can be reduced between 3.54% and 6.18%, depending on the PCM thickness. The performance of the office building including PCMs was then simulated using two practical architectural design strategies, namely windows to wall ratio (WWR) and rezoning of the interior spaces. Outcomes revealed that the annual energy consumption for HVAC can be reduced from 10% to 15.5% and from 6.1% and 8.54% when WWR is reduced by half to three-quarters and the perimeter zones are enlarged by one-third to two-thirds of the original space area, respectively. With combining both architectural design strategies with PCM, the annual electrical HVAC energy can be reduced between 12.08% and 15.69%, depending on the design configuration and PCM thickness. This design option provides additional benefits also since it reduces the vulnerability of increasing the lighting and fuel gas heating energy because more perimeter zones are exposed to daylighting and solar radiation, respectively.

Naval Special Warfare (NSW) operators are required to dive into cold waters for a prolonged time to infiltrate demanding environments. While underwater vehicles give the opportunity for longer infiltration ranges and deeper dives, the diving suit, which protects the diver from hypothermia, becomes the most essential diving equipment for the success of the mission. Although the first wetsuit was made in the 1950s, there has been no significant advancement in the neoprene material until recently, and the shrinking neoprene air pockets under depth pressure decrease the thermal insulation of the wetsuit and affect the diver’s buoyancy. To overcome this downside, the K-Suit Mk.4 prototype was created to give NSW operators an alternate diving wetsuit option with superior ergonomics, depth-independent thermal insulation and buoyancy, and possible sound protection. This wetsuit has a base layer of 3mm neoprene and two layers of composite materials. The first composite layer is composed of 8mm-thick glass microspheres mixed with a polymer and the second is thinner and forms solid ceramic beads coupled with the same polymer. Six experimental dives were carried out to gather temperature and pressure data. The data were analyzed, and the result is the K-Suit has the ability to outperform the traditional 7mm diving wetsuit specifications that NSW typically uses. ONR Plotarhis, Hellenic Navy Approved for public release. Distribution is unlimited.

In this paper, a series of coated fabrics based on Fe-doped BaSnO3 (BaSn1–xFexO3−δ, x = 0.00, 0.05, 0.10, 0.20, 0.25) powder pigments were prepared. The results indicate that the developed pigments...

The paper presents a novel kind of carbon foam composites reinforced by chopped glass fibers. Microstructure, mechanical properties and thermal insulation of the composites have been investigated by scanning electron microscopy, universal testing machine and laser thermal constant analyzer, respectively. Results showed that carbon foam composites had a spherical and closed-cell structure; chopped glass fibers were uniformly distributed in the carbon matrix along different directions. The mechanical properties exhibited optimum with the 7% glass fiber additives, 11.27 MPa of shear strength, higher than that of pure carbon foams by as much as 111%. Compressive and shear fracture were both characterized by gradient brittleness. Many tiny open-pores existed in carbon foams with a certain amount of glass fiber additives, giving rise to the higher thermal conductivity. Nevertheless, carbon foam composites possessed good thermal insulation, 0.311 W·m−1·K−1 at room temperature, and 1.04 W·m−1·K−1 in 800 °C at the most.