Nanofluid In Microchannel Research Articles

Heat and mass transfer analysis of s-PTT nanofluid in microchannels under combined electroosmotic and pressure-driven flows with wall slip using the homotopy perturbation method

The heat and mass transfer of the electroosmotic flow in microchannel transporting viscoelastic nanofluid is investigated considering Brownian motion of nanoparticles and slip boundary conditions. The simplified Phan-Thien-Tanner model is employed to describe the rheological behavior of fluid and the nonlinear Navier model with non-zero slip critical shear stress is considered at walls. The governing nonlinear momentum, mass, and heat transfer equations are solved using the Homotopy Perturbation Method. The study reveals that increasing the fluid elasticity, nanoparticle concentration, and size significantly enhances the flow rate, heat and mass transfer. Additionally, elasticity and Reynolds number decrease the friction factor. Reducing the double-layer thickness and increasing the Reynolds number lead to higher flow rates and fluid velocities. Notably, the findings emphasize the critical role of the slip conditions on the Sherwood and Nusselt numbers.

Comparative studies on heat transfer and flow resistance of nanofluid in microchannels with different sidewall micro-fins

Comparative studies on heat transfer and flow resistance of nanofluid in microchannels with different sidewall micro-fins

Thermal convective transport of nanofluids in a microannulus under electromagnetohydrodynamic and time-periodic pressure gradient

The study of the unsteady flow and heat transfer characteristics of nanofluids in microannulus is crucial for the optimal design and precise operation of microfluidic systems, and microfluidic technology has an important application value in microelectronic engineering. In this article, a theoretical analysis of the heat transfer characteristics of unsteady flow of Water-Al2O3 nanofluids through a microannulus under the coupling of an alternating electric field, a magnetic field, and a time-periodic pressure gradient is presented. Both the thermally completely developed flow assumption and the Debye–Hückel linear approximation are taken into consideration. The microannulus wall is subjected to a consistent heat flow while taking into account the effects of Joule heating and viscous dissipation. A semi-analytical solution of the temperature field is efficiently obtained using the Green’s function method. In addition, the Nusselt number and total entropy generation are further analyzed. The results show that the nanoparticle volume fraction and dimensionless frequency have a significant effect on the heat transfer characteristics of nanofluids. The increase of dimensionless frequency decreases the convective heat transfer and improves the cooling performance of microannulus. On the contrary, increasing the nanoparticle volume fraction improves the heat transfer performance of microannulus. Therefore, the results of this study can be used for electronic cooling of compact and micro-sized circuits. This study is instructive for unsteady flow and heat transfer of nanofluids in microchannels.

Effect of parameters-dependent viscosity and thermal conductivity on the thermo-hydraulic performance of Al2O3-based nanofluids in a rectangular microchannel

The multi-parameter dependence of nanofluid viscosity and thermal conductivity on the flow and heat transmission properties of Al2O3-H2O nanofluidin microchannels is investigated in this paper using a numerical simulation approach, exploring the effects of various parameters on flow and heat dissipation characteristics, such as flow velocity, pressure drop, temperature, and heat transfer coefficient, under different Reynolds numbers, etc. These parameters include the nanoparticles phericity (0.5~1.0), volume fraction (0.6%~6.0%), and temperature (290K~370K) of the nanofluids, as well as the boundary parameter Reynolds number (200~1000). The results show that the multi-parameter dependence of nanofluid viscosity and thermal conductivity setting has a significant impact on the flow and heat dissipation characteristics of nanofluids, comparing analysis with the nanofluid viscosity and thermal conductivity only related to the volume fraction under the same condition. Under the combined action of sphericity, volume fraction, and temperature, increasing the sphericity increases the pressure drop and decreases the heat transfer coefficient. For example, at a Reynolds number of 1000, the maximum rates of change for pressure drop and heat transfer coefficient are 0.85 and 4.26, respectively. The nanofluid thermo-hydraulic performance is sensitive to temperature, volume fraction and sphericity in turn. Setting up viscosity and thermal conductivity equations with multiple parameter dependencies can provide more accurate results for there search of nanofluids, further deepening the application research of nanofluids.

Experimental analysis of convective boiling heat transfer and nanoparticle deposition effect of TiO2-H2O nanofluids in microchannels

The convective boiling heat transfer characteristics of TiO2-H2O nanofluids in microchannels were experimentally investigated in this paper. The effects of the mass flow rate, mass fraction and nanoparticle size on the average flow boiling heat transfer coefficient were examined at heat fluxes of 138.4–220.5 kW/m2. The results have shown that the average flow boiling heat transfer coefficient of TiO2-H2O nanofluids increases with the increase of the mass flow rate and nanoparticle size. When the mass fraction of TiO2-H2O nanofluids ranges from 0.01 % to 0.1 %, the maximum heat transfer efficiency has reached with the mass fraction of 0.025 %. Considering the movement and deposition of the TiO2 nanoparticles in the convective boiling process, the difference of the absorbance value of TiO2-H2O nanofluids and heating surface morphology after boiling were observed. It proved that the distribution density of the nanoparticle deposition gradually increases along the flow direction of the microchannel. Furthermore, the mass fraction of TiO2-H2O has great influence on the nanoparticles deposition morphology and the nucleation condition of the boiling surface.

Cattaneo-Christov heat-mass flux model on mixed convection of Casson nanofluid in a porous medium microchannel with thermal radiation and chemical reaction

This article presents mixed convection of radiating and reacting Casson nanofluid in microchannel filed with a saturated porous medium with Cattaneo-Christov heat-mass flux model. The Buongiorno’s nanofluid flow model is used to study the effects of the Brownian motion and the thermophoresis whereas the Darcy-Forchheimer model is considered to examine the nanofluid and porous medium interaction. Thereafter, the highly nonlinear system of equations for momentum, energy and concentration are formulated and solved numerically by utilizing the Runge-Kutta-Fehlberg integration scheme with shooting technique. Consequently, the numerical simulation indicates that the Casson fluid parameter and the variable viscosity parameter play a great role in escalating the velocity field and temperature profile however chemical reaction, porous medium, radiation, thermal relaxation time and convective heating control over the temperature profile. Besides, an increase in the thermal relaxation time causes more transfer of heat from the hot microchannel wall to the fluid and thus, fluid temperature distribution is higher for Hence, the Cattaneo-Christov heat flux model is constructive in cooling process as compared to that of the classical Fourier’s law of heat conduction. Furthermore, heat and mass transfer rates are enhancing because of the thermal radiation and solutal Grashof number at both sides of the microchannel walls. Also, the current findings are compared with that of the existing literature and a sound agreement was established.

Cilia and electroosmosis induced double diffusive transport of hybrid nanofluids through microchannel and entropy analysis

Abstract A mathematical model is presented to analyze the double diffusive transport of hybrid nanofluids in microchannel. The hybrid nanofluids flow is driven by the cilia beating and electroosmosis in the presence of radiation effects and activation energy. Cu–CuO/blood hybrid nanofluids are considered for this analysis. Phase difference in the beatings of mimetic cilia arrays emerge symmetry breaking pump walls to control the fluid stream. Analytical solutions for the governing equations are derived under the assumptions of Debye–Hückel linearization, lubrication, and Rosseland approximation. Dimensional analysis has also been considered for applying the suitable approximations. Entropy analysis is also performed to examine the heat transfer irreversibility and Bejan number. Moreover, trapping phenomena are discussed based on the contour plots of the stream function. From the results, it is noted that an escalation in fluid velocity occurs with the rise in slippage effects near the wall surface. Entropy inside the pump can be eased with the provision of activation energy input or by the consideration of the radiated fluid in the presence of electroosmosis. The results of the present study can be applicable to develop the emerging thermofluidic systems which can further be utilized for the heat and mass transfer at micro level.

Delineation of heat transfer and flow analysis of Carreau nanofluid in microchannel using Buongiorno model

This paper reports the hydromagnetic mixed convective flow of Carreau nanofluid in the vertical microchannel with slip and convective mechanisms at the boundaries. The main objective of this work is to analyze the conduct of Carreau nanofluid under Buongiorno model as the nano-dimensions of the particle consequently encounters random motion. The novel impression is to retain the outcomes of the flow in regard of Brownian dispersion and thermophoresis. Parameters such as buoyancy ratio, Brownian motion and thermophoresis along with the effect of Weissenberg number are discussed on distribution of flow, temperature and concentration by using graphical demonstration. Surface drag coefficients, transport rates of mass and heat are portrayed by numeric esteems. Boundary layer approximations are made use to tackle nonlinear ordinary differential equations and solved by Runge–Kutta–Fehlberg 4-5th-order method. Results so obtained elaborate that velocity depletes with increased values of buoyancy ratio and viscosity ratio parameter along with power law index. Also, distinct behavior is noticed in the profile of velocity for varying Weissenberg number by boosting and diminishing depending on the power law index. On the other hand, temperature rises by augmentation of thermophoresis and Brownian motion parameter. Elevation in Brownian motion parameter accelerate the concentration panel of the fluid. Skin friction and Nusselt number are in direct proportion with buoyancy ratio parameter and Brownian motion parameter, respectively.

Performance improvements of microchannel heat sink using Koch fractal structure and nanofluids

With the rapid development of microelectronics technology, the heat flux density in the micro-component system is very high. Therefore, the design of new and efficient cooling and heat dissipation devices has become an urgent problem to be solved. We use the Koch fractal structure and nanofluid to create a new type of microchannel heat sink. In this paper, a single-phase method is used to numerically study the flow and heat transfer properties of TiO2-water nanofluids in microchannels and optimize the structure with Koch fractal baffles. The effects of various volume fractions of nanofluids and baffles with varying structures on the inlet and exit pressure drop, flow resistance coefficient, substrate temperature, and Nusselt number (Nu) in the microchannel are investigated. In the Reynolds number (Re) range of 100–1000, the Nu of nanofluid increases with the increase of Re and the Nu increases from 18.19 to 60.41, which increases by 3.32 times, and the flow resistance of nanofluid falls by 1.79 times. Nanofluids' improved heat transfer factors are not all larger than one. The critical point is Re = 439, indicating that the combined heat transfer performance of nanofluids is superior to that of deionized water within the Re range of 100–439.

Review on Coupled Thermo-Hydraulic Performance of Nanofluids and Microchannels.

As electronic components continue to be miniaturized, the heat flux density continues to increase. Scholars have proposed the use of microchannel heat sinks (MCHS) to dissipate heat from devices with high heat flux density, and have pointed out that the heat dissipation capability of MCHS can be improved in two ways: using nanofluids with high thermal conductivity and optimizing the structure of MCHS. In this paper, the thermophysical parameters and thermo-hydraulic performance of nanofluids in microchannels are reviewed. Improving the heat dissipation of MCHS is analyzed and discussed in terms of both thermal properties and flow properties, respectively.

A Numerical Study on Heat Transfer Characteristics of a Novel Rectangular Grooved Microchannel with Al2O3/Water Nanofluids

The microchannel heat exchanger is one of the most compact and effective heat exchangers used for cooling devices in building air conditioning system, while application of nanofluids in microchannel further enhance its thermal performance due to its much higher thermal conductivity. Considering the continuous rapid increase in energy consumption in the building sector, especially in air conditioning systems, the heat transfer performance of a microchannel with nanofluids should be further enhanced to realize energy savings. This study analyzes the influence of combining nanofluid and flow disturbance structure on the heat transfer enhancement of a microchannel, which is also the noted novelty. A rectangular grooved microchannel (RGMC) is proposed, and its thermal performance using Al2O3/water nanofluids is investigated using the CFD method, with the mixture model to simulate the Al2O3/water nanofluids considering the slip velocity between the base fluid and nanoparticles. The results show that at 1.5 m/s, Nu of RGMC with 2 vol% nanofluids is 38.5% larger than that of smooth microchannel (SMC) with the same nanofluids, and 36.7% larger than that of RGMC with pure water, indicating the much better heat transfer performance of the novel designed RGMC structure. The maximum temperature for RGMC is 5 K lower than SMC with 2 vol% Al2O3/water nanofluid at inlet velocity of 1.5 m/s. Further analysis on the integrated effect between fluid flow and heat transfer shows that the synergy angle β near the center line of RGMC is much lower than that of SMC, representing that the better thermal performance is caused by the flow structured induced by the grooves. Moreover, at 1.5 m/s, βα of SMC with 2 vol% nanofluid is 89.4 Deg, which is 1.66 Deg higher than the βα value of RGMC, while at 0.25 m/s, the βα of two types of microchannel are close to each other. This indicates that the groove structure shows greater enhancement at higher inlet velocity. It is concluded that combining nanofluid and groove structure can significantly enhance heat transfer of the microchannel. The nanofluid enhances heat transfer at lower inlet velocity, while the groove structure enhances it at higher inlet velocity. This study will be helpful for the design of a high-efficiency microchannel heat exchanger that promotes building energy savings.

Transient Two-Layer Electroosmotic Flow and Heat Transfer of Power-Law Nanofluids in a Microchannel.

To achieve the optimum use and efficient thermal management of two-layer electroosmosis pumping systems in microdevices, this paper studies the transient hydrodynamical features in two-layer electroosmotic flow of power-law nanofluids in a slit microchannel and the corresponding heat transfer characteristics in the presence of viscous dissipation. The governing equations are established based on the Cauchy momentum equation, continuity equation, energy equation, and power-law nanofluid model, which are analytically solved in the limiting case of two-layer Newtonian fluid flow by means of Laplace transform and numerically solved for two-layer power-law nanofluid fluid flow. The transient mechanism of adopting conducting power-law nanofluid as a pumping force and that of pumping nonconducting power-law nanofluid are both discussed by presenting the two-layer velocity, flow rates, temperature, and Nusselt number at different power-law rheology, nanoparticle volume fraction, electrokinetic width and Brinkman number. The results demonstrate that shear thinning conducting nanofluid represents a promising tool to drive nonconducting samples, especially samples with shear thickening features. The increase in nanoparticle volume fraction promotes heat transfer performance, and the shear thickening feature of conducting nanofluid tends to suppress the effects of viscous dissipation and electrokinetic width on heat transfer.

Heat Transfer Characteristics of Conventional Fluids and Nanofluids in Micro-Channels with Vortex Generators: A Review

An effective way to enhance the heat transfer in mini and micro electronic devices is to use different shapes of micro-channels containing vortex generators (VGs). This attracts researchers due to the reduced volume of the electronic micro-chips and increase in the heat generated from the devices. Another way to enhance the heat transfer is using nanofluids, which are considered to have great potential for heat transfer enhancement and are highly suited to application in practical heat transfer processes. Recently, several important studies have been carried out to understand and explain the causes of the enhancement or control of heat transfer using nanofluids. The main aim upon which the present work is based is to give a comprehensive review on the research progress on the heat transfer and fluid flow characteristics of nanofluids for both single- and two- phase models in different types of micro-channels. Both experimental and numerical studies have been reviewed for traditional and nanofluids in different types and shapes of micro-channels with vortex generators. It was found that the optimization of heat transfer enhancement should consider the pumping power reduction when evaluating the improvement of heat transfer.

Effect of NP shapes on Fe3O4 – Ag/kerosene and Fe3O4 – Ag/water hybrid nanofluid flow in suction/injection process with nonlinear-thermal-radiation and slip condition; Hamilton and Crosser's model

This study examines the flow and thermal properties of water and kerosene hybrid nanofluids in a horizontal microchannel. The effects of nonlinear thermal radiation, heat source coefficient, convective and slip boundary conditions on nanofluids in a microchannel have been studied. The impact of different nanoparticle shape factors on the temperature of nanofluids has also been analysed. The governing partial differential equations have been transformed in to ordinary differential equations using dimensionless terms. In the next step, the corresponding ordinary differential equations have been cracked using the RKF45 numerical approach, and the particles shape factor on dimensionless velocity and energy fields for hybrid nanofluid then reported. The results revealed that the spherical and lamina shape factors for both water and kerosene hybrid nanofluid differ the most, the water-based hybrid nanofluid has a higher velocity than the kerosene-based hybrid nanofluid, the thermal energy of both water and kerosene-based hybrid nanofluid was higher in the lower channel plate than the upper channel plate, flow rate falls near the lower channel wall and increases towards the upper channel wall as Reynolds number increases. Thermal energy and entropy generation decrease as the temperature parameter rises.

Simulation of nanofluid-cooled lithium-ion battery during charging: A battery connected to a solar cell

In this study, a lithium-ion battery hybrid cooling system is designed to cool the battery using nanofluid and extended surfaces (microchannels). The battery connected to a solar system is evaluated during charging mode. Initially, according to topology optimization based on the maximum heat transfer and minimum pressure drop, the model with maximum efficiency is proposed. A non-Newtonian hybrid nanofluid containing carbon nanotubes flows inside it. Numerical simulations are performed for this system. The Galerkin finite element algorithm is used to perform the calculations and the simulated results are performed to analyze the flow behavior and heat transfer of non-Newtonian nanofluid around the battery. The results demonstrate that the use of the A-3 model at the Reynolds number of 100 creates the lowest maximum temperature in the battery cell, which is 0.4 °C lower than that in the classic model. Also, at a Reynolds number of 1000, model A-2 has the lowest maximum temperature among different models, which is 0.11 °C lower than the classic model. The use of hybrid nanoparticles in all models reduces initial temperature value and enhances the amount of pressure drop at all Reynolds numbers. Among these, the classic model has the maximum and the A-4 model has the minimum pressure drop among different models at different Reynolds numbers, especially Re = 1000. Finally, it is revealed that adding carbon nanotubes to the base fluid and using the nanofluids in microchannels to cool the battery improves battery performance and enhances battery efficiency.

Forced convection heat transfer of non-Newtonian MWCNTs nanofluids in microchannels under laminar flow

Heat transfer process in micro/mini-scales becomes an urgent need for many applications where size and weight are severe constraints such as electronics. However, the latter led to developing new thermal fluids, the so-called nanofluids, with enhanced thermophysical properties to cover the high heat dissipation requirements due to the devices' miniaturization. In this work, a validated computational model is used to establish guidelines for the compact heat exchanger with microchannels, as well as to assist nanofluid properties tailoring. A finite volume method (FVM) approach is built considering laminar fluid flow conditions in a circular microchannel. The latter is used and validated against available experimental data, and the influence of temperature-dependent thermophysical properties and non-Newtonian behaviour of the MWCNTs (Multi-walled carbon nanotubes) nanofluids are considered. The results show that MWCNTs nanofluids enhance the heat transfer performance of the micro heat exchanger by up to 33%. Moreover, particular operating conditions are seen to improve the system energy efficiency, mainly near to Reynolds number (Re) equal to 1000, when taking into account both heat transfer performance and pressure drop. Additionally, a correlation of the average Nusselt number is proposed to estimate the heat transfer performance of nanofluids in microchannels.

Numerical Study on the Fluid Flow and Heat Transfer Characteristics of Al2O3-Water Nanofluids in Microchannels of Different Aspect Ratio.

The study of the influence of the nanoparticle volume fraction and aspect ratio of microchannels on the fluid flow and heat transfer characteristics of nanofluids in microchannels is important in the optimal design of heat dissipation systems with high heat flux. In this work, the computational fluid dynamics method was adopted to simulate the flow and heat transfer characteristics of two types of water-Al2O3 nanofluids with two different volume fractions and five types of microchannel heat sinks with different aspect ratios. Results showed that increasing the nanoparticle volume fraction reduced the average temperature of the heat transfer interface and thereby improved the heat transfer capacity of the nanofluids. Meanwhile, the increase of the nanoparticle volume fraction led to a considerable increase in the pumping power of the system. Increasing the aspect ratio of the microchannel effectively improved the heat transfer capacity of the heat sink. Moreover, increasing the aspect ratio effectively reduced the average temperature of the heating surface of the heat sink without significantly increasing the flow resistance loss. When the aspect ratio exceeded 30, the heat transfer coefficient did not increase with the increase of the aspect ratio. The results of this work may offer guiding significance for the optimal design of high heat flux microchannel heat sinks.

Cooling performance of an impinging synthetic jet in a microchannel with nanofluids: An Eulerian approach

Numerical investigations of heat transfer enhancement in a three-dimensional micro-channel with a single synthetic jet were conducted using Al2O3-water, CuO-water and TiO2-water nanofluids. The effects of different types of nanoparticles at particle volume concentrations of 1%, 2% and 5% on the thermal performance in the micro-channel were examined. The numerical tool was validated against existing experimental data on the heat transfer characteristic of nanofluids in micro-channel. Heat transfer enhancement using nanofluids based on the Eulerian single-phase model was assessed for the cases with and without the operation of the synthetic jet. In general, the overall thermal performance was greatly influenced by the thermal conductivity and dynamic viscosity of the working nanofluids. The former corresponds to thermal enhancement by conduction whilst the latter corresponds to convective enhancement due to the periodic oscillation of the synthetic jet diaphragm. As the particle volume concentration of a nanofluid increased, effectiveness of the synthetic jet to provide convective cooling became poorer on account of higher viscosity. Nevertheless, in some cases, this can be overcome by the enhancement in thermal conductivity, depending on the Peclet number of the working fluid. Synthetic jet microchannel with Al2O3-water nanofluid at φ = 5% showed the best overall cooling performance whereas TiO2-water nanofluid at φ = 5% failed to improve the thermal performance.

Numerical study of graphene-platinum hybrid nanofluid in microchannel for electronics cooling

The objective of this paper is to numerically study the heat transfer and hydrodynamic performance of a graphene-based hybrid nanofluid flowing through a microchannel for electronics cooling applications. Different concentrations of Graphene-Platinum/water hybrid nanofluid were employed as coolants. The thermophysical properties used in this study were considered to be temperature-dependent. The microchannel was modeled as a porous media. The effect of nanoparticle volume concentration on thermal resistance, pressure drop, friction factor and ratio of heat transfer coefficient to pressure drop (Figure of merit) was analyzed and the plots were generated for different Reynolds numbers of the working fluid. The results pointed out that introduction of nanoparticles resulted in the lowering of thermal resistance. However, the pressure drop and friction factor increased. Figure of merit is found to be higher for higher concentrations of hybrid nanofluids compared to base fluid water. On analyzing the results, it was understood that the utilization of Graphene-Platinum/water hybrid nanofluid through microchannels can be highly effective in the laminar region. It also suggests that this graphene based nanofluid has excellent potential as a coolant to remove excess heat from miniature electronic devices.

Thermal characterization and stability analysis of aqueous ZnO-based nanofluids numerically implemented in microchannel heat sinks

Water-based nanofluids prepared with ZnO nanoparticles (⩽17 nm) were characterized. The thermal conductivity and viscosity were measured as a function of temperature (278–303 K), for two ZnO concentration (1wt% and 3wt%) establishing that, whereas the nanofluid prepared with a concentration of 1wt% registered an average improvement of the thermal conductivity of 10.31% at a concentration of 3wt%, the viscosity decreased an average of 5.03% respect to the base fluid. An analysis of the stability of these nanofluids was carried out via UV–vis, finding that for a concentration of 3wt% the stability is better, since it requires 168 h to decrease its absorbance in the same amount as the sample of 1wt%. Additionally, the laminar three-dimensional flow of these nanofluids has been numerically studied considering symmetric microchannels (200 ⩽Re⩽ 1200) of fixed-width rectangular cross-section (283 μm) and three different heights (200 μm, 600 μm, and 400 μm), subjected to a constant heat flux in the lower wall (50 W/cm2). The microchannels have been simulated considering the properties of the nanofluid variable with respect to temperature through experimentally determined models (for 1wt% and 3wt%), finding that thermal conductivity improves mostly for a concentration of 1wt%, registering an increase in average 10.31% in the studied temperature range.The numerical results showed that the use of nanofluids favors heat transfer at low Reynolds numbers with the maximum improvement in the coefficient of heat transfer by convection (42.33%). A decrease in temperature of the base of the microchannel is also observed, which is more significant at low Reynolds numbers for a concentration of 1wt%. In the case of MCH-1 with Re=200, the decrease in the mean temperature of the lower wall is 5.65% (20.45 K), a value that decreases to 0.90% (2.94 K) for Re=1200. This configuration also offers the highest net heat gain, considering the increase in the coefficient of friction produced by the incorporation of ZnO nanoparticles. Finally considering the experimental studies of the thermal properties and stability of nanofluids, and the numerical results associated with the thermal and fluid-dynamic performance of the microchannels, a methodology is proposed to carry out a comprehensive approach to the application of nanofluids in microchannels.