Nanofluid In Microchannel Research Articles

Study on the flow and heat dissipation of water-based alumina nanofluids in microchannels

In this paper, the flow and heat dissipation performance of 0.1–0.5 vol per cent of Al2O3 -water nanofluid through serpentine micro-channel was experimentally studied in the Reynolds range 124–1000. By analyzing the experimental results of nanofluid flow and heat dissipation: In the experiment, the Nusselt number of nanofluids is 1.12–1.66 times that of deionized water, which indicates that Al2O3 -water nanofluids have significant heat transfer enhancement effect. Nanofluid flow resistance is 1.02–1.80 times that of deionized water, this indicates that Al2O3 -water nanofluid has the disadvantage of increasing energy consumption. From a comprehensive performance point of view: all the nanofluids used in the experiment have enhanced heat transfer factors more significant than one, and the enhanced heat transfer effect is better than that of deionized water, this suggests that Al2O3 -water nanofluid has the drawback of rising energy consumption. All the nanofluids used in the experiment have enhanced heat transfer factors more significant than one, and the enhanced heat transfer effect is better than that of deionized water. Nano-fluids, with a volume fraction of 0.4%, have an average increased heat transfer factor of 1.4, which is the best overall performance.

Effects of wall hydrophobicity on the thermohydraulic performance of the microchannels with nanofluids

Three-dimensional heat transfer of nanofluids in microchannels with hydrophilic, hydrophobic and, superhydrophobic surfaces were studied using numerical simulation. For this purpose, Navier Stokes and energy equations were solved using the finite volume method. The flow Reynolds numbers were in the range of 40–500. Water/Al2O3 and Water/TiO2 were considered as coolant fluids. By applying hydrophobic surfaces, the flow pressure drop decreased, especially for the case of superhydrophobic walls. Microchannel with hydrophobic walls required 12% less pumping power than those with hydrophilic walls. The superhydrophobic wall caused a 66% reduction in the required pumping power. The use of nanofluids as a coolant improved the thermal performance. The results showed that the simultaneous use of the hydrophobic surface and the addition of nanoparticles could increase the performance evaluation criterion to 1.75 at Re = 400 and caused the lowest substrate temperatures. In addition, for the flows with Re > 150, applying the superhydrophobic walls was more effective than the usage of nanofluids as coolants with conventional walls.

Thermal and Fluid Dynamic Performance Comparison of Three Nanofluids in Microchannels Using Analytical and Computational Models

The fluid dynamic and thermal performance of three nanofluids containing aluminum oxide, copper oxide, and silicon dioxide nanoparticles dispersed in 60:40 ethylene glycol and water base fluid as a coolant in a microchannel heatsink are compared here by two methods. The first is a simple analytical analysis, which is acceptable for very low nanoparticle volumetric concentration (1–2%). The second method is a rigorous three-dimensional finite volume conjugate heat transfer and fluid dynamic model based upon a constant heat flux boundary condition, which is applicable for cooling electronic chips. The fluids’ thermophysical properties employed in the modeling are based on empirically derived, temperature dependent correlations from the literature. The analytical and computational results for pressure drop and Nusselt number were in good agreement with the nanofluids showing a maximum difference of 4.1% and 2.9%, respectively. Computations cover the practical range of Reynolds number from 20 to 200 in the laminar regime. Based on equal Reynolds number, all of the nanofluids examined generate a higher convective heat transfer coefficient in the microchannel than the base fluid, while copper oxide provided the most significant increase by 21%. Based on the analyses performed for this study, nanofluids can enhance the cooling performance of the heatsink by requiring a lower pumping power to maintain the same maximum wall temperature. Aluminum oxide and copper oxide nanofluids of 2% concentration reduce the pumping power by 23% and 22%, respectively, while maintaining the same maximum wall temperature as the base fluid.

Single-phase fluid flow and heat transfer characteristics of nanofluid in a circular microchannel: Development of flow and heat transfer correlations

The convective heat transfer in microchannels with the use of nanofluids has proved to be a potential candidate for cooling of micro-electromechanical system devices. The current research article presents the experimental study on fluid flow and heat transfer characteristics of [Formula: see text]/water nanofluid in a microchannel under thermally developing laminar flow at Reynolds number ranging from 300 to 1000. The experimental set-up of a circular microchannel test section with an inner diameter of [Formula: see text] and length of [Formula: see text] is fabricated to conduct the experimental study. The effect of nanoparticle concentration ([Formula: see text]), Reynolds number ([Formula: see text]) on fluid flow and heat transfer characteristics of [Formula: see text]/water nanofluid have been measured and compared with that of distilled water (DW). The results indicate that the maximum enhancement in local heat transfer coefficient is achieved up to [Formula: see text], while friction factor is achieved up to [Formula: see text] for [Formula: see text]/water nanofluid with nanoparticle concentration of [Formula: see text] as compared to DW. The results showed that the performance evaluation criterion of [Formula: see text]/water nanofluid is greater than unity ([Formula: see text]), implying the benefits of nanofluids as compared to DW. Moreover, the predicted data obtained by the present proposed correlations for friction factor and local Nusselt number using [Formula: see text]/water nanofluid show reasonably good agreement with the deviations of [Formula: see text] and [Formula: see text], respectively, with the numerical data as compared to the predicted data obtained by the existing correlations available in the literature.

A Comparative Study of Cavitation Characteristics of Nano-fluid and Deionized Water in Micro-channels.

Hydrodynamic cavitation has been widely applied in micro-fluidic systems. Cavitating flow characteristics are closely related to the fluid properties. In this paper, the cavitation characteristics of Cu nano-fluid in micro-channels were numerically investigated and compared with those of the deionized (DI) water. The mathematical model was verified by comparing the numerical results with the experiment observation. The curved orifice (R = 0.3 mm) was found to have the highest efficiencies of cavitation for both fluids. With the increase of inlet pressure, cavitating jet lengths of the two fluids significantly increased. While, the cavitating jet length of the nano-fluid was shorter than that of the DI water at the same inlet pressure. The cavitation inception number of the DI water and nano-fluid were approximately 0.061 and 0.039, respectively. The results indicate that the nano-particles played negative effects on the cavitation inception. In addition, with the decrease of outlet pressure, the cavitation strength gradually increased and the mass flow rate remained nearly unchanged at the same time.

Field synergy analysis on flow and heat transfer characteristics of nanofluid in microchannel with non-uniform cavities configuration

Microchannel cooling technology using nanofluid is one of the effective ways to solve the rapid heat dissipation in a limited space for high power density device. In this work, the field synergy and heat transfer performance of nanofluid in the microchannel with non-uniform internal spoiler cavities configuration based on conjugate heat transfer and homogenous model were investigated. The heat transfer enhancement mechanism of nanofluid in this complex microchannel was discussed through the analysis of field synergy angle, field synergy factor, and flow and heat transfer characteristics. It was found that the flow and heat transfer performance of the nanofluid in the microchannel can be well explained by the field synergy principle. The nanofluid heat transfer enhancement phenomenon could be attributed to the improvement of the field synergy of the thermal boundary layer under the axial thermal conductive effect. In addition, the field synergy analysis of nanofluid in complex microchannel revealed that the heat transfer enhancement was affected by the combination of perturbation effect, the axial thermal conduction effect and the thermal boundary redevelopment.

Modeling heat transfer of nanofluid flow in microchannels with electrokinetic and slippery effects using Buongiorno’s model

PurposeThis paper aims to study the heat transfer of nanofluid flow driven by the move of channel walls in a microchannel under the effects of the electrical double layer and slippery properties of channel walls. The distributions of velocity, temperature and nanoparticle volumetric concentration are analyzed under different slip-length. Also, the variation rates of flow velocity, temperature, concentration of nanoparticle, the pressure constant, the local volumetric entropy generation rate and the total cross-sectional entropy generation are analyzed.Design/methodology/approachA recently developed model is chosen which is robust and reasonable from the point of view of physics, as it does not impose nonphysical boundary conditions, for instance, the zero electrical potential in the middle plane of the channel or the artificial pressure constant. The governing equations of flow motion, energy, electrical double layer and stream potential are derived with slip boundary condition presented. The model is non-dimensionalized and solved by using the homotopy analysis method.FindingsSlip-length has significant influences on the velocity, temperature and nanoparticle volumetric concentration of the nanofluid. It also has strong effects on the pressure constant. With the increase of the slip-length, the pressure constant of the nanofluid in the horizontal microchannel decreases. Both the local volumetric entropy generation rate and total cross-sectional entropy generation rate are significantly affected by both the slip-length of the lower wall and the thermal diffusion. The local volumetric entropy generation rate at the upper wall is always higher than that around the lower wall. Also, the larger the slip-length is, the lower the total cross-sectional entropy generation rate is when the thermal diffusion is moderate.Originality/valueThe findings in this work on the heat transfer and flow phenomena of the nanofluid in microchannel are expected to make a contribution to guide the design of micro-electro-mechanical systems.

Experimental investigation on heat transfer characteristic of TiO2-H2O nanofluid in microchannel for thermal energy storage

In order to enhance the heat transfer performance of phase change material (PCM) for thermal energy storage (TES) in tiny devices, such as battery thermal management, light-emitting diode and electronic device cooling, TiO2-H2O nanofluids and the microchannel were combined in this paper. Two crystal forms of TiO2-H2O nanofluids were prepared by using a two-step method. And paraffin was used as PCM. The stability and thermophysical properties of the above two nanofluids were tested and compared. It can be found that R TiO2-H2O nanofluid has better stability, and its thermal conductivity increases maximally by 3.27%, while the value is 2.88% of A TiO2-H2O. Besides, R TiO2-H2O nanofluid increases the viscosity by a maximum of 4.87%, while A TiO2-H2O increases by 7.45%. Considering these properties, R TiO2-H2O nanofluid was chosen to study the heat transfer characteristics in the microchannel within a TES unit. The results indicate that R TiO2-H2O nanofluid with 1.0 wt% increases Nu by 19 ∼ 41% and 6 ∼ 14% during the melting process and solidification process respectively. In addition, the melting time of paraffin decreases by a maximum of 32.90% and the solidifying time of paraffin decreases by a maximum of 22.57%. During the whole TES process, there is an increase in pressure drop of no more than 8%.

An Investigation on the Forced Convection of Al2O3-water Nanofluid Laminar Flow in a Microchannel Under Interval Uncertainties

Nanofluids are regarded as an effective cooling medium with tremendous potential in heat transfer enhancement. In reality, nanofluids in microchannels are at the mercy of uncertainties unavoidably due to manufacturing error, dispersion of physical properties, and inconstant operating conditions. To obtain a deeper understanding of forced convection of nanofluids in microchannels, uncertainties are suggested to be considered. This paper studies numerically the uncertain forced convection of Al2O3-water nanofluid laminar flow in a grooved microchannel. Uncertainties in material properties and geometrical parameter are considered. The uncertainties are represented by interval variables. By employing Chebyshev polynomial approximation, interval method (IM) is presented to estimate the uncertain thermal performance and flow behavior of the forced convection problem. The validation of the accuracy and effectiveness of IM are demonstrated by a comparison with the scanning method (SM). The variation of temperature, velocity, and Nusselt number are obtained under different interval uncertainties. The results show that the uncertainties have remarkable influences on the simulated thermal performance and flow behavior.

Numerical analysis of forced convective heat transfer of nanofluids in microchannel for cooling electronic equipment

Abstract Electronic components depend on the passage of electric current to perform their duties, and they become potential sites for excessive heating, since the current flow through a resistance is accompanied by heat generation. The heat generated must be removed by designing a suitable thermal management system for reliable operation of the electronic device. Also the size of electronic systems used in industries such as microelectronics, telecommunications, aerospace, biomedical, robotics and similar other areas are rapidly decreasing. Unless properly designed and controlled, high rates of heat generation result in high operating temperatures for electronic equipment, which jeopardizes its safety and reliability. With the advent of micro-manufacturing technology, multiple micro channels are machined on the back of the substrates of electronic components in integrated circuits. The heat generated by the electronic component is transferred to the coolant by forced convection. In the present study analysis on a rectangular microchannel heat sink was done by using water, Al2O3-water, and TiO2-water nanofluids as working fluids. The nanofluid properties were evaluated with correlations available in the literature. The hydrodynamic and thermal behavior of a microchannel was studied in the present work. The variation wall temperature, pressure drop in the channel and the heat transfer rate was calculated. The effect of Reynolds number on heat transfer in the microchannel was also studied. A significant improvement in the heat transfer was found with microchannel heat sink due to decrease in convective heat transfer resistance as the size of the thermal boundary layer decreased with microscopic size of the channels. It was also found from the simulation results that there was no extra pressure drop at low volume fractions of nanoparticles in the base fluid. The simulation results generated were compared with the analytical data available in the literature and found good agreement.

Numerical investigation of fluid flow and heat transfer of nanofluids in microchannel with longitudinal fins

Thermal and hydraulic characteristics of laminar nanofluid flow in square microchannel with longitudinal inner fins are numerically investigated. The external walls of microchannel are heated at constant heat flux and four rectangular fins are fixed on the internal walls. Four different types of nanofluid are used as working fluids which are SiO2, Al2O3, CuO and ZnO dispersed in pure water base fluid. Different volume fractions of 1-2 and different nanoparticle diameters of 30-60 nm are employed. The results show that the SiO2 nanofluid has the highest heat transfer rate among all of four tested nanofluids. The increase in nanoparticle volume fraction and the decrease in the nanoparticle diameter would increase the Nusselt number value. The friction factor does not change significantly by using nanofluid with different volume fractions and different nanoparticle diameters. Moreover, the results indicate that nanofluid can enhance the performance of microchannel with longitudinal fins. © 2018 Ain Shams University

Investigation of MHD effect on nanofluid heat transfer in microchannels

An incompressible preconditioned lattice Boltzmann method (IPLBM) is proposed to investigate the fluid flow and heat transfer characteristics of nanofluid in microchannel with hydrophilic or superhydrophobic walls and partially under the influence of transverse magnetic field as well as a heat flux. The modified IPLBM is shown to overcome the velocity inaccuracy in developing regime under partial magnetic field with respect to standard LBM. Then, the method is utilized to resolve the velocity and temperature fields at Re = 100 and various volume fractions of nanoparticles (0 ≤ φ ≤ 0.2%), Hartmann numbers (0 ≤ Ha ≤ 30) and slip coefficients (0 ≤ B ≤ 0.1). Superhydrophobic walls are shown to reduce the wall shear stress at B = 0.1 of up to 38.4, 58.5 and 70%, respectively, for Ha = 0, 15 and 30. Ignoring the temperature jump in modeling overestimates the Nusselt number with an error that culminates at B = 0.1 and φ = 0.2% to 19.6, 22.7 and 25%, respectively, for Ha = 0, 15 and 30. It is concluded that with magnetic field presence and realistic temperature jump, the surface material of superhydrophobic walls should be chosen properly to avoid inevitable and uncontrolled reduction in heat transfer, such that the highest hydrophobicity is not always the best choice. Reasonable agreements are achieved by comparing our results with credible analytic and numerical solutions and also with an experimental study.

Flow and heat transfer behaviour of nanofluids in microchannels

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).

Numerical evaluation on thermal–hydraulic characteristics of dilute heat-dissipating nanofluids flow in microchannels

The present work deals with numerical investigations on heat transfer characteristics and friction factor of aqueous CuO nanofluids flow in a set of four microchannels connected in parallel under laminar regime. For each single phase, volume of fluid, mixture and Eulerian models, a particular computer code is developed to carefully simulate this problem. The three-dimensional steady-state governing equations are solved through finite volume method. The primary aim of this study is to comparatively distinguish the most appropriate and accurate model for numerical studies of nanofluids in microchannels. The results are compared with one another and the data obtained from an experimental work. Regarding the results, an acceptable consistency is observed for all models with the experimental data. The current study truly demonstrates that applying single-phase model to simulate and evaluate the laminar flow of CuO–water nanofluid inside microchannels with uniform wall temperature is more modest, precise and reliable compared with two-phase models.

CFD simulation of the heat transfer using nanofluids in microchannel with dimple and protrusion

ABSTRACTIn this study, the heat transfer characteristics of CuO–H2O nanofluid flowing through a microchannel having dimples/protrusions were investigated. The effect of the depth of the dimple/protrusion on heat transfer and friction factor was investigated using FLUENT (ANSYS 14). The dimples/protrusions were arranged in a staggered manner. Using computational fluid dynamics, three dimensional numerical solutions were carried out for various Reynolds numbers (100, 300, 500 and 700). The heat transfer characteristics were obtained at various inlet velocities (1.2–8.7 m/s), volume fraction (0–4%) of nanofluid and the depth of the dimple/protrusion (10–25 µm). To compute heat transfer enhancement, thermal performance parameter (TP) was used. Thermal performance was found to increase with an increase in concentration of CuO in nanofluid and Reynolds number (fluid velocity). TP was found to increase with an increase in the dimple/protrusion depth up to 20 µm where as a depth of 25 µm has shown a decrease in TP due to increase in form friction.

The effect of rib shape on the behavior of laminar flow of oil/MWCNT nanofluid in a rectangular microchannel

In this research, the laminar and forced flow and heat transfer of oil/multi-walled carbon nanotubes nanofluid in a microchannel have been numerically investigated. The studied geometrics is a two-dimensional rectangular microchannel with the proportion of length to height of 150 (L/d = 150). The purpose of this research is to investigate the effect of using rectangular, oval, parabolic, triangular and trapezoidal rib shapes on behavior and heat transfer of nanofluid flow in the rectangular microchannel. This research has been simulated in Reynolds numbers of 1, 10, 50 and 100 and volume fractions of 0, 2 and 4% of nanoparticles by using finite volume method. The results of this research indicate that the existence of ribs enhances the friction factor and Nusselt number, significantly. Also, the shape of rib is one of the most important factors for determining the behavior and heat transfer of cooling fluid flows. Among the investigated rib shapes, the parabolic rib, comparing to the augmentation of friction factor, has the best proportion of Nusselt number enhancement.

Numerical Study on the Forced Convection Heat Transfer of Nanofluids in Micro-Channels

Numerical Study on the Forced Convection Heat Transfer of Nanofluids in Micro-Channels

Flow Boiling Characteristics of Nanofluids in Microchannels

Mikrocihazlarda giderek artan isi akisi degerleri nedeniyle geleneksel isi transfer arttirim yontemleri mikrosistemlerin sogutulmasinda yetersiz kalmaktadir. Kaynama ile isi transferi yuksek isi transfer katsayilarinin elde edilmesi yaninda yuzey sicakliginin neredeyse sabit olmasi nedeniyle yuksek isi atimini gerektiren mikrosistem uygulamalari icin onemli bir potansiyele sahiptir. Diger yandan geleneksel akiskanlar yerine nanoakiskanlarin kullanimi yuksek isil performans icin onemli bir alternatif olarak dusunulmektedir. Nanoakiskanlarin tek fazli isi transferiyle ilgili bircok calisma olmasina ragmen mikrokanallarda kaynamali akis durumunda nanoakiskan kullanimiyla ilgili sinirli sayida calisma mevcuttur. Literaturde nanoakiskanlarin kaynamali akista kullaniminin bazi calismalara gore uygun olup olmadigi yonunde belirsizlikler vardir. Bu nedenle nanoakiskanlarin kaynamali akis sartlarinda kullanilabilirligi ile ilgili daha kapsamli calismalara ihtiyac vardir. Bu calismada, farkli nanoakiskanlar ile yapilan deneysel calismalar derlenmis ve nanoakiskanlarin mikrokanallarda kaynamali akista kullaniminin avantaj ve dezavantajlari belirlenmeye calisilmistir.

Investigation of flow boiling performance and the resulting surface deposition of graphene oxide nanofluid in microchannels

Graphene oxide (GO)-water nanofluid was prepared and applied in flow boiling experiment in microchannels. Boiling heat transfer experiments were performed at various mass flow rates, with the nanofluid concentration ranging from 0 to 0.05wt%. The heat transfer performance was found to be deteriorated for graphene oxide nanofluids. Nanofluid with higher concentration had lower heat transfer coefficient. Surface deposition was found after experiment for different concentration and flow rate. The nanoparticle interaction mechanism and absorption between nanoparticles was proposed to clarify the deposition process: higher temperature, concentration and fluid flow would accelerate the interaction and deposition process. The film-like shape of graphene oxide contributed to the formation of non-porous structure of deposition that blocked nucleation sites. An energy dispersive spectrometer (EDS) analysis of the deposit was carried out and the graphene oxide was found to be reduced chemically during boiling process and thus causing the deposition. Finally, the deposition morphology of graphene oxide was compared with those observed by other researchers and similar deposition characteristics were confirmed. It further indicates that the deposition which was reported to increase critical heat flux could have a negative effect on heat transfer coefficient.

Investigation of the Flow Characteristics of Titanium - Oxide - Water Nanofluid in Microchannel with Circular Cross Section

The presented paper reports the analysis of the flows characteristic of TiO2-water nanofluid flowing inside a horizontal microchannel with circular cross section area. The flow is investigated by CFD techniques using a finite volume method. A recently introduced viscosity correlation was used to model the effective viscosity of the nanofluid. A range of Re number is tested in the present study. Various temperature ranges were used as constant temperature boundary conditions. The increase of the nanoparticle volume fraction was found to increase the heat transfer rate; water showed less enhancement in heat transfer compared to the nanofluid. The increase in Re number promoted Nu number. The effect of the temperature on the effective viscosity in the channel was also reported. The change of the velocity in the entrance region was studied and discussed. The velocity gradient in the microchannel is calculated, and the results are shown and discussed.