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

随着VLSI芯片技术的快速发展和对有效散热的需求，人们对离散热源阵列的对流换热产生了兴趣。最近，一个重要的冷却选择已经变得很明显，它涉及将电子元件直接浸入介电液体中，并且在使用该选项来散热大热流(100W/cm2)方面正在进行相当大的努力。这类努力通常涉及单相强制对流和强制对流沸腾，以及实现强化传热的措施。然而，人们认为，在寻求通过强制对流实现更大水平的耗散时，对于中等热通量的应用没有给予足够的关注，对于这些应用来说，如果不是强制性的，那么在没有强制流动的情况下冷却是必要的。这种包括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，从而减少了与高速流动引起的流体动力载荷和振动相关的机械问题。未来的高性能台式计算机和工作站将构成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。这项拟议的研究旨在评估可通过哪些方法加强来自离散源阵列的非沸腾和沸腾换热，以实现腔内的自由对流。对于具有和不具有延伸表面的热源，将使用实验和数值模拟来建立对相关流动和热条件的基本理解，并确定操作使单位包装体积的换热最大化的条件。要考虑的换热强化方案包括但不限于低轮廓螺柱、针翅片阵列、纵向翅片阵列和多孔翅片阵列。三维模型，包括衬底导电的共轭问题，将被用来与实验结果进行比较。这项工作有望加深对介质液体中与离散源相关的基本流动和传热的理解，特别是对在低冷却剂体积流速和低冷却剂系统体积下最大化热通量的传热强化方案的关注。

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.