共查询到20条相似文献,搜索用时 78 毫秒
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针对以槽式太阳能集热器为背景的高密度、高度非均匀热流下水平管内的混合对流换热问题,采用大涡模拟方法,研究了热流密度非均匀性对水平管内混合对流瞬态涡结构、脉动强度、湍流热通量及局部平均壁温的影响;揭示了非均匀热流下自然对流对管内湍流特性的影响规律;提出了适用于不同热边界条件下管内混合对流换热的强化措施。结果表明:均匀热流时,自然对流会抑制管顶部的湍流脉动,使流动层流化,造成传热能力局部恶化;非均匀热流时,随着自然对流的增强,近壁面速度脉动强度先减小后增大,二次流逐渐增强,换热能力逐渐提高,故管内换热能力受湍流脉动与二次流协同影响;在自然对流影响下,均匀加热时管顶部可采用针对层流的强化换热措施,非均匀加热时需着重提高管底部高热流区域的湍流脉动与涡强度。 相似文献
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通过数值模拟的方法,研究了小翼式涡产生器对错排圆管管片式换热芯子换热与阻力特性的影响,比较了光板与加涡产生器强化板芯的速度场、横向平均Nu数以及平均对流换热系数、阻力系数的变化规律,为进一步提高其换热性能、改进翅片结构、设计新型换热器提供了理论依据。 相似文献
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通过数值模拟的方法,研究了三角小翼式涡产生器式错排圆管管片换热板芯在1,2,3,4四种不同管排数下的局部对流换热系数以及平均对流换热系数、阻力系数,得出管排数对换热与阻力性能的影响规律,为进一步提高换热器换热性能提供了理论依据。 相似文献
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将纵向涡强化换热技术应用于矩形管槽,研究以水为换热介质在过渡流状态下的换热效果。实验结果表明有纵向涡发生器的换热效果明显优于无纵向涡发生器的情况。利用PHEON ICS计算软件对实验进行数值模拟,模拟值与实验值符合较好。在此基础上,改变纵向涡的翼高和形状来模拟,发现两者均为换热影响的因素,相比之下,高宽比为0.4纵向涡发生器的换热效果比高宽比为0.5和0.6的要好。而采用相同高宽的矩形翼时,N u高于三角翼,但其换热性能指标却低于直角三角翼。 相似文献
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对端壁加装翼刀的涡轮静叶栅的三维流场进行了数值模拟,分析了翼刀对叶栅沿流向各截面二次流及叶栅气动特性的影响,并研究了翼刀改善二次流的机理.结果表明:与常规叶栅的二次流特性比较,翼刀的存在一方面降低了端壁附面层内横向压力梯度,减弱了低能流体向吸力面/壁角区的堆积;另一方面产生反向翼刀涡,限制了马蹄涡压力面分支的发展,从而达到减小通道涡尺寸和强度的目的.最后,还对几个不同高度的翼刀方案进行了比较,发现翼刀高度为2/3δ时,对二次流的控制最佳. 相似文献
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阐述了配出中性导体的IT系统应用于船舶岸电的条件及优越性,综合考虑电压畸变率、中性导体电流等因素,分析了配出中性导体的IT系统带非线性负载时谐波电流规律。在Simulink/MATLAB中建立了系统仿真模型,并搭建了原型系统进行试验,结果表日月,配出中性导体的IT系统带非线性负载时满足现行国标对低压配电系统电能质量的相关要求。 相似文献
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The possibility of using lead or lead—bismuth mixed oxides as positive materials in organic electrolyte lithium cells with a working voltage similar to those of conventional systems (1.5 V) has been considered. Performances and main characteristics of this new class of lithium batteries are described. 相似文献
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风电并网的静态电压稳定性研究 总被引:1,自引:0,他引:1
应用P-V曲线法对含风电场(基于变速恒频机组构成)的电力系统的静态电压稳定问题进行研究。提出基于连续潮流法的灵敏度指标来分析风电场并网后系统的静态电压稳定裕度及与相关支路的参与程度情况。通过含有变速恒频机组的风电场并网的简化模型算例进行了仿真研究,结果表明在电压稳定极限点附近,风电功率注入使得风电场及其附近节点成为电压不稳定的关键区域。 相似文献
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M. Hammerli 《International Journal of Hydrogen Energy》1983,8(4):269-280
How Canada's successful CANDU (CANada Deuterium Uranium) nuclear power reactors would benefit from an emerging hydrogen-electric economy and vice versa is discussed with reference to the Combined Electrolysis Catalytic Exchange (CECE) process for recovering byproduct heavy water from electrolytic hydrogen. At the heart of this process is a hydrophobic, dispersed-platinum catalyst which has been under development at Chalk River for about a decade. Other potential applications of the CECE process are presented, including tritium recovery from both light and heavy water. Based on preliminary data and cost estimates, the net heavy water dollar credit appears to be at least comparable to the byproduct oxygen credit of electrolytic hydrogen. The potential for byproduct heavy water production from hydrogen in general, and from electrolytic hydrogen in particular, is discussed in relation to Canada's present primary heavy water production capacity. 相似文献
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Corbus D. Lew D. Jordan G. Winters W. Van Hull F. Manobianco J. Zavadil B. 《Power and Energy Magazine, IEEE》2009,7(6):36-46
As wind power continues to be one of the fastest-growing energy sources worldwide, utility planners and operators must meet the challenge of integrating increasing levels of wind power into their electrical power systems. These challenges stem from the nondispatchable nature of wind power and can be broken down into components associated with variability (i.e., effects due to the changing wind resource) and uncertainty (i.e., effects related to our inability to perfectly forecast the weather). In the past, utilities were often motivated to conduct an integration study to determine the costs associated with integrating wind power into their systems; recently, however, there has been a move away from a simple determination of wind-integration costs and towards a balanced view of both integration costs and operational savings due to displaced fuel and emissions. 相似文献