翻訳と辞書 Words near each other ・ Heat recovery ventilation ・ HEAT repeat domain ・ Heat rock ・ Heat rub ・ Heat Rush ・ Heat sealer ・ Heat Seekers ・ Heat shield ・ Heat Shield Rock ・ Heat shock ・ Heat shock factor ・ Heat shock protein ・ Heat shock protein 47 ・ Heat shock protein 70 (Hsp70) internal ribosome entry site (IRES) ・ Heat shock protein 90kDa alpha (cytosolic), member A1 ・ Heat sink ・ Heat sink (disambiguation) ・ Heat spreader ・ Heat stabilization ・ Heat storage ・ Heat stroke ・ Heat syncope ・ Heat Team ・ Heat therapy ・ Heat torch ・ Heat transfer ・ Heat transfer coefficient ・ Heat transfer efficiency ・ Heat transfer enhancement ・ Heat transfer physics Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Heat sink ： ウィキペディア英語版 Heat sink A heat sink is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device into a coolant fluid in motion. Then-transferred heat leaves the device with the fluid in motion, therefore allowing the regulation of the device temperature at physically feasible levels. In computers, heat sinks are used to cool central processing units or graphics processors. Heat sinks are used with high-power semiconductor devices such as power transistors and optoelectronics such as lasers and light emitting diodes (LEDs), where the heat dissipation ability of the basic device is insufficient to moderate its temperature. A heat sink is designed to maximize its surface area in contact with the cooling medium surrounding it, such as the air. Air velocity, choice of material, protrusion design and surface treatment are factors that affect the performance of a heat sink. Heat sink attachment methods and thermal interface materials also affect the die temperature of the integrated circuit. Thermal adhesive or thermal grease improve the heat sink's performance by filling air gaps between the heat sink and the heat spreader on the device. ==Heat transfer principle== A heat sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium. The fluid medium is frequently air, but can also be water, refrigerants or oil. If the fluid medium is water, the heat sink is frequently called a cold plate. In thermodynamics a heat sink is a heat reservoir that can absorb an arbitrary amount of heat without significantly changing temperature. Practical heat sinks for electronic devices must have a temperature higher than the surroundings to transfer heat by convection, radiation, and conduction. The power supplies of electronics are not 100% efficient, so extra heat is produced that may be detrimental to the function of the device. As such, a heat sink is included in the design to disperse heat to improve efficient energy use. To understand the principle of a heat sink, consider Fourier's law of heat conduction. Fourier's law of heat conduction, simplified to a one-dimensional form in the ''x''-direction, shows that when there is a temperature gradient in a body, heat will be transferred from the higher temperature region to the lower temperature region. The rate at which heat is transferred by conduction, $q\_k$, is proportional to the product of the temperature gradient and the cross-sectional area through which heat is transferred. :$q\_k\; =\; -k\; A\; \backslash frac$ Consider a heat sink in a duct, where air flows through the duct, as shown in Figure 2. It is assumed that the heat sink base is higher in temperature than the air. Applying the conservation of energy, for steady-state conditions, and Newton’s law of cooling to the temperature nodes shown in Figure 2 gives the following set of equations: :$\backslash dot\; =\; \backslash dotc\_(T\_\; -\; T\_)$ (1) :$\backslash dot\; =\; \backslash frac\}\; =\; \backslash frac\}$ (3) Using the mean air temperature is an assumption that is valid for relatively short heat sinks. When compact heat exchangers are calculated, the logarithmic mean air temperature is used. $\backslash dot$ is the air mass flow rate in kg/s. The above equations show that * When the air flow through the heat sink decreases, this results in an increase in the average air temperature. This in turn increases the heat sink base temperature. And additionally, the thermal resistance of the heat sink will also increase. The net result is a higher heat sink base temperature. * * The increase in heat sink thermal resistance with decrease in flow rate will be shown later in this article. * The inlet air temperature relates strongly with the heat sink base temperature. For example, if there is recirculation of air in a product, the inlet air temperature is not the ambient air temperature. The inlet air temperature of the heat sink is therefore higher, which also results in a higher heat sink base temperature. * If there is no air flow around the heat sink, energy cannot be transferred. * A heat sink is not a device with the "magical ability to absorb heat like a sponge and send it off to a parallel universe".〔Kordyban, T., 1998, Hot air rises and heat sinks – Everything you know about cooling electronics is wrong, ASME Press, NY.〕 Natural convection requires free flow of air over the heat sink. If fins are not aligned vertically, or if fins are too close together to allow sufficient air flow between them, the efficiency of the heat sink will decline. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Heat sink」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.