Thermal–Hydraulic Performance in a Microchannel Heat Sink Equipped with Longitudinal Vortex Generators (LVGs) and Nanofluid (original) (raw)
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In this study, the contributions of Au, Cu and Ag nanoparticles for enhancing the heat transfer in the rectangular microchannel heat sink with vortex generators are compared in this work. A two dimensional numerical method is used to simulate the forced convection of water-based suspensions of different nanoparticles in the microchannel heat sink submitted to a constant and uniform temperature (T= 303K) at the wall . The gouverning equations are solved numerically using code FLUENT based on CFD method. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. The effect of volume fraction, Reynolds number and type of nanoparticles on the fluid flow and heat transfer processes within the microchannel are analyzed. In addition, an analysis of isothermals and streamlines based on the different nanofluid are developed and presented. It is shown that the different nanoparticles within different thermal conductivity valu...
In this work, a numerical study is conducted to investigate the effects of hybrid nanofluid (Al2O3-Cu/water) on the thermal and hydraulic performance of a three-dimensional double-layer counterflow microchannel heat sink. The heat sink comprises a silicon block to which a constant heat flux of q = 1.0 MW/m 2 is applied at the base. Different volume concentrations of alumina and copper nanoparticles are considered, with the Reynolds number varying between 200 and 1000. The conjugate heat transfer problem is solved numerically using the two-phase Eulerian-Eulerian model in ANSYS-Fluent environment. Experimental validation shows a good agreement between the numerical models and the experiment. Nanofluids exhibit higher heat transfer coefficients and pressure drops than the base fluid; however, nanoparticle hybridization has a minimal effect on the pressure drop.
International Communications in Heat and Mass Transfer, 2018
Simultaneous effects of using nanoparticle (Al 2 O 3) in water along with the converging flow passages on the forced convection heat transfer coefficient in a microchannel heat sink (MCHS) are investigated using a finite volume numerical simulation. The accurate KKL (Koo-Kleinstreuer-Li) model, considering particles' material density, volume fraction, diameter and Brownian motion, is implemented to model the thermophysical properties of Al 2 O 3-water nanofluid. The numerical simulation is performed based on a non-uniform structured grid. Results have shown that nanoparticles can enhance the convection heat transfer coefficient of the base fluid and the enhancement obtained by the nanoparticles are 33% higher for the case of the converging flow passages than that of straight passages. Simulation results have proved that implementation of an enhanced working fluid (i.e. Al 2 O 3-water nanofluid) and using geometrical enhancement (i.e. converging flow passages) reveal synergetic thermal response and shows an effective enhancement on the convection heat transfer coefficient as high as 2.35 times greater than the heat transfer coefficient of a pure water flows through a straight channel with no convergence. The present results suggest implementing nanofluids along with converging flow passages to achieve the effective enhancement in the convection heat transfer coefficient and to boost the improvement obtained by each individual enhancement technique, especially in the thermally developed regions wherein the convection heat transfer coefficient cannot be increased by increasing the inlet velocity/pressure in the laminar flow regime.
Thermo-hydraulic performance of a circular microchannel heat sink using swirl flow and nanofluid
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Increasing the power and reliability of microelectronic components requires heat sinks with greater heat transport performance. This study investigates the hydraulic and heat transport performance of a silicon heat sink under a constant heat flux of 100 W/cm 2 with liquid coolant running through parallel microchannels. The coupled heat transfer through the silicon walls and the coolant, modelled as a single-phase fluid, is examined over the Reynolds number range 100 ≤ ≤ 350 for micro-channels of circular cross-section, with a straight tape, and with a twisted tape that induces swirl in the flow. Al2O3 nanofluid at nanoparticle volume fractions = 0, 1, 2 and 3% is used as the coolant. The microchannel heat sink with swirl flow and with the highest nanoparticle volume fraction concentration provides the lowest thermal resistance and contact temperature. Whilst it has a higher flow resistance than the micro-channel with no tape cooled by pure water, it has a positive tradeoff between the gains in cooling performance and in flow resistance. This makes these configurations attractive for designing more performing heat sinks for temperature limited or temperature sensitive microelectronics .
Convective Heat Transfer of Al2O3-water Nanofluids in a Microchannel Heat Sink
Current Nanoscience, 2012
The research presents an experimental study on the heat transfer and pressure drop characteristics of Al2O3-water nanofluids flowing through a microchannel heat sink (MCHS). The effects of Reynolds number and particle concentrations on the heat transfer and flow behavior are investigated. Comparison of the heat transfer coefficient obtained from water-cooled MCHS and nanofluids-cooled MCHS is also presented. MCHS with rectangular flow channel made from aluminum with dimension of 50x50 mm is used as the test section. Al2O3-water nanofluids with particle concentrations of 1.0, 2.0 and 3.0 wt.% are tested. Two electric heaters each with a capacity of 50 W are used to supply heat to the test section. The results indicate that the heat transfer performance of MCHS increases with increasing Reynolds number as well as particle concentrations. Compared with pure water, the results indicate that at particle concentration of 3.0 wt%, the heat transfer coefficient for nanofluid-cooled MCHS is range between 1,100-1,700 W/m 2 K which is higher than that of water by about 7-15%. The pressure drop is between 8 and 25 kPa which is close to the water.
Numerical Investigation of Forced Convection of Nanofluid in Microchannels Heat Sinks
2018
This paper presents a numerical study of laminar forced convective flow of nanofluid-based water/Al2O3 in a two-dimensional horizontal microchannel heat sink. The governing equations are solved by using the finite volume method based on simple algorithm. The effect of solid nanoparticles on the heat transfer is investigated after comparing our results with experimental data. The founding results showed that the use of nanofluid has enhanced the heat transfer in comparison with pure fluid, and the increasing of Al2O3 concentration enhances the thermal and dynamic parameters. Nusselt number and friction coefficient have been enhanced with the increasing of Reynolds number. This work contributes to ameliorate the cooling systems by integrating the nanofluids in the next generation of microchannels heat sinks.
Micromachines, 2021
In this paper, a common and widely used micro-heat sink (H/S) was redesigned and simulated using computational fluid dynamics methods. This H/S has a large number of microchannels in which the walls are wavy (wavy microchannel heat sink: WMCHS). To improve cooling, two (Al2O3 and CuO) water-based nanofluids (NFs) were used as cooling fluids, and their performance was compared. For this purpose, studies were carried out at three Reynolds numbers (Re) of 500, 1000, and 1500 when the volume percent (φ) of the nanoparticles (NPs) was increased to 2%. The mixture two-phase (T-P) model was utilized to simulate the NFs. Results showed that using the designed WMCHS compared to the common H/S reduces the average and maximum temperatures (T-Max) up to 2 °C. Moreover, using the Al2O3 NF is more suitable in terms of WMCHS temperature uniformity as well as its thermal resistance compared to the CuO NF. Increasing the φ is desirable in terms of temperature, but it enhances the pumping power (PP)....
Springer, 2018
In this study, laminar and steady flow of hybrid Al2O3–Cu/water nanofluid is done for volume fraction of solid nanoparticles 0–2% in a double-layered microchannel with sinusoidal walls. The results of this study show that the sinusoidal shape of the microchannel walls has a strong effect on increasing heat transfer, and increasing solid nanoparticle volume fraction in base fluid can have a significant difference for increasing Nusselt number, so that the value of Nusselt number for solid nanoparticles volume fraction of 2% for Re = 50, 300, 700 and 1200 experiences 23%, 22% 19% and 13% increase compared with the base fluid. By increasing fluid viscosity, the shear stress especially in the areas close to wall and in fluid layers is increased and this factor can increase pressure drop in higher solid nanoparticles volume fractions. The static temperature profiles are affected by hot surfaces and their sinusoidal shapes in lower Reynolds numbers, and the curve for temperature of flow centerline for Re = 700 and 1200 is straight lines. Therefore, the usage of it for Reynolds numbers above 700 is not recommended.
Flow and heat transfer behaviour of nanofluids in microchannels
Progress in Natural Science: Materials International, 2018
Flow and heat transfer of aqueous based silica and alumina nanofluids in microchannels were experimentally investigated. The measured friction factors were higher than conventional model predictions at low Reynolds numbers particularly with high nanoparticle concentrations. A decrease in the friction factor was observed with increasing Reynolds number, possibly due to the augmentation of nanoparticle aggregate shape arising from fluid shear and alteration of local nanoparticle concentration and nanofluid viscosity. Augmentation of the silica nanoparticle morphology by fluid shear may also have affected the friction factor due to possible formation of a core/shell structure of the particles. Measured thermal conductivities of the silica nanofluids were in approximate agreement with the Maxwell-Crosser model, whereas the alumina nanofluids only showed slight enhancements. Enhanced convective heat transfer was observed for both nanofluids, relative to their base fluids (water), at low particle concentrations. Heat transfer enhancement increased with increasing Reynolds number and microchannel hydraulic diameter. However, the majority of experiments showed a larger increase in pumping power requirements relative to heat transfer enhancements, which may hinder the industrial uptake of the nanofluids, particularly in confined environments, such as Micro Electro-Mechanical Systems (MEMS).