Search Results (98)

This study evaluates the performance degradation of spray rigid polyurethane foam (RPUF) insulation on reservoir dam structures under multi-physics coupling conditions. Focusing on characteristic environmental exposures in Hot Summer and Cold Winter (HSCW) climate zones, accelerated aging tests simulating coupled temperature–humidity effects were conducted to comparatively analyze the thermal resistance and durability evolution between unprotected and encapsulated RPUF configurations. Scanning electron microscopy (SEM), infrared spectroscopy (IR), and other methods were used to characterize and analyze the structure of RPUF. Research has shown that in HSCW climate zones, the thermal conductivity of RPUF gradually increases with the number of degradation cycles, and the insulation performance decreases, mainly due to the damage of the pore structure caused by temperature aging and the combined effect of moisture absorption aging. In comparison, the RPUF after protection can effectively slow down the rate and degree of decline of its insulation performance. On this basis, a time-varying prediction model for the thermal conductivity of RPUF under long-term service in HSCW climate environments was fitted, providing a scientific basis for the durability evaluation of reservoir dam insulation. Full article

This study explores how production technology influences spray-applied rigid polyurethane (PUR) foam insulation’s cryogenic performance. In cryogenic applications such as liquid gas storage, insulation must minimise heat transfer and resist moisture ingress under severe thermal gradients. Experimental aluminium vessels were insulated with PUR foam of varying thicknesses and surface conditions—rough, machined smooth, and with a urea-based protective coating—and then tested using dynamic boil-off of liquid nitrogen (LN₂). Foam properties, including adhesion, mechanical strength, thermal expansion, thermal conductivity, and closed-cell content, were evaluated. The results revealed that thicker insulation reduced both effective thermal conductivity and moisture uptake. Although the urea-coated vessel showed minimal water absorption, the coating increased overall thermal conductivity due to its heat conduction and condensation behaviour. Moisture was primarily absorbed near the foam surface, and no cumulative effects were observed during repeated tests. The effective thermal conductivity was determined by interpolating boil-off data, confirming that insulation performance strongly depends on thickness, surface condition, and environmental humidity. These findings provide valuable guidance for the design and application of PUR foam insulation in cryogenic environments. Full article

This study presents a novel water mist fire fighting system that integrates water mist sprays and water mist curtains, designed to achieve simultaneous fire suppression, thermal insulation, and smoke control. Three full-scale experiments were conducted under various fire scenarios, and the changes in fire behavior and heat release rate were examined to evaluate the effectiveness of the water mist system in extinguishing fires. Additionally, the spatiotemporal changes in ceiling temperature were monitored to assess the cooling and protective effects of the water mist. The thermal insulation capability of the system was also investigated by detecting the temperature distribution inside the tunnel. Moreover, the smoke conditions upstream and downstream of the tunnel were analyzed to evaluate the smoke-blocking performance of the water mist system. The findings demonstrate that the water mist fire fighting system is highly efficient in attenuating the fire and restricting its progression. Within the water mist spray section, the average ceiling temperature decreased exponentially during both the initial and steady burning phases across all tested fire scenarios. Nonetheless, the smoke-carrying capacity of the water mist spray is limited. Fortunately, the dispersed smoke was diluted by water mist, markedly enhancing visibility and mitigating the impact of smoke on tunnel illumination. Full article

Foamed geopolymer materials are increasingly studied due to their inherent fire resistance. To date, these materials have primarily been produced by casting into moulds, with foaming occurring during mixing or within the moulds, shortly before setting. For practical applications, however, it is advantageous to apply these materials directly onto surfaces with complex geometries. Although several techniques for geopolymer spraying have been described in the literature, many exhibit limitations that restrict their practical implementation. This study presents a novel spraying technology developed on a dedicated process line, enabling in situ dosing of the foaming agent immediately before application. The system integrates infrared heating to ensure controlled curing of the geopolymer. This paper outlines the design of the process line and its core functionalities while presenting selected results of material tests conducted on the obtained geopolymer coatings. Tests performed on approximately 200 m² of surface confirmed the functionality of the process. The thermal conductivity of the sprayed foams was about 0.07 W/m-K. The inclusion of a phase-change material (PCM) in the geopolymers further enhanced their ability to store and regulate thermal energy. The adhesion strength results, consistently exceeding 1 MPa across various substrates (steel, geopolymer, gypsum board), confirmed the practical suitability of the proposed solution. This was also demonstrated by the homogeneous foamed structure obtained. Full article

As environmental pollution has become a global concern, regulations on carbon emissions from maritime activities are being implemented, and interest in using renewable energy as fuel for ships is growing. Hydrogen, which does not release carbon dioxide and has a high energy density, can potentially replace fossil fuels as a renewable energy source. Notably, storage of hydrogen in a liquid state is considered the most efficient. In this study, a 0.7 m³ liquid hydrogen fuel tank suitable for small vessels was designed, and a structural analysis was conducted to assess its structural integrity. The extremely low liquefaction temperature of hydrogen at −253 °C and the need for spatial efficiency in liquid hydrogen fuel tanks make vacuum insulation essential to minimize the heat transfer due to convection. A composite insulation system of sprayed-on foam insulation (SOFI) and multilayer insulation (MLI) was applied in the vacuum annular space between the inner and outer shells, and a tube-shaped supporter made of a G-11 cryogenic (CR) material with low thermal conductivity and high strength was employed. The material selected for the inner and outer layers of the tank was STS 316L, which exhibits sufficient ductility and strength at cryogenic temperatures and has low sensitivity to hydrogen embrittlement. The insulation performance was quantitatively assessed by calculating the boil-off rate (BOR) of the designed fuel tank. Structural integrity evaluations were conducted for nine load cases using heat transfer and structural analyses in accordance with the IGF code. Full article

Traditional conservation strategies often prioritize minimizing water use; nevertheless, water can also enhance thermal comfort by incorporating a water-to-air heat exchanger (WAHE) alongside non-direct evaporative and radiant cooling techniques. A WAHE can be installed in features such as ponds, water tanks, or rainwater cisterns. This article assesses the cooling potential of two prototypes of roof ponds and a green roof connected to a WAHE, and the results are compared to a baseline unit featuring a roof that meets California’s energy code standards. Several testing units, measuring 1.35 × 1.35 × 1.35 m, with identical heat characteristics, excluding the roof, were constructed and tested. In the first system, the heat that the green roof could not absorb was transferred to a water reservoir and then dissipated to the outside. The first roof pond prototype features a 0.35 m deep water pond topped with a 0.03 m thick insulating panel and a spray system. The second roof pond variant has an aluminum sheet with a 0.10 m air gap above a 0.25 m deep water pond. The results suggest that combining a WAHE with different roof configurations offers promising benefits while keeping water consumption limited. Notably, when the WAHE is operating, the green roof increase its performance by 47%, the insulated roof pond by 22%, and the roof pond with an aluminum sheet by 13%. Full article

This study establishes a numerical simulation model based on heat and mass transfer theory to reflect the variations in temperature and humidity conditions within a tunnel. It analyzes the impact of high-temperature fissure water, humid porous media, and drainage methods on the temperature and humidity distribution in a tunnel. The results indicate the following: (1) When the area of the humid porous media increases from 150 m² to 300 m², the relative humidity (RH) of the air in the tunnel rises from 52.7% to 55.8%, but the impact on air temperature (T_a) is minimal. (2) The heating and humidification effects of hot water in a drainage ditch on the airflow cannot be overlooked. Meanwhile, the hot water transfers heat to the surrounding rock, with heat transfer predominantly driven by the surrounding rock convection. Compared to a drainage pipe, the heat transfer amount increases by 44.9%, and RH rises by 9.3%. (3) For every increase of 5 °C in water temperature (water volume of 90 m³/h), the ventilation outlet T_a linearly increases by 0.15 °C, and the rate of increase in RH accelerates with rising water temperature. (4) Covering a drainage ditch with a cover plate can reduce RH by 12.3%, while spraying a 10 cm insulation layer on the tunnel walls can significantly lower T_a by 0.66 °C. These findings provide a potential solution for the application of insulation materials in reducing the thermal hazards of deep high temperatures. Full article

The spray pyrolysis deposition of nanostructured Pb_1−xSn_xSe alloy films, x = 0.0 to 1.0, from as-prepared Pb_1−xSn_xSe alloy colloids as the starting solution is reported. The colloidal dispersions were prepared by dissolving selenium in an amine–thiol mixture, reacted with the Sn and Pb precursors in propylene glycol, and subsequently sprayed onto glass substrates at 300 °C. Structural characterization indicated the formation of the alloyed rock-salt cubic phase for 0.0 ≤ x ≤ 0.75, oxidized Pb and Se phases produced during the deposition, and only orthorhombic SnSe for x = 1.0 with Se and SnSe₂ as impurities. Nanocrystalline films ranging from 16 to 16.5 nm in size were obtained. The films displayed a shift in their optical structure and a non-monotonic variation in the band gap energy, first a decrease, reaching the minimum at x = 0.30 and a further increase in the Sn content. The decrease in the optical band gap resembles that of a topological insulator behavior. The morphology of the alloyed films confirmed the large nanocrystal formation by self-assembly processes in both the PbSe and SnSe phases and segregated PbSnSe platelets for x ≥ 0.30. Seebeck coefficient revealed that a typical semiconductor behavior dominated by bipolar transport, and p-type conductivity, but only for x = 0.0 n-type conductivity was exhibited. The maximal Seebeck coefficient magnitude behaved similarly to the band gap energy, evidencing the influence of energy band structure and the topological character. Full article

Spray-on fireproofing materials (SFRMs) and intumescent paints are commonly used to enhance the fire resistance of steel structures. Despite extensive studies on the performance of SFRMs and intumescent paints, there remains a significant lack of research on the material properties of certified products used in real-world applications, especially according to exposed temperatures. In this study, heating experiments were conducted to investigate the material properties of two widely used certified materials in Korea, focusing on their application thickness and exposure temperature. The experiments set target temperatures ranging from room temperature to 900 °C in increments of 100 °C. Additionally, various material properties, such as changes in shape and the insulation performance of the SFRM and intumescent paint, were observed at each temperature. Notably, the moisture content and discoloration depth of the SFRM displayed a consistent trend under different exposure temperatures, a material property that has not been previously reported. Furthermore, the insulation performance of the two materials differed by approximately 17% to 25% compared to an uncoated specimen exposed to the same temperature. The findings on the properties of SFRMs and intumescent paint relative to the exposure temperature presented in this study can serve as valuable data for selecting materials to improve fire resistance performance across various construction sites in the future. Additionally, they can act as key reference data in the diagnostic evaluation process for assessing the impact of fire on steel structures. Full article

Wood is the most commonly used material for framing single-family houses in the USA, yet alternative materials like Insulated Concrete Forms (ICFs) offer potential advantages in energy efficiency and thermal performance. This study evaluates ICFs as a viable alternative by analyzing the energy performance and indoor temperature stability of five single-family houses in Oklahoma, USA, monitored over 12 months. The sample included a total of five single-family houses: two wood-framed houses with blown fiberglass insulation, one wood-framed house with spray foam insulation in the attic, and two houses with ICF exterior walls. Results demonstrated that ICF houses consumed up to 41% less electricity and at least 5% less natural gas compared to wood-framed houses, with improved indoor temperature stability. Occupants also saved approximately USD 270 annually on energy costs, highlighting the advantage of ICF’s efficiency. This study provides empirical evidence of the benefits of ICF construction, which previously relied heavily on simulations or anecdotal claims. However, findings are limited by the specific geographic focus of the study. Future research should expand on these findings by incorporating a wider range of climates and housing designs to better understand the broader applicability of an ICF as an alternative to conventional wood-framed construction. Full article

Various polyurethane foams (i.e., rigid, flexible, and spray polyurethane foams) offer diverse applications due to their unique properties, including thermal insulation, cushioning, and seamless gap filling. These foams provide solutions across industries such as construction, automotive, and refrigeration. However, the foaming process presents several challenges that may result in various defects in the final products. This work provides innovative predictive techniques for polyurethane foam expansion and applications in advanced manufacturing processes. The foaming height of the third polyurethane foaming agent (PU-3) closely aligned with the experimentally measured values. The relationship between foaming height and time is influenced by the type and concentration of catalysts, as well as the blowing agents used. However, simulations using Moldex 3D Version 2024 revealed a nonlinear relationship between foaming height and time, characterized by three distinct foaming rates. Zone B demonstrated the highest foaming rate, followed by Zone C, while Zone A showed the lowest rate. The foaming height and rate were significantly influenced by the foaming angle, with smaller angles enhancing both parameters. At a mold temperature of 30 °C and with an expansion coefficient of 35, the predicted foaming height of the polyurethane agent achieved an average accuracy of approximately 96% across four foaming angles. Based on these experimental findings, this study introduces three mechanisms involved in the foaming process of polyurethane foam components. Full article

Chromium salt fillers commonly used in current anti-corrosion coatings are highly toxic. However, due to the unique high–low valence transformation and passivation mechanisms of chromium-based functional fillers and their wide applicability, chromium-free coatings find it challenging to achieve the same performance and industry acceptance. This study introduces an innovative approach that uses zinc to reduce molybdate (MoO₄²⁻) in an acidic solution, thereby forming a multivalent MoO₄²⁻ system (PMZ system), and applies it to chromium-free insulating coating for oriented silicon steel. The effects of reductant dosage on the valence composition of molybdenum in the PMZ system and the corrosion resistance of the coating were investigated. Additionally, the difference in the valence composition of molybdenum between the PMZ system and the multivalent phosphomolybdate system (PMNZ system) and its impact on corrosion resistance were studied. The results indicate that the PMZ system contains trivalent molybdenum and hexavalent molybdenum, while the PMNZ system contains pentavalent molybdenum and hexavalent molybdenum. The systems leverage the reactivity of lower-valence molybdenum to delay the corrosion by reacting with oxygen while maintaining the original mechanism of molybdenum salt fillers and forming sediment with iron ions to form a passivation layer. As the content of trivalent molybdenum in the PMZ system increases, the corrosion resistance of the insulating coating improves. When the amount of zinc added in the PMZ system is 0.006 g, the relative proportion of trivalent molybdenum reaches 20.52%, and the salt spray resistance of the coating developed with the PMZ system reaches 248 h with a corrosion area of less than 5%. When the contents of the main components and sodium molybdate in the PMZ coating and the PMNZ coating are the same, the corrosion resistance of the PMZ coating, which contains trivalent molybdenum, is better than that of the PMNZ coating, and the salt spray resistance exceeds 192 h. Full article

This study explored the influence of graphene oxide (GO) on morphological and mechanical properties of Nafion^® 115 membranes with the objective of enhancing the mechanical properties of the most widely employed membrane in Proton Exchange Membrane Water Electrolyzers (PEMWE) applications. The membrane surface was modified by ultrasonically spraying a GO solution and different annealing temperatures were tested. Scanning Electron Microscopy (SEM) cross-sectional images revealed that annealing the composite membranes was sufficient to favor an interaction between the graphene oxide and the surface of the Nafion^® membranes. The GO covering only 35% of the membrane surface increased the composite’s wettability from hydrophobic (105.2°) to a highly hydrophilic angle (84.4°) while slightly reducing membrane swelling. Tensile tests depicted an increase in both the strain levels and tensile loads before breaking. The samples with GO presented remarkable mechanical properties when the annealing time and temperature increased; while the Nafion^® control samples failed at elongations of 95% and 98%, their counterparts with GO on the surface achieved elongations of 248% and 191% when annealed at 80 °C and 110 °C respectively, demonstrating that the presence of GO mechanically stabilizes the membranes under tension. In exchange, the presence of GO altered the smoothness of the membrane surface going from an average 1.4 nm before the printing to values ranging from 8.4 to 10.2 nm depending on the annealing conditions which could affect the quality of the subsequent catalyst layer printing. Overall, the polymer’s electrical insulation was unaffected, making the Nafion^®-GO blend a more robust material than those traditionally used. Full article

The distribution morphology and density of micro-agglomerated particles are the main microstructural characteristics of embedded micro-agglomerated particle thermal barrier coatings. The study of their effect on the sintering resistance of coatings can help to further improve the service life of thermal barrier coatings. Strain tolerance and thermal insulation performance are important evaluation indicators for the sintering resistance of thermal barrier coatings. In this study, embedded micro-agglomerated particle thermal barrier coatings were prepared by plasma spraying, and the distribution morphology and density of micro-agglomerated particles were analyzed and counted. Different simulation models were established to analyze the compressive stress and thermal stress of the coating, as well as the influence of the microstructure characteristics on the strain tolerance and thermal insulation performance of the coating. A machine learning model was established to evaluate the nonlinear relationship between the microstructure characteristics of the coating and its strain tolerance and thermal insulation performance. The results show that the horizontal angle of the micro-agglomerated particles in the coating has the most significant effect on the sintering resistance and is predicted using the PSO-SVM machine learning model. The predicted effects are the most important, and the coefficients of determination for strain tolerance and thermal insulation are as high as 0.988 and 0.945, respectively, indicating a strong correlation between the predicted and actual values. This research technique used experimental research-simulation computation-machine learning can be used to optimize the microstructure of coatings and guide the preparation of high-performance thermal barrier coatings. Full article

Aircraft engine turbine blades are covered with protective coatings. These coatings should have the best thermophysical convergence with the blade’s parent material. The aim is to create heat-resistant covering for aircraft engine turbine blades made of nickel superalloy. The results of tests on coatings are presented; the inner layer is an adhesive layer of the MeCrAlY type, applied to the blade by means of supersonic thermal spraying, and the outer layer is diffusion-aluminized in the first case using the Vapor Phase Aluminizing method, and in the second using the suspension method. The inner layer of the coating protects the blade material against high-temperature corrosion, and the outer layer against high-temperature fuel combustion product stream. The protective coatings applied to aircraft engine turbine blades were subjected to an engine test in test bench conditions and then to material tests. A protective coating with an internal layer of MeCrAlY type applied to the blade by supersonic spraying and an external layer aluminized by the Vapor Phase Aluminizing method protects the nickel superalloy against high-temperature diffusion changes, protects it against oxidation and provides it thermal insulation. Full article