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Multichip LED arrays are widely used for lighting to provide high luminance. Luminous efficacy, lifetime, and color temperature are highly dependent on the temperature at p-n junction. This paper investigated the effects of distance, number of chips, and driving current on the thermal resistance of LED module. Thermal resistance dramatically increased as the distance between LED chips decreased due...
In this study, temperature uniformity and heating rate of multi-well vapor chambers of different materials were simulated and analyzed by CFD software at natural convection condition. Heat sources with a total heating power of 1200W were uniformly distributed to six 30×30mm2 rectangular vapor chambers for heating. Model size of the vapor chamber is 112×75×17.2mm, and its structure is consisted of...
The objective of this paper is to provide an effective and accurate analytical solution to compute the spreading thermal resistance of a vapor chamber thermal module, as well as the surface temperatures and the heat flux distributions at the heating surface. The analytical solutions are expressed in a reduced unit system with the governing parameters of the corresponding distance between heat sources,...
In this investigation, a gamma-configuration Stirling engine is designed and constructed. The single and twin power cylinder engines are tested with air at atmospheric pressure by using an electric heater as a heat source. The engine is tested with heater input of 156.3W, 187.6W, and 223.2W. Variations of engine torque, shaft power and brake thermal efficiency with engine speed and engine performance...
Thermal spreading is a technology of decreasing the hot spot for electronic cooling and other high heat flux applications, and is characterized by high heat transfer, uniformity of heat removal. Vapor chamber is one of the Thermal spreading technologies which depend on two phase heat pipe technology. This paper provides an introduction to vapor chamber for electronic cooling, high power LEDs, multi...
The power dissipation of CPU used in desktop computers has been steadily increasing with time. The tendency for a rise in the CPU capacity resulted at present in increasing heat release to 50-100W for desktop PC. The problem of the CPU cooling consists in restricting its temperature to 80-90degC. Current desktop computers use a heat sink of approximately 60 times 80 mm2 base area. Desktop computers...
This study utilizes a silver nano-fluid on a flat heat pipe. It studies the effect of various concentrations on flat heat pipe thermal performance by air-cooling testing equipment. The particles used in these experiments were silver particles 35 nm in size. The base working fluid was pure-water. Nano- fluids were prepared using a two-step method. In the experiment, the thickness and length of the...
This research paper was performed to study and utilizes two kinds of materials which match with two different fabrications in order to design an ideal shape of microneedles. The technology employs the polymer microneedles and the silicon microneedles with the height of 236 mum and 350 mum respectively. Moreover, the transdermal drug delivery investigation was conducted by using the fabricated samples...
Two-phase convective flow in micro channels has numerous promising applications such as electronic cooling. This study investigates evaporation phenomena and capillary-driven heat in a rectangular micro channels structure with hydraulic diameters of 100 ~ 250nm and length of 75mm. The micro channels made of (110)-orientated silicon is fabricated by bulk micromachining. The temperature distributions...
In this study, commercially available software CFD was adopted for analyzing the performance of straight-walled and curved-walled micro nozzle/diffuser. Such nozzle/diffuser was used in valve-less micro-pumps. This model tested different types of nozzle/diffuser and the results showed that the pressure loss coefficient for nozzle/diffuser decreases with the increase of Reynolds number. At the same...
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