High Solid Volume Fraction Research Articles

A magnetohydrodynamic flow of a water-based hybrid nanofluid past a convectively heated rotating disk surface: A passive control of nanoparticles

Abstract One of the basic fluid mechanics problems of fluid flows over a revolving disk has both theoretical and real-world applications. The flow over a rotating disk has been the subject of numerous theoretical studies because it has many real-world applications in areas like rotating machinery, medical equipment, electronic devices, and computer storage. It is also crucial for engineering processes. Therefore, this article deals with a time-independent water-based hybrid nanofluid flow containing copper oxide and silver nanoparticles past a spinning disk. The Newtonian flow is taken into consideration in this analysis. The influence of magnetic field, thermophoresis, nonlinear thermal radiation, Brownian motion, and activation energy has been considered. The present analysis is modeled in a partial differential equation form and is then converted to ordinary differential equations using appropriate variables. A numerical solution using the bvp4c technique is accomplished using MATLAB software. The current results are matched with the previous literature and established a close relationship with previous studies. The purpose of this investigation is to numerically investigate the time-independent hybrid nanofluid flow comprising copper oxide and silver nanoparticles over a rotating disk surface. The results show that the increased magnetic parameters increase the friction force at the surface, which decreases the radial and azimuthal velocity distribution. At the sheet surface, the radial velocity of the hybrid nanofluid shows dominant performance compared to the nanofluid. On the other hand, the magnetic factor has dominant behavior on the azimuthal velocity component of the nanofluid flow compared to the hybrid nanofluid flow. The higher volume fraction and magnetic factor enhance the skin friction at the disk surface. Furthermore, greater surface drag is found for the hybrid nanofluid flow. The higher solid volume fraction, temperature ratio, and Biot number enhance the rate of heat transmission. Also, a higher rate of heat transmission is observed for the hybrid nanofluid flow.

Optimizing heat transport in a permeable cavity with an isothermal solid block: Influence of nanoparticles volume fraction and wall velocity ratio

Abstract This study examines the influence of wall velocity ratio on mixed convective heat transport in a permeable cavity containing an isothermal solid block at its center. The analysis considers the characteristics of various flow variables, i.e., Darcy number, wall velocity ratio, Richardson number, and volume fraction of suspended nanoparticles, on heat transport and material flow characteristics. The principal equations are solved implementing the semi-implicit method for pressure linked equations algorithm, and the outcomes are compared with existing literature. The study shows that rising estimations of Darcy number, velocity ratio, Richardson number, and nanoparticles volume fraction lead to improved heat transfer rates. For example, at high Richardson number (100) and solid volume fraction (0.05), increasing the velocity ratio from 0.5 to 1.5 results in a 6% (5%) upsurge in heat transport rate. Conversely, at smaller Richardson number (0.01), the heat transport rate upsurges by 29% (28%). Similarly, at high Darcy numbers and low wall velocity ratios, a 3% (4%) escalate in heat transport rate is observed with an increase in nanoparticles concentration from 0 to 0.05, while a 9% (8%) increase in thermal performance is achieved at low Darcy numbers. The study emphasizes the importance of optimizing the combination of nanoparticles volume fraction, Darcy number, velocity ratio, and Richardson number to maximize thermal performance in the porous cavity.

Investigating the thermal properties of single-grade engine oil (SAE 50) with the simultaneous addition of MWCNT and CuO nanoparticles

This study examines the MWCNT-CuO (20%–80%)/SAE50 nanofluid (NF) by considering the temperature changes, solid volume fraction (SVF), and shear rate (SR) parameters. The temperature range is 30–50 °C and SVF of 0.0625, 0.125, 0.25, 0.5, 0.75 and 1%, and different SRs are investigated. Viscosity is obtained using a Brookfield CAP 2000+ viscometer. The results show that the NF has a non-Newtonian behavior and the values of the power-law index are variable. Increasing the temperature of the NF decreases the viscosity because the intermolecular distance increases and the intermolecular forces decrease. Increasing the SVF in all SVFs except SVF = 0.0625 and 0.125% increases the viscosity, and therefore the SVF = 0.0625 and 0.125% have special importance. Modeling the viscosity of NF with the response surface methodology (RSM) has good accuracy so that the values of R2 and R2-adj are equal to 0.9993 and 0.9992, respectively. The sensitivity of NFs increases by adding 10% of the SVF in higher SVFs.

Shear thickening of cementitious suspensions: effect of high-volume fraction and hydration

The lubrication layer (LL) formed at the concrete–pipe interface plays a crucial role in facilitating concrete pumping. Shear thickening in this layer significantly affects concrete pumping. However, very few studies are available for understanding the onset and intensity of shear thickening of the LL. In this study, the effect of solid volume fraction (SVF), superplasticiser dosage, supplementary cementitious materials and hydration on the shear thickening (continuous and discontinuous) behaviour of cementitious suspensions were investigated. Results show that an increase in SVF reduces the shear thickening intensity for systems using ordinary Portland cement (OPC), whereas the intensity is amplified for systems with fly ash (FA) or ground granulated blast furnace slag (GGBS). An increase in superplasticiser dosage results in an early onset of shear thickening and increases the shear thickening intensity, regardless of the binder used. Systems including GGBS exhibit the highest shear thickening intensity, followed by OPC- and FA-based systems. Based on these results, it is evident that the superplasticiser dosage for OPC-based systems needs to be optimised based on the structural buildup, while, for FA- or GGBS-based systems, the superplasticiser dosage needs to be optimised based on shear thickening behaviour with respect to hydration.

THERMAL MANAGEMENT OF LITHIUM-ION BATTERY PACKS BY USING CORRUGATED CHANNELS WITH NANO-ENHANCED COOLING

In this study, a cooling system using corrugated cooling channels and Al<sub>2</sub>O<sub>3</sub>-Cu/water hybrid nanofluid is offered as the battery thermal management system (BTMS) for prismatic Li-ion batteries. A computational model built based on the finite element approach uses hybrid nanofluid at solid volume fractions ranging from 0 to 2% at various Reynolds numbers. The cold plates are corrugated and have a variety of square grooves positioned between prismatic Li-ion battery cells. The maximum temperature decreases as the volume fraction of solid nanoparticles and the number of corrugated cooling channels increases. When cases of using lowest and highest number of cooling channels are compared, maximum temperature reduction is found as 3.07 K when using water and 1.86 K when using Al<sub>2</sub>O<sub>3</sub>-Cu/water hybrid nanofluid (at the largest solid volume fraction). The number of square grooves in the cooling channels does not have any significant impact on the temperature drop when using nanofluid at the highest solid volume fraction.

Investigation of the thermal characteristics of water-based hybrid and mono nanofluids containing cerium oxide-CuO-MWCNT nanoparticles at various temperatures and volume fraction of nanoparticles and propose a new relationship

In this study, the preparation of nanofluid (NF) is performed by the two-stage method by dispersing nanoparticles (NP) into the base fluid (BF). Hybrid nanofluids (HNFs) were prepared in the solid volume fractions (SVFs) of SVF = 0.1, 0.2, 0.3, 0.4 and 0.5% and mono nanofluids (MNFs) were made in SVF = 0.1 and 0.3%. After ensuring stability, the thermal conductivity (TC) of HNFs and MNFs is measured by the hot wire method at a temperature range of T = 20–60 °C. The results indicate that the TC (For HNFs and MNFs) increases as the temperature increases. Increasing the SVF also increases TC, which is more evident in the higher SVFs. According to the obtained results, the highest increase in the TC is related to the MWCNT-CuO-cerium oxide/water HNF in SVF = 0.5% and T = 60 °C, which is a 26.7% increase compared to BF. In SVF = 0.3%, the MNFs containing MWCNTs NPs have a better performance than the HNFs. Compared to the results with the relationship of Lu-Lin, it was found that the temperature is critical in increasing the TC. There are no temperature parameters in the Lu-Lin model, therefore there is a difference between the laboratory results and the Lu-Lin model results. Finally, based on experimental data, a mathematical relationship between temperature and SVF was proposed to predict the TC for HNF water/cerium oxide-CuO-MWCNT. Comparing the experimental data to the outputs of the proposed relationship shows that this relationship is accurate.

Rheological characterization of limestone calcined clay cement pastes with various generations of superplasticizers for pumping applications

The present study investigates the effect of commercially available superplasticizers (SP) of various generations, such as lignosulphonate, Sulphonated Naphthalene Formaldehyde (SNF) and Polycarboxylate Ether (PCE), on the fresh properties of Limestone Calcined Clay Cement (LC3) pastes which simulates the lubrication layer formed during the pumping of concrete. LC3 cementitious pastes with different w/b (0.25–0.55), corresponding to various concrete strength grades adopted in the construction industry, were investigated. The study involves superplasticizer optimization and rheological assessment of cementitious pastes. The findings highlight the efficacy of different generations of superplasticizers, the transient flow behaviour at varied shear rates and the solid volume fractions on the rheological behaviour of LC3 pastes. The research findings indicate that LC3 based mixtures, at optimized SP dosages with increased shear rates exhibit a notable transition in behaviour from shear thinning to shear thickening (crucial for controlling the discharge of concrete during pumping). Moreover, the study reveals that LC3 pastes containing lignosulphonate based SP demonstrate superior performance at lower solid volume fractions. On the other hand, PCE based SP combinations exhibit enhanced effectiveness at higher solid volume fractions. This research outcome helps with the rational selection of superplasticizers and its dosage for LC3 mixtures in high-shear applications, particularly for the purpose of mitigating shear thickening during pumping operations.

Optimization of response function on hydromagnetic buoyancy-driven rotating flow considering particle diameter and interfacial layer effects: Homotopy and sensitivity analysis

Alumina is one of the modern era and most utilized ceramic materials. One example of an electrical insulating substance is alumina. It has an enhanced temperature, chemical stability and higher thermal conductivity. It is mostly used in medical, industry, household items, military purposes, production of batteries and electrical parts. Therefore, the authors have formulated a mathematical model of the three-dimensional magnetohydrodynamic mixed convective flow of a nanofluid containing Alumina nanoparticles past a stretching surface. Preliminary assumptions bound the nanofluid flow to be rotational, electrically conducting, dissipative, buoyancy driven, thermally heated and convective. An important investigation based on the effects of nanoparticle diameter and nanolayer of the nanofluid makes the novelty of this investigation. The modeled problem is solved with a homotopic approach, which is suitable for the solution of the highly nonlinear differential equations and has quick convergence. The outcomes of the present analysis are shown with the help of Tables and Figures. The outcomes showed that the higher resistive force at the sheet surface caused by the higher solid volume fraction (varies from 1% to 4%), diminishes the primary velocity, while escalates the secondary velocity. Additionally, the greater solid volume fraction (which ranges from 1% to 4%) raises the thermal conductivity of the nanofluid flow, resulting in an increasing conduct in the thermal function. The enhancing nanolayer to base fluid conductivity ratio (which ranges from 1.1 to 65.25), results in an increase in both velocities and thermal functions, gives the nanofluid flow a higher thermal conductivity. Additionally, the local Nusselt number and skin friction increase as a result of the higher thermal conductivity. The primary velocity and temperature are reduced due to the decrease in thermal and momentum boundary layer thicknesses brought on by the rising nanoparticle diameter (which ranges from 1 nm to 50 nm). The rate of heat transfer is significantly achieved at the higher levels of the volume fraction and radiation factor while heat source is at lower level. The friction rate at the surface is dominant at higher level values of magnetic and volume fraction factor and medium level of rotation factor. The transport of heat has highest sentivity at the middle level of thermla radaition and volume fraction of the nanoparticle and low level of heat source, while the highest sensitivity of friction factor is observed at the middle level of thermal rotation and high level nanoparticle volume fraction and magnetic factor.

Numerical Investigation of Hydrodynamics in a U-Shaped Open Channel Confluence Flow with Partially Emergent Rigid Vegetation

The effects of partially emergent rigid vegetation on the hydrodynamics of a curved open-channel confluence flow were simulated using OpenFOAM. The numerical model using the Volume of Fluid method and the RNG k-ε turbulence model in the Reynolds-averaged Navier–Stokes equations was first validated by existing experimental data with good agreement. Then the characteristics of hydrodynamics were analyzed in aspects of separation zone, water level, streamwise velocities, secondary flows, bed shear stress and flow resistance. Some main conclusions can be drawn from the results. Compared to the non-vegetated cases, the separation zones in vegetated cases are smaller in both length and width. With higher vegetation Solid Volume Fraction (SVF), the separation zone is divided into two parts, a smaller one right after the confluence point and a larger one on the second half of the curved reach after the confluence. The main circulation cell shrinks and the circulation near the concave bank moves towards the channel midline. The differences in velocities and bed shear stress between the convex and concave banks become larger with a higher SVF. Under the same SVF, a larger vegetation density has more disturbance on the tributary than a larger stem diameter.

Extrusion-based 3D printing of fully dense zirconia ceramics for dental restorations

Extrusion-based 3D printing using zirconia ceramics shows promising results in biomedical applications, but the challenges in deployment are still significant. In this study, we developed an optimized extrusion-based 3D printing method for fabrication of intricate, fully dense ceramics based on gelled zirconia suspensions. The viscoelastic properties of the suspensions were tailored to facilitate smooth flow through a 150–250 µm nozzle at high solid volume fraction (52%) and produce self-supporting features. Because of the minimal organic content, the as-dried zirconia specimens could be directly sintered without binder-removal steps. The maximum relative density, flexural strength, and hardness of the sintered zirconia ceramics were 99.3%, 1010 MPa, and 15.9 GPa, respectively. Zirconia dental restorations were fabricated, and the occlusal details were preserved by co-printing a novel polyacrylate supporting material which can be removed by cooling owing to its temperature-dependent rheological behavior.

Numerical analysis of the chemically reactive EMHD flow of a nanofluid past a bi-directional Riga plate influenced by velocity slips and convective boundary conditions

This report presents the three-dimensional electromagnetohydrodynamic flow of a zinc-oxide–water nanofluid past a bidirectional Riga plate with velocity slips and thermal and mass convection conditions. The Cattaneo–Christov heat and mas flux model, thermal radiation, chemical reaction and activation energy are considered to analyze the flow problem. The volume fraction of the ZnO nanoparticles is taken 6% in this analysis. An appropriate set of similarity variables is used to transform the partial differential equations into ordinary differential equations. During this process, some parameters are found and influences of these factors on the flow profiles are shown and discussed in detail. A numerical technique called NDSolve is considered for the solution of the nanofluid flow problem. The results showed that higher solid volume fraction and slip parameter have reduced velocities profiles and the increasing solid volume fraction and thermal Biot number have increased the temperature profile. Additionally, the concentration Biot number has increased the concentration profile. The modified Hartmann number has significantly increased the velocity profile. Dual impacts in velocity profiles along primary and secondary direction has been observed due to stretching ratio parameter. A comparison of current results has been carried with a fine agreement amongst current and established results.

Investigating sedimentation process in the plutonium reconversion using Eulerian Two-Fluid simulations and experimental verification

Batch settling simulations were used to investigate the sedimentation behaviour of cerium oxalate particles (surrogate to plutonium) in the nitric-oxalic acid solution which will be useful for the design of continuous process equipment used in plutonium reconversion. The effects of overall solid fractions (OSF), initial dispersion height (ht), and cylinder diameter (d) on the settling curve were investigated numerically and comparisons were made with experimentally obtained results. Further, the solid volume fraction distributions of cerium oxalate obtained by varying the dispersion height, OSF, and cylinder diameter were numerically analysed. The increase in OSF (dispersed phase concentration) led to the presence of high solid volume fraction inside the settler. Since, the dispersed phase volume fraction is more and closely packed, it experiences the delay in settling time. The analysis of pressure variation was done by varying ht, d, and OSF. The bulk settling velocity was computed for different OSF and ht values. It was observed that the settling velocity was reduced with an increase in OSF and was independent of d. The changes in bulk settling velocity with time helped to explain the separation process in detail. The vorticity and velocity fluctuations obtained along the height of the batch settler confirmed the random motion of solid phase during settling. The clear liquid separated at the top region of the batch cylinder was investigated as a function of sedimentation velocity which will be helpful for any future design optimization of a continuous separation equipment.

Thermal Conductivity and Rheological Studies for Graphene-Al<sub>2</sub>O<sub>3</sub> / Ethylene Glycol-Water Hybrid Nanofluid at Low Temperatures

In this study, the effect of nanoparticle concentration and temperature on the thermophysical properties of graphene-Al2O3/ethylene glycol-water hybrid nanofluid at low temperatures was experimentally investigated. The nanoparticles were characterized by XRD, SEM, TEM and BET methods. The dynamic viscosity and thermal conductivity of the hybrid nanofluids were experimentally determined at different volume concentrations of nanoparticles (0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, and 2.5%) and at temperatures ranging from 263 to 303 K. The experimental results showed that the incorporation of nanoparticles into the base fluid significantly increased the viscosity. The hybrid nanofluid with solid volume fractions less than 0.5% exhibited Newtonian behavior, while those with higher solid volume fractions (0.5% - 2.5%) exhibited shear-thinning non-Newtonian behavior and followed the power law model. The hybrid nanofluids showed surprising behavior at sub-zero temperatures and low concentration, which can be attributed to oleic acid and graphene nanoplatelets. The thermal conductivity of the hybrid nanofluids increased with increasing temperature and volumetric concentration of the nanoparticles. The ratios of thermal conductivity were increased by about 44.02% and 4.07% at 303 K and 263 K, respectively, with a solid concentration of 2.5 vol%. Based on the experimental results, a reliable correlation was presented to evaluate the thermal conductivity of graphene-Al2O3/ethylene glycol-water hybrid nanofluid at different temperatures and nanoparticle concentrations.

Experimental investigation on the effect of nano silica fume on physical properties and microstructural characteristics of lightweight cement slurry

The aim of this study is to investigate the effect of nano silica fume (NSF) on the physical properties and microstructural characteristics of lightweight cement slurry (LWCS) with a high solid volume fraction (SVF) above 45%. The slurries were prepared with various contents of NSF (0%, 5%, 10%, 15%, 20%, 30%). A series of tests were conducted to determine the rheological properties, compressive strength, settlement stability and uniformity. The reaction products and microstructures were characterized through XRD, SEM, micro-CT. Furthermore, the properties of pores of hardened cement stone, such as the fractal dimension of pores, were also analyzed based on micro-CT to track the influence of nano silica fume on the specimens. The results revealed that the incorporation of NSF significantly improved the compressive strength and the microstructural of LWCS. The improvement in strength resulted from the pozzolanic effect, filling effect and nucleation effect of NSF. NSF consumes portlandite to form more calcium silicate hydrate, acts as a filler to fill the empty space, provides nucleation sites for cement hydration, and finally makes the internal structure of the LWCS denser. Moreover, the water-to-cement ratio (w/c) and the SVF of LWCS both have a linear correlation with the content of NSF in LWCS.

Application of experimental and statistical methods in the study of rheology of MWCNT (25%)-TiO2 (75%)/ SAE40 HNF to identify and use in the lubrication industry

In the present study, the viscosity behavior of MWCNT (25%)-TiO2 (75%)/ SAE40 Combined nanofluid is studied in different laboratory conditions with a solid volume fraction (SVF) range of 0.0625% − 1%, a temperature range of T = 25–50 °C and a shear rate (SR) range of 666.5–7998Ss−1. The aim is to study how nanotechnology behavior works using experimental and statistical (RSM) methods. Due to the dependence of viscosity on SR and its variable slope, HNFs have a non-Newtonian pseudo-plastic behavior. Experimental findings show that in high and low SVFs, Viscosity has maximum and minimum values compared to pure fluid, which is equal to + 20.02% and − 14.58%, respectively. To predict the experimental results and present the mathematical relation, the statistical technique of response surface methodology (RSM) with a detection coefficient of 0.9980 was used.

A simple and efficient parallel immersed boundary-lattice Boltzmann method for fully resolved simulations of incompressible settling suspensions

This study presents an efficient and parallel fully resolved direct numerical simulation (FR-DNS) of settling suspensions on multiple CPU cores based on the boundary-thickening direct forcing immersed boundary method (BTDF-IBM) and incompressible lattice Boltzmann method (LBM). The simple BTDF-IBM is used to meet the no-slip and no-penetration conditions on particle boundaries, and the incompressible LBM is used to achieve the capability of large pressure fluctuations in suspensions. In addition, a theoretical force model is used to compensate for the unresolved lubrication force between the two approaching particles. A swap strategy for the streaming step is used to reduce the memory storage of the LBM particle density functions to half. A distribution and communication strategy is proposed to handle the IBM computing and complete the immersed boundary (IB) force of the particles residing in the interface region between adjacent subdomains. The developed BTDF-IBM-LBM solver “PFlows” can simulate large particle-laden flows with more than O(106) particles and with a particle volume fraction of up to 0.4. An almost linear parallel speedup and efficiency of higher than 0.8 are obtained by testing three-dimensional (3D) cases (up to 1.0 billion fluid grids and 0.45 million particles) and two-dimensional (2D) cases (up to 1.2 billion fluid grids and 2.39 million particles). Finally, the framework is applied to three large-scale real simulations involving 50,000 particles settling in 2D and 3D bounded and unbounded domains for qualitative and quantitative validations. The particle settling behaviors and disturbed complex fluid flows in the vertical channel are demonstrated. The Boycott effect in the inclined channel is uncovered by a new mechanism that combines particle sliding at the lower sidewall with fluid convection in the upper region. The hindered settling of particles in the 3D periodic domain, which is affected by the strong particle-fluid hydrodynamic interactions and particle-particle many-body interactions at a high solid volume fraction, are analyzed. The complex behaviors and statistical characteristics of the suspensions are preliminarily revealed and analyzed, which demonstrates the prospective capability of the present framework for FR-DNS of large-scale 2D and 3D suspension flows that are relevant to many industrial applications by IB-LBM.

Studying the effect of shear induced lift on the transport behavior of solid particles in an inclined channel using 2D segregation-dispersion model

In this study, a 2D segregation-dispersion model has been used to study the effect of shear induced lift on elutriation within a Reflux Classifier under continuous process conditions. The Reflux Classifier is a beneficiating technology comprising a fluidized bed with a set of parallel inclined channels above it. A 2D segregation-dispersion model of the device was utilized to study the mechanism of shear induced lift introduced as a contribution to the dispersion in the x-direction within the inclined channel. A multi-solid feed, 42 types of particle species having different densities and sizes, was simulated. It was observed that due to the shear induced lift, a phenomenon of particle resuspension occurred causing relatively higher solid volume fractions in the middle zone of the inclined channel. This happened because the coarse low-density particles experienced a higher shear induced lift and their concentration increased toward the middle zone. These coarse low-density particles and fine low-density particles moved out from the system via the overflow. Whereas, the fine dense particles experienced a low shear induced lift, hence, settled, slide backward, and discharged in the underflow. The lower Ep values ranging from 0.03 to 0.05 were obtained showing an improved separation performance.

Numerical and Experimental Study of Hydraulic Performance and Wear Characteristics of a Slurry Pump

The slurry pump is widely used in ore mining, metal smelting, petrochemical, and other industries, mainly to transport fluid media containing large solid particles. Importantly, it is easy to damage the impeller of a slurry pump in the operation process, which greatly affects the performance of the pump. In this paper, a 25 MZ slurry pump was selected as the research object, and the Euler–Euler multiphase flow model was employed to analyze the internal flow characteristics of the slurry pump under the conditions of clear water and solid–liquid two-phase flow. Additionally, the flow characteristics of each part under different flow conditions were studied, and the effects of different particle volume concentrations, particle sizes, and pump speeds on the impeller’s wear characteristics and hydraulic performance were analyzed. In order to verify the reliability and accuracy of the numerical simulation results, clean water and solid–liquid two-phase flow wear tests of the slurry pump were carried out, and the results showed that a high solid volume fraction and solid–phase slip velocity were generated at the junction of the blade leading edge and the rear cover plate, thus leading to easier wear of the blade. Therefore, enhancing the strength of the junction between the blade leading edge and the rear cover plate is beneficial for improving service life and should be considered in the design of slurry pumps.

Thermal management for conjugate heat transfer of curved solid conductive panel coupled with different cooling systems using non-Newtonian power law nanofluid applicable to photovoltaic panel systems

Thermal performance features for a coupled conjugate thermo-fluid system with different cooling configurations (flat channel (F-C), grooved channel (G-C) and impinging jets (I-J)) are explored numerically by using non-Newtonian nanofluid. The numerical work is performed for different Reynolds numbers (100≤Re≤300), index of power law (0.8≤n≤1.2), height (0.1H≤b≤0.6H) and number (2≤N≤9) of corrugation in the G-C system, number (2≤Nj≤9) and distance (5w≤sx≤25w) between jets in the I-J flow system. Different volume fractions (0≤ϕ≤0.04) and particle sizes (20nm≤dp≤80nm) of nanoparticles are used. When systems operating at the highest and lowest Re are compared, 9 K, 11 K and 8 K temperature reduction are achieved for F-C, G-C and I-J cooling systems. However, I-J flow system at higher Re is very effective on the thermal performance improvement when shear thickening fluid is used. For the G-C flow system, increasing the height and number of the corrugation waves resulted in improvement in the thermal performance. Up to 46% increment in the Nu number (average) and reduction of 6.5 K in the average surface temperature are achieved with varying the height of the corrugation while these values are 17% and 1.6 K when wave number is increased. The average Nu number rises by about 32% and temperature drops by about 6.5 K when jet number is varied from 3 to 11, while these values are obtained as 8% and 4 K for when distance between jets are varied from sx=5w to sx=25w. For F-C, G-C and I-J flow systems, average Nu rises by about 15.5% and 14.5% and 16.3% for shear thinning fluid while they become 16.6%, 9.94% and 12.8% for shear thickening fluid at the highest solid volume fraction. As the nanoparticle size is increasing, there is 6% and 7% reduction in the average Nu number. Thermal performance estimations are made with four inputs and four outputs system by using artificial neural networks.

Impacts of Particle Properties on Gas Holdup under Four Flow Regimes in Three‐Phase Bubble Columns

AbstractThe impacts of the solid volume fraction Vs and particle size dp on the total and local gas holdups in gas‐liquid‐solid bubble columns under different flow regimes were investigated. The flow regimes discussed were the discrete bubble regime (DBR), transition regime (TR), bubble coalescence regime (BCR), and strong turbulent regime (STR). The results demonstrated that the bed average gas holdup εg decreased with higher solid volume fraction in DBR, TR, and BCR. The increment of the solid volume fraction promoted bubble coalescence and also can enhance the particle effect on the average gas holdup. The εg changed slightly when shifting the Vs or dp in STR. A new correlation for εg was developed considering the particle properties and the flow regimes studied.