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Showing papers on "Heat pipe published in 2010"


Journal ArticleDOI
TL;DR: A colloidal mixture of nano-sized particles in a base fluid, called nanofluids, tremendously enhances the heat transfer characteristics of the original fluid, and is ideally suited for practical applications due to its marvelous characteristics.
Abstract: A colloidal mixture of nano-sized particles in a base fluid, called nanofluids, tremendously enhances the heat transfer characteristics of the original fluid, and is ideally suited for practical applications due to its marvelous characteristics. This article addresses the unique features of nanofluids, such as enhancement of heat transfer, improvement in thermal conductivity, increase in surface volume ratio, Brownian motion, thermophoresis, etc. In addition, the article summarizes the recent research in experimental and theoretical studies on forced and free convective heat transfer in nanofluids, their thermo-physical properties and their applications, and identifies the challenges and opportunities for future research.

713 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured the dependence of thermal resistance on the thickness and particle size of sintered copper powder wick surfaces, both under evaporation and boiling conditions, and demonstrated that for a given wick thickness, an optimum particle size exists which maximizes the boiling heat transfer coefficient.

251 citations


Journal ArticleDOI
TL;DR: In this paper, a transient and implicit model based on computational fluid dynamics was developed to predict the thermal performance and cooling capacity of earth-air-pipe heat exchanger systems, which was validated against experimental investigations on an experimental set-up in Ajmer (Western India). Good agreement between simulated results and experimental data is obtained.

247 citations


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional analysis is used to study the thermal performance of a cylindrical heat pipe utilizing nanofluids, and the existence of an optimum mass concentration for nanoparticles in maximizing the heat transfer limit is established.

229 citations


Journal ArticleDOI
TL;DR: In this article, a thermal network model is developed and used to analyze heat transfer in a high temperature latent heat thermal energy storage unit for solar thermal electricity generation, where the benefits of inserting multiple heat pipes between a heat transfer fluid and a phase change material (PCM) are of interest.

217 citations


Patent
Jonathan S. Dahm1
01 Mar 2010
TL;DR: In this article, a method for cooling the light emitting diodes and mounting the same on heat pipe in a manner which delivers ultra high power in UV, visible and IR regions is presented.
Abstract: The present invention provides a method and apparatus for using light emitting diodes for curing and various solid state lighting applications. The method includes a novel method for cooling the light emitting diodes and mounting the same on heat pipe in a manner which delivers ultra high power in UV, visible and IR regions. Furthermore, the unique LED packaging technology of the present invention utilizes heat pipes that perform very efficiently in very compact space. Much more closely spaced LEDs operating at higher power levels and brightness are possible because the thermal energy is transported in an axial direction down the heat pipe and away from the light-emitting direction rather than a radial direction in nearly the same plane as the “p-n” junction.

184 citations


Journal ArticleDOI
TL;DR: In this article, an experimental investigation was performed on the thermal performance of an oscillating heat pipe (OHP) charged with base water and spherical Al2O3 particles of 56nm in diameter.

181 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the thermal performance of flat-shaped and disk-shaped heat pipes using nanofluids and found that the nanoparticles presence within the working fluid results in a decrease in the thermal resistance and an increase in the maximum heat load capacity.

169 citations


Journal ArticleDOI
TL;DR: In this article, the effect of water-based Al2O3 nanofluids as working fluid on the thermal performance of a flat micro-heat pipe with a rectangular grooved wick is investigated.

164 citations


Journal ArticleDOI
TL;DR: In this paper, the authors report the fabrication of dense arrays of super-hydrophilic Cu microposts at solid fractions as high as 58% and aspect ratios as much as four using electrochemical deposition and chemical oxidation techniques.
Abstract: We report the fabrication of dense arrays of super-hydrophilic Cu microposts at solid fractions as high as 58% and aspect ratios as high as four using electrochemical deposition and chemical oxidation techniques. Oxygen surface plasma treatments of photoresist molds and a precise control of the initial electrodeposition current are found to be critical in creating arrays of nearly defect-free Cu posts. The capillary performance of the micropost arrays is characterized using capillary rate of rise experiments and numerical simulations that account for the finite curvatures of liquid menisci. For the given wick morphology, the capillary performance generally decreases with increasing solid fraction and is enhanced by almost an order of magnitude when thin nanostructured copper oxide layers are formed on the post surface. The present work provides a useful starting point to achieve optimal balance between the capillary performance and the effective thermal conductivity of advanced wicks for micro heat pipes.

145 citations


Journal ArticleDOI
TL;DR: In this article, a copper-water compact loop heat pipe (LHP) with a unique flat, square evaporator with dimension of 30mm (L )×30mm (W )×15mm (H ) and a connecting tube having an inner diameter of 5mm.

Journal ArticleDOI
TL;DR: In this article, the authors constructed a low thermal resistance, multi-artery heat pipe spreader vapor chamber by designing a thin (monolayer) evaporator wick and distributed permeable columnar arteries supplying liquid (water) to highly concentrated heat source region.

Journal ArticleDOI
TL;DR: In this article, an experimental study was performed to investigate the thermal performance of an inclined miniature grooved heat pipe using water-based CuO nanofluid as the working fluid.

Journal ArticleDOI
TL;DR: In this paper, a sintered-grooved composite wick structure has been developed for two-phase heat transfer devices, and with ethanol as the working fluid, risen meniscus test is conducted to study the capillary force of wick structures.

Journal ArticleDOI
TL;DR: In this article, the effect of nanofluids on the thermal performance of heat pipes is experimentally investigated by testing circular screen mesh wick heat pipes using water-based Al 2 O 3 nanoflids with the volume fraction of 1.0 and 3.0 VOL%.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a 3.5 mm-thick Ti-based flat heat pipe for thermal ground plane (TGP) applications, which is constructed by laser welding two microfabricated titanium substrates to form a hermetically sealed vapor chamber.
Abstract: A novel 3 cm × 3 cm × 600 μm-thick Ti-based flat heat pipe is developed for Thermal Ground Plane (TGP) applications. The Ti-based heat pipe architecture is constructed by laser welding two microfabricated titanium substrates to form a hermetically sealed vapor chamber. The scalable heat pipes' flat geometry facilitates contact with planar heat sources, such as microprocessor chip surfaces, thereby reducing thermal contact resistance and improving system packaging. Fluid transport is driven by the wicking structure in the TGP, which consists of an array of Ti pillars that are microfabricated from a titanium substrate using recently developed high-aspect-ratio Ti processing techniques. The hydrophilic nature of the Ti pillars is increased further by growing ~200-nm hairlike nanostructured titania of the pillar surfaces. The resulting super hydrophilic wick offers the potential to generate high wicking velocities of ~27.5 mm/s over distances of 2 mm. The experimental wetting results show a diffusive spreading behavior that is predicted by Washburn dynamics. The maximum effective thermal conductivity of a heat pipe is directly related to the speed of capillary flow of the working fluid through the wick and is measured experimentally in the first-generation device to be k = 350 W/m · K. A dummy TGP with a cavity volume of ~170 μL was used to test the hermiticity level of the laser packaging technique. The device gave a 0.067% of water loss based on ~60 μL of charged water at 100°C in air for over a year.

Journal ArticleDOI
TL;DR: In this article, parallel grooves are made on the inner surface of the top plate, with inter-groove openings, to replace the conventional porous wick to achieve smaller liquid flow resistance and hence high anti-dryout capability.

Journal ArticleDOI
TL;DR: In this article, the evaporation resistances of flat-plate heat pipes with sintered multi-layer copper-mesh wick were measured for heat fluxes of 16-100 W/cm2.

Journal ArticleDOI
TL;DR: A literature review on the application of horizontal heat pipe heat exchangers for air conditioning in tropical climates was conducted by as discussed by the authors, where the authors focused on the energy saving and dehumidification enhancement aspects of HPTs.

Journal ArticleDOI
TL;DR: In this paper, a novel micro heat pipe array was used in solar panel cooling, and both of air-cooling and water cooling conditions under nature convection condition were investigated, and compared with the ordinary solar panel, the maximum difference of the photoelectric conversion efficiency is 2.6%, the temperature reduces maximally by 4.7℃, the output power increases maximally, while the daily radiation value is 21.9 MJ.
Abstract: A novel micro heat pipe array was used in solar panel cooling. Both of air-cooling and water-cooling conditions under nature convection condition were investigated in this paper. Compared with the ordinary solar panel, the maximum difference of the photoelectric conversion efficiency is 2.6%, the temperature reduces maximally by 4.7℃, the output power increases maximally by 8.4% for the solar panel with heat pipe using air-cooling, when the daily radiation value is 26.3 MJ. Compared with the solar panel with heat pipe using air-cooling, the maximum difference of the photoelectric conversion efficiency is 3%, the temperature reduces maximally by 8℃, the output power increases maximally by 13.9% for the solar panel with heat pipe using water-cooling, when the daily radiation value is 21.9 MJ.

Journal ArticleDOI
TL;DR: In this paper, an experimental study of a flat plate heat pipe (FPHP) is presented, where temperature fields in the FPHP are measured for different filling ratios, heat fluxes and vapour space thicknesses.

Journal ArticleDOI
TL;DR: In this paper, a 3 m long borehole containing a single U-pipe with surrounding bedrock was studied by a three-dimensional, steady-state CFD model and the results showed that induced natural convective heat flow significantly decreases the thermal resistance in the borehole.

Journal ArticleDOI
TL;DR: In this article, the authors deal with thermally induced meniscus oscillations in a two-phase system consisting of a liquid plug and a vapor bubble in a capillary tube of circular cross-section.

Journal ArticleDOI
TL;DR: In this paper, an experimental study was carried out to understand the heat transfer performance of a miniature thermosyphon using water-based carbon nanotube (CNT) suspensions as the working fluid.

Journal ArticleDOI
09 Nov 2010
TL;DR: In this article, the authors systematically review the experimental, theoretical/analytical, and modeling methodologies to predict these hydrodynamic properties in unidirectional two-phase Taylor bubble flows, in the context of Pulsating Heat Pipes.
Abstract: Global thermal performance modeling of Pulsating Heat Pipes (PHPs) requires local, spatio-temporally coupled, flow and heat transfer information during the characteristic, self-sustained thermally driven oscillating Taylor bubble flow, under different operating conditions. Local hydrodynamic characteristics such as velocities, lengths, shapes and profiles of bubbles and slugs, their dynamic contact angles, thickness of the liquid film that surrounds the bubbles, enhanced mixing/ flow circulation within the liquid slugs and net pressure drop along the flow, etc., are needed to predict local heat transfer and thus, the global thermal performance. In this paper, we systematically review the experimental, theoretical/analytical, and modeling methodologies to predict these hydrodynamic properties in unidirectional two-phase Taylor bubble flows, in the context of Pulsating Heat Pipes. Indeed, there is little literature available for oscillating Taylor bubbles flows. In view of the state-of-the-art, we therefore recommend some directions and perspectives for furthering research on understanding and modeling PHPs.

Journal ArticleDOI
TL;DR: In this paper, the authors present the results of experimental and theoretical analysis on the heat extraction process from solar pond by using the heat pipe heat exchanger using R134a was used as the heat transfer fluid in the experiment.

Journal ArticleDOI
TL;DR: In this article, the effect of the condenser and evaporator resurfacing on overall performance of a 1 m height closed two-phase thermosyphon was investigated at 44 power inputs from 43 W to 668 W.

Journal ArticleDOI
TL;DR: In this paper, the performance of a multi-stage water desalination still connected to a heat pipe evacuated tube solar collector with aperture area of 1.7 m2 was investigated.

Journal ArticleDOI
TL;DR: In this paper, the evaporation resistances of loosely-sintered copper-powder evaporators were measured in operating flat-plate heat pipes and visualized through a top glass plate.

Journal ArticleDOI
TL;DR: In this article, a thermometer/heater for high heat-flux cooling of the CNT biwick structure is presented, which is a 100-nm-thick and 600 μm wide Z-shaped platinum wire resistor, fabricated on a thermally oxidized silicon substrate of a CNT sample to heat a 2 ×2 mm 2 wick area.
Abstract: With the increase in power consumption in compact electronic devices, passive heat transfer cooling technologies with high-heat-flux characteristics are highly desired in microelectronic industries. Carbon nanotube (CNT) clusters have high thermal conductivity, nanopore size, and large porosity and can be used as wick structure in a heat pipe heatspreader to provide high capillary force for high-heat-flux thermal management. This paper reports investigations of high-heat-flux cooling of the CNT biwick structure, associated with the development of a reliable thermometer and high performance heater. The thermometer/heater is a 100-nm-thick and 600 μm wide Z-shaped platinum wire resistor, fabricated on a thermally oxidized silicon substrate of a CNT sample to heat a 2 ×2 mm 2 wick area. As a heater, it provides a direct heating effect without a thermal interface and is capable of high-temperature operation over 800°C. As a thermometer, reliable temperature measurement is achieved by calibrating the resistance variation versus temperature after the annealing process is applied. The thermally oxidized layer on the silicon substrate is around 1-μm-thick and pinhole-free, which ensures the platinum thermometer/heater from the severe CNT growth environments without any electrical leakage. For high-heat-flux cooling, the CNT biwick structure is composed of 250 μm tall and 100 μm wide stripelike CNT clusters with 50 μm stripe-spacers. Using 1 ×1 cm 2 CNT biwick samples, experiments are completed in both open and saturated environments. Experimental results demonstrate 600 W/cm 2 heat transfer capacity and good thermal and mass transport characteristics in the nanolevel porous media.