Thermal Insulation Technology Research Articles

Wall-applicable metamaterial: mitigating resonance dip for enhanced sound transmission loss

In recent years, there has been a significant advancement in thermal insulation technology, allowing for the implementation of energy-efficient solutions in existing buildings while preserving their architectural and cultural significance. This recognition has led to the widespread adoption of External Thermal Insulation Composite Systems (ETICS). However, this brings the common challenge in acoustic engineering, the resonance dip, into the spotlight. When the frequency of an incident sound wave coincides with a mass-spring-mass resonance of the thermally insulated wall, the sound insulation drop occurs, possibly resulting in a reduction in transmission losses. This study introduces a wall-applicable design of Plate-type Acoustic Metamaterial (PAM) to effectively enhance sound transmission loss. We investigated in development a transfer matrix method combined with the effective mass density of PAM to model the ideal metamaterial wall and further compared it with the results based on mass-law methods. Design strategies to construct the ideal bandgap were developed by analyzing dispersion curves.

New robust multi-criteria decision-making framework for thermal insulation of buildings under conflicting stakeholder interests

The choice of thermal insulation technology for existing building retrofit can be a complex multi-criteria decision-making (MCDM) problem characterized by multiple stakeholders with conflicting interests. The conflicting interests of the building owners and the policymakers could negatively influence the adoption of low-carbon energy retrofit measures by building possessors, slowing down the progress toward sustainable development. The investigation of this issue is, therefore, crucial to support more informed decisions and offer policymakers useful insights to develop future economic incentives for energy refurbishment of buildings. Most of the existing MCDM studies on the subject do not emphasize the differences among different stakeholders nor consider the outcomes' robustness. To overcome this gap, this paper integrates multi-stakeholder analyses and robustness assessments to provide broad-spectrum and reliable results. An innovative robust MCDM framework for building thermal insulation under conflicting stakeholder interests is proposed and tested on a real case study building (located in Southern Italy) using building dynamic energy simulation. Several alternatives of thermal insulation are evaluated under environmental, energy, and economic key performance indicators (KPIs). The Analytic Hierarchy Process is used to define criteria weights for conflicting decision-makers representing collectivity (policymakers) and private interests. TOPSIS, VIKOR, WASPAS, and MULTIMOORA methods are integrated to perform initial rankings of the alternatives. A rank similarity analysis is performed to evaluate the consensus between MCDM methods, and an ensemble ranking is obtained for each decision-maker using an approach based on the half-quadratic theory. A Confidence Index and a Trust Level are used to evaluate the agreement among the MCDM approaches, verifying the reliability of the final ensemble ranking. The robustness of the framework is attained by complying with well-established literature guidance. The hybrid MCDM analysis showed that porous materials like expanded clay and expanded perlite lead to better results under the KPIs investigated. The worst performances are attained by vacuum insulation panels and aerogel, mainly due to high values of embodied CO2 emissions and long payback periods. Insights upon the performance of different thermal insulating alternatives are also highlighted by the study and a stakeholder comparative analysis demonstrates that global rankings obtained for the different decision-makers show some similarities, but also important deviations, and a full compromise solution is not achieved.

Experimental study on creep characteristics of glazed hollow beads-cement/sodium silicate grouting materials

This study introduces a new thermal insulation grouting material designed for high-temperature mine environment. The thermal insulation effect of cement/sodium silicate grouting materials can be enhanced by adding glazed hollow beads with outstanding thermal insulation properties. The ratio with the best comprehensive performance was selected through orthogonal tests, and the long-term creep mechanical characteristics of glazed hollow beads-cement/sodium silicate grouting materials were analyzed. Graded equal incremental loading with different loading durations was used to test the specimens' instantaneous strain, creep strain, creep rate, critical stress, and microscopic structures. For each loading stage, the Burgers model was used to fit the creep curve. The results show that graded loading intensity surpasses uniaxial loading across different loading durations. The different loading durations significantly affect the creep parameters, and stress concentration damage initially manifests on the surface of glazed hollow beads. Finally, the theoretical curve obtained by the Burgers model fits well with the creep test curve. This study has good practical significance for high-temperature roadway thermal grouting insulation technology.

A comprehensive study on transient thermal behaviors and performances of the modular pipe-embedded energy wall system under intermittent operation conditions

The active thermal insulation technology based on utilizing low-grade thermal energy makes the opaque envelopes gradually be treated as multifunctional components with structural and energy properties. In this study, the dynamic thermal behaviors of modular pipe-embedded energy (MPE) walls integrated with pipe installation cavity and backfilling material are numerically studied, and then the impacts of key variables on MPE walls are explored. Results show that the thermal behaviors of MPE walls can be significantly improved under all intermittent charging modes, while the maximum extra heat loss caused by applying filler cavity and backfilling material is only 2.4%. When the injection time is kept constant, MPE walls operated in multi-pulse modes, especially those with higher heat injection frequency (e.g., 3On3Off mode), can achieve a better performance enhancement and operating energy reduction effect. Besides, a reasonable increase in λf-value or a:b-value can effectively alleviate the heat accumulation around water pipes. In addition, the energy consumption of heat charging systems can be significantly reduced when performance indicators can be slightly sacrificed. Results highlight the effectiveness of adding pipe cavity and backfilling materials in enhancing the performance of MPE walls, which can provide theoretical guidance and data support for such walls in the future.

Thermal Insulation, Antifreeze, and Anti-Drainage Technology for Tunnels in the Cold Area of Jinpen Bay

There are a large number of tunnels built in permafrost regions every year in China. When investigating the road tunnels that have been in operation in cold regions, it was found that most of these tunnels have various freezing damages. Therefore, in the design, construction, operation, and maintenance of tunnels in cold regions, there are still many technical problems that need to be solved urgently. Among them, the problems of heat preservation, anti-freezing, and anti-drainage are the key technical problems to determine whether the tunnels in cold regions are affected by freezing damage. The project was based on the completed highway tunnels in Inner Mongolia. Given a series of special problems faced by the construction and management of tunnels in cold regions, a large number of reference documents were consulted. This paper designed thermal insulation, antifreeze, and anti-drainage technology for tunnels in the cold area of Jinpen Bay. The research in this paper can effectively reduce the probability of the occurrence of tunnel freezing damage, ensure the safety of the long-term operation of the tunnel lining structure, and greatly reduce maintenance costs, which have good economic and social benefits.

An Air Heat Tracing System of Firefighting Pipeline in Cold Region Highway Tunnel

Ensuring the proper operation of tunnel firefighting systems in cold regions is a key issue at hand. According to the characteristics of cold region tunnel fire control systems, this paper puts forward a kind of air heat tracing system (AHTS) that is suitable for cold region tunnel firefighting systems. In the AHTS, an annular air duct was used to heat the firefighting pipe and keep it warm, so that the water temperature in the firefighting pipe is above the freezing point, which helps prevent the water in the firefighting pipe from freezing and avoids the failure of the firefighting system. Meanwhile, the finite element software ANSYS was used to simulate the working state of the AHTS under different conditions, and the insulation effect under different conditions was evaluated. The results showed that the AHTS has a good heating and heat preservation function, which can effectively maintain the normal operation of the tunnel firefighting system in cold regions under a low temperature environment (below 0 °C). Furthermore, increasing the air temperature and air speed in the system was beneficial to the working effect of the AHTS, and the “high temperature and low speed” mode was beneficial to reduce the system power consumption. It is recommended that v = 5 m/s and Ta = 50 °C be used as the preset operating parameters. Finally, according to the numerical analysis results, the scientific and reasonable working parameters of the AHTS under different working conditions were optimized. The research content can provide new ideas and theoretical support for the thermal insulation technology of tunnel firefighting systems in cold regions in the future.

Processing and Advancements in the Development of Thermal Barrier Coatings: A Review

Thermal barrier coating is critical for thermal insulation technology, making the underlying base metal capable of operating at a melting temperature of 1150 °C. By increasing the temperature of incoming gases, engineers can improve the thermal and mechanical performance of gas turbine blades and the piston cylinder arrangement. Recent developments in the field of thermal barrier coatings (TBCs) have made this material suitable for use in a variety of fields, including the aerospace and diesel engine industries. Changes in the turbine blade microstructure brought on by its operating environment determine how long and reliable it will be. In addition, the effectiveness of multi-layer, composite and functionally graded coatings depends heavily on the deposition procedures used to create them. This research aims to clarify the connection between workplace conditions, coating morphology and application methods. This article presents a high-level overview of the many coating processes and design procedures employed for TBCs to enhance the coating’s surface quality. To that end, this review is primarily concerned with the cultivation, processing and characteristics of engineered TBCs that have aided in the creation of specialized coatings for use in industrial settings.

Brief Discussion on New Building Materials and Energy Saving and Thermal Insulation Technology of Buildings

Brief Discussion on New Building Materials and Energy Saving and Thermal Insulation Technology of Buildings

An analytical and numerical investigation into conductive-radiative energy transfers in evacuated honeycombs. Application to the optimisation and design of ultra-high temperature thermal insulation

Ultra-high temperature thermal and latent energy storage technologies offer a potential solution to the decarbonisation of the energy sector. However, uneconomical thermal energy losses are a barrier to their development and where significant, their minimisation requires knowledge about the different modes of thermal transport and their interaction in a given structure. In this paper, evacuated rectangular honeycomb structures are investigated as candidates for efficient ultra-high temperature thermal insulation.First, a theory is laid out along with its numerical implementation for the modelling of coupled non-linear conduction and radiation in three-dimensional cuboid multi-media structures with rarefied gaseous and opaque or semi-transparent solid media. The model is then applied to the study, optimisation and design of efficient ultra-high temperature thermal insulation based on rectangular honeycomb structures.A dimensionless number Nrc is defined and an analytical thermal analysis of rectangular honeycombs is developed which correlates Nrc to the optimal geometry and equivalent thermal conductivity of a honeycomb insulator. A numerical optimisation procedure is then presented and the correlations are validated, and thus constitute simple practical design tools for honeycomb insulators. Finally, it is shown that with an appropriate choice of geometry and materials, thin-walled honeycombs have the capacity to outperform existing high-temperature thermal insulation technologies with thermal conductivities lower than 0.01 W/m/K at 1600 K. In particular, a wall thickness of 50μm on a titanium alloy honeycomb would suffice to outperform ceramic fibre insulation over its entire range of operating temperatures.

Optimal Design of Central Drainage Ditch Buried Depth for Highway Tunnel in Seasonally Frozen Region

In seasonally frozen regions, the drainage ditch of highway tunnels is usually set below the maximum frost depth. Hence, the deeply buried drainage ditch is often used, which increases the cost, difficulty, and time of tunnel construction. And it affects the stability of the surrounding rock and the tunnel structure safety. To solve these difficulties, this study investigated the optimal design of buried depth of central drainage ditch by numerical simulation. Based on a tunnel in Northwest China, a transient heat transfer model, which involves heat conduction and phase transition, was established. Then, the influences of different water amounts and thermal insulation technologies on the minimum buried depth of central drainage ditch were investigated. The results indicate that the thermal insulation layer, regardless of whether it is an internal thermal insulation layer, external thermal insulation layer, or foam concrete backfilled in invert arch, can prevent the drainage ditch from freezing and increase its elevation. The findings of this study can be helpful in optimizing the buried depth, selecting reasonable thermal insulation technology for central drainage ditch in seasonally frozen regions.

Living cool: An approach for Architectural “COOL ROOF” to Decrease the Electricity Consumption in Iraq

One of the most important problems in Iraq is the insufficient and inefficiency of the electrical power generating station, that is causing many problems in the availability of electricity in public and private buildings. This problem is leading to use privet power generators, causing air pollution and highly energy consumption. The second exploratory symposium “the reality of power in Iraq and its impact on the society” which had been held on May 2011 in Iraq proposed a large number of recommendations, a standout amongst these proposals was: urge the utilization of the thermal insulation in the building’s roofs to reduce the energy consumption. This study will prompt to the new idea of “living cool” in the Iraqi houses and different types of buildings throughout the day without the electricity’s power using by utilizing the new thermal insulation technology. This study eventually examines the idea of the “COOL ROOF” innovation to Iraqi’s houses and public buildings. The problem of the energy consumption might be the critical issue over the world generally, what’s more done Iraq specially. The transmission of the energy through top roofs might be more than (50%) starting with those general transmission energies through the other surfaces. Roofs with “high solar reflection”, high daylight reflection and high thermal emittance “high heat radiant” are remaining unflappable throughout the day. Previous researches approved that “the roof surfaces with low thermal emittances properties and high solar reflection might also remain cool in the sun and throughout the day. Use this type of roofs (cool roof) will reduce cooling electricity power in the different types of buildings in Iraq. Cool roofs can also reduce the citywide encompassing air temperature over summer by decreasing those gigantic number for air-conditioning equipment, abating ozone framing furthermore, eventually expanding human comfort demands by using the nature and minimum requirements to reach human comfortable zones. This research has been used practical details to apply the cool roof technology in Iraq.

Energy saving technology of wall insulation of harbor building based on energy cost analysis

Seaport buildings have been affected by marine moisture for a long time, but most of the wall thermal insulation studies have not considered the moisture transfer effect of the wall structure. Therefore, considering the moisture transfer function of the wall structure and the energy consumption of solar radiation, based on the energy cost analysis, the paper puts forward the research on the wall thermal insulation and energy-saving technology of the harbor building based on the energy cost analysis. Grey clustering is used to analyze the project cost and environmental benefits to determine the index weight. By using two kinds of thermal insulation materials and three kinds of insulation positions, the thermal performance and condensation characteristics of the wall are analyzed. It is found that increasing the thickness of the insulation layer is conducive to reducing the heat loss of the wall. Extruded polystyrene foam (XPS) thermal insulation material is better than expandable polystyrene board (EPS) insulation material, while EPS is more economical and energy-saving than XPS.

The Renaissance of Liquid Metal Batteries

Next-generation batteries with long life, high-energy capacity, and high round-trip energy efficiency are essential for future smart grid operation. Recently, Cui et al. demonstrated a battery design meeting all these requirements—a solid electrolyte-based liquid lithium-brass/zinc chloride (SELL-brass/ZnCl2) battery. Such a battery design overcomes some inherent problems of conventional ZEBRA batteries and lithium ion batteries.

A high-efficiency liquid hydrogen storage system cooled by a fuel-cell-driven refrigerator for hydrogen combustion heat recovery

Effective thermal insulation technology is served as the key to liquid hydrogen storage. Existing studies have mainly been shedding light on the performance optimization of the passive thermal insulation systems or the direct introduction of refrigerators to achieve zero-boil-off storage. However, considering the immense combustion heat that is taken away by gaseous hydrogen discharged from the passive thermal insulation system, and the additional electric power required to be introduced in driving the refrigerator under the current zero-boil-off system, this paper is intended to propose a novel liquid hydrogen storage system that is cooled by a fuel-cell-driven refrigerator for hydrogen combustion heat recovery. In an effort to reduce the heat leakage, the combustion heat is recovered and converted into electricity, which can then be used to drive the refrigerator in cooling the passive insulation material. In this paper, a thermodynamic calculation model composite of the fuel cell, refrigerator, and passive thermal insulation system was established and verified. According to the results, at a fuel cell efficiency of 50%, the insulation efficiency of the proposed system is improved by up to 80.3% compared with the traditional multi-layer insulation system. Besides, the effects of fuel cell efficiency, refrigerator efficiency, cold shield position, storage pressure, boundary temperature, and system vacuum on the insulation performance were also analyzed.

Kajian Parametrik Analisis Terma Bumbung Menggunakan Teknik Berangka

The ever-increasing temperature of current climate has brought the attention on reducing the incoming solar heat energy into buildings. The efforts on reducing the dependency on air-conditioning for indoor cooling has led to the implementation of passive cooling strategies in buildings. This paper investigates the implementation of reflective technologies in the form of reflective insulation and radiant barrier systems in a gable roof assembly. The thermal performance of reflective insulation and radiant barrier systems was investigated by using Computational Fluid Dynamics (CFD) simulation. The thermal performance of the reflective technologies was presented in terms of thermal resistivity, RSI value. The study was conducted for several roof configurations where the thickness of reflective air space, roof pitch and the roof material were varied. The results obtained from the CFD simulation was validated against empirical measurements to ensure the simulation gives high accuracy prediction. From the parametric analysis, it was found that thicker reflective air space would provide better air ventilation in the air space area which led to higher thermal resistivity. Besides that, steeper roof pitch would enhance the buoyancy effect and increases the heat exhaustion through the ridge which also results in higher thermal resistivity. In terms of roof tiles material, only small difference was observed in terms of thermal resistivity when switching the roof tiles material between clay tiles and concrete tiles. This research was able to demonstrate the use of CFD simulation in investigating thermal insulation technologies in buildings and this method should be explored further in the future.

A Novel Composite Insulation System of Hollow Glass Microspheres and Multilayer Insulation with Self‐Evaporating Vapor Cooled Shield for Liquid Hydrogen Storage

The efficient storage method of hydrogen energy is a major concern in its practical application. Compared with other hydrogen storage methods, liquid hydrogen (LH2) storage has the advantages of high energy storage density and low storage pressure. However, the temperature of LH2 is significantly lower than room temperature, and heat leakage causes it to evaporate continuously. Thus, an efficient thermal insulation technology is a key to LH2 storage. Herein, based on the traditional multilayer insulation (MLI), a novel insulation system combining hollow glass microspheres (HGMs) that is not sensitive to vacuum with self‐evaporating vapor cooled shield (VCS) that can recover hydrogen cold‐energy is introduced and analyzed. Based on the layer‐by‐layer method, a thermodynamic calculation model is established, and related experimental verification is completed. The results show that the heat leakage of the proposed insulation system is decreased by 45% under high vacuum (10−3 Pa) and 81% under low vacuum (1 Pa) compared with the traditional MLI. The influences of the VCS position, LH2 storage pressure, hot boundary temperature, and vacuum on the thermal insulation performance of the composite thermal insulation system are also analyzed.

The Numerical Simulation and Experimental Research on Combustion Process in 660MW Boiler

In order to solve the problems of thermal insulation and ash prevention of the furnace combustion layer temperature detection devices installed on the boiler furnace, FLUENT software is used to numerically simulate the actual combustion process in the furnace of 660 MW power plant boiler, and the combustion status of each layer in the furnace is analyzed and studied. And then, according to the results of data simulation the thermal insulation and ash prevention technology implementation of the furnace combustion temperature detection devices is guided. The installation operation test results show that the furnace combustion temperature detection devices work within the range of instrument allowed −20°C∼85°C temperature, which can obtain the direct, rapid, real-time furnace combustion temperature data that provides a valuable source of data for further optimization control of boiler combustion process.

Research on Energy Saving greenhouse based on Sunlight Environment

This paper combs the current research on the energy-saving greenhouse in a daylight environment. The application and research progress of thermal insulation and energy-saving technology in the solar greenhouse in China are introduced from the aspects of location, type, orientation, front roof, rear roof, wall, multi-layer cover in a greenhouse, cold prevention ditch, cheap energy, utilization and cultivation of energy-saving equipment, operation, and management. Finally, some suggestions are given for the future research of energy-saving greenhouse in the solar environment, to make a certain contribution to the research of energy-saving greenhouse in the solar environment.

Kajian Parametrik Analisis Terma Bumbung Menggunakan Teknik Berangka

The ever-increasing temperature of current climate has brought the attention on reducing the incoming solar heat energy into buildings. The efforts on reducing the dependency on air-conditioning for indoor cooling has led to the implementation of passive cooling strategies in buildings. This paper investigates the implementation of reflective technologies in the form of reflective insulation and radiant barrier systems in a gable roof assembly. The thermal performance of reflective insulation and radiant barrier systems was investigated by using Computational Fluid Dynamics (CFD) simulation. The thermal performance of the reflective technologies was presented in terms of thermal resistivity, RSI value. The study was conducted for several roof configurations where the thickness of reflective air space, roof pitch and the roof material were varied. The results obtained from the CFD simulation was validated against empirical measurements to ensure the simulation gives high accuracy prediction. From the parametric analysis, it was found that thicker reflective air space would provide better air ventilation in the air space area which led to higher thermal resistivity. Besides that, steeper roof pitch would enhance the buoyancy effect and increases the heat exhaustion through the ridge which also results in higher thermal resistivity. In terms of roof tiles material, only small difference was observed in terms of thermal resistivity when switching the roof tiles material between clay tiles and concrete tiles. This research was able to demonstrate the use of CFD simulation in investigating thermal insulation technologies in buildings and this method should be explored further in the future.

Studies on active thermal insulation technology based on heat sink principle

Based on the principle of heat sink, the active thermal insulation technology was proposed in this article. An artificial low temperature zone was created during the adiabatic process, and the heat amount that needs to be blocked could be reabsorbed by this zone, then redistributed and recycled within the thermal equipment, without any energy loss, the thermal insulation could be achieved. To verify the effect of this technology, a heat sink device was designed and a new type electric storage water heater was converted. The device’s heat reallocation ability and equivalent thermal resistance were studied, along with the experimental method, the rationality of new type water heater was verified. The results show that an artificial low temperature zone was constructed within the water heater cavity, reduced internal and external temperature difference from 60 °C to 10.5 °C, the thermal insulation was improved. Besides that, according to exergy calculation, the heat reallocation function of heat sink device enabled the energy matching more reasonable, which is beneficial to enhance the thermal efficiency and achieve energy-saving.