Heat Sinks
"A heat sink is a colloquial term for a component or assembly that efficiently transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Heat sinks are primarily used to remove unwanted heat from a device to keep it from overheating. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator (also a heat exchanger) in a car. Heat sinks also help to cool electronic and optoelectronic devices, such as higher-power lasers and light emitting diodes (LEDs)." Wikipedia /Heat Sinks 4/7/2010
Filled Heat Sinks "Electrical appliances require electrical insulation. Good electrical insulators, also tend to be good thermal insulators which may be undesirable. Thermal insulation reduces efficiency and durability by trapped heat. Smith, Stevens and Wood increase thermal conductivity of electrical insulation using closely spaced thermally conductor filler particles. The mean distance between the thermally conductive particles is below the phonon mean free path length. This reduces the phonon scattering and produces a greater net flow or flux of phonons away from the heat source. This material may then be part of a multi-layered electrical insulating tape. The host resin networks include epoxy, polyimide-epoxy, liquid crystal epoxy, cyanate-ester, polybutadiene or their mixtures. The high thermal conductivity fillers may be diamond, aluminum nitride, boron nitride silicon nitride and silicon carbide particles." Carbon Nanotube Heat Sinks ”As electronic components become smaller heat dissipation requirements are increased. A heat sink is used between the electronic components to efficiently dissipate heat generated during operation. Conventional heat sinks are composites filled with thermally conductive particles. Such particles include graphite, boron nitride, silicon oxide, alumina, silver or other metals. However, a heat conduction of most composites is too low for many contemporary applications.. The thermal conductivity of a carbon nanotube is very high but carbon nanotube heat sinks are not satisfactory, probably due to interface resistances. Huang et al has developed an effective heat sink based on a carbon nanotube array anchored in a phase change material. As the exposed nanotubes are heated the heat flows to the phase change material which quickly absorbs the energy through the phase change. Such phase change materials include paraffins, polyolefins, low molecular weight polyesters, low molecular weight epoxies, and low molecular weight acrylics. The composite shows very low thermal resistance for both high and low heat fluxes.” Huang et al, US Patent 7,655,295, 3/9/2010
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Editor's Notes
As the literature is reviewed, and items of interest concerning this topic are found. These may be added in an abbreviated form with the reference. Readers and contributors are invited to add their own notes. Contributors may add them directly and other readers can simply send their notes to the editor, Roger Corneliussen at rcorneliussen@4spe.org. He may edit and add them to this page at his discretion.