Experimental and numerical investigations of thermal characteristics of heat exchangers in oscillatory flow
Experimental and numerical investigations of thermal characteristics of heat exchangers in oscillatory flow
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DOI：
10.1016/j.applthermaleng.2018.07.073
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发表时间：
2018-11
影响因子：
6.4
通讯作者：
Olusegun M. Ilori;A. Jaworski;Xiaoan Mao
中科院分区：
文献类型：
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作者：
Olusegun M. Ilori;A. Jaworski;Xiaoan Mao
振荡流条件下的热交换器是热声发动机和冷却器的关键部件，目前还没有有效的设计方法。本文采用实验和数值模拟相结合的方法，对紧凑型列管式换热器在振荡流条件下的传热和压降特性进行了研究。建立了一套由Q驱动线性交流发电机驱动的驻波实验装置，并开发了一种同时测量T-HEX附近温度和声压的测量技术。三个相同的热交换器的对称布置，一个“热”热交换器，两个“冷”热交换器之间的中心放置，用于改进的热分析。此外，在热交换器气体通道上使用空气动力学形状，以改善与横截面的突然变化相关联的流动条件。实验结果与三维计算流体动力学（CFD）模型的预测吻合得很好。努塞尔数和由于微小损失引起的压降显示出对传动比（测量的最大振荡压力与系统平均压力）、边缘形状和热的热交换器温度的依赖性。在高振幅下，边缘形状显著地最小化微小损失压差，对热性能的影响可以忽略不计。本文的研究结果将有助于热声发动机/制冷机或斯特林发动机/制冷机在低温应用中的紧凑型热交换器的开发。
Heat exchangers under oscillatory flow conditions constitute a critical component of thermoacoustic engines and coolers for which effective design methodologies are not yet available. In this study, the thermal and pressure drop performance of compact Tube Heat Exchanger (T-HEX) under oscillatory flow conditions is investigated using experimental and numerical methods. A standing wave experimental set-up, driven by the Q-drive linear alternator, and a measurement technique were developed to measure the temperature and acoustic pressure near the T-HEX simultaneously. The symmetric arrangement of three identical heat exchangers, one ‘hot’ heat exchanger, centrally placed between two ‘cold’ heat exchangers, is employed for an improved thermal analysis. Furthermore, aerodynamic shape is used on the heat exchangers gas channels to improve flow conditions associated with a sudden change in the cross-section. Experimental results are found to agree well with the predictions from three-dimensional Computational Fluid Dynamics (CFD) models. The Nusselt number and pressure drop due to minor losses show dependency on the drive ratio (measured maximum oscillating pressure to the system mean pressure), the edge shape and hot heat exchanger temperature. At a high amplitude, the edge shape significantly minimises the minor loss pressure difference, with negligible effect on the thermal performance. The results reported in this study will benefit the development of compact heat exchangers for the thermoacoustic engines/refrigerators or Sterling engines/coolers in cryogenic applications.