Single and Two-Phase Thermosyphon Heat Transfer from Arrays of Discrete Heat Sources Submerged in a Dielectric Liquid

VLSI芯片技术的快速发展和对有效散热的需求激发了人们对离散热源阵列对流传热的兴趣。最近，很明显，一种重要的冷却方法涉及将电子元件直接浸入介电液体中，并且正在努力使用这种方法来消散大热通量（100 W/cm2）。这种努力通常涉及单相强制对流和强制对流沸腾，并采取措施加强传热。然而，人们认为，在寻求通过强制对流实现更大水平耗散的过程中，对中等热通量应用的重视不够，这种应用即使不是强制性的，也需要在没有施加介电液体流动的情况下进行冷却。这种涉及单相或两相热虹吸管的冷却方案提供了良性的被动条件，消除了泵送要求，从而减少了与流体动力载荷和高速流动引起的振动相关的机械问题。高性能台式电脑和未来的工作站将是这项技术的重要应用，因为复杂的冷却剂分配装置不能在这种情况下使用。提出的研究旨在评估由离散源阵列的非沸腾和沸腾传热可能增强的方法，以促进腔内的自由对流。对于有或没有延伸表面的热源，实验和数值模拟将用于建立对相关流动和热条件的基本理解，并确定最大限度地提高单位包装体积传热的操作条件。要考虑的传热增强方案包括，但不限于，低轮廓螺柱，钉鳍阵列，纵鳍阵列和多孔鳍阵列。三维模型，包括衬底传导的共轭问题，将用于与实验结果进行比较。这项工作有望加强对介电液体中与离散源相关的基本流动和传热的理解，特别关注在低冷却剂体积流量和低冷却剂系统体积下最大化热流的传热增强方案。

Interest in convection heat transfer from arrays of discrete heat sources has been stimulated by rapid advancements in VLSI chip technologies and the attendant need for effective heat dissipation. Recently, it has become clear that an important cooling option involves direct immersion of electronic components in a dielectric liquid, and considerable effort is being directed towards use of this option to dissipate large heat fluxes ( 100 W/cm2). Such efforts typically involve single-phase forced convection and forced convection boiling, with measures for effecting heat transfer enhancement. However, it is believed that, in the quest for achieving larger levels dissipation with forced convection, insufficient attention is being given to moderate heat flux applications for which cooling with no imposed flow of the dielectric liquid is desirable, if not mandatory. Such cooling schemes, involving either single-or two-phase thermosyphons, offer benign, passive conditions for which pumping requirements are eliminated, thereby reducing mechanical problems related to the hydrodynamic loads and vibrations induced by high speed flows. High-powered desktop computers and workstations of the future would constitute an important application of this technology, since complex coolant distribution units cannot be used in such situations. The proposed study seeks to assess means by which non boiling and boiling heat transfer from arrays of discrete sources may be enhanced for free convection in a cavity. For heat sources with and without extended surfaces, experiments and numerical simulations will be used to establish a basic understanding of related flow and thermal conditions and to determine operating conditions which maximize heat transfer per unit package volume. Heat transfer enhancement schemes to be considered include, but are not restricted to, low-profile studs, pin-fin arrays, longitudinal fin arrays, and porous fin arrays. Three-dimensional models, including the conjugate problem of substrate conduction, will be used for comparison with experimental results. The work is expected to enhance understanding of basic flow and heat transfer associated with discrete sources in a dielectric liquid with particular attention to heat transfer enhancement schemes which maximize heat flux at low coolant volumetric flow rate and low coolant system volume.