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.

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.

PTFE Modification to Enhance Boiling Performance of Porous Surface

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Ya-Qiao Wang ◽  
Jia-Li Luo ◽  
Yi Heng ◽  
Dong-Chuan Mo ◽  
Shu-Shen Lyu
Keyword(s):  
Boiling Heat Transfer ◽  
Heat Dissipation ◽  
Flat Surface ◽  
Hydrophobic Surface ◽  
High Heat ◽  
High Heat Flux ◽  
Pin Fin ◽  
Original Surface ◽  
Wall Superheat ◽  
Hybrid Modification

Abstract Boiling heat transfer is one of the most effective methods to meet the challenge of heat dissipation of high heat flux devices. A wetting hybrid surface has been shown to have better performance than the hydrophilic or hydrophobic surface. This kind of wetting hybrid modification is always carried out on a plain or flat surface. In this paper, polytetrafluoroethylene (PTFE) powders were coated on a superhydrophilic microcopper dendrite fin surface to build a wetting hybrid surface. The pool-boiling experimental results showed that after applying the coating, the wall superheat dramatically decreased to 8 K, which is 9 K lower than that on the original surface at 250 W·cm−2, and has a better performance than a silicon pin-fin-based wetting hybrid surface.

Thermal Conductivity and Operating Temperature Effect on the Interline Region in a Micro/Miniature Heat Pipe

2008 ◽  
Author(s):  
Hani H. Sait ◽  
Steve M. Demsky ◽  
HongBin Ma
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Operating Temperature ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Thin Film Evaporation ◽  
Film Evaporation ◽  
Frictional Shear Stress

An analytical model describing thin film evaporation is developed that includes the effects of surface tension, frictional shear stress, wetting characteristics and disjoining pressure. The effects of thermal conductivity of working fluids and operating temperature on the evaporating thin film region are also studied. The results indicate that when the thermal conductivity of the working fluid increases, a high heat flux can be removed from the evaporating thin film region. The operating temperature affects the thin film evaporation. The higher the operating temperature, the more heat flux can be removed from the region. The information of thin film evaporation presented in the paper results in a better understanding of heat transfer mechanism occurring in micro heat pipes.

scholarly journals Diamond monochromator for high heat flux synchrotron x-ray beams

10.2172/87836 ◽  
1993 ◽  
Author(s):  
A.M. Khounsary ◽  
R.K. Smither ◽  
S. Davey ◽  
A. Purohit
Keyword(s):  
Heat Flux ◽  
High Heat ◽  
High Heat Flux ◽  
X Ray

scholarly journals Visualization Experimental Study on Silicon-Based Ultra-Thin Loop Heat Pipe Using Deionized Water as Working Fluid

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1080
Author(s):  
Wenzhe Song ◽  
Yanfeng Xu ◽  
Lihong Xue ◽  
Huajie Li ◽  
Chunsheng Guo
Keyword(s):  
Heat Pipe ◽  
Heat Dissipation ◽  
Experimental System ◽  
High Heat ◽  
Deionized Water ◽  
Working Fluid ◽  
Stable Operation ◽  
High Heat Flux ◽  
Loop Heat Pipe ◽  
Silicon Based

As a type of micro flat loop heat pipe, s-UTLHP (silicon-based ultra-thin loop heat pipe) is of great significance in the field of micro-scale heat dissipation. To prove the feasibility of s-UTLHP with high heat flux in a narrow space, it is necessary to study its heat transfer mechanism visually. In this paper, a structural design of s-UTLHP was proposed, and then, to realize the working fluid charging and visual experiment, an experimental system including a holding module, heating module, cooling module, data acquisition module, and vacuum chamber was proposed. Deionized water was selected as a working fluid in the experiment. The overall and micro phenomena of s-UTLHP during startup, as well as the evaporation and condensation phenomena of s-UTLHP during stable operation, were observed and analyzed. Finally, the failure phenomenon of s-UTLHP was analyzed, and several solutions were proposed. The observed phenomena and experimental conclusions can provide references for further related experimental research.

A Mathematical Modeling Method for Capillary Limit of Micro Heat Pipe with Sintered Wick

2011 ◽  
Vol 175 ◽  
pp. 335-341
Author(s):  
Xi Bing Li ◽  
Chang Long Yang ◽  
Gong Di Xu ◽  
Wen Yuan ◽  
Shi Gang Wang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Heat Dissipation ◽  
High Heat ◽  
Experimental Investigations ◽  
High Heat Flux ◽  
Micro Heat Pipe ◽  
Copper Powders ◽  
Capillary Limit

With heat flux increasing and cooling space decreasing in microelectronic and chemical products, micro heat pipe has become an ideal heat dissipation device in high heat-flux products. Through the analysis of its working principle, the factors that affect its heat transfer limits and the patterns in which copper powders are arrayed in circular cavity, this paper first established a mathematical model for the crucial factors in affecting heat transfer limits in a circular micro heat pipe with a sintered wick, i.e. a theoretical model for capillary limit, and then verified its validity through experimental investigations. The study lays a powerful theoretical foundation for designing and manufacturing circular micro heat pipes with sintered wicks.

scholarly journals Heat Dissipation in Epoxy/Amine-Based Gradient Composites with Alumina Particles: A Critical Evaluation of Thermal Conductivity Measurements

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1131 ◽  
Author(s):  
Matthias Morak ◽  
Philipp Marx ◽  
Mario Gschwandl ◽  
Peter Filipp Fuchs ◽  
Martin Pfost ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Critical Evaluation ◽  
Laser Flash ◽  
Element Analysis ◽  
Epoxy Amine ◽  
Alumina Particles ◽  
Laser Flash Analysis ◽  
Key Aspects ◽  
Guarded Heat Flow Meter

Abstract: For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based composite materials with high thermal conductivity. The inorganic fillers, however, are often available only in submicron- and micron-scaled dimensions and, consequently, can sediment during the curing reaction of the polymer matrix. In this study, an epoxy/amine resin was filled with nano- and submicron-scaled alumina particles, yielding a gradient composite. It was found that the thermal conductivity according to laser flash analysis of a sliced specimen ranged from 0.25 to 0.45 W·m−1·K−1 at room temperature. If the thermal conductivity of an uncut specimen was measured with a guarded heat flow meter, the ‘averaged’ thermal conductivity was measured to be only 0.25 W·m−1·K−1. Finite element analysis revealed that the heat dissipation through a gradient composite was of intermediate speed in comparison with homogeneous composites exhibiting a non-gradient thermal conductivity of 0.25 and 0.45 W·m−1·K−1.

Topology Optimization for an Internal Heat-Conduction Cooling Scheme in a Square Domain for High Heat Flux Applications

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Jaco Dirker ◽  
Josua P. Meyer
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Topology Optimization ◽  
Internal Heat ◽  
High Heat ◽  
High Heat Flux ◽  
Internal Cooling ◽  
Conductive Heat ◽  
Conducting Materials ◽  
The Cost

Conductive heat transfer is of importance in the cooling of electronic equipment. However, in order for conductive cooling to become effective, the use of high-conducting materials and the correct distribution thereof is essential, especially when the volume which needs to be cooled has a low thermal conductivity. An emerging method of designing internal solid-state conductive systems by means of topology optimization is considered in this paper. In this two-dimensional study, the optimum distribution of high conductive material within a square-shaped heat-generating medium is investigated by making use of the “method or moving asymptotes” (MMA) optimization algorithm coupled with a numerical model. The use of such a method is considered for a number of cost (driving) functions and different control methods to improve the definiteness of the boundaries between the heat-generating and high-conduction regions. It is found that the cost function used may have a significant influence on the optimized material distribution. Also of interest in this paper are the influences of thermal conductivity and the proportion of the volume occupied by the high-conducting solid on the resulting internal cooling structure distribution and its thermal conduction performance. For a square domain with a small exposed isothermal boundary centered on one edge, a primary V-shaped structure was found to be predominantly the most effective layout to reduce the peak operating temperature and to allow for an increase in the internal heat flux levels.

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