Experimental and Numerical Investigation Into the Heat Transfer Study of Nanofluids in Microchannel
01 Dec 2011-Journal of Heat Transfer-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 133, Iss: 12, pp 121701
About: This article is published in Journal of Heat Transfer-transactions of The Asme.The article was published on 2011-12-01. It has received 43 citations till now. The article focuses on the topics: Microchannel & Nanofluid.
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TL;DR: In this article, the authors provide a comprehensive review of published literature concerning heat transfer benefits of nanofluids for both macro-channels and micro channels, including both experimental and numerical findings concerning several important performance parameters, including single-phase and two-phase heat transfer coefficients, pressure drop, and critical heat flux.
Abstract: This paper provides a comprehensive review of published literature concerning heat transfer benefits of nanofluids for both macro-channels and micro-channels. Included are both experimental and numerical findings concerning several important performance parameters, including single-phase and two-phase heat transfer coefficients, pressure drop, and critical heat flux (CHF), each being evaluated based on postulated mechanisms responsible for any performance enhancement or deterioration. The study also addresses issues important to heat transfer performance, including entropy minimization, hybrid enhancement methodologies, and nanofluid stability, as well as the roles of Brownian diffusion and thermophoresis. Published results point to appreciable enhancement in single-phase heat transfer coefficient realized in entrance region, but the enhancement subsides downstream. And, while some point to the ability of nanofluids to increase CHF, they also emphasize that this increase is limited to short duration boiling tests. Overall, studies point to many important practical problems associated with implementation of nanofluids in cooling situations, including clustering, sedimentation, and precipitation of nanoparticles, clogging of flow passages, erosion to heating surface, transient heat transfer behavior, high cost and production difficulties, lack of quality assurance, and loss of nanofluid stability above a threshold temperature.
136 citations
TL;DR: In this paper, the hydraulic and thermal fields of a 29nm CuO nanoparticle-water nanofluid with various volume fractions, 0.24, 1.03% and 4.5%, were investigated inside a rectangular microchannel heat sink under both laminar and turbulent conditions.
Abstract: This paper presents an experimental investigation of the hydraulic and thermal fields of a 29 nm CuO nanoparticle–water nanofluid with various volume fractions, 0.24%, 1.03% and 4.5% flowing inside a rectangular microchannel heat sink under both laminar and turbulent conditions. The isothermal and heated tests are conducted for Reynolds number up to ≈5000 and to ≈2500, respectively. For a given fluid flow rate experimental results show an increase of the pressure drop and the friction factor with respect to water. This increase can be as high as 70%, 25%, and 0–30%, respectively, for the 4.5%, 1.03%, and 0.24% particle volume fractions. Although the laminar-to-turbulent transition was observed at nearly the same critical Reynolds number Rec ≈ 1000 for water and the tested nanofluids, this value of Rec is clearly lower than that corresponding to a smooth surface microchannel. Results show a slight heat transfer enhancement with respect to water for nanofluids with low particle volume fractions, 0.24% and 1.03%, while for the 4.5% fraction a clear decrease of heat transfer was found. In general, the nanofluid overall energetic performance, defined by the heat transferred/pumping power ratio, remains lower than that of water for a given Reynolds number. This ratio decreases with an augmentation of the particle volume fraction.
119 citations
TL;DR: In this paper, the effect of nanoparticle mass fraction and Re on local convective heat transfer coefficients, and the local Nusselt number was also studied. But the experimental results showed that increased mass fraction of nanoparticles from 0.05 to 0.3 wt% resulted in lower thermal resistances of up to 21%.
Abstract: The utilization of nanofluids of various types as cooling or heating working fluids has given incentive to enhanced heat transfer resulting in even smaller heat exchangers for a given heat duty. In this study, convective heat transfer coefficients and friction factor of copper nanofluids in a cylindrical microchannel heat sink were investigated. Copper nanoparticles with various mass fractions were used for two heat fluxes of 35 and 50 kW/m2. The effect of nanoparticle mass fraction and Re on local convective heat transfer coefficients, and the local Nusselt number was also studied. The experimental results showed that increased mass fraction of nanoparticles from 0.05 to 0.3 wt% resulted in lower thermal resistances of up to 21%. Moreover, the local heat transfer coefficients helped to experimentally determine the thermal entrance length for the microchannel heat sink. The presence of nanoparticles enhanced the entrance Nu up to 43% while the friction factor also increased up to 45.5% compared with that of pure water. Two correlations were finally proposed for the prediction of the Nusselt number and friction factor for the attempted nanofluid in the microchannel which agreed well with the experimental data.
96 citations
TL;DR: In this paper, the influence of flow maldistribution on temperature distribution in parallel microchannel system was investigated and it was observed that the flow distribution among the channels improves significantly with a decrease in the channel hydraulic diameter due to higher pressure drop offered by each individual channels simultaneously.
Abstract: This paper brings out the phenomenon of the influence of flow maldistribution on temperature distribution in parallel microchannel system that is supposed to have an adverse effect on hot spot formation in microelectronic devices. An extensive experimental study is carried out where in the parameters affecting the flow maldistribution such as channel hydraulic diameter, channel flow configurations (U, Z, I type) and chip power are varied to study their effect on the pressure drop and temperature distribution across the parallel channels designed for liquid cooling of a CPU using distilled water. It is observed that the flow distribution among the channels improves significantly with a decrease in the channel hydraulic diameter due to higher pressure drop offered by each individual channels simultaneously. This results in a considerable reduction in both the peak temperature and the average temperature of the device with decrease in channel diameter and better temperature distribution. It is observed that a higher pressure drop in d = 88 μm induces more uniform distribution compared to d = 176 μm resulting in a 3 °C improvement in the standard deviation of temperature on the chip surface and a reduction in maximum surface temperature. Higher heat fluxes induce a reduction in viscosity of the fluid resulting in higher flow maldistribution.
63 citations
References
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Book•
11 Sep 1985
TL;DR: This paper introduced the physical effects underlying heat and mass transfer phenomena and developed methodologies for solving a variety of real-world problems, such as energy minimization, mass transfer, and energy maximization.
Abstract: This undergraduate-level engineering text introduces the physical effects underlying heat and mass transfer phenomena and develops methodologies for solving a variety of real-world problems.
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TL;DR: In this article, an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat-transfer fluids, which are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluid, and they represent the best hope for enhancing heat transfer.
Abstract: Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in many industrial applications. In this paper we propose that an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat transfer fluids. The resulting {open_quotes}nanofluids{close_quotes} are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluids, and they represent the best hope for enhancement of heat transfer. The results of a theoretical study of the thermal conductivity of nanofluids with copper nanophase materials are presented, the potential benefits of the fluids are estimated, and it is shown that one of the benefits of nanofluids will be dramatic reductions in heat exchanger pumping power.
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TL;DR: In this paper, a water-cooled integral heat sink for silicon integrated circuits has been designed and tested at a power density of 790 W/cm2, with a maximum substrate temperature rise of 71°C above the input water temperature.
Abstract: The problem of achieving compact, high-performance forced liquid cooling of planar integrated circuits has been investigated. The convective heat-transfer coefficient h between the substrate and the coolant was found to be the primary impediment to achieving low thermal resistance. For laminar flow in confined channels, h scales inversely with channel width, making microscopic channels desirable. The coolant viscosity determines the minimum practical channel width. The use of high-aspect ratio channels to increase surface area will, to an extent, further reduce thermal resistance. Based on these considerations, a new, very compact, water-cooled integral heat sink for silicon integrated circuits has been designed and tested. At a power density of 790 W/cm2, a maximum substrate temperature rise of 71°C above the input water temperature was measured, in good agreement with theory. By allowing such high power densities, the heat sink may greatly enhance the feasibility of ultrahigh-speed VLSI circuits.
4,214 citations
TL;DR: In this article, the authors used a Brookfield rotating viscometer to measure the viscosities of the dispersed fluids with γ-alumina (Al2O3) and titanium dioxide (TiO2) particles at a 10% volume concentration.
Abstract: Turbulent friction and heat transfer behaviors of dispersed fluids (i.e., uttrafine metallic oxide particles suspended in water) in a circular pipe were investigated experimentally. Viscosity measurements were also conducted using a Brookfield rotating viscometer. Two different metallic oxide particles, γ-alumina (Al2O3) and titanium dioxide (TiO2), with mean diameters of 13 and 27 nm, respectively, were used as suspended particles. The Reynolds and Prandtl numbers varied in the ranges l04-I05 and 6.5-12.3, respectively. The viscosities of the dispersed fluids with γ-Al2O3 and TiO2 particles at a 10% volume concentration were approximately 200 and 3 times greater than that of water, respectively. These viscosity results were significantly larger than the predictions from the classical theory of suspension rheology. Darcy friction factors for the dispersed fluids of the volume concentration ranging from 1% to 3% coincided well with Kays' correlation for turbulent flow of a single-phase fluid. The Nusselt n...
3,730 citations