scholarly journals An effective thermal conductivity and thermomechanical homogenization scheme for a multiscale Nb3Sn filaments

2021 ◽  
Vol 10 (1) ◽  
pp. 187-200
Author(s):  
Xiaoyu Zhao ◽  
Guannan Wang ◽  
Qiang Chen ◽  
Libin Duan ◽  
Wenqiong Tu
Keyword(s):  
Volume Fraction ◽  
Material Design ◽  
Axial Direction ◽  
High Heat ◽  
Thermomechanical Properties ◽  
Homogenization Theory ◽  
High Heat Flux ◽  
Element Analysis ◽  
Hierarchical Microstructure ◽  
Thermal Conductivities

Abstract A comprehensive study of the multiscale homogenized thermal conductivities and thermomechanical properties is conducted towards the filament groups of European Advanced Superconductors (EAS) strand via the recently proposed Multiphysics Locally Exact Homogenization Theory (LEHT). The filament groups have a distinctive two-level hierarchical microstructure with a repeating pattern perpendicular to the axial direction of Nb3Sn filament. The Nb3Sn filaments are processed in a very high temperature between 600 and 700°C, while its operation temperature is extremely low, −269°C. Meanwhile, Nb3Sn may experience high heat flux due to low resistivity of Nb3Sn in the normal state. The intrinsic hierarchical microstructure of Nb3Sn filament groups and Multiphysics loading conditions make LEHT an ideal candidate to conduct the homogenized thermal conductivities and thermomechanical analysis. First, a comparison with a finite element analysis is conducted to validate effectiveness of Multiphysics LEHT and good agreement is obtained for the homogenized thermal conductivities and mechanical and thermal expansion properties. Then, the Multiphysics LEHT is applied to systematically investigate the effects of volume fraction and temperature on homogenized thermal conductivities and thermomechanical properties of Nb3Sn filaments at the microscale and mesoscale. Those homogenized properties provide a full picture for researchers or engineers to understand the Nb3Sn homogenized properties and will further facilitate the material design and application.

On modal analysis of axially functionally graded material beam under hygrothermal effect

2019 ◽  
Vol 234 (5) ◽  
pp. 1085-1101 ◽  
Author(s):  
Pankaj Sharma ◽  
Rahul Singh ◽  
Muzamal Hussain
Keyword(s):  
Modal Analysis ◽  
Functionally Graded Material ◽  
Volume Fraction ◽  
Axial Direction ◽  
Functionally Graded ◽  
Element Analysis ◽  
Hygrothermal Effect ◽  
Graded Material ◽  
Eigen Frequencies ◽  
Axially Functionally Graded Material

This investigation focuses on the modal analysis of an axially functionally graded material beam under hygrothermal effect. The material constants of the beam are supposed to be graded smoothly along the axial direction under both power law and sigmoid law distribution. A finite element analysis with COMSOL Multiphysics® (version 5.2) package is used to find the Eigen frequencies of the beam. The accuracy of the technique is authenticated by relating the results with the prior investigation for reduced case. The effects of moisture changes, temperature, and volume fraction index, length-to-thickness ratio on the Eigen frequencies are investigated in detail. It is believed that the present investigation may be useful in the design of highly efficient environmental sensors for structural health monitoring perspective.

Tailoring anisotropic thermal conductivity by varying filler particle organization in nickel-polydimethylsiloxane composites

2019 ◽  
Vol 53 (18) ◽  
pp. 2569-2577
Author(s):  
Peiying J Tsai ◽  
Souvik Pal ◽  
Suvojit Ghosh ◽  
Ishwar K Puri
Keyword(s):  
Thermal Conductivity ◽  
Additive Manufacturing ◽  
Volume Fraction ◽  
Filler Particle ◽  
Material Design ◽  
Interparticle Spacing ◽  
Element Analysis ◽  
Anisotropic Thermal Conductivity ◽  
Transverse Conductivity ◽  
Filler Particles

Anisotropic properties can be imparted to composite materials by arranging filler particles along specific directions inside the polymer matrix. These anisotropic patterns can be produced through dynamic field-assisted assembly of the filler particles during additive manufacturing. Using finite element analysis, we explore how chainlike arrangements of nickel particles embedded in a polydimethylsiloxane matrix modify bulk thermal conductivities in the axial and transverse directions. The axial conductivity increases up to nine times of the matrix conductivity with increasing filler volume fraction. While the axial conductivity decreases with increasing interparticle spacing, the transverse conductivity is uninfluenced. When particles within a chain are arranged in a zigzag pattern, increasing the interparticle zigzag angle decreases axial conductivity but increases transverse conductivity. As that angle increases to ∼55 º, the axial conductivity approaches a minimum, while the transverse conductivity approaches its maximum. An empirical model that includes effects of interparticle spacing and zigzag angle to predict the anisotropic thermal conductivity of a composite containing particle chains is presented. These results are relevant for the material design of particulate-reinforced polymer composites for advanced field-assisted additive manufacturing strategies.

scholarly journals Numerical Study on the Fluid Flow and Heat Transfer Characteristics of Al2O3-water Nanofluids in Microchannels of Different Aspect Ratio

2021 ◽  
Author(s):  
Huajie Wu ◽  
Shanwen Zhang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
High Heat ◽  
High Heat Flux ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Transfer Capacity

The study of the influence of the nanoparticle volume fraction and aspect ratio of microchannels on the fluid flow and heat transfer characteristics of nanofluids in microchannels is important in the optimal design of heat dissipation systems with high heat flux. In this work, the computational fluid dynamics method was adopted to simulate the flow and heat transfer characteristics of two types of water–Al2O3 nanofluids with two different volume fractions and five types of microchannel heat sinks with different aspect ratios. Results showed that increasing the nanoparticle volume fraction reduced the average temperature of the liquid–solid heat transfer surface and thereby improved the heat transfer capacity of the nanofluids. Meanwhile, the increase of the nanoparticle volume fraction led to a considerable increase in the pumping power of the system. Changing the aspect ratio of the microchannel effectively improved the heat transfer capacity of the heat sink. Moreover, increasing the aspect ratio effectively reduced the average temperature of the heating surface of the heat sink without significantly increasing the flow resistance loss. When the aspect ratio exceeded 30, the heat transfer coefficient did not increase with the increase of the aspect ratio. The results of this work may offer guiding significance for the optimal design of high heat flux microchannel heat sinks.

A FRACTAL MODEL FOR NUCLEATE POOL BOILING OF NANOFLUIDS AT HIGH HEAT FLUX INCLUDING CHF

Fractals ◽  
2010 ◽  
Vol 18 (04) ◽  
pp. 409-415 ◽  
Author(s):  
BOQI XIAO ◽  
SONGHUA GAO ◽  
LINGXIA CHEN
Keyword(s):  
Heat Flux ◽  
Volume Fraction ◽  
Pool Boiling ◽  
High Heat ◽  
Fractal Model ◽  
High Heat Flux ◽  
Nucleate Pool Boiling ◽  
Empirical Constant ◽  
Nucleation Sites ◽  
Proposed Model

A fractal model for nucleate pool boiling of nanofluids at high heat flux and critical heat flux (CHF) is developed based on the fractal distribution of nanoparticles and nucleation sites on boiling surfaces in this paper. The formula of calculating high heat flux and CHF for nanofluids in nucleate pool boiling is given by taking into account heat convection between nanoparticles and liquids due to the Brownian motion of nanoparticles in fluids. The proposed model is expressed as a function of temperature of nanofluids, the effective thermal conductivity of nanofluids, the average size of nanoparticles, the fractal dimension of nanoparticles and nucleation sites, the nanoparticles volume fraction of suspension, and physical properties of fluids. No additional/new empirical constant is introduced in this fractal model. An agreement between the proposed model predictions and experimental data is found. The validity of the fractal model for nucleate pool boiling of nanofluids at high heat flux and CHF is thus verified.

Effect of Fiber Volume Fraction on Thermal Conductivity of a Woven-Mat Composite Lamina

2005 ◽  
Author(s):  
Hossein Golestanian
Keyword(s):  
Thermal Conductivity ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Epoxy Composite ◽  
Fiber Volume ◽  
Element Analysis ◽  
Fiber Mats ◽  
The Common ◽  
Thermal Conductivities

Models are presented for the determination of thermal conductivity of a composite lamina with woven fiber mats. In analyzing the cure cycle of a composite part, the common practice has been to use weight-averaged thermal properties. The limitation of this approach becomes apparent when one finds that thermal conductivity calculated for fiberglass/epoxy composite is very close to thermal conductivity of carbon/epoxy composite. This happens for composite parts with the same fiber volume fraction. In weight-average formulations the effect of fiber thermal conductivity is overshadowed by the density of the constituents. To overcome this problem, one needs to take another approach. In this investigation finite element analysis is performed to determine thermal conductivities of fiberglass/epoxy and carbon/epoxy composite lamina. The resulting thermal conductivities are different for the two composite types. These results make more physical sense since thermal conductivity of carbon fiber mat is much higher than that of fiberglass mat.

The Recent Progress of FGM on Nuclear Materials - Design and Fabrication of W/Cu Functionally Graded Material High Heat Flux Components for Fusion Reactor

2009 ◽  
Vol 631-632 ◽  
pp. 353-358 ◽  
Author(s):  
Zhang Jian Zhou ◽  
Yong Jin Yum ◽  
Chang Chun Ge
Keyword(s):  
Heat Flux ◽  
Functionally Graded Material ◽  
High Heat ◽  
Functionally Graded ◽  
High Heat Flux ◽  
Element Analysis ◽  
Thermally Induced ◽  
Operation Conditions ◽  
Graded Material ◽  
Graded Structures

Two kinds of W/Cu functionally graded material based high heat flux components, including monoblock concept and flat tile concept, are designed and fabricated. Thermally induced stresses and strains under operation conditions in these components are analyzed using finite element analysis. The effect on stress and strain of using different graded structures to join Cu to W is examined and compared. There has no obvious difference on operation thermal stress mitigating between monoblock design and flat tile design. The component with monoblock concept was fabricated by a one step fast resistance sintering, and the component with flat tile concept was fabricated by infiltration-welding method successfully.

scholarly journals The inverse problem in zero linear ablation of aluminizing carbon composites under high heat flux

2013 ◽  
Vol 17 (5) ◽  
pp. 1323-1327 ◽  
Author(s):  
Haiming Huang ◽  
Weijie Li ◽  
Chenghai Xu ◽  
Xiaoliang Xu
Keyword(s):  
Heat Flux ◽  
Volume Fraction ◽  
Thermal Protection ◽  
Thermal Environment ◽  
Shape Change ◽  
High Heat ◽  
Carbon Composites ◽  
High Heat Flux ◽  
Linear Ablation ◽  
Heat Response

The concept of zero linear ablation is introduced to describe the mass ablation without shape change, and it is employed to design thermal protection materials under an extreme thermal environment. Aluminizing carbon composites are used as a sample to study numerically the heat response. As indicated in the numerical results, the shape of the composites did not change under a high heat flux because the phase transition (melt or evaporation) of aluminum can absorb a lot of energy before the ablation of carbon, and the zero linear ablation depends on not only the volume fraction of aluminum, but also the heating period and the heat flux.

Micromechanics of Active Composites With SMA Fibers

1994 ◽  
Vol 116 (3) ◽  
pp. 337-347 ◽  
Author(s):  
D. C. Lagoudas ◽  
J. G. Boyd ◽  
Z. Bo
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shape Memory ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Thermomechanical Properties ◽  
Martensitic Phase ◽  
Loading Path ◽  
Element Analysis ◽  
Thermomechanical Response

The study of the effective thermomechanical response of active fibrous composites with shape memory alloy (SMA) fibers is the subject of this work. A 3-D constitutive response for the SMA fibers is formulated first. To model thermomechanical loading path dependence, an incremental approach is used assuming that within each stress and temperature increment the volume fraction of the martensitic phase remains constant in the SMA fibers. The Mori-Tanaka averaging scheme is then used to give an estimate of the instantaneous effective thermomechanical properties in terms of the thermomechanical properties of the two phases and martensitic volume fraction. A unit cell model for a periodic active composite with cubic and hexagonal arrangement of fibers is also developed to study the effective properties using finite element analysis. It is found that since the fibers and not the matrix undergo the martensitic phase transformation that induces eigenstrains, the Mori-Tanaka averaging scheme accurately models the thermomechanical response of the composite, relative to the finite element analysis, for different loading paths. Specific results are reported for the composite pseudoelastic and shape memory effect for an elastomeric matrix continuous SMA fiber composite.

scholarly journals Numerical Study on the Fluid Flow and Heat Transfer Characteristics of Al2O3-Water Nanofluids in Microchannels of Different Aspect Ratio

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 868
Author(s):  
Huajie Wu ◽  
Shanwen Zhang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
High Heat ◽  
High Heat Flux ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Transfer Capacity

The study of the influence of the nanoparticle volume fraction and aspect ratio of microchannels on the fluid flow and heat transfer characteristics of nanofluids in microchannels is important in the optimal design of heat dissipation systems with high heat flux. In this work, the computational fluid dynamics method was adopted to simulate the flow and heat transfer characteristics of two types of water-Al2O3 nanofluids with two different volume fractions and five types of microchannel heat sinks with different aspect ratios. Results showed that increasing the nanoparticle volume fraction reduced the average temperature of the heat transfer interface and thereby improved the heat transfer capacity of the nanofluids. Meanwhile, the increase of the nanoparticle volume fraction led to a considerable increase in the pumping power of the system. Increasing the aspect ratio of the microchannel effectively improved the heat transfer capacity of the heat sink. Moreover, increasing the aspect ratio effectively reduced the average temperature of the heating surface of the heat sink without significantly increasing the flow resistance loss. When the aspect ratio exceeded 30, the heat transfer coefficient did not increase with the increase of the aspect ratio. The results of this work may offer guiding significance for the optimal design of high heat flux microchannel heat sinks.

scholarly journals Production and Heat Properties of an X-ray Reflective Anode Based on a Diamond Heat Buffer Layer

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 241 ◽  
Author(s):  
Xinwei Li ◽  
Xin Wang ◽  
Ye Li ◽  
Yanyang Liu
Keyword(s):  
Thermal Conductivity ◽  
Buffer Layer ◽  
Heat Dissipation ◽  
Target Surface ◽  
High Heat ◽  
High Heat Flux ◽  
Element Analysis ◽  
X Ray ◽  
Spot Area ◽  
Power Limit

This paper introduces an X-ray reflective anode with a diamond heat buffer layer, so as to improve heat dissipation of micro-focus X-ray sources. This also aids in avoiding the destruction of the anode target surface caused by the accumulation of heat generated by the electron beam bombardment in the focal spot area. In addition to the description of the production process of the new reflective anode, this study focuses more on the research of the thermal conductivity and compounding ability. This paper also introduces a method that combines finite element analysis (FEA) in conjunction with thermal conductivity experiments, and subsequently demonstrates the credibility of this method. It was found that due to diamonds having a high thermal conductivity and melting point, high heat flux produced in the micro-focus spot region of the anode could be conducted and removed rapidly, which ensured the thermal stability of the anode. Experiments with the power parameters of the radiation source were also completed and showed an improvement in the power limit twice that of the original.

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