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Analysis of time-dependent heat transfer with periodic excitation in microscale systems
Applied Thermal Engineering ( IF 6.1 ) Pub Date : 2021-06-24 , DOI: 10.1016/j.applthermaleng.2021.117225
Tomer Shockner , Tanvir Ahmed Chowdhury , Shawn A. Putnam , Gennady Ziskind

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.



中文翻译:

微尺度系统中周期性激发的瞬态传热分析

本研究调查了微尺度系统中周期性激发的瞬态热传递。具体而言,这项研究揭示了与微系统中周期性热传递相关的时间和长度尺度。首先,系统的基板被建模为有限厚度的板,其中热传导方程在瞬态周期过程的整个范围内针对周期温度边界条件进行解析求解。使用解析解,系统反应的时间尺度和微系统典型的材料特性被表征。“穿透深度”被定义为一个参数,该参数指示距周期性加热边界/表面的最大距离,在该距离处周期性热激发仍然明显。然后,作为案例研究,一个实验装置被检查,它使用圆形的冲击水射流冷却由脉冲激光加热的表面。最后,通过与实验相验证的三维数值模拟来阐明系统的预期热行为,包括空间和时间温度场变化、测量的相关时间尺度以及传热系数的空间分布。结果表明,分析结果可以相当准确地表征真实行为。这些发现有助于设计具有不稳定加热的系统,并有助于未来的研究,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。一个三维数值模拟,经过验证与实验,用于阐明系统的预期热行为,包括空间和时间温度场变化,测量的相关时间尺度,以及传热系数的空间分布。结果表明,分析结果可以相当准确地表征真实行为。这些发现有助于设计具有不稳定加热的系统,并有助于未来的研究,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。一个三维数值模拟,经过验证与实验,用于阐明系统的预期热行为,包括空间和时间温度场变化,测量的相关时间尺度,以及传热系数的空间分布。结果表明,分析结果可以相当准确地表征真实行为。这些发现有助于设计具有不稳定加热的系统,并有助于未来的研究,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。以及传热系数的空间分布。结果表明,分析结果可以相当准确地表征真实行为。这些发现有助于设计具有不稳定加热的系统,并有助于未来的研究,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。以及传热系数的空间分布。结果表明,分析结果可以相当准确地表征真实行为。这些发现有助于设计具有不稳定加热的系统,并有助于未来的研究,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。

更新日期:2021-07-04
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