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金属泡沫集优良的力学、声学、电磁学和传热学性能于一体,易于集成换热器和散热器。本文基于局部非热平衡模型对纳米流体在金属泡沫内的双强化换热效果进行了数值研究,分析了泡沫形态参数和纳米颗粒浓度对其流动和换热的影响。研究了以水作为基本介质的纳米流体在金属泡沫内流动时的二次项效应、热弥散效应以及局部非热平衡效应,比较了不同模型对强化换热效果的影响。结果表明,换热随孔隙率减小或孔密度增加而逐渐增强,纳米颗粒使流体压降和换热性能都增加;对于含纳米颗粒的水,在金属泡沫内对流换热的惯性效应和热弥散效应在流速较大时更明显;局部非热平衡特性在固体导热系数较大时比较明显。 相似文献
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小通道扁管内纳米流体流动与传热特性 总被引:2,自引:0,他引:2
建立了测量小通道扁管内纳米流体流动与对流换热性能的实验系统,测量了不同粒子体积份额的水-Cu纳米 流体的管内对流换热系数和摩擦阻力系数,实验结果表明,在相同雷诺数条件下,小通道扁管内纳米流体的对流换热系数 大于纯液体,且随粒子的体积份额的增加而增大,而纳米流体的阻力系数并未明显增大。 相似文献
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纳米流体对流换热的实验研究 总被引:12,自引:3,他引:12
建立了测量纳米流体对流换热系数的实验系统,测量了不同粒子体积份额的水-Cu纳米流体在层流与湍流状态下的管内对流换热系数,实验结果表明,在液体中添加纳米粒子增大了液体的管内对流换热系数,粒子的体积份额是影响纳米流体对流换热系数的因素之一。综合考虑影响纳米流体对流换热的多种因素,提出了计算纳米流体对流换热系数的关联式。 相似文献
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Enhancement of heat transfer in a heat exchanger via a DC corona discharge was studied experimentally using a single-tube shell-and-tube heat exchanger. Air was the working fluid in both the tube and shell sides. Excitation of the tube side was via a single wire electrode, while that of the shell side was via four rod electrodes oriented symmetrically at 90° intervals. Three series of experiments were performed: (1) excitation of the tube side only, (2) excitation of the shell side only, and (3) simultaneous excitation of the tube and shell sides. Both heat transfer and pressure drop measurements were performed, with Reynolds number and electric field potential as parametric quantities in the tube and shell sides. It was found that highest enhancements take place when the tube and shell sides are excited simultaneously, yielding a 322% increase in the overall heat transfer coefficient. Study of the heat transfer enhancements per unit pumping power indicates that for the range of parameters studied, the technique is most efficient at moderate Reynolds numbers and at electrode potentials in the midrange between threshold and sparkover limits. 相似文献