Al2O3-water Nanofluid Research Articles

A comprehensive parametric study on heat transfer optimization of a triangular enclosure subjected to a magnetic field using neural network machine learning

The free heat convection of Al2O3-water nanofluids considering the radiation effects in an isosceles right triangle under the influence of a uniform magnetic field is numerically simulated. The SIMPLE algorithm is used in a staggered-grid structure to study the effects of Rayleigh number, Ra, Hartmann number, Ha, the location and the length of the hot part, solid volume fraction, radiation parameter, and the angles of the magnetic field and enclosure on the flow characteristics, heat transfer, entropy generation. The results show that the heater length and the radiation strength are the two most effective factors, followed by Ra and Ha. The maximum potential of the enclosure to reach the highest heat transfer rate is shown to be 22 times in Nuave, which is accompanied by a mere 7 times increase in entropy generation. In the best and worst cases of design, with respect to the second law of thermodynamics, the entropy generation does not increase significantly. Sensitivity analysis indicates that designers should not be casual about the length of the heater as it has the highest impact on the Nuave and Stot necessitating paying much attention to its tolerance, especially in its larger values.

Combined convection heat transfer in a lid driven cavity filled with nanofluids

AbstractA simulation study is performed of laminar steady combined convection heat transfer in a lid‐driven cavity containing various types of nanofluid (CuO–water nanofluid and Al2O3–water nanofluid) at various boundary conditions. The influence of two different types of temperature distributions applied to the cavity's bottom wall is investigated. There are two types of temperature distributions: constant temperature (Th) and a sinusoidal temperature distribution applied to the bottom wall, which has a higher temperature than the top moving wall (Tc). In both circumstances, the sidewalls are kept adiabatic. The finite element method is utilized for the current issue. The influence of the Richardson number, which ranges from 0.01 to 10, and the volume fraction of nanoparticles, which ranges from 0 to 0.1, on the heat transfer rate has been explored. The influence of the sinusoidal temperature distribution's amplitude and phase angle is also examined. The isotherm and streamline patterns within the cavity are diverse with distinct nanoparticle volume fractions, and the Richardson numbers are presented and analyzed. The numerical findings showed that lowering the Richardson number raises the average Nusselt number. Also, the existence of nanoparticles in pure water increases heat transmission. Additionally, raising the sinusoidal temperature's amplitude increases the average Nusselt number. The results show that the increase of average Nusselt number at (φ = 0, Gr = 104, Pr = 1, Ɣ = 3π/2) for amplitude 0.25, 0.5, 0.75, and 1 is 0.53, 0.9, 1.3, and 1.87, respectively.

Thermo-fluid characteristics and second law analysis of an inclined two-fluid system with variable surface roughness

The present numerical study focuses on the analysis of thermodynamic characteristics of an inclined two-fluid system (Al2O3-water and CuO-water nanofluids) having a heat conducting partition wall of variable surface roughness with constant geometric orientation. A further level of thermal control that results in an optimum system orientation for greater thermo-physical transport along with less entropy generation and thermal optimization is explored by examining the effect of system inclination. Based on the second law of thermodynamics, the quantitative results include the variation of average Nusselt number, average fluid temperature, average entropy generation, and average Bejan number for a wide range of Rayleigh number and inclination angle. Current study realizes that the mean quantitative properties of the system are significantly affected by the change of Rayleigh number and inclination angle, despite having a weak dependency on the partition roughness. The variation of average Bejan number with Rayleigh number assumes a reverse trend compared to the same for average Nusselt number and entropy generation and decreases continuously as the flow circulation strengthens. The rate of thermal transport is significantly regulated by the system orientation. Each Rayleigh number conforms to a critical angle of the system inclination for highest thermal transport and entropy generation.

Experimental evaluation of performance of a hybrid solar photovoltaic (PV/T) panel integrated with effective cooling solutions with water base nanofluids and phase change materials

ABSTRACT The overall performance of photovoltaic (PV) panels is prejudiced by the operating temperature of the solar cell owing to the absorbed solar radiation. In this experimental study, the in-house hybrid PV/thermal (PV/T) system is designed, fabricated, and parametrically studied for effective and practical applications of the solar panels. The water and water-based nanofluids are used for the active cooling of the PV/T system. The effect of phase change material (PCM) along with the active cooling is also studied, and results are comprehensively discussed. The in-house stable water-based Al2O3 and TiO2 nanofluids are engineered by the two-step method with two different nanoparticle concentrations of 0.05 and 0.1 vol.%. The thermal conductivity and stability of the nanofluids are experimentally measured and discussed to understand their effects on heat transfer from the PV panel. The thermal conductivity of nanofluids is increased with the concentration of nanoparticles in the base fluid. The maximum enhancement of around 30% is observed with Al2O3-water nanofluid at a concentration of 0.1 vol.%. The PV/T system is experimentally simulated in the indoor experimental setup with the solar simulator to provide the variable intensity of solar irradiance from 450 to 1050 W/m2. The maximum decrement in the panel’s temperature is found to be around 25% using both active and passive cooling simultaneously and the electrical efficiency is improved by approximately 10.3% at the 1050 W/m2. The electrical efficiency has found 13% more with Al2O3-water nanofluid of 0.1 vol% as compared to water cooling at 450 W/m2. The use of nanofluids also improved the system’s thermal efficiency compared to the water, and the maximum improvement of around 10% is achieved with the Al2O3-water nanofluid at 0.1 vol.% concentration. These results are significant for the design of the PV/T system from the application viewpoint.

Influence of oblique angle variations on the thermo-hydraulic characteristics of the oblique fin heat sink with Al2O3 water nanofluid

The flow mixing through secondary flow is critical for improving the heat transfer of microchannel heat sinks. This study investigates oblique fin heat sinks (OFHSs) under forced convection conditions with Al2O3-water nanofluid under the Re 100–500. The study is referenced with a straight channel heat sink for benchmarking purposes. Five oblique angle configurations (15°, 25°, 35°, 45°, and 55°) were investigated at the constant fin pitch and constant width ratio (primary width-to-secondary width ratio) of 2:1. The RNG k-ε model has been employed with enhanced thermofluidic effect and wall treatment. The findings revealed that secondary flow generation leads the thermal boundary layer to redevelop at each fin, resulting in continuous fluid flow development. Pressure drop increment has been noticed with oblique angles 15° to 25°, and the variation is almost insignificant among the 35°, 45°, and 55° OFHS. The secondary flow rates were found to have a profound effect in all the cases. The 25° degree shows a higher average convection coefficient among all the OFHSs. Also, the convection coefficient varied in the following order for both water and nanofluid: 15° < 25° > 35° > 45° > 55°. The 25° OFHS enables a more uniform water/nanofluids temperature to build up in the streamwise direction than the 35°, 45°, and 55° OFHS. The thermofluidic analysis suggests that the proposed designs have superior heat convection performance than their flow resistance penalty. Therefore, the 25° OFHS offers a promising option for further parametric research in the future.

Effect of Nanofluid Flows on Heat Transfer Intensification of Corrugated Channels with an Oscillating Blade

Heat transfer characteristics of Al2O3-water nanofluid inside a corrugated channel with a flat blade were investigated. In total, 380 simulations were performed to study the simultaneous effects of the blade's status (stationary or oscillating) and the channel wall's geometry (straight or corrugated) on thermal-hydraulic performance at different Reynolds numbers (25-500), nanoparticle volume fractions (0-4%) and diameters (25-100 nm). The results indicated that, at high Reynolds numbers, using a stationary/oscillating blade could significantly enhance thermal performance of the corrugated channel compared to the straight one. In both straight and corrugated channels with/without stationary/oscillating blade, the overall Nusselt number increased with increasing the volume fraction and decreasing the nanoparticle diameter. Examining thermal-hydraulic performance index (PI) showed a critical Reynolds number could be detected in the presence of stationary and oscillating blades, at which PI was the maximum and minimum, respectively. Accordingly, activating the oscillating blade at high Reynolds numbers and inactivating the blade at low Reynolds numbers could significantly improve PI. Moreover, PI of both channels, with/without stationary/oscillating blades, was improved with decreasing the volume fraction and increasing the nanoparticle diameter. Although PI had lower sensitivity to the nanoparticle diameter than the volume fraction, increasing the volume fraction increased this sensitivity.

Thermal fluid fields reconstruction for nanofluids convection based on physics-informed deep learning

Based on physics-informed deep learning method, the deep learning model is proposed for thermal fluid fields reconstruction. This method applied fully-connected layers to establish the mapping function from design variables and space coordinates to physical fields of interest, and then the performance characteristics Nusselt number Nu and Fanning friction factor f can be calculated from the reconstructed fields. Compared with reconstruction model based on convolutional neural network, the improved model shows no constrains on mesh generation and it improves the physical interpretability by introducing conservation laws in loss functions. To validate this method, the forced convection of the water-Al2O3 nanofluids is utilized to construct training dataset. As shown in this paper, this deep neural network can reconstruct the physical fields and consequently the performance characteristics accurately. In the comparisons with other classical machine learning methods, our reconstruction model is superior for predicting performance characteristics. In addition to the effect of training size on prediction power, the extrapolation performance (an important but rarely investigated issue) for important design parameters are also explored on unseen testing datasets.

Simulation of solar thermal panel systems with nanofluid flow and PCM for energy consumption management of buildings

The present study simulates a solar thermal panel using the finite element method (FEM) in COMSOL Multiphysics. A cropper pipe of a water-Al2O3 nanofluid flow was used under a solar panel. A number of elliptic fins were attached to the pipe. The fins were holed and configured in three models. The system of the pipe and fins was placed in a chamber filled with CaCl2.6H2O as a phase change material (PCM) under the panel. The proposed solar system was used on a pitched roof to partially supply the energy demand of the Boarding clinic. The energy calculations were carried out in Design Builder. It was found that PCM began to melt at t=40 min. The fins with a central hole led to 10.4% higher melted PCM than double-hole fins at t=100 min. The centrally-holed fins minimized the output flow temperature. However, they also minimized the PVT temperature. It was also found that the proposed system could supply 9.11% of the heating demand of the building in the coldest month of the year. In hot months, however, up to 33.3% of the energy required to heat water could be supplied by the PVT + PCM system.

Magnetohydrodynamic mixed convection and entropy generation analysis of Al2O3-water nanofluid past a confined circular cylinder

Numerical simulations are carried out for transient magnetohydrodynamic mixed convective heat transfer of alumina–water nanofluid flow past an isothermal circular cylinder confined in an electrically insulated rectangular duct in the presence of a uniform transverse magnetic field. A control volume method is used to solve the governing equations on a nonuniform Cartesian grid, and the cylinder is imposed using the immersed boundary method. Numerical experiments are performed for a Reynolds number based on the cylinder diameter of ReD=200, blockage ratio of BR=0.2, Richardson numbers of (Ri=−1;0;2), nanoparticle volume fractions of (φ=0.0;0.1;0.2), and Hartmann numbers in the range 0≤Ha≤13. In this work, mean and instantaneous flow and thermal distributions are analyzed graphically, and their corresponding sensitivity to the nanoparticle volume fraction has been determined. Numerical predictions demonstrate the impact of buoyancy and magnetic parameters regarding the spatial development and shedding characteristics of the near wake, and we explore their potential use to selectively excite or suppress vortex shedding, augmentation of heat transfer, and entropy generation minimization in nanofluid flow. The results reported herein indicate that depending on the parametric set, linear and nonlinear flow response to magnetic excitation is observed with bifurcations between different states. The outcome of the study shows that vortex shedding is completely suppressed when a critical value of the Hartmann number is reached, and that the threshold value of the Hartmann number strongly depends on the value of the buoyancy parameter and nanoparticle volume fraction. Based on the entropy distributions, we show that for all values of the nanoparticle volume fraction and in the range of buoyancy and magnetic parameters considered in this work, the entropy generation is dominated by irreversibilities due to heat transfer and the relative contributions of entropy generation due to fluid friction and magnetic effect are not preponderate.

The effect of using phase change materials in solar panel cooling to provide green and sustainable energy of a building

The present study numerically investigates the use of solar energy for heating in a building using EnergyPlus and COMSOL. A solar panel with a size of 0.5 × 1 m was simulated. A rectangular chamber containing CaCl26H2O as a phase change material (PCM) was positioned below the solar panel. A pipe with an Al2O3-water nanofluid flow and fins was placed in the middle of the PCM chamber. The hot water outflow of the solar panel was employed to supply the hot water demand of a small residential building. Also, the amount of carbon dioxide production for this house in different months of the year for the house with and without solar thermal panel was compared. Furthermore, the panel temperature and melted PCM fraction below the panel were studied at different nanofluid flow velocities. It was found that a higher flow velocity (20 mm/s) led to a lower panel temperature than a lower velocity (5 mm/s). Thus, a higher nanofluid flow velocity would increase the fraction of energy demand supplied through the solar system during the day (up to 19.1%); however, a rise in the velocity at night diminished the energy fraction. In July, using a solar heating panel to supply hot water to the house reduced carbon dioxide emissions by 43%.

Entropy Generation Analysis of Al2O3–Water Nanofluid Flow Past a Permeable Cone Under the Effect of Suction/Injection and Viscous Ohmic Dissipations

Entropy Generation Analysis of Al2O3–Water Nanofluid Flow Past a Permeable Cone Under the Effect of Suction/Injection and Viscous Ohmic Dissipations

Numerical Study of the Elasto-Hydrodynamic Behavior of a Metallic Structure Subjected to a Nanofluid Flow

In this paper, the behavior of an elastic barrier subjected to isothermal laminar flow of Al2O3-water nanofluid in a channel has been studied numerically by the finite element method. A CFD based on the arbitrary Lagrange-Euler (ALE) formulation, has been developed in an attempt to solve the Navier-Stokes and stress-strain equations of the structure. The objective is to study the effects of inertia (Re) and nanoparticle volume fraction (φ) on the overall hydrodynamic behavior, as well as on the nanofluid-structure interface. The results showed that the deformation of the structure was mainly caused by the pressure loading of the nanofluid and the viscous drag imposed on the structure walls. In addition, the structure was strongly affected by the increase in Reynolds number and volume fraction of the nanoparticles. Finally, a numerical correlation was established to determine the maximum displacement caused by the bending of the structure.

Enhancing the thermal performance of different flow configuration minichannel heat sink using Al2O3 and CuO-water nanofluids for electronic cooling: An experimental assessment

Several previous studies on liquid cooling of high-power density electronic servers have been conducted for different configurations of the liquid channels, operating conditions and coolant, pure liquid or using nanofluid. Most of these studies have been done numerically or analytically without comprehensive experimental validation and comparison. To fill this research gap, a comprehensive experimental study was conducted in the present work to evaluate and compare the thermal performance of electronic devices using liquid cooling system by passing water, Al2O3 or CuO nanofluid in different flow mini-channels configurations (Serpentine, parallel and wavy channels). The results of the present experimental investigations showed that (i) heat sinks with serpentine mini-channels has a better thermal performance than heat sinks with wavy and parallel mini-channels heat sinks, (ii) the wavy channel heat sinks has a better thermal performance than parallel channel heat sinks, (iii) the presence of the nanoparticles provides a decrease in the thermal resistance and an augmentation in the average Nusselt number compared with pure water for all the liquid channels configurations with better performance of CuO-water nanofluid compared with Al2O3-water nanofluid, and (iv) for serpentine channels at 120 W power density, the minimum and maximum increase in the Nusselt number is (4.49%–12.5%) for 0.1% vol. Al2O3-water nanofluid and (5.77%–16.01%) at 0.1% vol. CuO-water nanofluid. For the purpose of validations and assessments, the results of the present experimental work were compared with the results of the previous analytical/numerical work as well as with the cases of the previous experimental works.

Heat transfer and thermodynamic analysis of the impact of porous media and nano‐powder types in an open cavity equipped with an electronic component

AbstractIn this study, a numerical investigation has been carried out to analyze thermal and flow behavior with thermodynamic perspectives in a cooling application problem. The configuration under consideration in this analysis consists of a cubic electronic chip placed in an open cavity filled with porous media. The solver's reliability is achieved by comparing our results with experimental studies. In this regard, various parameters were considered, which consist of different nanoparticles (Al2O3, TiO2, Cu, and Ag), porosities (0.85–0.97), and Reynolds numbers under turbulent conditions within the range (5000 ≤ Re ≤ 30,000). Their imprints have been highlighted on temperature distribution, streamlines, local and average Nusselt numbers, pressure drop, global entropy generation, and exergy efficiency. Results reveal that there is an optimal porosity to achieve the highest cooling performance based on the Reynolds number. In addition, using Al2O3–water nanofluid as a working fluid, the highest values of the mean Nusselt numbers were recorded. Furthermore, operating the system with a porous medium and the Al2O3–water nanofluid results in only a minor increase in pressure drop. Finally, the results substantiate that using porous media reduces global entropy production and slightly decreases the exergy efficiency in the system.

Oscillatory natural convection of Al2O3-water nanofluid near its density maximum in a narrow horizontal annulus

In order to reveal the oscillatory characteristics of the natural convection of nanofluid, this paper presents a comprehensive numerical work on the oscillatory natural convection of Al2O3-water nanofluid near its density maximum in a narrow horizontal annulus. The influences of nanoparticle volume fraction, Rayleigh number and density inversion parameter on the flow pattern evolution and heat transfer ability are analyzed. Results show that the density inversion of the working fluid affects the velocity and temperature distributions of the natural convection of Al2O3-water nanofluid significantly. Adding nanoparticles is beneficial to stabilizing the flow of nanofluid and keeping the symmetry of the flow structure. The convective heat transfer is enhanced with the increase of the volume fraction of nanoparticles. Furthermore, the evolution of the flow regime with the Rayleigh number at different volume fractions of nanoparticles is summarized.

Comparison of single-phase Newtonian and non-Newtonian nanofluid and two-phase models for convective heat transfer of nanofluid flow in backward-facing step

The aim is to investigate the application of nanofluids for improving the heat transfer in a backward-facing step channel. Numerical simulations are performed using single-phase models for both Newtonian and non-Newtonian fluids in the Reynolds number range 280–470. Constant and temperature-dependent thermo-physical properties of different volume fractions (0–4%) of nanoparticles are considered. The thermal enhancement of the nanofluids within the channel is analyzed and compared with the experimental data. A detailed comparison of different CFD models is established. Numerical results are obtained with two types of single-phase models (Newtonian and non-Newtonian) and three types of two-phase models (mixture, volume of fluid (VOF), Eulerian) and compared with experimental results obtained for the Nusselt number. The finite volume method is used to solve the system of governing partial differential equations describing the steady-state, two-dimensional, laminar, mixed convective flow in a micro backward facing step channel with uniform heat flux. The single-phase and two-phase models predict practically equivalent hydrodynamic fields, but significantly different thermal fields are observed in our results. The performance efficiency coefficient (PEC) is determined using single-phase and two-phase methods for Al2O3-water nanofluids at different Reynolds numbers to investigate their thermal performance.

Study of the performance of thermoelectric generator for waste heat recovery from chimney: impact of nanofluid-microchannel cooling system.

A huge number of chimneys all over the world utilized in many industrial applications and applications like restaurants, homes, etc. contribute badly on the global warming and climate change due to their waste heat. So, in this paper, the performance of thermoelectric generator (TEG) cooled by microchannel heat spreader having nanofluid and used for waste heat recovery from vertical chimney is investigated. Using heat spreader with microchannel cooling system increases the output TEG power compared to natural convection cooling system. In this paper, the impact of microchannel sizes, using nanofluid and heat spreader with different sizes on the TEG performance and cooling, is considered. Three-dimensional mathematical models including TEG, microchannel, nanofluid, and heat spreader are presented and solved by Ansys Fluent software utilizing user-defined memory, user-defined function, and user-defined scalar. All TEG effects (Joule, Seebeck, and Thomson) are considered in TEG model. Results indicate that TEG power rises with increasing the heat spreader and microchannel sizes together. Increasing microchannel and heat spreader sizes four times of TEG size raises the TEG output power by 10%. This also achieves the maximum cooling system efficiency of 88.9% and the maximum net output power. Microchannel heat spreader cooling system raises the system (TEG power-pumping power) net power by 125.2% compared to the normal channel and decreases the required cooling fluid flow rate. Utilizing copper-water and Al2O3-water nanofluids rises maximally the TEG output power by 14% and 4%, respectively; however, it increases the pumping power. Moreover, using nanofluids increases the net output power at low Reynolds number and decreases it at higher Reynolds number.

Numerical study of natural convective heat transfer of nanofluids within a porous corrugated triangular cavity in the presence of a magnetic field

In the present study, a nonorthogonal multi-relaxation time (MRT) lattice Boltzmann method (LBM) was realized to numerically study the natural convective heat transfer characteristics of Al2O3-water nanofluid inside a porous corrugated triangular cavity in the presence of a magnetic field. The comparison of the nonorthogonal MRT-LB model with the orthogonal MRT-LB in simulating the natural convective heat transfer considering the magnetic field effect and the filling of porous media was presented. The effects of Ra (Rayleigh number), Da (Darcy number), Ha (Hartmann number), φ (nanoparticle volume fraction), and the d (structural parameter of the corrugated wall) on the natural convective heat transfer characteristics inside the corrugated triangular cavity were investigated in detail. The results showed that the nonorthogonal MRT-LB model can accurately simulate such problems and it has higher computational accuracy than the orthogonal MRT-LB in simulating the natural convective heat transfer in porous cavities under the magnetic field effect. The magnetic field has no effect on the conduction but suppresses the convection process. The increase of Ha number significantly weakens the heat transfer performance when the convection dominates. When Ra = 104, the heat transfer performance weakens with increasing d. When Ra = 105, the heat transfer performance fluctuates with increasing d, among the structural parameters d in the current study, the optimal is reached at d = 24 while the worst is at d = 72. The average Nusselt number increases with increasing the φ for different Ha numbers at Ra = 104 and Ra = 105.

Enhancement of heat transfer in shell and tube heat exchanger using mini-channels and nanofluids: An experimental study

This study aimed to experimentally investigate the effects of Al2O3-water nanofluids with six different volume concentrations (0.02%, 0.1%, 0.2%, 0.4%, 0.6%, and 0.8%) instead of water as working fluid on heat transfer and pressure drop on the tube side of a mini-channel shell and tube heat exchanger (MC-STHE). The shell-side hot fluid flow rate was kept constant at 180 L/h, while the flow rate of the tube-side cold fluids ranged from 125 to 600 L/h. The convective heat transfer coefficient (CHTC) of the nanofluids increased in the transition and turbulent regions. The nanofluids also extended the transition region. The nanofluids had higher friction factors than water. The nanofluids had an optimal volumetric concentration and a flow rate of 0.4% and 375 L/h, respectively, at which the CHTC enhanced by 49%, while the friction factor increased by 21% compared to water. Compared to macrotube heat exchangers, the CHTC enhanced 3 to 7 times with the combined effect of the mini-channels and nanofluids in the shell-and-tube heat exchanger (STHE). Consistent with earlier studies (maximum TEF of 1.8), the thermal enhancement factor (TEF) for the optimal volumetric concentration Al2O3-water nanofluid in the MC-STHE was 1.6 at most under the same hydrodynamic conditions. The performance evaluation criterion (PEC) and the efficiency evaluation criterion (EEC) showed that there was no point (not enhancement) in using nanofluids instead of the base fluid (water) in the MC-STHE.

Numerical analysis on heat transfer enhancement of Al2O3 nanofluid in the flattened conically coiled tubes

AbstractEnhancement in the heat transfer of the working fluid flowing inside the tube is achieved by modification of tubes and changing the direction of fluid flow. For this purpose, the straight tube can be changed into a conical coil tube, thereby, heat transfer is increased due to the centrifugal effect caused by the curvature of the tube. Furthermore, the circular cross‐section of the tube is modified into an oblong shape for more heat transfer enhancement. In this study, the numerical heat transfer and pressure drop characteristics of Al2O3–water nanofluids in the flattened conically coiled tube are studied. The effect of the aspect ratio, cone angle, coil pitch, and solid volume fraction of nanofluids on heat transfer and pressure drop are examined. It is found that the heat transfer coefficient and pressure drop increase with the rise of aspect ratio, Reynolds number, and solid volume fraction of nanofluid, while it decreases with the increment of cone angles and coil pitches of conical coil tube. Furthermore, the effect of aspect ratio on the heat transfer enhancement factor, pressure drop ratio, and thermal performance index for Al2O3–water nanofluid are presented.