共查询到20条相似文献,搜索用时 140 毫秒
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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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《Revue Generale de Thermique》1998,37(4):277-283
An extended temperature oscillation measurement technique based on the axial dispersion model is proposed for the determination of both heat transfer coefficients and axial dispersion coefficients in heat exchangers. The test technique uses a sinusoidal inlet temperature variation which is realized with a computer controlled compact electric heater. The corresponding analytical solution of the outlet temperature response in the initial stage is obtained and used to evaluate the heat transfer coefficients and axial dispersion coefficients. Experiments were carried out on a standard test core. Comparison was made between the experimental results and data available in the literature. 相似文献
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伴随有水蒸气凝结的烟气对流换热的实验研究 总被引:13,自引:0,他引:13
本文通过实验研究了冷凝式燃气热水器中烟气伴随有水蒸气凝结的受迫对流换热过程。着重介绍实验系统、测试方法和对塔板式换热器和肋片板式换热器的实验研究结果。实验表明,有水蒸气凝结时的烟气对流换热系数远大于无凝结时的换热系数,可提高数倍。在冷凝式换热器中,塔板式换热器的换热系数大于肋片板式换热器。 相似文献
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该设计解决了低温工程与低温技术等领域所使用的高纯度气体介质换热的要求,具有显著的经济效益和社会效益。其换热器是由四个管壳式热交换器串联组合而成,壳体呈窄矩形,换热管采用U形换热管,四个管壳式热交换器呈方阵置放在低温换热器筒体内。低温换热器采用的材料是0Cr18N i9/304,该种材料的透气性小、耐磨损、抗腐蚀能力强和性能稳定,防止了气体被污染。另外在低温下,考虑了材料的热胀冷缩所产生的应力,使应力能够自行消除,提高了它的密封性能,最终使低温换热器密封性能好,防止了气体被污染,保证了气体的高纯度。 相似文献
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A model is developed for thermoacoustic devices that have neither stack nor regenerator. These "no-stack" devices have heat exchangers placed close together in an acoustic standing wave of sufficient amplitude to allow individual parcels of gas to enter both exchangers. The assumption of perfect heat transfer in the exchangers facilitates the construction of a simple model similar to the "moving parcel picture" that is used as a first approach to stack-based engines and refrigerators. The model no-stack cycle is shown to have potentially greater inviscid efficiency than a comparable stack model. However, losses from flow through the heat exchangers and on the walls of the enclosure are greater than those in a stack-based device due to the increased acoustic pressure amplitude. Estimates of these losses in refrigerators are used to compare the possible efficiencies of real refrigerators made with or without a stack. The model predicts that no-stack refrigerators can exceed stack-based refrigerators in efficiency, but only for particular enclosure geometries. 相似文献
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在换热网络优化问题中,采用内部公用工程代替换热温度交叉的不可行匹配能使优化得以继续,同时扩大求解空间,但可能因增加额外的固定投资费用而使其作为差解在进化过程中被接受下来,导致优化效率下降.鉴于此,首先分析内部公用工程对优化进程可能造成的负面影响,提出一种内部公用工程的进化策略,对于具有一对内部公用工程的结构,首先通过扩大其年综合费用以进行惩罚,从而降低其接受的概率,继之,针对仍被接受的内部公用工程结构,在每次迭代时均强制内部公用工程进行随机游走,合理调整其大小,从而改善结构性能.采用两个算例验证策略提升了算法优化效率. 相似文献
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Hireche O Weisman C Baltean-Carlès D Le Quéré P Bauwens L 《The Journal of the Acoustical Society of America》2010,128(6):3438-3448
A model of an idealized thermoacoustic engine is formulated, coupling nonlinear flow and heat exchange in the heat exchangers and stack with a simple linear acoustic model of the resonator and load. Correct coupling results in an asymptotically consistent global model, in the small Mach number approximation. A well-resolved numerical solution is obtained for two-dimensional heat exchangers and stack. The model assumes that the heat exchangers and stack are shorter than the overall length by a factor of the order of a representative Mach number. The model is well-suited for simulation of the entire startup process, whereby as a result of some excitation, an initially specified temperature profile in the stack evolves toward a near-steady profile, eventually reaching stationary operation. A validation analysis is presented, together with results showing the early amplitude growth and approach of a stationary regime. Two types of initial excitation are used: Random noise and a small periodic wave. The set of assumptions made leads to a heat-exchanger section that acts as a source of volume but is transparent to pressure and to a local heat-exchanger model characterized by a dynamically incompressible flow to which a locally spatially uniform acoustic pressure fluctuation is superimposed. 相似文献
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