变压器过热会减少变压器使用寿命。为分析片式散热器的散热性能,以某典型的片式散热器为研究对象,采用Fluent数值模拟研究与试验验证相结合的方法,对自然油循环、强迫油循环2种条件下散热器的散热性能进行研究,以油流阻力、平均油温升系...变压器过热会减少变压器使用寿命。为分析片式散热器的散热性能,以某典型的片式散热器为研究对象,采用Fluent数值模拟研究与试验验证相结合的方法,对自然油循环、强迫油循环2种条件下散热器的散热性能进行研究,以油流阻力、平均油温升系数2个指标评价散热器散热性能。结果表明:自然循环下,当油流量不变时,相对于自冷散热,风冷散热平均油温升系数降低了0.17,散热效果较强;强迫循环下,在油流量45 m^3/h至65 m^3/h范围内,随着油流量的增加,油流阻力增大了4 k Pa,平均油温升系数基本保持不变,约为0.198,散热器的散热量增加了8.8 k W,散热性能增强。研究结果为片式散热器的优化设计提供了指导。展开更多
The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1...The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1. The activation energy（Q） for the tested steel is calculated to be around 682.99 k J/mol at a deformation strain of 0.6. Microstructural analysis by SEM shows that the dynamic recrystallization（DRX） behavior is dependent sensitively on the deformation strain, temperature and strain rate, while an exponential relationship between DRX grain size and Z parameter is obtained from the computational formula. Moreover, the M6C-type carbides（〈1 μm） act as the main prohibitor of grain coarsening, and the polynomial regression relationship between them is worked out. With electron backscatter diffraction（EBSD） observation, DRX is the main nucleation mechanism responsible for the formation of new grains during hot compression. In conclusion, the interaction between DRX affected by hot deformation parameters and carbides precipitation determines the ultimate grain size refinement.展开更多
In this paper, thermal characteristics of the high-power LED spot lamp are reported. The emphasis is placed upon optimizing design of the heat sink of LED spot lamp using the optimization module and the orthogonal-exp...In this paper, thermal characteristics of the high-power LED spot lamp are reported. The emphasis is placed upon optimizing design of the heat sink of LED spot lamp using the optimization module and the orthogonal-experiment method. Results demonstrate that the weight of the heat sink is decreased to 46.1% of that for the initial structure, and the influence of each factor on junction temperature and weight of the heat sink is acquired by range analysis. Finally, the influence of ambient temperature and natural convection coefficient on the LED maximum temperature is analyzed. The results and the optimizing methodology are of great importance to the thermal design of LED lamps.展开更多
文摘变压器过热会减少变压器使用寿命。为分析片式散热器的散热性能,以某典型的片式散热器为研究对象,采用Fluent数值模拟研究与试验验证相结合的方法,对自然油循环、强迫油循环2种条件下散热器的散热性能进行研究,以油流阻力、平均油温升系数2个指标评价散热器散热性能。结果表明:自然循环下,当油流量不变时,相对于自冷散热,风冷散热平均油温升系数降低了0.17,散热效果较强;强迫循环下,在油流量45 m^3/h至65 m^3/h范围内,随着油流量的增加,油流阻力增大了4 k Pa,平均油温升系数基本保持不变,约为0.198,散热器的散热量增加了8.8 k W,散热性能增强。研究结果为片式散热器的优化设计提供了指导。
基金Project(2012AA03A503) supported by the National High Technology Research and Development Program of China
文摘The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1. The activation energy（Q） for the tested steel is calculated to be around 682.99 k J/mol at a deformation strain of 0.6. Microstructural analysis by SEM shows that the dynamic recrystallization（DRX） behavior is dependent sensitively on the deformation strain, temperature and strain rate, while an exponential relationship between DRX grain size and Z parameter is obtained from the computational formula. Moreover, the M6C-type carbides（〈1 μm） act as the main prohibitor of grain coarsening, and the polynomial regression relationship between them is worked out. With electron backscatter diffraction（EBSD） observation, DRX is the main nucleation mechanism responsible for the formation of new grains during hot compression. In conclusion, the interaction between DRX affected by hot deformation parameters and carbides precipitation determines the ultimate grain size refinement.
基金supported by the Natural Science Foundation of Zhejiang Province (No.Y104436)the Science and Technology Fund Projects of Zhejiang Province (No.2008C21158)the Innovative Basement Project of Graduate Education of Zhejiang Province
文摘In this paper, thermal characteristics of the high-power LED spot lamp are reported. The emphasis is placed upon optimizing design of the heat sink of LED spot lamp using the optimization module and the orthogonal-experiment method. Results demonstrate that the weight of the heat sink is decreased to 46.1% of that for the initial structure, and the influence of each factor on junction temperature and weight of the heat sink is acquired by range analysis. Finally, the influence of ambient temperature and natural convection coefficient on the LED maximum temperature is analyzed. The results and the optimizing methodology are of great importance to the thermal design of LED lamps.
