Heat Insulation Effect Research Articles

Sub-nanosecond pulse programming and device design strategy for analog resistive switching in HfOx-based resistive random access memory

The analog switching behavior of resistive random access memory (RRAM) is crucial for its application in neuromorphic computing. This paper investigates the switching mechanism of RRAM under sub-nanosecond and nanosecond pulse programming, with selected device materials and structures, using the kinetic Monte Carlo simulation method. The microscopic distribution of oxygen vacancies is simulated in all three spatial dimensions and in the time dimension (four-dimensional). According to the simulation results, thermal effects are a critical factor affecting the switching behavior. The thermal effects inside the HfOx switching layer can be almost completely eliminated by using sub-nanosecond pulses with low voltage, finally leading to good analog behavior. When nanosecond pulses are applied, effective heat insulation is the key to realizing analog characteristics. In general, the switching process is proposed to involve three stages. Having the lowest energy consumption, the first stage shows the greatest potential for achieving analog behavior. The use of heat-isolating structures, like capping layers and side wall materials with lower thermal conductance, could be a solution to improve the analog behavior of RRAM at the first stage when down-scaling the device size.

Heat Transfer Coefficient, Heat Release and Gas Hazard Tests for Expanded Polystyrene Heat Insulating Materials with Aluminum Foil

The purpose of this study is to enhance heat insulation effect and to decrease fire hazard by attaching aluminum foil to expanded polystyrene, which is mainly used for insulating materials, to have fire retardant. The result of the test confirmed that the insulating materials, expanded polystyrene of 10 kg/m3 and 14 kg/m3 of density attached aluminum foil on both sides, showed 12%, 14% of improved heat transfer coefficient respectively compared to existing expanded polystyrene of the same density. Besides, they met all the standards for the testing of heat release and gas hazard. On the other hand, the one made of general expanded polystyrene could not meet the standards of the heat release test and the gas hazard test.

Investigation of the interfacial heat transfer coefficient of sheet aluminum alloy 5083 in warm stamping process

The interfacial heat transfer coefficient (IHTC) between die and blank is an important boundary condition needed for numerical simulation of warm stamping of sheet aluminum alloys. The heat transfer behaviors of sheet aluminum alloy AA5083 are investigated through cylindrical-die stamping experiments. The methods for calculating IHTC such as the heat balance method and Beck's nonlinear estimation method are introduced. The IHTC during blank transportation and stamping-cooling stages are calculated and the influencing factors are analyzed. Both contact pressure and initial temperature positively influence the IHTC and the relationship can be expressed by a compound power function. Lubricant is found to have heat insulation effect beneficial to stamping and cooling in addition to its main function of lubrication. Finally, the heat transfer behaviors under one side contact the other side free and one side contact the other side insulated situations are investigated.

Insulating material based on shredded used tires and inexpensive polymers for different roofs

Thermal insulation is the ability of the material to prevent or reduce the heat transfer through the insulating material or between thermally contacted objectives. The increasing of the greenhouse effect leads to a continuous rising of the temperature especially in the summer, thus, there is a continuous research that aims to find more effective and environmental friendly insulation materials. Nowadays, a great number of proportions from polyurethane foam are produced every year in order to be used as an insulating material. Polyurethane foam shows an effective heat insulation results, but the price of the polyurethane is getting more expensive each day in Egypt due to the continuous rising of the hard currency as it is imported from abroad. This paper aims to prepare, design and develop effective heat insulation composite based on shredded used automobile tires. This was done by preparation different ratio composite from shredded used automobile tires and polyester along with polyurethane and shredded used automobile tires. These heat insulation tiles were characterized by the following testing, thermal insulation test, compression test, density measurement, abrasion test to measure the effect of adding the shredded used automobile tires to these polymers. It was found that, the composite of 66.7 wt % polyurethane foam and 33.3 wt % shredded automobile tires was the best choice to be used as it provides efficient thermal insulation of K value of 0.1663 W/m.℃. It also has a low density of 0.0313 kg/l. Furthermore, the addition of shredded used automobile tires reduces the cost by 33%. Furthermore, the compression strength of the polyurethane foam was increased by adding the shredded used automobile tires. Hence, using cheap materials such as shredded used tires, which considered as undesirable waste material, results in both producing a cheap national heat insulating roof tile with good mechanical, waterproofing and thermal insulating characteristics along with solving a serious environmental problem that occurs to get rid of the shredded waste automobile tires, as in some cases the tires are being burned resulting in air pollution and causing various diseases, which finally leading to more waste treatment management strategies. Finally, this heat insulation composite directly results in lowering the energy consumption required to cooling and heating systems inside the buildings.

Characteristics of porous ceramics prepared from sandblasting waste and waste diatomite by co‐sintering process

The purpose of this research is to recycle sandblasting waste from the surface treatment process of solar cell industry to replace waste diatomite (with a replacement ratio of 0–20%) to make water‐retention porous ceramics, and adopts the method of molding by semi‐dry pressing under a pressure of 5 MPa, as the heating temperature fluctuated between 1000, 1100, 1200, and 1270°C. With a heating rate of 5°C/min, the heating process continued for 120 minutes. The sintered samples were then examined to determine whether its mechanical properties were met the CNS 382 R2002 Brick Criteria in terms of compressive strength (>3 MPa); while FTIR, and MIP instruments were used to measure the changes in the sintered samples according to pore size and total pore volume. The results indicated that the waste diatomite and sandblasting waste consisted of quartz, and porosities of porous ceramics with sandblasting waste about higher than 58.5–64.7%, water absorption of about 72.2–92.2%, and compressive strength of about 2.4–7.3 MPa can be produced using a porous ceramics of raw materials. The porous ceramics samples with 0–20% sandblasting waste prepared at the heating temperature of above 1100°C meet the Standards for Japan Interlocking Block Pavement Engineering Association (compressive strength > 3 MPa, water absorption > 70%). Moreover, the thermal conductivity of cement paste was 0.57 W/m.K, which was significantly higher than 0.28–0.49 W/m.K of porous ceramics with sandblasting waste, the porous ceramics have good heat insulation effects. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 321–328, 2019

Numerical analysis of heat extraction performance of a deep coaxial borehole heat exchanger geothermal system

The coaxial borehole heat exchanger (CBHE) can effectively develop deep geothermal resources with larger heat exchange area than traditional U-tube BHE. However, few studies focus on its parameters optimization and temperature field dynamic response. Hence, an unsteady-state heat transfer model is established for a deep CBHE. The finite difference method is adopted to solve the model, and the model is validated with experiment data. The effects of key factors on the CBHE performance are comprehensively analyzed. Simulation results depict that the outlet temperature decreases greatly at the initial stage, and then remains relatively stable. There is a critical value for flow rate to obtain higher thermal power with appropriate pressure drop. The insulated pipe can significantly reduce heat dissipation of working fluid in central pipe. There is an optimal insulation length in terms of heat insulation effect and costs. The thermal conductivity of cement sheath has remarkable influence on the thermal process and partial cementing with high thermal conductivity cement is favorable. The temperature field analysis shows that the impact scope is limited, and the temperature in the reservoir before the next heating period would almost recover its original condition, verifying the sustainability of CBHE system.

Bonding Strength and Thermal Insulation Property of Thermal Barrier Coating with Nanometer Alumina Coated Zirconia

The thermal barrier coating samples of different thickness with alumina coated zirconia and zirconia as coating materials were prepared on the surface of heat resistant alloy steel substrate after activation treatment with NiCoCrAlY as adhesive transition layer by plasma spraying method and spray gun quick spraying process. The bonding strength and thermal insulation property of two kinds of ceramic coating with the same thickness were compared by the test results of bonding strength, high temperature heat insulation and microstructure, and the relationship between the coating thickness and heat insulation effect were investigated. The results indicate that the structure and property of thermal barrier coating using nanoAl2O3coated ZrO2-Y2O3powder are superior to that using single zirconia powder. The thermal insulation property of the thermal barrier coating increased with the increasing of coating thickness, and the advantage is more obvious with temperature increasing.

Numerical investigation on thermal insulation layer of a tunnel in seasonally frozen regions

As an effective engineering measure, thermal insulation layer is used to prevent tunnel from frost heave damage in seasonally frozen regions. Two different methods are generally adopted to lay insulation layer. One is to lay the insulation layer between the preliminary lining and the secondary lining. The other is to lay the insulation layer on the surface of the secondary lining. But, there is no evidence to show which method is more useful. Meantime, the relationship between the insulation effect and thermal conductivity as well as thickness of insulation layer should be identified. To solve these problems, a numerical heat-moisture coupled model for the tunnel in a seasonally frozen region is established, which involves heat conduction, water migration and phase transition. And then, a representative tunnel in the Northwest of China is taken as an example to explore the heat-moisture state of the tunnel. Afterwards, the thermal insulation effect and the effect of location of thermal insulation layer on thermal state are analyzed. Subsequently, the methods on thermal conductivity and thickness of thermal insulation layer are constructed and the relationship among the insulation effect, thermal conductivity and thickness is obtained for heat insulation effect.

Transient heat transfer analysis of laminated materials based on extended separation of variables

In general, when the one-dimensional heat conduction equation is solved by the method of separation of variables, we need to know the governing equations, two boundary conditions and initial condition. Because the thermophysical parameters in different layers of laminated materials are different, the heat conduction model cannot be expressed by the same governing equation. For each layer of laminated material, the boundary condition is unknown. That equation can-not be solved directly by the general separation variable method. In this work the separation of variable method is extended. The temperature field of laminated material's heat transfer is divided into many minute time intervals on the time axis. Based on differential conception, in a minimum time interval, the temperature at the junction of laminated materials can be considered to be proportional to time. Assume that the slope coefficient makes the boundary condition known, then for each layer of laminated materials, the general separation of variables method will be used to solve the temperature field. According to the same temperature and the energy continuity at the junction of laminated materials, one can solve the slope coefficient. The temperature field in the whole time domain can be obtained through cycling. Then the three-layer insulation materials are analyzed by the extended separation variable method. The correctness of the method is verified by comparing the calculated results with those from the finite element method. The influences of the type and thickness of heat insulation layer, heat transfer coefficient, air temperature on the heat insulation are studied. It is found that the thermal conductivity of the thermal insulation layer has a great influence on the insulation. The material with low heat conduction coefficient can enhance the heat insulation effect. The thicker the thickness of the insulation layer, the more slowly the surface temperature of the heat insulation material rises, and the lower the final temperature, the better the insulation effect is. The thicker the thickness of the insulation layer, the smaller the heat flux density of the heat insulation material shell is, and the better the heat insulation effect when the heat transfer reaches a stable state. All calculation results are consistent with physical phenomena. In this work, the analytical method is used to solve the heat transfer problem of laminated materials. Compared with the general numerical methods, the analytical method presents clear physical meaning and high efficiency of operation as well.

Effect of wall heat insulation on wall heat transfer mechanism in rapid compression and expansion environment

Effect of wall heat insulation on wall heat transfer mechanism in rapid compression and expansion environment

07.18: Cold‐formed C‐sections encased in ultra‐lightweight concrete: Development of a Eurocode‐based design method

ABSTRACTA new direction of development in the field of light‐gauge building systems is when the load bearing elements made of cold‐formed steel (CFS) sections are encased in an ultra‐lightweight material. This material, apart from heat insulation and fire protection effects, can provide bracing effect to the CFS elements, too, therefore can increase the resistance against stability failures. Such lightweight material is the polystyrene aggregate concrete (PAC). Based on previous experimental results this paper develops design method for calculating local, distortional and global resistance of PAC‐encased CFS C‐sections. The proposed design method is based on the specifications of Eurocode, therefore applies the effective width method for calculating local buckling. The proposed procedure considers the effect of continuous bracing of PAC by replacing it with an elastic half‐space, similar to sandwich beam theory. Close form equations are derived to be able to calculate the effective width of plate elements by hand calculation. Distortional buckling is treated as buckling of an equivalent beam resting on elastic foundation, considering the additional stiffness provided by the infill material. The global flexural buckling failure modes of columns are dealt with separately using different mechanical models. Each calculation procedure was compared to existing experimental results in order to evaluate them.

Application of Mg-Al Layered Double Hydroxides Composite Fillers in the Water-Based Heat Insulation Coating

The water-based heat insulation coatings were prepared based on self-made Mg-Al layered double hydroxides (LDH), kaolin, titanium dioxide, barium sulfate and talcum powder. The heat insulation effects of different fillers single use and Mg-Al layered double hydroxides (LDH) compound use with them were investigated. The results of heat insulation test experiments reveal that Self-made Mg-Al layered double hydroxides (LDH) shows good heat insulation effect. Furthermore, after combining LDH with kaolin and titanium dioxide, the heat insulation effect is improved obviously and shows a positive synergy effect; whereas combining LDH with barium sulfate, the heat insulation effect is reduced obviously and shows a negative synergy effect. Finally, the Mg-Al layered double hydroxides (LDH) and the reflection of the prepared film were characterized by X-ray Powder diffraction (PXRD) and ultraviolet visible diffused reflection (UV-DRS ), respectively. Moreover, the results indicated that the heat insulating effect is mainly caused by the reflection of the coating film.

The Study on the Evaluation of Thermal Insulation Efficiency with Typical Plant Species of Roof Greenery in Kaohsiung

This research focuses on the buildings with relevant landscape engineering, and taking the public building as the targets including the sustainable campus project in Kaohsiung. Relevant studies and cases regarding roof greening are also collected and compiled as references for this research. Temperatures of the surface layers, soil layers and ceiling surfaces of different greening types are simultaneously measured in different locations on a 24-hour basis to explore the price-performance ratio of an effective heat-insulation green roof that meets users’ demands.Through filed experiment from real projects, the study compares the highest temperature of the top floors and ceilings with different roof greening types, with the data analyzed through the time-lag effect. The results show that factors influencing the heat capacity of greening types in their performance of temperature reduction and heat dissipation are surface temperature, solar radiation, height of the greening installations, shade and ventilation. Ranking of the most effective types from the best to the worst is: solar panel>planting at a certain height>soil with a certain thickness>planting>stony building materials>wood plastic composite path>soil>original surface. The one with the best price-performance ratio is planting at a certain height and a large shade, which can create a temperature difference by 10 Celsius degrees and achieve a constant indoor temperature. The test result is expected to serve as a reference to create an effective roof greening type in energy saving, temperature reduction and heat insulation. It can be applied to cities with overheating problems, and thus improve the comfort of the urban space in the future by creating a sustainable green space for living.

Characteristics of Ceramic Fiber Modified Asphalt Mortar.

Ceramic fiber, with a major composition of Al2O3 and SiO2, has advantages of stability at relatively high temperature, big specific surface area and resistance to external mechanical vibration. It has the potential contribution of improving the rutting resistance and temperature sensitivity of modified asphalt binder by proper modification design. In this research, ceramic fiber was introduced into both pen 60/80 and pen 80/100 asphalt binder by different weight ratios. An asphalt penetration test, softening point test, ductility test and dynamic viscoelastic behavior were conducted to characterize and predict the ceramic fiber modified asphalt mortar (CFAM). Research results indicated that the ceramic fiber has a great effect on reinforcement of asphalt, which makes the asphalt stiffer so that the asphalt can only undertake less strain under the same stress. The heat insulation effect of the ceramic fiber will improve the temperature stability. Complex modulus and phase angle results indicate that the ceramic fiber can significantly enhance the high temperature resistance of soft binder.

Effects of SiC Particle Size and Inorganic Binder on Heat Insulation of Fumed Silica-based Heat Insulation Plates

Heat insulation plates of fumed silica were prepared by mixing fumed silica, SiC powder and chopped glass fiber by a high speed mixer followed by pressing of the mixture powder in a stainless steel mold of 100 × 100 mm. Composition of the plates, particle size of SiC, and type of inorganic binder were varied for observation of their contribution to heat insulation of the plate. The plate was installed on the upper portion of an electric furnace the inside temperature of which was maintained at 400°C and 600°C, for investigation of heat transfer through the plate from inside of the electric furnace to outside atmosphere. Surface temperatures were measured in real time using a thermographic camera. The particle size of SiC was varied in the range of 1.3 ~ 17.5 μm and the insulation was found to be most excellent when SiC of 2.2 μm was incorporated. When the size of SiC was smaller or larger than 2.2 μm, the heat insulation effect was decreased. Inorganic binders of alkali silicate and phosphate were tested and the phosphate was found to maintain the heat insulation property while increasing mechanical properties.

Effect of air cooled spraybar heat insulation sleeve height on performance of mixer and diffuser

Effect of air cooled spraybar heat insulation sleeve height on performance of mixer and diffuser

Effects of Concentrations of NaCl on the Sintering and Thermal Conductivity of Forsterite

This paper aims to study the effects of NaCl on the sintering of forsterite as well as the thermal conductivity of the sintering products. In the sintering process, NaCl played a role in the system by mainly providing a liquid phase sintering environment in order to promote grain growth and forsterite sintering. Moreover, the model of liquid phase sintering was established in this paper. In the initial sintering stage, the phenomenon of particle re-arrangement was not significant, and dissolution-precipitation was regarded as the dominant sintering mechanism. With the extension of the sintering time, the middle and later stages of the sintering process were mainly controlled by the diffusion mechanism. A test of the thermal conductivity of samples with 40% and 50% NaCl was carried out, which indicated that the thermal conductivity of the two samples ranged from 0.3 to 0.4 W·m-1·k-1. At the same temperatures, the thermal conductivity of the sample with a salt content of 50% was lower than that of the sample with a salt concentration of 40%. Also, the heat insulation effect of the sample with a salt content of 50% was better than that of the sample of 40% . Hence, it can be concluded that the higher the salt content in the sample, the lower the thermal conductivity of the sample.

Влияние частичной теплоизоляции камеры сгорания дизеля на теплоотдачу в систему охлаждения

Влияние частичной теплоизоляции камеры сгорания дизеля на теплоотдачу в систему охлаждения

The effect of pyrolysis gaseous and condensed char of PC/PPSQ composite on combustion behavior

Polycarbonate (PC) is flame retarded by polyphenylsilsesquioxane (PPSQ) with a ladder structure. The flame retardant mechanism of PC/PPSQ composite between the gas phase and condensed phase is investigated using a thermo-gravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR), pyrolysis/gas chromatography and mass spectrometry (Py–GC/MS), cone calorimeter and scanning electron microscope-energy disperse spectroscopy (SEM-EDS). TG-FTIR results indicate that the thermal stability of the PC/PPSQ composite is marginally better than that of PC, and evolving gaseous products during the pyrolysis and infrared analysis, such as CO2, ester groups, aromatic components and isopropyl groups, are found. Py–GC/MS results show that higher concentrations of micromolecule gas products are released from the PC/PPSQ composite, which is beneficial for creating an intumescent char layer. Cone calorimeter tests and temperature variations of the top and bottom char layers indicate that the PC/PPSQ composite and the char layer have a good heat insulation effect. The results of char residues from FTIR indicate that SiO2 is composed of fumed silica which is attached to the internal surface char, white SiO2 is exposed to outside when the char is burned broken and the condensed phase of top char is composed of Si–O–Si and Si–C. The main structure of the bottom char is inorganic carbon. The SEM-EDS analysis indicates that the condensed phase of the char residue structure is composed of three elements, C, O and Si, the content of O and Si is much higher than C.

Conjugate Heat Transfer Characteristics of a Highly Thermal-Loaded Film Cooling System in Hot and Multicomposition Gas Condition

Radiation would be more important in turbine heat transfer due to higher temperature and multicomposition gas conditions in the future. The main goal of the current study is analyzing the characteristics of conjugate heat transfer considering radiation heat transfer, multicomposition gas, either with or without TBC coated. Both experimental and numerical studies were carried out. By comparing the experimental and the numerical results, it was concluded that the implemented thermal conduction/convection/radiation simulation method is valid for the cases studied. The results have shown that higher percentage of steam in the gas composition leads to higher temperature (lower normalized temperature) on the plate. With the percentage of steam in the hot gas increasing per 7%, the normalized temperature on the plate decreases about 0.02. The heat insulation effect of TBC is more obvious when the radiation effects are strong.