共查询到20条相似文献,搜索用时 15 毫秒
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Effect of hole shape on the heat transfer in a rectangular duct with perforated blockage walls 总被引:2,自引:0,他引:2
Heat transfer coefficients were measured by the improved hue detection based liquid crystal technique in a turbine blade internal
cooling passage model with blockage walls. In the experiments, blockages with 9 holes of circular, wide, narrow shapes were
used and for the circular shape, the number of hole of 7, 9, and 11 were tested. For all cases, the perforated area was kept
same. Results showed that the staggered impingement jets increased heat transfer coefficient, however, pressure drop also
increased greatly. Generally, Nusselt number ratio and the thermal performance factor decreased as Reynolds number increased.
For all Reynolds numbers tested, the blockage wall with wide holes gave more uniform heat transfer coefficient and higher
thermal performance factor. As the number of hole increased from 7 to 11, the distribution of heat transfer coefficient became
uniform and the thermal performance factor increased.
This paper was presented at the 9th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007. 相似文献
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论述低温气体雾化射流冷却原理及特点,以池内膜态沸腾为基础,将喷雾颗粒的冲击作为一种扰动,建立雾滴射流进入切削区冷却高温壁面的模型,讨论雾滴冷却高温壁面的换热系数,着重探讨工艺参数水流密度对喷雾冷却换热系数的影响.进行了不同水剂量的低温气体雾化射流冷却钛合金高温壁面的瞬态实验,获得了钛合金试件表面温度分别为100℃、150℃、200℃和250℃时,低温气体雾化射流冷却达到最佳冷却效果时水剂量,分析了水剂量对冷却效果的理论依据,结果证实该模型对实际应用具有一定的指导作用. 相似文献
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在铸造凝固过程的数值模拟中,铸件/铸型间的界面传热系数是非常关键的一个参数.为提高数值模拟精度,文中采用铝合金铸件设计了金属型铸造试验,考虑了铸型厚度对结果的影响,使用特制的热电偶采集了铸件内部不同位置的温度值.以此实测的温度场数据为基础,结合数值模拟技术和界面传热系数“反问题”的求法,得到界面传热系数与时间的函数关系.结果表明:铸型厚度不同会影响铸件铸型间的热流和界面传热系数的变化规律,且界面传热系数在铸件冷却中并非常数,随着凝固过程的继续而减小.最后将所得界面传热系数用于凝固过程的温度场模拟,与试验结果进行了对比分析,得到了合理的分布,说明此界面传热系数测定方法可行. 相似文献
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Guo Zhipeng Xiong Shoumei Cho SangHyun Choi JeongKil 《Frontiers of Mechanical Engineering in China》2007,2(3):283-287
The present work focused on the determination of the interfacial heat transfer coefficient (IHTC) between metal and die during
the high pressure die casting (HPDC) process. Experiments were carried out on an aluminum alloy, ADC12Z, using “step shape”
casting—so-called because of its shape. The IHTC was successfully determined by solving one of the inverse heat problems using
the nonlinear estimation method first used by Beck. The calculation results indicated that the IHTC immediately increased
after liquid metal was brought into the cavity by the plunger and decreased as the solidification process of the liquid metal
proceeded. The liquid metal eventually solidified completely, a condition when the IHTC tended to be stable. Casting thickness
played an important role in affecting the IHTC between the metal and die not only in terms of its value but also in terms
of its change tendency. Also, under the test conditions, different change tendencies of the metal solid fraction were found
between castings with different thicknesses and the die.
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Translated from Acta Metallurgica Sinica, 2007, 43(1): 103–106 [ 译自: 金属学报] 相似文献
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Jin Gi Paeng Kyung Hwan Kim Young Hwan Yoon 《Journal of Mechanical Science and Technology》2009,23(2):536-543
The air-side forced convective heat transfer of a plate fin-tube heat exchanger is investigated by experimental measurement
and numerical computation. The heat exchanger consists of a staggered arrangement of refrigerant pipes with a diameter of
10.2 mm and a fin pitch of 3.5 mm. In the experimental study, the forced convective heat transfer was measured at Reynolds
numbers of 1082, 1397, 1486, 1591 and 1649 based on the diameter of the refrigerant piping and on the maximum velocity. The
average Nusselt number for the convective heat transfer coefficient was also computed for the same Reynolds number by using
the commercial software STAR-CD with the standard k - ɛ turbulent model. It was found that the relative errors of the average Nusselt numbers between the experimental and numerical
data were less than 6 percent in a Reynolds number range of 1082∼1649. The errors between the experiment and other correlations
from literature ranged from 7% to 32.4%. However, the literature correlation of Kim et al. is closest to the experimental
data within a relative error of 7%.
This paper was recommended for publication in revised form by Associate Editor Man-Yeong Ha
Jin-Gi Paeng recieved a bachelor’s degree in Aero Mechanical Engineering from Gyeong-sang National University in 2000. He then went on
to recieve his M.S. degrees from Changwon National University in 2004. Currently, he completed the doc-tor’s course and a
doctoral dissertation in 2007 and 2008, respectively. He will take a doctorate in 2008. 相似文献
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The study of cooling channel optimization in blast furnace cast steel stave based on heat transfer analysis 总被引:1,自引:0,他引:1
Wu Lijun Zhou Weiguo Cheng Hui’er Su Yunlong Li Xiaojing Song Canyang 《The International Journal of Advanced Manufacturing Technology》2006,29(1-2):64-69
The three-dimensional heat transfer and thermal stress of a steel cooling stave in a blast furnace at Maanshan Iron and Steel
Co. Ltd. are built. The temperature and thermal stress fields of cooling stave are calculated by using finite element method
software ANSYS. The results show the rise in maximum temperature and thermal stress of the stave hot surface is not high when
cooling pipe is replaced by cooling elliptical tube. Because of the decrease in the cross-sectional area for cooling elliptical
tube, the thickness of the cooling stave is reduced and cooling water flow is saved. As a result, the iron-making cost can
be reduced. 相似文献
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叶片前缘气膜冷却数值模拟 总被引:4,自引:0,他引:4
为了研究叶片前缘区域的换热特性,采用非结构化网格和realizable紊流模型,求解三维N-S方程,对前缘带有一排冷气孔的涡轮叶片进行了换热特性的数值模拟.分析了不同动量比,湍流度,孔间距及径向角下冷气射流的运动规律,换热分布以及冷效分布特点.结果表明,当动量比Ⅰ大于1时,在相同孔型下,动量比越高,冷效越大.在相同动量比下,孔间距越小,冷效越大.但动量比,孔间距及径向角对换热系数影响不大.当湍流度增加时,换热系数增加而冷效降低.沿展向,气膜孔中心区域冷效较高,两孔之间区域较低;而换热系数则相反,气膜孔中心区域换热系数较小,两孔之间区域较大. 相似文献
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通过换热管测试台对A、B2种双侧强化蒸发管的换热性能进行了测试研究。研究结果显示:对于同一管型而言,在工况不变的情况下,管内流速在1.0-2.0m/s时,换热管的综合换热系数会随着管内水流速的增加而呈上升趋势:两者的综合换热系数与其外齿周向齿数和轴向齿数有很大关系,外内齿数多综合换热系数高:新开发的高效换热蒸发管-B比原仃的蒸发管-A换热性能高6.6%。通过采用新开发的高效蒸发管-B每年可为公司节省成本约256.6余万元。 相似文献
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Heat/mass transfer characteristics on the near-tip blade surface under combustor-level high inlet turbulence have been investigated
within a high-turning turbine rotor passage by using the naphthalene sublimation technique. The inlet turbulence intensity
and length scale are 14.7% and 80 mm, respectively. The tip gap-to-chord ratio is changed to beh/c = 0.74, 1.47, and 2.94 percents. Increasingh/c results not only in higher heat/mass transfer in the pressure-side tip region but also in more convective transport on the
pressure surface even far away from the tip edge. Severe heat/mass transfer is always observed in the suction-side tip-leakage
flow region which can be divided into two distinct high transport regions. There is a local maximum of heat/mass transfer
along the trailing-edge centerline. This arises from the interaction of a tip-leakage vortex with a trailing-edge vortex shedding.
Comparisons of the present data forh/c = 2.94 percents with the previous low turbulence one show that there is a large discrepancy of heat/mass transfer in the
pressure-side near-tip area, which diminishes with departing from the tip edge. The suction-side heat/mass transfer in the
tip-leakage flow region is less influenced by the high inlet turbulence than that at the mid-span. The leading-edge heat/mass
transfer under the high inlet turbulence is always higher than that in the low turbulence case, while there is no big difference
in the trailing-edge heat/mass transfer between the two cases. 相似文献
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Zhaogao Luan 《Tribology International》2009,42(5):762-769
A numerical investigation of conjugate heat transfer of turbulent flow within a mechanical seal chamber is presented. The computational model takes into account the heat generation at the contact interface between the rotating ring and the stationary ring, heat conduction into the rings, and heat convection into the surrounding fluid in the chamber. Correlations are developed for predicting the average heat transfer coefficient on the wetted outer surfaces of the seal rings assuming that the flow in the seal chamber is turbulent. 相似文献
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为解决汽车空-空中冷器冷却扁管最优换热性能的问题,运用FLUENT软件,建立了4种不同断面结构的冷却扁管导热和管内流动换热耦合数学模型,采用CFD方法对该传热问题进行了数值模拟计算.将数值计算的传热努塞尔特数与Gnielinski传热关联式、摩擦因子f与Webb实验关联式、Filonenko经验公式、Blasius关联式进行了对比;良好的结果吻合性验证了数值计算方法的正确性;通过4种冷却扁管换热因子j和流动摩擦因子f的对比分析,提出了冷却扁管综合性能的评价方法(jlf)1/3.研究结果表明,采用无量纲因子(jlf)1/3方法评价口琴式冷却扁管具有最优换热性能,斜撑式冷却扁管次之,从而可为汽车空-空中冷器结构设计或匹配选型提供重要的理论依据. 相似文献
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Kyoo Woan Kim Nguyen Ba Chien Kwang-Il Choi Jong-Taek Oh 《Journal of Mechanical Science and Technology》2014,28(10):4301-4308
We report experimental data of boiling heat transfer of R-1234yf in horizontal small tubes. The experimental data obtained in the horizontal circular small tubes of 1.5 and 3.0 mm inner diameter, the lengths of 1000 and 2000 mm, the mass flux range from 200–650 kg/m2s, the heat flux range from 5–40 kW/m2 and saturation temperature of 10 and 15°C, was used to develop a modified correlation for the heat transfer coefficient. The flow pattern of the experimental data was mapped and analyzed with existing flow pattern maps. The heat transfer coefficient was also compared with some well-known correlations. 相似文献
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Xiaohui Lin Chibin Zhang Juekuan Yang Shuyun Jiang Weisong Ren Jun Gu 《机械工程学报(英文版)》2013,26(6):1277-1284
In current research about nanofluid convection heat transfer, random motion of nanoparticles in the liquid distribution problem mostly was not considered. In order to study on the distribution of nanoparticles in liquid, nanofluid transport model in pipe is established by using the continuity equation, momentum equation and Fokker-Planck equation. The velocity distribution and the nanoparticles distribution in liquid are obtained by numerical calculation, and the effect of particle size and particle volume fraction on convection heat transfer coefficient of nanofluids is analyzed. The result shows that in high volume fraction ( 0 _-- 0.8% ), the velocity distribution of nanofluids characterizes as a "cork-shaped" structure, which is significantly different from viscous fluid with a parabolic distribution. The convection heat transfer coefficient increases while the particle size of nanoparticle in nanofluids decreases. And the convection heat transfer coefficient of nanofluids is in good agreement with the experimental result both in low (0 ~〈 0.1% ) and high ( q = 0.6% ) volume fractions. In presented model, Brown motion, the effect of interactions between nanoparticles and fluid coupling, is also considered, but any phenomenological parameter is not introduced. Nanoparticles in liquid transport distribution can be quantitatively calculated by this model. 相似文献