scholarly journals Design of Thermal Insulation Materials with Different Geometries of Channels

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2217
Author(s):  
Daniela Șova ◽  
Mariana Domnica Stanciu ◽  
Sergiu Valeriu Georgescu
Keyword(s):  
Thermal Conductivity ◽  
Porous Structure ◽  
Base Material ◽  
Cost Effective ◽  
Heat Radiation ◽  
Average Temperature ◽  
Temperature Regimes ◽  
The Face ◽  
Inclined Channels ◽  
Air Channels

Investigating the large number of various materials now available, some materials scientists promoted a method of combining existing materials with geometric features. By studying natural materials, the performance of simple constituent materials is improved by manipulating their internal geometry; as such, any base material can be used by performing millimeter-scale air channels. The porous structure obtained utilizes the low thermal conductivity of the gas in the pores. At the same time, heat radiation and gas convection is hindered by the solid structure. The solution that was proposed in this research for obtaining a material with porous structure consisted in perforating extruded polystyrene (XPS) panels, as base material. Perforation was performed horizontally and at an angle of 45 degrees related to the face panel. The method is simple and cost-effective. Perforated and simple XPS panels were subjected to three different temperature regimes in order to measure the thermal conductivity. There was an increase in thermal conductivity with the increase in average temperature in all studied cases. The presence of air channels reduced the thermal conductivity of the perforated panels. The reduction was more significant at the panels with inclined channels. The differences between the thermal conductivity of simple XPS and perforated XPS panels are small, but the latter can be improved by increasing the number of channels and the air channels’ diameter. Additionally, the higher the thermal conductivity of the base material, the more significant is the presence of the channels, reducing the effective thermal conductivity. A base material with low emissivity may also reduce the thermal conductivity.

Thermoelectric properties of Zn– and Ce–alloyed In2O3 and the effect of SiO2 nanoparticle additives

2021 ◽  
Author(s):  
Cheng-Lun Hsin ◽  
Jen-Che Hsiao ◽  
You-Ming Chen ◽  
Sheng-Wei Lee
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Porous Structure ◽  
Energy Conversion ◽  
Thermoelectric Module ◽  
Cost Effective ◽  
Sio2 Nanoparticle ◽  
Thermoelectric Oxides ◽  
The Matrix ◽  
Nanoparticle Additives

Abstract Thermoelectric materials are considered promising candidates for thermal energy conversion. This study presents the fabrication of Zn– and Ce–alloyed In2O3 with a porous structure. The electrical conductivity was improved by the alloying effect and an ultra–low thermal conductivity was observed owing to the porous structure, which concomitantly provide a distinct enhancement of ZT. However, SiO2 nanoparticle additives react with the matrix to form a third-phase impurity, which weakens the electrical conductivity and increases the thermal conductivity. A thermoelectric module was constructed for the purpose of thermal heat energy conversion. Our experimental results proved that both an enhancement in electrical conductivity and a suppression in thermal conductivity could be achieved through nano–engineering. This approach presents a feasible route to synthesize porous thermoelectric oxides, and provides insight into the effect of additives; moreover, this approach is a cost-effective method for the fabrication of thermoelectric oxides without traditional hot-pressing and spark–plasma–sintering processes.

Establishment of a digital simulated testing platform for radiation protection performance and preparation of three-layer coated flexible composites

2021 ◽  
pp. 004051752110028
Author(s):  
Guoyi Liu ◽  
Xiaoming Zhao ◽  
Yuanjun Liu ◽  
Yuhong Shen
Keyword(s):  
Thermal Conductivity ◽  
Thermal Radiation ◽  
Radiation Protection ◽  
Protective Coating ◽  
Base Material ◽  
Heat Radiation ◽  
Material Structure ◽  
Testing Platform ◽  
Flexible Composites ◽  
Test Platform

Fire proximity suits serve as the highest level of thermal protective clothing for firefighters when passing through the scene of a fire and within close range of open fire. A digital simulated testing platform for radiation protection performance was established based on the TPP701D thermal protective performance tester, by comparison of simulated data and measured results for the outer material of the fire proximity suit. Using single-, double- and three-layer flexible composites and the fabric as the base material, the reliability of the established simulation test platform was investigated. Based on this simulated test platform, in this paper the influence of the material structure and performance parameters (thickness, thermal conductivity, specific heat, density, emission rate and thermal reflectivity) of the heat radiation layer possessed by the three types of coating (thermal radiation protective coating, fireproof heat insulated coating and heat insulating coating) of three-layer coated flexible composites are discussed, thus providing the theoretical basis for the optimization and preparation of alternative outer materials for fire proximity suits. Based on the simulation data and measured results, the radiation protection performance of the three-layer structure is enhanced. Improving the average reflectivity of the heat rays for the thermal radiation protective coating, increasing the thickness of the heat insulating coating and reducing the thermal conductivity of the heat insulating coating are effective means of improving the radiation protection performance of the three-layer coated flexible composites.

Effective thermal conductivity of open-pore metal foams as a function of the base material

2015 ◽  
Vol 57 (10) ◽  
pp. 825-836 ◽  
Author(s):  
Alexander Martin Matz ◽  
Bettina Stefanie Mocker ◽  
Norbert Jost ◽  
Peter Krug
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Base Material ◽  
Metal Foams

Research on Porous Properties of Air-Entrained Lightweight Aggregate Concrete

2013 ◽  
Vol 652-654 ◽  
pp. 1209-1212
Author(s):  
Wei Xin Hu ◽  
Abulitipu. Abudula
Keyword(s):  
Thermal Conductivity ◽  
Porous Structure ◽  
Concrete Strength ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete ◽  
Materials Properties ◽  
Porous Properties ◽  
Concrete Materials ◽  
The Right

Lightweight aggregate concrete with bleed air : the air-entraining agent added to the lightweight aggregate concrete , cement paste to form the porous structure of the porous structure of the right amount of artificial lightweight aggregate concrete . Reduce the density of the concrete to improve the insulation properties of the concrete . Applied to structural insulation concrete strength than 20Mpa, the thermal conductivity is less than 0.36W / ( m • K) . Of lightweight aggregate structure insulation concrete materials properties and microstructure of variation with air entraining agent .

scholarly journals Polycrystalline SnSe with a thermoelectric figure of merit greater than the single crystal

2021 ◽  
Author(s):  
Chongjian Zhou ◽  
Yong Kyu Lee ◽  
Yuan Yu ◽  
Sejin Byun ◽  
Zhong-Zhen Luo ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
High Performance ◽  
Figure Of Merit ◽  
Waste Heat ◽  
Electric Energy ◽  
Cost Effective ◽  
Tin Selenide ◽  
Tin Oxides ◽  
Thermally Conductive

AbstractThermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m–1 K–1 at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material.

Thermal Conductivity Performance Modeling and Characterization of a Novel Anisotropic Conductive Adhesive Used in Lead-Free Electronics Packaging

2012 ◽  
Author(s):  
Matthew J. Combs ◽  
S. Manian Ramkumar ◽  
Satish Kandlikar
Keyword(s):  
Thermal Conductivity ◽  
Base Material ◽  
Bond Line ◽  
Thermal Interface Material ◽  
The Novel ◽  
Conductive Adhesives ◽  
Curing Conditions ◽  
Bond Line Thickness ◽  
Significant Research ◽  
American Society

The continued desire to utilize an alternative to lead-based solder materials for electrical interconnections has led to significant research interest in Anisotropic Conductive Adhesives (ACAs). The use of ACAs in electrical connections creates bonds using a combination of metal particles and epoxies to replace solder. The novel ACA discussed in this paper allows for bonds to be created through aligning columns of conductive particles along the Z-axis. These columns are formed by the application of a magnetic field, during the curing process. The benefit of this novel ACA is that it does not require precise printing of the adhesive on pads and also enables the mass curing without creating shorts in the circuitry. This paper will present the findings of the thermal conductivity performance tests using the novel ACA and its applicability as a thermal interface material and for assembling bottom termination components, power devices, etc. The columns that act as electrical conduction paths also contribute towards the thermal conductivity. The thermal conductivity of the novel ACA was measured utilizing a system that is similar to that in ASTM (American Society of Testing Materials) D5470 standard. The goal was to examine the influence of Bond Line Thickness (BLT), particle loading densities, particle diameters and adhesive matrix curing conditions on the electrical and thermal performance of the novel ACA. This paper will also present a numerical model to describe the thermal behavior of the novel ACA. The novel ACA’s applicability for PCB-level assembly has also been successfully demonstrated by RIT, including base material characterization, effect of process parameters, failures, and long-term reliability. Reliability testing included the investigation of the assembly performance in temperature and humidity aging, thermal aging, air-to-air thermal cycling, and drop testing.

scholarly journals Effective Thermal Conductivity of Open Cell Polyurethane Foam Based on the Fractal Theory

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Kan Ankang ◽  
Han Houde
Keyword(s):  
Thermal Conductivity ◽  
Fractal Dimension ◽  
Effective Thermal Conductivity ◽  
Polyurethane Foam ◽  
Solid Phase ◽  
Fractal Theory ◽  
Heat Radiation ◽  
Total Thermal Conductivity ◽  
Equivalent Thermal Conductivity ◽  
Open Cell

Based on the fractal theory, the geometric structure inside an open cell polyurethane foam, which is widely used as adiabatic material, is illustrated. A simplified cell fractal model is created. In the model, the method of calculating the equivalent thermal conductivity of the porous foam is described and the fractal dimension is calculated. The mathematical formulas for the fractal equivalent thermal conductivity combined with gas and solid phase, for heat radiation equivalent thermal conductivity and for the total thermal conductivity, are deduced. However, the total effective heat flux is the summation of the heat conduction by the solid phase and the gas in pores, the radiation, and the convection between gas and solid phase. Fractal mathematical equation of effective thermal conductivity is derived with fractal dimension and vacancy porosity in the cell body. The calculated results have good agreement with the experimental data, and the difference is less than 5%. The main influencing factors are summarized. The research work is useful for the enhancement of adiabatic performance of foam materials and development of new materials.

Thermal Conductivity and Prandtl Number of Carbon Dioxide and Carbon-Dioxide Air Mixtures at One Atmosphere

1961 ◽  
Vol 83 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Jerome L. Novotny ◽  
Thomas F. Irvine
Keyword(s):  
Carbon Dioxide ◽  
Thermal Conductivity ◽  
Prandtl Number ◽  
Maximum Error ◽  
Intermolecular Force ◽  
Temperature Range ◽  
Average Temperature ◽  
Pure Carbon ◽  
Prandtl Numbers ◽  
Pure Carbon Dioxide

By measuring laminar recovery factors in a high velocity gas stream, experimental determinations were made of the Prandtl number of carbon dioxide over a temperature range from 285 to 450 K and of carbon-dioxide air mixtures at an average temperature of 285 K with a predicted maximum error of 1.5 per cent. Thermal conductivity values were deduced from these Prandtl numbers and compared with literature values measured by other methods. Using intermolecular force constants determined from literature experimental data, viscosities, thermal conductivities, and Prandtl numbers were calculated for carbon-dioxide air mixtures over the temperature range 200 to 1500 deg for mixture ratios from pure air to pure carbon dioxide.

scholarly journals An analytical method to estimate temperature distribution of typical radiant floor cooling systems with internal heat radiation

2021 ◽  
pp. 014459872199800
Author(s):  
Xiaolong Wang ◽  
Wenke Zhang ◽  
Qingqing Li ◽  
Zhenqiang Wei ◽  
Wenjun Lei ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Internal Heat ◽  
Single Layer ◽  
Heat Radiation ◽  
Transfer Model ◽  
Cooling Systems ◽  
Average Temperature ◽  
Floor Surface ◽  
Floor Structure

Radiant floor cooling systems are increasingly used in practice. The temperature distribution on the floor surface and inside the floor structure, especially the minimum and average temperature of floor surface, determines the thermal performance of radiant floor systems. A good temperature distribution of the floor structure is very important to prevent occupant discomfort and avoid possible condensation in summer cooling. In this study, based on the heat transfer model of the single-layer homogeneous floor structure when there is no internal heat radiation in the room, this paper proposes a heat transfer model of single-layer floor radiant cooling systems when the room has internal heat radiation. Using separation variable methods, an analytical solution was developed to estimate temperature distribution of typical radiant floor cooling systems with internal heat radiation, which can be used to calculate the minimum temperature and the average temperature of typical composite floor structure. The analytical solution was validated by experiments. The values of the measured experiments are in a good agreement with the calculations. The absolute error between the calculated and the measured floor surface temperatures was within 0.45°C. The maximum relative error was within 2.31%. Prove that this model can be accepted. The proposed method can be utilized to calculate the cooling capacity of a typical multi-layer composite floor and will be developed in the future study for design of a typical radiant floor cooling system.

USE OF THE MICROWAVE ENERGY FOR ALUMINUM WASTE FOAMING

2019 ◽  
Vol 25 (4) ◽  
pp. 43-49
Author(s):  
LUCIAN PAUNESCU ◽  
MARIUS FLORIN DRAGOESCU ◽  
SORIN MIRCEA AXINTE ◽  
ANA CASANDRA SEBE
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Porous Structure ◽  
Powder Mixture ◽  
Aluminum Foam ◽  
Fine Powder ◽  
Microwave Energy ◽  
Raw Material ◽  
Foaming Agent ◽  
Foaming Process

The paper presents an aluminum foam experimental technique using the microwave energy. The raw material was recycling aluminum waste processed by ecological melting and gas atomizing to obtain the fine powder required in the foaming process. The powder mixture was completed with dolomite as a foaming agent. The products had a fine and homogeneous porous structure (pore size between 0.4-0.9 mm). The density (1.17-1.19 g/cm3), the compressive strength (6.83-7.01 MPa) and the thermal conductivity (5.71-5.84 W/m·K) had values almost similar to the foams made by conventional methods.

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