Analysis of time-dependent heat transfer with periodic excitation in microscale systems
Analysis of time-dependent heat transfer with periodic excitation in microscale systems
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DOI：
10.1016/j.applthermaleng.2021.117225
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发表时间：
2021-07-03
影响因子：
6.4
通讯作者：
Ziskind, Gennady
中科院分区：
文献类型：
--
作者：
Shockner, Tomer;Chowdhury, Tanvir Ahmed;Ziskind, Gennady
本研究探讨微尺度系统中周期性激励下的时变热传。具体来说，这项研究揭示了与微系统中的周期性传热相关的时间和长度尺度。首先，一个系统的基板被建模为一个有限厚度的平板，其中的热传导方程解析求解的周期性温度边界条件在整个范围内的瞬态周期性过程。使用的解析解，系统反应的时间尺度和材料特性的特点是典型的微系统。“穿透深度”被定义为指示距热-热激发仍然明显的热-热边界/表面的最大距离的参数。然后，作为一个案例研究，一个实验装置进行检查，使用一个圆形的，冲击水射流冷却由脉冲激光加热的表面。最后，一个三维数值模拟，验证与实验，是用来阐明系统的预期的热行为，包括空间和时间的温度场变化，相关的时间尺度的测量，和传热系数的空间分布。结果表明，分析结果可以用来描述真实的行为，而准确。这些发现可以帮助设计具有不稳定加热的系统，并在未来的研究中旨在了解更复杂的物理驱动的瞬态现象，如微系统中的流动沸腾。
This study investigates time-dependent heat transfer with periodic excitation in micro-scale systems. Specifically, this study sheds light on time and length scales relevant to periodic heat transfer in micro systems. First, a system's substrate is modeled as a slab of finite thickness, in which the heat conduction equation is solved analytically for a periodic temperature boundary condition over the entire range of transient-periodic process. Using the analytical solutions, the system reaction in time is characterized for time scales and material properties typical for micro-systems. A "penetration depth" is defined as a parameter which indicates the maximum distance from the periodically-heated boundary/surface at which the periodic-thermal excitations are still noticeable. Then, as a case study, an experimental device is examined that uses a round, impinging water jet to cool a surface heated by pulsing laser. Finally, a three-dimensional numerical simulation, validated versus experiments, is used to elucidate the system's expected thermal behavior, including spatial and temporal temperature field variation, relevant time scales for measurements, and the spatial distribution of the heat transfer coefficient. It is demonstrated that the analytical findings can serve to characterize the real behavior rather accurately. The findings can assist in the design of systems with unsteady heating, and in future studies aiming at understanding more complex physically-driven transient phenomena, like flow boiling in micro-systems.