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多股流换热器的(火积)耗散热阻分析 总被引:1,自引:0,他引:1
在分析多股流换热器特点的基础上,考虑流体在通道出口非等温混合产生的(米积)耗散,将板翅式多股流换热器的(火积)耗散分为通道换热(火积)耗散和混合(米积)耗散两部分,定义了多股流换热器的(米积)耗散热阻。通过对不同通道排列下的多股流板翅式换热器的计算,发现多股流换热器换热量与其(米积)耗散热阻一一对应,(米积)耗散热阻越小,换热量越大。在对多股流板翅式换热器的通道进行排列时,应采用冷热通道间隔布置的形式,并使冷热通道的换热负荷相近。 相似文献
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In this paper, the numerical simulations for a helical baffles heat exchanger and a segmental baffles heat exchanger with component clearance are performed to reveal the features of leakage streams and their effect on heat exchanger performance. Helical baffles heat exchanger models with four different angles and segmental baffles heat exchanger model were established and calculated via Gambit and Fluent software. The results reveal that the heat exchanger with a 40° helix angle shows the best comprehensive heat transfer performance in turbulent state, and the heat exchanger with a 50° helix angle shows better comprehensive heat transfer performance in laminar flow state. The leakage streams proportion of the helical baffles heat exchanger varies from 5.5% to 6.1%, compared with the leakage streams proportion changes from 16.6% to 21.0% in the segmental baffles heat exchanger. In both turbulent flow state and laminar flow state, with the rise of shell-side Reynolds number, the main spiral stream B proportion decreases and the leakage streams proportion increases in the segmental baffles heat exchanger, while the stream B proportion increases and the leakage streams proportion decreases in helical baffles heat exchanger. The proportion of stream B increases with the increase of the helix angle β and the proportions of leakage streams decrease with the increase of β. The proportion of the tube-baffle leakage stream A increases in radial direction. Both the proportion of stream A and that of the baffle-shell leakage stream E fluctuate in the intermediate zone in axial direction; the stream A proportion decreases at the inlet and outlet zone, while the stream E proportion increases at the inlet and decreases at the outlet zone. The results of this paper could be of great significance in the optimal design and manufacture of the helical baffles heat exchanger. 相似文献
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有分流节点非结构模型(NNM-SS)应用于换热网络优化时,因难以生成合适的分流结构而使优化陷入局部极值.根据NNM-SS的优化特点及网络结构中分流次数对费用的影响,提出结构摄动策略,并将其引入强制进化随机游走算法(RWCE-SS).策略的主要思想为:在优化过程中,以一定的概率随机抽取一个无分流结构的换热器,并在该位置上生成一组新的分流结构以增加网络中的分流次数,通过对结构的摄动实现对算法搜索能力的提升.算例验证表明应用该策略改进的算法可获得更好的优化结果. 相似文献
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The thermochemical sulfur-iodine cycle is a potential method for hydrogen production, and the hydrogen iodide (HI) decomposition is the key step to determine the efficiency of hydrogen production in the cycle. To further reduce the irreversibility of various transmission processes in the HI decomposition reaction, a one-dimensional plug flow model of HI decomposition tubular reactor is established, and performance optimization with entropy generate rate minimization (EGRM) in the decomposition reaction system as an optimization goal based on finite-time thermodynamics is carried out. The reference reactor is heated counter-currently by high-temperature helium gas, the optimal reactor and the modified reactor are designed based on the reference reactor design parameters. With the EGRM as the optimization goal, the optimal control method is used to solve the optimal configuration of the reactor under the condition that both the reactant inlet state and hydrogen production rate are fixed, and the optimal value of total EGR in the reactor is reduced by 13.3% compared with the reference value. The reference reactor is improved on the basis of the total EGR in the optimal reactor, two modified reactors with increased length are designed under the condition of changing the helium inlet state. The total EGR of the two modified reactors are the same as that of the optimal reactor, which are realized by decreasing the helium inlet temperature and helium inlet flow rate, respectively. The results show that the EGR of heat transfer accounts for a large proportion, and the decrease of total EGR is mainly caused by reducing heat transfer irreversibility. The local total EGR of the optimal reactor distribution is more uniform, which approximately confirms the principle of equipartition of entropy production. The EGR distributions of the modified reactors are similar to that of the reference reactor, but the reactor length increases significantly, bringing a relatively large pressure drop. The research results have certain guiding significance to the optimum design of HI decomposition reactors. 相似文献
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针对大功率LED光源存在的散热问题,在风冷散热条件下,对加装导流罩的大功率LED散热器进行优化设计。在肋片结构参数固定的条件下,利用流体分析软件对导流罩的内径、高度、进气口直径以及散热器肋片夹角进行优化。通过改变这些参数来改变散热片表面气体流体的流形、风速等值,最终改变肋片表面对流换热系数。获得的导流罩和肋片夹角参数:导流罩高度85 mm,进气口直径76 mm,出气口直径83 mm,散热器肋片夹角9。通过优化使散热器温度有一定程度的降低,为大功率LED灯具散热设计提供了一种优化方案。 相似文献