Suspension Of Al2O3 Nanoparticles Research Articles

Sensitivity analysis of electroosmotic magnetohydrodynamics fluid flow through the curved stenosis artery with thrombosis by response surface optimization

The current numerical investigation focuses on the sensitivity analysis of the pertinent parameters of the electrically conducting fluid (blood) with the suspension of Al2O3 nanoparticles through the constricted arteries in the presence of stenosis, thrombosis and catheter. The mathematical model is developed to simulate the blood flow through the catheterized artery having irregular stenosis at the wall and thrombosis at the centre. The interactions of different physical phenomena like electroosmosis, radiation, Joule heating and a uniform radial magnetic field actuate the fluid flow. The nanoparticles shape effect is taken into account by considering the Crocine model. The governing equations are discretized by employing the Crank-Nicolson scheme, and the graphical portrayals for the impact of significant parameters on the flow characteristics have been devised and discussed. The statistical experiment is designed based on the parametric range of the parameter. The sensitivity analysis is performed on response surfaces after getting the best-fitted response surface relative to each response variable. The WSS profile negatively correlates with hematocrit parameter hm, Hartmann number M and positively related with Debye–Huckel parameter qe, while the reverse trend is observed for the impedance profile. The present work may be helpful in biomedical engineering, such as magnetic resonance angiography (MRA), which creates artery images. The integrated medical imaging and hemodynamic framework assist surgeons and researchers in better understanding the abnormalities caused by cardiovascular diseases and gaining a deeper grasp of the hemodynamic flow and other bodily fluids for surgical restoration.

Thermal Performance of Car Radiator Operated by Al2O3–Ethylene Glycol/Water-Based Nanofluids: A Computational Fluid Dynamics Study

Abstract This study analyzed the heat transfer potential of nanofluids (suspension of Al2O3 nanoparticles in 60:40 mixtures of ethylene glycol and water by volume) compared to the base fluid by modeling the flow in both laminar and turbulent flow regimes in a flat tube of a radiator using both single-phase and Eulerian–Eulerian multiphase approaches of computational fluid dynamics (CFD) simulation. Nusselt number is calculated by varying the Reynolds number for both the models and compared with the theoretical correlations and the experimental data available in the literature. The effect of change in volumetric concentrations, inlet velocities, inlet temperatures, and particle sizes on the heat transfer performance parameters of nanofluids was evaluated. The multiphase approach showed a 5–45% greater increase in Nusselt number than the single-phase approach for the same volume fraction up to 1% and thereafter multiphase approach showed an even higher Nusselt number. The multiphase model revealed that raising the volume fraction up to 2% increases the Nusselt number of nanofluid by approximately thrice that of the base fluid but after that further increase in volume fraction does not show any significant increment. With the increase in Reynolds number, the Nusselt number, as well as surface heat transfer coefficient, increased for both laminar and turbulent flow regimes. Skin friction coefficient, pressure drop across inlet and outlet, and pumping power required increased slightly with the increase in volume fractions. Also, on varying the nanoparticle size, superior performance was observed at the particle size of 25 nm.

Physically Consistent Implementation of the Mixture Model for Modelling Nanofluid Conjugate Heat Transfer in Minichannel Heat Sinks

As much as two-phase mixture models resolve more physics than single-phase homogeneous models, their inconsistent heat transfer predictions have limited their use in modelling nanofluid cooled minichannel heat sinks. This work investigates, addresses, and solves this key shortcoming, enabling reliable physically sound predictions of minichannel nanoflows, using the two-phase mixture model. It does so by applying the single-phase and the two-phase mixture model to a nine-passages rectangular minichannel, 3 mm deep and 1 mm wide, cooled by a 1% by volume suspension of Al2O3 nanoparticles in water, over the Reynolds number range 92 to 455. By varying the volume fraction αnf of the second phase between 2% and 50%, under a constant heat flux of 16.67 W/cm2 and 30 Celsius coolant inflow, it is shown that the two-phase mixture model predicts heat transfer coefficient, pressure loss, friction factor, exergy destruction rate, exergy expenditure rate, and second law efficiency values converging to the single-phase model ones at increasing αnf. A two-phase mixture model defined with 1% second phase volume fraction and 100% nanoparticles volume fraction in the second phase breaks the Newtonian fluid assumption within the model and produces outlier predictions. By avoiding this unphysical regime, the two-phase mixture model matched experimental measurements of average heat transfer coefficient to within 1.76%. This has opened the way for using the two-phase mixture model with confidence to assess and resolve uneven nanoparticle dispersion effects and increase the thermal and mass transport performance of minichannels.

Study on the novel suppression of heat transfer deterioration of supercritical water flowing in vertical tube through the suspension of alumina nanoparticles

One of the novel strategies of improving the heat transfer characteristics of heat exchanger systems is the application of nanofluids as the heat transfer media. The purpose of the current study is to evaluate the effectiveness of utilizing the suspension of nanoparticles in water at supercritical pressures in the mitigation of heat transfer deterioration (HTD), an adverse phenomenon in supercritical fluids heat exchanger systems. The thermohydraulic performances of the supercritical water-based nanofluids are analysed using the dimensionless parameters based on normalized Nusselt numbers and Fanning friction factors, Nunf/Nubf, fnf/fbf and PEC = (Nunf/Nubf)/(fnf/fbf)1/3. The results reveal that the suspension of Al2O3 nanoparticles increase the mitigation of HTD, with 1.5% of Al2O3 nanoparticles volume fraction achieving up to 20.22% suppression of wall temperature peaks. In accordance with the Reynold’s analogy, the results show a positive correlation between heat transfer performance and pressure loss. Furthermore, the effect of nanoparticles on buoyancy flow are investigated based on Jackson's buoyancy criterion (Gr/Re2.7). It is obtained that (Gr/Re2.7) decreases at the pseudo-critical region as the nanoparticles volume fraction increases because the increase in the volume fraction leads to the reduction in difference between the bulk and near-wall fluid densities, thus leading to weakening of buoyancy flow and subsequent mitigation of HTD. Also, the increasing nanoparticles volume fraction causes the reduction of kinematic viscosity but enhances the velocity and turbulent kinetic energy close to the wall, which also, contributes to the mitigation of HTD.

Heat transfer studies of Al2O3/water-ethylene glycol nanofluid using factorial design analysis

The experimental study of the heat transfer coefficient of nanofluid plays a significant role in improving the heat transfer rate of the heat exchanger. A natural convection apparatus was used to study heat transfer in the suspension of Al2O3 nanoparticles in a water-ethylene glycol mixture base fluid. The effects of the heat input, the nanoparticle volume fraction, and the base fluid concentration on the heat transfer coefficient were studied using a 23 full factorial design matrix (16 experimental runs) and the MINITAB Design software. The levels for the heat input, nanoparticle volume fraction, and base fluid concentration were 10 and 100 W, 0.1 and 1 vol.%, and 30 and 50 vol.%, respectively. The residual, contour, 3D surface plots, and Pareto chart were drawn from the experimental results. The observed heat transfer coefficient showed the highest enhancement with the high level of the nanoparticle volume fraction and a moderate enhancement with the high level of heat input, and a slight enhancement with the base fluid concentration.

CO2-wettability reversal of cap-rock by alumina nanofluid: Implications for CO2 geo-storage

The usage of nanofluids is vast in different applications of nano-energy. These minute nanoparticles can be used to alter the hydrophobicity into hydrophilicity for CO2-brine-mineral systems in the presence of organic acids. Nonetheless, the literature lacks the information for the behavior of nanoparticles and its associated concentrations in the presence of organic acids at the reservoir (high temperature and high pressure) conditions.In this study, we have investigated that how different alkyl chain organic acids impact the wettability of mica muscovite for different ageing times (7 days and one year) and how this impact can be reversed by nanofluid priming at different concentrations. To do that, we have used different organic acids with different alkyl chain lengths (hexanoic acid C6, lauric acid C12, stearic acid C18, and lignoceric acid C24) at 10−2 mol/L. We have also used different Al2O3 nanoparticle suspensions (0.05 wt%, 0.1 wt%, 0.25 wt% and 0.75 wt%) in deionized water.When mica substrates were exposed to organic acids for a longer ageing time of 1 year, it has lost its water-wetness rapidly at maximum. Whereas this effect was optimally reduced by 0.25 wt% of alumina nano-formulation and mechanical irreversible adsorption of alumina nanoparticles was noted on mica substrates. This reversal of wettability may raise the containment security and CO2 structural trapping potential.

Cu-Al2O3 hybrid nanofluid natural convection in an inclined enclosure with wavy walls partially layered by porous medium

A parametric numerical investigation is performed of the natural convection and heat transfer in an enclosure with opposing wavy walls, layered by a porous medium, saturated by a hybrid nanofluid, at different inclination angles. The Galerkin finite element method is used to obtain steady-state solutions of the heat and mass convection laws by application of the semi-implicit method for pressure linked equations algorithm. The Darcy-Brinkman model is used for representing the state variables change in the porous layer. The influence of six parameters on the flow and heat transfer rate is described. These are the inclination angle, varied from 0° to 90°, the Rayleigh number (104 ≤ Ra ≤ 107), the Darcy number (10−5 ≤ Da ≤ 10−2), the porous layer width (0.2 ≤ Wp ≤ 0.8), the number of undulation (1≤ N ≤ 4), and the nanoparticle volume fraction (0 ≤ ϕ ≤ 0.2). It is found that the inclination angle is a very influential control parameter for the hybrid nanofluid in the enclosure. Its effect is modulated by the other parameters. The model predicts that adding the nanoparticles enhances the heat transfer between the opposing walls of the cell compared to the pure fluid over the whole range of inclination angles. Finally, a comparison of the heat transfer enhancement based on the suspension of Al2O3 nanoparticles in water as a single nanofluid versus using Cu-Al2O3 nanoparticles in water as a hybrid nanofluid indicates better heat transfer performance by the hybrid nanofluid.

Numerical study on forced convection of water-based suspensions of nanoencapsulated PCM particles/Al2O3 nanoparticles in a mini-channel heat sink

The contributions of Al2O3 nanoparticles and nanoencapsulated PCM particles for enhancing the heat transfer in the rectangular mini-channel heat sink are compared in this work. A three-dimensional numerical method is used to simulate the forced convection heat dissipation of water-based suspensions of nanoencapsulated PCM particles/Al2O3 nanoparticles in the mini-channel heat sink. A homogenous mixture formulation by means of the pseudo-vorticity-velocity formulation together with the energy equation is adopted to evaluate the cooling characteristics. Several important factors in the system such as the friction factor, the thermal resistance, the figure of merit, and the average heat transfer coefficient ratio are investigated at various concentrations of Al2O3 nanoparticles and nanoencapsulated PCM particles, flow Reynolds numbers, and heat fluxes. The numerical results clearly reveal that the maximum thermal resistance reduction of 1.2% and 6.9% can be observed by adding the nanoencapsulated PCM suspension with the concentrations of 2% and 10%, respectively. For the case of water-based suspension of Al2O3 nanoparticles, the heat transfer coefficient ratios are larger than unity for all values of heat flux and Reynolds number. The usage of Al2O3 nanoparticles provides better cooling performance as compared with the case of nanoencapsulated PCM particles. As a result, the beneficial effect of Al2O3 nanoparticles is much greater as compared with that of nanoencapsulated PCM particles.

Computational fluid dynamic evaluation of heat transfer enhancement in microchannel solar collectors sustained by alumina nanofluid

AbstractNanofluids have produced a wide range of researches for various cooling/heating purposes, owing to the enhanced thermophysical properties they bring by suspending nanoparticles in the base fluid. This work proposes a detailed computational fluid dynamic (CFD) study of heat transfer enhancement in microchannel solar collectors coupled with nanofluid. The accuracy of the numerical model is ensured through a reliable finite element analysis considering the complexity of the three‐dimensional structure of microchannel solar collector. The thermophoretic motion induced by the suspension of Al2O3 nanoparticles was also evaluated to further understand the thermal enhancement observed in forced convection regimes. The accuracy of the model was first validated with respect to propylene glycol/water fluid, and then applied to evaluate the performance for Al2O3/water nanofluid. A detailed comparison of the performance of the two fluids with an assessment of the temperature and velocity profiles, was adopted to evaluate the thermal efficacy of adding nanofluids. A further investigation of the effect of solar collector inclination angles (0, π/6, π/4,and π/3) at the optimal volumetric concentration of the nanofluid was also done to determine the impact of the system geometry on the efficacy of the heat removal. It was established that the optimal heat removal is achieved at 2% nanoparticle concentration. Finally, it was also detected that increasing the inclination angle of the solar collector (from 0 to π/3) obstructed the heat removal efficiency.

A combined numerical and experimental study on the forced convection of Al2O3-water nanofluid in a circular tube

This research investigates the contribution of Al2O3 nanoparticle suspensions on laminar forced convection heat transportation of Al2O3-water nanofluid flowing through a circular tube. In this regard, initially, the variation of the wall and bulk fluid temperatures and the values of local Nusselt numbers are experimentally evaluated along the tube. Next, numerically, the effect of various inlet temperatures from 25 to 50 °C on the important characteristics of the problem under study including pressure drop, Nusselt number and entropy generation are further examined through the constant property and temperature-dependent property modeling. The flow rate of the working fluid was ranged from 24 to 180 cm3/min corresponding Re = 120–2000. The imposed heat flux was 5.51 × 102–1.23 × 104 W/m2. It is found that the addition of nanoparticles leads to the reduction of wall temperature and the enhancement of the Nusselt number, while it also causes an increase in the pressure drop along the tube. The results further reveal that the variable-property simulation provides more accurate predictions. The predicted pressure drop is decreased, and the predicted Nusselt number is increased by considering the temperature dependency of thermophysical properties of the nanofluid.

An experimental study of forced convection effectiveness of Al2O3-water nanofluid flowing in circular tubes

In the present study, experimental efforts have been performed to explore the forced convection heat transfer using water-based suspension of Al2O3 nanoparticles (nanofluid) to replace the pure water as the working fluids in circular tubes. The nanofluid was prepared as a functional forced convection fluid and the thermal properties including the density, thermal conductivity, and dynamic viscosity were investigated experimentally. Besides, forced convection heat transfer in circular tubes was investigated with water-based nanofluid containing various mass fractions of the Al2O3 nanoparticles (2, 5, and 10wt%) under the following operating conditions: the volume flow rate Qf=23.6–183.5cm3/min (the Reynolds number Ref,0=188–2095), the heating power applied at the outer wall of the tube qo,eff.″=1908–7362W/m2, and the inlet fluid temperature Tin=24.5–25.5°C or 49.5–50.5°C. Measured data showed that the dispersion of increasing mass fraction of Al2O3 nanoparticles can effectively improve the thermal conductivity relative to the pure water. Besides, higher average heat transfer effectiveness ε−h,btd and figure of merit FOM are noted for the cases with higher inlet fluid temperature Tin.

An experimental investigation of the effect of the addition of nano Aluminum oxide on pool boiling of refrigerant 134A

The pool boiling of R-134a has been experimentally investigated with an addition of nano particles of Aluminum oxide. The experiments were carried out using a cylindrical stainless-steel heater. The roughness of the heater surface was changed. Different concentrations of nano Aluminum oxide particles to the base R-134a were tested. Different heat fluxes as well as different boiling pressures were considered during the experimental tests. The results show that the suspension of Al2O3 nano particles enhances heat transfer coefficient in the nucleate pool boiling zone for concentrations ranging from 0.01 to 0.25% by volume. Higher heat flux and pressure result in enhancements of 37.6, 55.4, 90.2 and 167.7% corresponding to 0.042, 0.84, 1.54 and 2.35 μm surface roughness respectively. The more concentration of Al2O3 nano particles deteriorates the heat transfer coefficient. An empirical correlation was deduced to formulate the relation among heat transfer coefficient, heat flux, pressure, concentration, and surface roughness within a maximum deviation of about ±9%.

Tribological Performance and Lubrication Mechanism of Alumina Nanoparticle Water-Based Suspensions in Ball-on-Three-Plate Testing

The lubrication performance of alumina (Al2O3) nanoparticle water-based suspensions was systematically investigated using a ball-on-three-plate testing configuration with alloy steel on stainless steel contact. The size and concentration of Al2O3 nanoparticle were varied to obtain optimal performance. The effects of testing load, sliding speed and contact surface roughness on the lubrication performance of the Al2O3 suspensions were investigated. It was found that 1 to 2 wt.% 30 nm Al2O3 nanoparticle suspensions showed up to 27% friction and 22% wear reduction, in comparison with water glycerol solution. Under different testing conditions, the suspensions also showed noticeably more stable and improved tribological performance. Wear mark analysis revealed that during tribological testing the nanoparticles formed a layer of dynamically balanced tribo-thin film, preventing the direct contact between asperities of alloy steel ball and stainless steel plate. The nanoparticles were also believed to fill up the trenches of the plate surface through mending effect and carry the wear debris induced in running-in period to avoid abrasive wear.

Thermal and hydrodynamic characteristics of water-based suspensions of Al2O3 nanoparticles in a novel minichannel heat sink

Abstract In this study, the effect of using nanofluids on heat transfer and fluid flow characteristics in triangular shaped minichannel heat sink is numerically investigated. The minichannel heat sink performance using alumina-water (Al2O3-H2O) nanofluid as a coolant with different volume fractions is examined. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using finite volume method (FVM). The heat sink performance is evaluated in terms of Nusselt number, friction factor, thermal resistance and pumping power. The results indicate that, using of nanofluid instead of pure fluid as a coolant leads to enhanced heat transfer performance by increasing the amount of heat dissipated. Also, the results reveal that when the volume fraction of nanoparticles is increased under the extreme heat flux, both the heat transfer coefficient and friction factor are increased while the thermal resistance of the heat sink is decreased. Furthermore, only a slight increase in the pressure drop across the minichannel heat sink is found compared with the pure water-cooled heat sink.

Impulse space charge and dielectric characteristics of an Al2O3 nanoparticle suspension in propylene carbonate using various electrode materials

We tested the impulse breakdown voltage of Al2O3 “nano-modified” propylene carbonate between different electrode materials. At any given concentration, the breakdown voltage was highest with stainless steel electrodes, followed by copper, and then aluminum. The space charge and electric field distributions were measured too. Results show that less space charge was injected by the electrodes, and the electric field was less distorted, than in pure propylene carbonate. However, the hoped-for reduction of the influence of the electrodes did not take place. Substantial differences in the space charge density and electric field distortion remained between the different electrode materials.

Contemplation of thermal characteristics by filling ratio of Al2O3 nanofluid in wire mesh heat pipe

An experimental investigation on the thermal efficiency and thermal resistance with respect to the inclined angle using heat pipe was carried out. The working fluids used for this are Al2O3 nanofluid and deionized water. The performance of heat pipe in terms of overall heat transfer coefficient and thermal resistance is quantified by varying the volume of working fluid and the performance parameters are contemplated. For this purpose Al2O3 nanoparticles with a density of 9.8g/cm3 and a volume concentration of 1% are used as the working fluid in experimental heat pipe. The performance of heat pipe was evaluated by conducting experiments with different thermal loads and different angle of inclinations. Thermocouples are used to record the temperature distribution across the experiment. Volume of nanoparticles in the base fluid and the consequence of filling ratio on the thermal resistance of the nanofluids are investigated. The results provide evidence that the suspension of Al2O3 nanoparticles in the base fluid increases the thermal efficiency of heat pipe and can be used in practical heat exchange applications.

Decoration of graphene sheets with Pd/Al2O3 hybrid particles for hydrogen storage applications

In this work, we developed a heterogeneous catalyst consisting of Al2O3 nanoparticle and low amounts of Pd that markedly enhances the hydrogen uptake of reduced graphene oxide (RGO). The Pd/Al2O3 hybrid particles were prepared by ultrasound-assisted impregnation of PdCl2 in aqueous suspension of Al2O3 nanoparticles. Hybrid particles were immobilized onto the RGO support, giving Pd/Al2O3–RGO nanocomposites. It was shown that incorporation of 1 wt% heterogeneous catalyst (<0.3 wt% Pd) significantly increased the hydrogen storage capacity of RGO from 0.17 wt% to 0.31 wt%. This indicated a raise of hydrogen uptake by factor of 1.8 in RGO nanocomposite. The improving hydrogen storage capacity of RGO nanocomposites by change of Al2O3 particle size and Pd content was linked to activation of processes usually grouped as spillover.

HEAT TRANSFER STUDIES IN A CLOSED LOOP PULSATING HEAT PIPE

Thermal resistance as a function of heat load and startup temperature with respect to time have been investigated for a pulsating heat pipe(PHP) at different inclination angle using different working fluids. PHP was made of 1.45 mm inner diameter copper tubes having 6 turns. The performance of de-ionized water and methanol as working fluid has been compared in terms of startup conditions, thermal resistance and performance at different orientation. The optimum filling ratio for water was 50% and for methanol 40%. Nanoparticle can further enhance the heat transfer characteristics of the working fluid; hence Al2O3 nanoparticle suspension in DI water with varying concentration was also used as the working fluid. The optimum concentration in vertical mode and at 45° inclinations was 1% by wt. while for horizontal orientation was 0.5% by wt. Further a correlation has been proposed to validate the experimental data.

Temperature Dependence of Convective Heat Transfer with Al&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Nanofluids in the Turbulent Flow Region

An experimental investigation on the characteristics of the convective heat transfer in the fully developing region of a circular straight tube with a constant heat flux was carried out with Al2O3 nanofluids. Stable nanofluids, which were water-based suspensions of Al2O3 nanoparticles, were prepared by two-step method. The effects of the thermal conductivity, viscosity, and heat capacity of the nanofluids on convective heat transfer were investigated. The result showed that the coefficient enhancement of the convective heat transfer in the Al2O3 nanofluids was increased with increasing fluid temperature compared to that of water at a volume fraction of 3.0% in the turbulent flow region. Thermal conductivity was increased from 8% to 20%, and the increment of convective heat transfer coefficient was enhanced from 14% to 30% with fluid temperature from 22 degrees C to 75 degrees C, respectively. We observed that the increment of convective heat transfer coefficient in nanofluids was much higher than that of the thermal conductivity at a given temperature condition. The enhancement of Brownian motion due to the decreasing kinematic viscosity led to a higher convective heat transfer coefficient at a higher temperature condition.

Correlations of heat transfer effectiveness in a minichannel heat sink with water-based suspensions of Al2O3 nanoparticles and/or MEPCM particles

In this work, an experimental study is carried out to examine the cooling performance of a minichannel heat sink using water-based suspensions of alumina nanoparticles (nanofluid), and/or microencapsulated phase change material (MEPCM) particles in terms of the averaged Nusselt number Nu¯itd, the wall temperature control effectiveness εTw, and the averaged thermal resistance control effectiveness εRavg for the relevant parameters in the following ranges: the Reynolds number, Re=133–1515; the mass fractions of the nanoparticles and/or MEPCM particles dispersed in the water-based suspensions, ωnp or ωmepcm=0–10wt.%; and the heating power. The heat sink was fabricated from copper with 10 rectangular minichannels which were maintained at a uniform base heat flux. The resulting experimental data for the various effectivenesses of using the water-based suspensions formulated in the minichannel sink were found well correlated with the relevant dimensionless parameters in general forms.