Insulation Effect Research Articles

Study on the thermal control performance of lightweight minimal surface lattice structures for aerospace applications

With the rapid evolution of aerospace technology and the increasing complexity of space environments, the demand for lightweight, thermally insulated, and highly efficient heat dissipation materials in aircraft equipment has surged. This study addresses this critical need by investigating Triply Periodic Minimal Surface (TPMS) lattice structures, offering a novel design approach to enhance spacecraft thermal management under extreme temperatures. Our work introduces a methodology to quantitatively assess the thermal insulation and heat dissipation performance of various lightweight lattice sandwich structures. We constructed implicit function models of low volume fractions, including Gyroid, Diamond, Primitive, and IWP, and conducted experiments using an active cooling setup under controlled heating conditions at 300 °C. Key findings reveal that, at flow velocities ranging from 0.25 to 1.5 m/s, the Diamond model exhibited the highest convective heat transfer coefficient, surpassing the Gyroid, Primitive, and IWP models by 6.9 % to 427.3 %, 87.1 % to 485.6 %, and 1.5 % to 98.7 %, respectively. Conversely, at velocities between 1.5 and 3.75 m/s, the Gyroid model demonstrated superior heat exchange performance, improving by 14.6 % to 67.2 %, 73 % to 167.7 %, and 9 % to 64.8 % compared to the Diamond, Primitive, and IWP models. During thermal insulation tests at temperatures from 200 to 400 °C, the Diamond model showed the best insulation effect, while the Primitive model performed poorly. Based on the experimental data, we established empirical relationships between the Nusselt number, friction coefficient, and Geometric Surface Ratio (GS). These findings not only underscore the significant potential of TPMS lattice structures in aerospace applications but also provide a robust theoretical framework and practical guidelines for achieving efficient thermal management in lightweight aerospace manufacturing.

Quantum anomalous Hall effect for metrology

The quantum anomalous Hall effect (QAHE) in magnetic topological insulators offers great potential to revolutionize quantum electrical metrology by establishing primary resistance standards operating at zero external magnetic field and realizing a universal “quantum electrical metrology toolbox” that can perform quantum resistance, voltage, and current metrology in a single instrument. To realize such promise, significant progress is still required to address materials and metrological challenges—among which, one main challenge is to make the bulk of the topological insulator sufficiently insulating to improve the robustness of resistance quantization. In this Perspective, we present an overview of the QAHE; discuss the aspects of topological material growth and characterization; and present a path toward a QAHE resistance standard realized in magnetically doped (Bi,Sb)2Te3 systems. We also present guidelines and methodologies for QAHE resistance metrology, its main limitations and challenges, as well as modern strategies to overcome them.

Study on the Inhibition Effect of Fly Ash on Alkali–SilicaReaction and Its Influence on Building Energy Performance

Abstract: Cracks and other defects in concrete will affect its durability, thermal insulation effect, and energy consumption. ASR is one of the common causes of concrete cracks. In this study, mortar specimens modified with fly ash were prepared using the mortar bar rapid method, and the inhibition effect of ASR in two alkali environments and the building energy efficiency characteristics were comparatively analyzed. SEM, EDS, and XRD were used to analyze the microstructure, elemental distribution, and products in the specimens’ interfacial transition zone comparatively. The results show that a replacement amount of 20–30% fly ash can restrain ASR expansion and maintain high mechanical strength. In both alkaline environments, K and Al are enriched in the interface transition zone and combine with SiO2 and Al2O3 to form a stable framework aluminosilicate mineral. In addition to the inhibition effect of fly ash on ASR, the external wall heat dissipation flux decreased from 132.6 W/m2 to 117.6 W/m2, a decrease of 11.3%, and the overall envelope heat dissipation flux decreased by 9.2%, significantly reducing building energy consumption. This study provides a new perspective for the development of building energy-saving materials and helps green buildings and sustainable development.

PCC Slab Temperature Gradients as a Function of Structure and Environment Experience from the SHRP II R21 Composite Pavement Test Track

The Strategic Highway Research Program (SHRP) II R21 Composite Pavement Research Project test track constructed at University of California Pavement Research Center (UCPRC) ATIRC facility has yielded significant Portland cement concrete (PCC) temperature data over the nearly past two years of testing. The nine different test sections consisted of combinations of plain and hot mix asphalt (HMA) overlaid jointed plain concrete (JPCP) pavement sections of varying thicknesses. Over 135 thermo couples were placed at five depths and three locations within each slab and have been continuously monitored since test track construction. This paper will identify the changes in PCC slab temperature gradients as a function of PCC slab thickness (178mm and 127mm), HMA overlay thickness (114mm, 64mm, and 0mm) and type (Polymer modified and rubber). Results provide important information about the thermal insulation effect of HMA layer to reduce temperature gradients in PCC layers and provide experimental data for continued evaluation of the effects of reduced temperature gradients on PCC layer cracking performance.

Optimizing Thermal Efficiency of Building Envelopes with Sustainable Composite Materials

The growing global energy demand, particularly in India, calls for innovative strategies to improve building energy efficiency. With buildings contributing significantly to energy consumption, especially in cooling-dominated climates, sustainable insulation materials are essential in minimizing energy usage. This study explores the potential of bamboo biochar, fly ash, and lime as sustainable insulation materials for building envelopes. This study also addresses the critical issue of energy efficiency in building construction, specifically focusing on the comparative analysis of three materials for their thermal performance, environmental impact, and economic viability. This research aims to identify the most sustainable material choice by assessing each material’s life cycle energy consumption, thermal resistance, and associated costs. The research methodology involves an extensive review of 125 relevant studies to assess the thermal performance of these materials. U-values were computed from the reported thermal conductivity data and systematically arranged in chronological order to evaluate and compare their insulation effectiveness over time. Additionally, these materials were analyzed under sustainability criteria, incorporating life cycle analysis and a carbon footprint assessment. This study identifies existing research gaps and offers recommendations for future research, creating structure for the development of sustainable insulation system.

Analysis of the Influence of Incorporating Different Thermal-Insulating Materials into the Sub-Ballast Layers

Adverse climatic conditions, particularly excessive water and frost, necessitate the design of thick protective sub-ballast layers when dealing with frost-susceptible subgrade surfaces, especially when using standard natural materials (crushed aggregate or gravel–sand). Given the current preference for conserving natural construction materials and promoting sustainable development in the dimensioning of sub-ballast layers, it is advisable to incorporate various thermal insulation, composite, or suitable recycled materials in their design. Therefore, the paper analyses the impact of incorporating different thermal insulation materials (including extruded polystyrene, Liapor, Liapor concrete, and composite foam concrete) into sub-ballast layers. As part of the experimental research, these modified sub-ballast layers were constructed on a real scale in the outdoor environment of the University of Žilina (UNIZA) campus. They were subsequently compared in terms of their thermal resistance to climatic loads. The research results demonstrate that extruded polystyrene provides the optimal thermal insulation effect in modified sub-ballast layers, which was subsequently used in the numerical modelling of railway track structure freezing under different climatic loads.

Experimental Investigation on the Effects of Wall Chamber Insulation on Nusselt Number and Heat Loss Reduction in a Natural Convection Oven

Experimental Investigation on the Effects of Wall Chamber Insulation on Nusselt Number and Heat Loss Reduction in a Natural Convection Oven

Safety assessment of microwave ablation in sheep vertebral bodies

Background Spine is the most common location for bone metastases. Microwave ablation (MWA) is a technique for minimally invasive tumor treatment. The aim of the current study was to determine whether MWA is a safe option for treatment in vertebral bodies and to gain data on the amount of cortical insulation in the spine. Method MWA was applied with different settings for power and time in both in- and ex-vivo sheep vertebral bodies. Safety was evaluated by temperature measurements at critical surrounding structures (e.g. spinal cord, nerve root). Furthermore, the distribution of heat through the bone at 5 mm from the ablation needle was measured and compared to the temperature at the posterior wall. Results An effect of cortical insulation in the spine was found, for ablations with 20–30 and 50 W (p < 0.01). Ablations with wattage levels of 40–50 W almost instantly led to temperatures over 60 °C at the posterior wall. The temperature remained below 60 °C for 4 min in ex-vivo ablations with 20 and 30 W. However, in the in-vivo experiment paralysis was frequently seen (10/12 sheep) in lower wattages (20–30 W) as well and the experiment was therefore terminated. Conclusion MWA is an effective approach for local bone destruction in the spine. However, given the high risk of complications, caution is advised for treatment in vertebral bodies without better local distribution accuracy. Since cortical insulation appears insufficient to protect the spinal canal from excess heat, MWA involves a risk of paralysis.

A sound insulation cooling fin for broadband noise control and ventilation

Abstract The noise generated by the ultrathin centrifugal fan in a laptop can significantly impact user comfort. While optimizing the fan itself for noise control is important, addressing noise propagation is also crucial. Due to space limitations inside a laptop, adding an extra component for noise control is nearly impossible. Therefore, modifying the cooling fin outside of the fan outlet for sound insulation can be an effective solution. A sound insulation cooling fin is proposed to provide broadband noise insulation while maintaining proper ventilation. Through the introduction of a coupled area change passage, noise at specific frequencies at the passage outlet can be managed to be insulated due to the destructive interference. The effectiveness of the unit’s sound insulation is verified through an impedance tube measurement. Moreover, combining different units can create a multi-peak sound insulation effect which is suitable for various noise conditions. To meet the demand of real situations, a reversal design flow combining neural network and nonlinear constrained optimization algorithm is developed. As a result, a sound cooling fin combing 2 sound insulation units featuring 4013 Hz and 6000 Hz is fabricated and the actual insulation performance is measured in an anechoic chamber. The sound transmission loss at the designed frequency range reaches 5 dB, aligning well with the simulation results. The sound insulation cooling fin has the potential to be widely used for noise control in small-scale electronic devices.

Dirt Ingestion Impacts on Cooling within a Double-Walled Combustor Liner

Abstract Double-walled liners consisting of impingement and effusion cooling are commonly used to cool gas turbine combustor chambers. Engine ingestion of particulate such as dirt, sand, or ash leads to particulate deposition and blockage of cooling holes in these liners. Prior work on double-walled liners has shown that deposition leads to flow blockage, however, no experimental work has studied the reductions in cooling that result from the deposition. The goal for the present work was to quantify this reduction in cooling by evaluating the heat transfer coefficient on the cold-side of an effusion plate with and without dirt buildup. Heat transfer coefficients were quantified over a range of Reynolds numbers, pressure ratios, plate-to-plate spacings, and dirt injection amounts. The injection of dirt onto the cold-side effusion plate surface resulted in flow blockages and cooling reductions as high as 55%, with these effects differing for pressure ratio and plate-to-plate spacing. Scan data of the dirty effusion plate was used to characterize the deposition thicknesses for the different parameters tested. Overall, the heat transfer when having deposition on the effusion plate affected the cooling much beyond the insulation effect of the dirt layer. These results suggest that the effects of particulate buildup on the cooling flow field are an important driver in double-wall combustor liners.

The Coupled Thermal Response Analysis of Green Roofs Based on the Discrete Element Method

As an effective energy-saving measure, green roofs significantly improve the thermal environment of buildings by covering the roof with vegetation and soil. This paper compares the thermal transfer performance of concrete roofs and green roofs under different temperature conditions. First, a uniaxial compression discrete element method (DEM) was used to calibrate the mesoscopic parameters of concrete, ensuring an accurate representation of concrete properties. The results indicate that green roofs have significant insulation effects under high-temperature conditions in summer. After being exposed to high temperatures for 5 h, the temperature of the green roof was 23.4 degrees Celsius lower than that of the ordinary concrete roof. In addition, different initial temperatures of the model also have a certain impact on heat transfer. The higher the initial temperature, the slower the temperature increase under high-temperature conditions. In winter, the green roof significantly delays the cooling at the top of the building, demonstrating excellent thermal insulation performance. The maximum temperature difference compared with the concrete roof is 8 °C. Finally, there is an exponential relationship between the thermal resistivity of the green roof and the temperature. In conclusion, green roofs have significant energy-saving and environmental protection value.

The Role of Sea Ice Insulation Effects on the Probability of AMOC Transitions

Abstract Recent simulations performed with the Community Earth System Model (CESM) have suggested a crucial role of sea ice processes in Atlantic meridional overturning circulation (AMOC) hysteresis behavior under varying surface freshwater forcing. Here, we further investigate this issue using additional CESM simulations and a novel conceptual ocean–sea ice box model. The CESM simulations suggest that the presence of sea ice gives rise to the existence of statistical equilibria with a weak AMOC strength. This is confirmed in the conceptual model, which captures similar AMOC hysteresis behavior as in the CESM simulation and where steady states are computed versus freshwater forcing parameters. In the conceptual model, transition probabilities between the different equilibrium states are determined using rare event techniques. The transition probabilities from a strong AMOC state to a weak AMOC state increase when considering sea ice insulation effects and indicate that sea ice promotes these transitions. On the other hand, sea ice insulation effects strongly reduce the probabilities of the reverse transition from a weak AMOC state to a strong AMOC state and this implies that sea ice also limits AMOC recovery. The results here indicate that sea ice effects play a dominant role in AMOC hysteresis width and influence transition probabilities between the different equilibrium states. Significance Statement We develop a novel conceptual ocean–sea ice box model to explain AMOC hysteresis behavior recently found in a modern complex climate model (the Community Earth System Model) and determine how sea ice insulation effects influence the hysteresis width and the probability of AMOC transitions.

Effects of Dental Sound Insulation System on Stress and Dental Fear Reduction in Pediatric Patients

This study aimed to assess the effectiveness of dental sound insulation in alleviating stress and fear during dental scaling in pediatric patients. It also examined the influence of a noise-canceling application on dentist-patient communication and convenience of dental procedures. This study included 60 children and adolescents aged 7 - 16 years between April 2022 and March 2023. All participants underwent dental plaque control using an ultrasonic scaler on the maxilla first, followed by plaque control on the mandible. Dental sound insulation with active noise canceling was randomly applied to either the maxilla or mandible. Findings revealed that the stress index was significantly reduced when the application was used, with a score of 5.85 compared to 8.43 without it (p &lt; 0.0001). Similarly, the dental fear score was significantly reduced to 1.17 with the application, as opposed to 2.97 without it (p &lt; 0.0001). The dental sound insulation did not affect the communication between dentists and patients or the convenience of treatment. This study demonstrated that active noise canceling during pediatric dental care significantly reduced stress and fear, suggesting that it could be a valuable behavior guidance tool, particularly for children who find dental visits challenging.

Thermodynamic Analysis of Asteroid Mining Systems: Insights from Optical Mining Bag Materials

This study investigates the thermodynamic behaviors of materials within an optical mining system aimed at extracting water from asteroids. The spacecraft utilizes solar reflectors to concentrate sunlight onto the captured asteroid, initiating the extraction process. The focus lies on analyzing the thermodynamic properties of the asteroid mining bag, constructed with layers of Nomex (outer layer), Kevlar (supporting layer), and a PANI thin film (inner layer). Through a MATLAB Simulink model, a 10-day mining simulation is conducted, revealing the system's capability to extract water at a rate of 77 g/s. Key parameters such as temperature, pressure, heat flow rate, and gas flow rate are measured within the mining bag. Additionally, the study accounts for thermal insulation effects on the asteroid bag and heat losses to the surrounding environment. The thermodynamic equations governing heat transfer, mass conservation, and energy within the asteroid bag are analyzed, providing insights into the efficiency and effectiveness of the mining process. This research contributes to understanding the thermodynamic principles underlying asteroid mining operations and guides future developments in this field.

Influence of the mass percentage of binders on the properties of LHC

This paper investigates the effects on the physical and mechanical properties and microstructure of lime-hemp concrete (LHC) materials at different binder mass ratios. A mixture of three cementitious materials, slaked lime, cement, and coal gangue powder, was used as binder, and hemp shives were used as concrete aggregate, and five test groups were designed, i.e., binder/hemp shives (B/H) mass ratios of 1.2, 1.4, 1.6, 1.8, and 2.0. The physical properties of LHC, including density, drying rate, water absorption, thermal conductivity coefficients, and mechanical properties (compressive strength and flexural strength) with different binder ratios were investigated. In addition, the microstructural properties of 56d LHC were investigated by SEM, XRD, and TG-DTG micro-scale analysis methods. The results showed that with the increase in binder content, the drying speed of LHC became faster, the thermal conductivity coefficients, compressive strength, and flexural strength increased, and the water absorption was just the opposite. With a fit ratio of 2.0, the strength is the greatest and the toughness is the best; with a fit ratio of 1.2, the thermal conductivity coefficient is the smallest and the insulation effect is the best. In addition, the hydration of the binder produced different forms of hydration products (CaCO3 and C-S-H), and the hydration products increased in quantity with the increase of the binder, resulting in stronger CaCO3 and C-S-H diffraction peaks. The hydration products produce a better bond with the rough cannabis particle surface, filling the internal voids of the LHC, improving the density of the material, and enhancing the mechanical properties of the material.

Magnetic control of phonon transport in magnetic insulator thulium iron garnet

The coupling between magnons and phonons and the associated phenomena have long been a focus of research in condensed matter physics. Contrary to its recognized role in magnon relaxation, its impact on phonon transport remains largely unexplored. Here, we fill this gap by investigating the effect of magnon-phonon coupling on phonon excitation, relaxation, and transport with magneto-optical reflectometry. Through simultaneous measurements of magnon and phonon populations in magnetic insulator thulium iron garnet, we observe the excitation of excessive phonons driven by non-equilibrium magnons, demonstrating the magnetic control of phonons. Furthermore, our time-resolved experiments reveal the magnetic field-dependent phononic thermal conductivity, signaling the potential of magnetic manipulation of heat transport. Our finding indicates that phonons can be controlled by magnetic means through magnon-phonon coupling and thereby opens a new avenue to harness magneto-thermoelectric effects in magnetic insulators.

Study on Thermal Insulation Performance of Silica Aerogel Thermal Insulation Blankets.

In this paper, the thermal insulation performance of silica aerogel was studied. Aerogel heat insulation blankets can be widely used in the military, cold storage, aerospace, automotive and other industries. The heat insulation principle of aerogel was analyzed theoretically, and the heat transfer model of aerogel was established. Experiments are designed to verify the accuracy of the model, and it is concluded that the distance between the aerogel and the target is more important for the thermal insulation effect than the thickness of the aerogel.

Superior flame retardancy, thermal insulation, and mechanical properties of konjac glucomannan/sodium alginate biomass aerogel modified by supramolecular assembled phytic acid-melamine nanosheet

The development of biomass-based eco-friendly aerogel with superior flame retardancy, thermal insulation, and mechanical properties at the same time has long been a tough challenge. In this study, the polysaccharide-based aerogels composed of konjac glucomannan, sodium alginate, and supramolecular assembled melamine phytate (MPA) nanosheets were successfully fabricated through the freeze-drying method. Owing to the excellent charcoal-forming and non-combustible gas-releasing effect of MPA nanosheets, the thermal stability and flame retardancy properties of the aerogels were both significantly enhanced, with the highest limiting oxygen index value reaching 42.4 %. Meanwhile, appropriate MPA embedded in the pore walls greatly enhanced the compressive strength of the aerogel (364.9 kPa) and can withstand >7100 times its weight without visual deformation. Moreover, the thermal insulation effect was quite attractive with a thermal conductivity of 0.0385–0.0420 W/mK. The present work provided an environmentally friendly method for the fabrication of multifunctional sustainable fire-resistant aerogels, which showed promising prospects in the future.

Insulator-donor electron wavefunction coupling in pseudo-bilayer organic solar cells achieving a certificated efficiency of 19.18.

The incorporation of polymeric insulators has led to notable achievements in the field of organic semiconductors. By altering the blending concentration, polymeric insulators exhibit extensive capabilities in regulating molecular configuration, film crystallinity, and mitigation of defect states. However, current research suggests that the improvement in such physical properties is primarily attributed to the enhancement of thin film morphology, an outcome that seems to be an inevitable consequence of incorporating insulators. Herein, we report a general and completely new effect of polymeric insulators in organic semiconductors: the insulator-donor electron wavefunction coupling effect. Such insulators can couple with donor polymers to reduce the energy barrier level and facilitate intramolecular electron transport. Besides the morphological effects, we observed that this coupling effect is another mechanism that can significantly enhance electron mobility (up to 100 times) through the incorporation of polymeric insulators in a series of donor systems. With this effect, we proposed a polymeric insulator blending approach to fabricate state-of-the-art pseudo-bilayer organic solar cells, and the PM6/L8-BO device exhibits a high efficiency of 19.50% (certificated 19.18%) with an improved interfacial electron transport property. This work not only offers a novel perspective on the quantum effect of polymeric insulators in organic semiconductors, but also presents a simple yet effective method for enhancing the performance of organic solar cells.

Multi-pronged strategies for enhancing building envelopes toward nearly-zero energy in hot climatic regions

Abstract Growing concerns about climate change and rising energy demands necessitate advancements in building energy efficiency. This study investigates the effectiveness of radiative coatings and thermal insulation, both individually and combined, in reducing energy consumption and carbon footprint for buildings in hot and humid climates. This research contributes to a growing body of knowledge by comprehensively evaluating the combined effects of these strategies. A comparative analysis was conducted using data on energy usage and carbon emissions. The research highlights the effectiveness of envelope-enhancing techniques in reducing energy consumption and carbon emissions. The application of radiative coating led to a significant 13.1% decrease in energy usage, totaling 681.95 MWh, and corresponding emissions of 482.14 tons of CO2. Radiative coating offers the most cost-effective solution with an LCOS of $0.045 kWh−1. When integrating thermal insulation with radiative coating, there was a substantial 12.0% reduction in energy consumption, amounting to 690.39 MWh, and emissions of 488.11 tons of CO2. The integrated model provides significant energy savings at a slightly higher LCOS of $0.052 kWh−1, making it a balanced choice between efficiency and cost-effectiveness compared to using thermal insulation alone. Moreover, the study emphasizes that the combination of Glazing Integrated Photovoltaic (GIPV) with radiative coating can lead to the creation of nearly zero-energy buildings, resulting in a significant energy savings of 34.9%. These results underscore the efficacy of these technologies in achieving significant energy savings and environmental benefits. This study demonstrates that radiative coatings significantly reduce energy consumption and carbon footprints. The combined method with thermal insulation reduces energy, suggesting further optimization strategies in hot and humid conditions. The results of this investigation recommend utilizing Glazing Integrated Photovoltaic (GIPV) to achieve nearly zero-energy buildings. Such integrated solutions not only improve energy efficiency but also make a substantial contribution to environmental sustainability in the building sector.