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Optimaal ontwerp van koellichamen voor vloeistofkoeling van elektronica

机译：电子设备液体冷却的最佳散热器设计

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The cooling of electronic devices is essential to guarantee their functional performance and operational lifetime. Due to continued miniaturization and integration of transistors in packaged chips, the heat dissipation rate has surpassed the limits of classical air-cooled heat sinks. This has triggered a lot of research towards alternatives for high heat flux cooling. Liquid cooling with micro heat sinks is one of these candidate solutions. Cold liquid flows through microscopic channels to extract heat from the chip. These microchannels are manufactured in a heat sink attached on top of the chip, or even in the chip itself, to minimize the conduction path. By using very small flow channels, high heat transfer rates can be achieved as demonstrated by Tuckerman and Pease using a heat sink with parallel channels. However, these small channels lead to elevated pressure drops.The design of flow paths in micro heat sinks plays a crucial role in harmonizing high cooling rates with moderate pumping requirements. This is traditionally approached by optimizing the size of the channels. Furthermore, alternative layouts involving a topological change of the flow network have been proposed. Advanced design optimization methods such as shape optimization and topology optimization have proven their virtue in other engineering disciplines such as aerodynamics and structural mechanics. These methods can be useful in heat sink design to exploit further improvement potential and automate the design process in a systematic and flexible way.In this thesis advanced numerical design methods for micro heat sinks are developed. Two approaches have been investigated: shape optimization of single microchannels, and topology optimization of heat sinks. The first part of this thesis focusses on microchannel shape optimization. The streamwise width distribution of a single microchannel element is optimized using a correlation-based analytical model. This work continues on the work of Bau by considering more degrees of freedom. It is shown in this thesis that optimized microchannels can be used to reduce thermal resistance by 8% compared to a microchannel with constant width, or alternatively to eliminate non-uniformities in the source temperature. In the second part of this thesis, a topological heat sink design method is developed. A two-dimensional model of partial-differential equations for the simulation of fluid flow and heat transfer in the heat sink is presented. The hybrid nature of this model enables to distinguish solid material from fluid by tuning a fictitious porosity. The topology optimization problem is solved by optimally controlling this porosity. The minimization of the objective functional is performed by the method of moving asymptotes, which is a robust gradient-based optimization algorithm. The set of adjoint equations corresponding to the heat sink model equations is derived. The solution of these equations provides an efficient means for calculation of the objective gradient.The topological design method is appliedto two test cases with different boundary conditions to represent the heat source. The first case considers a constant temperature source, which admits a simpler heat sink model. The second case involves a constant flux heat source. Both cases show a significant thermal resistance reduction of respectively 50% and 30% with respect to an optimized parallel channel heat sink. Typically, the optimized heat sink layouts consist of a branched network of channels. It is concluded that topology optimization is a promising method for automated heat sink design.
机译：电子设备的冷却对于保证其功能性能和使用寿命至关重要。由于晶体管在封装芯片中的不断小型化和集成化，其散热速率已经超过了传统风冷散热器的极限。这引发了对高热通量冷却替代方案的大量研究。带有微型散热器的液体冷却是这些候选解决方案之一。冷液体流经微观通道以从芯片中吸收热量。这些微通道是在附在芯片顶部的散热器中，甚至在芯片本身中制造的，以最大程度地减少传导路径。通过使用非常小的流动通道，可以实现高传热率，正如Tuckerman和Pease使用具有平行通道的散热器所证明的那样。但是，这些小通道会导致压力下降。微型散热器中的流路设计在协调高冷却速率与适度泵送要求之间起着至关重要的作用。传统上，这是通过优化通道大小来实现的。此外，已经提出了涉及流动网络的拓扑变化的替代布局。诸如形状优化和拓扑优化之类的高级设计优化方法已在其他工程学科（如空气动力学和结构力学）中证明了它们的优点。这些方法可用于散热器的设计，以进一步开发改进潜力，并以系统化，灵活的方式使设计过程自动化。本文开发了先进的微型散热器数值设计方法。研究了两种方法：单个微通道的形状优化和散热器的拓扑优化。本文的第一部分集中在微通道形状优化上。使用基于相关的分析模型优化单个微通道元素的沿流宽度分布。通过考虑更多的自由度，这项工作继续在鲍尔（Bau）的工作中进行。本论文表明，与具有恒定宽度的微通道相比，优化的微通道可用于将热阻降低8％，或者可用于消除源温度的不均匀性。在本文的第二部分，开发了一种拓扑散热器设计方法。提出了二维微分方程模型，用于模拟散热器中的流体流动和热传递。该模型的混合性质能够通过调整虚拟孔隙率将固体材料与流体区分开。通过优化控制该孔隙率可以解决拓扑优化问题。目标函数的最小化是通过移动渐近线的方法执行的，该方法是基于梯度的鲁棒优化算法。得出与散热器模型方程相对应的伴随方程组。这些方程的解为目标梯度的计算提供了一种有效的手段。拓扑设计方法被应用于两个具有不同边界条件的测试案例来表示热源。第一种情况考虑的是恒温源，这允许采用更简单的散热器模型。第二种情况涉及恒定流量的热源。相对于优化的平行通道散热器，这两种情况均显示出显着的热阻降低，分别为50％和30％。通常，优化的散热器布局由分支的通道网络组成。结论是，拓扑优化是用于自动化散热器设计的有前途的方法。

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