Convective Flow Research Articles

Nanoparticle’s Shape Effect on Mixed Convection Heat Transfer and Flow of Carbon Nanotubes: Numerical Approach

Nanoparticle’s Shape Effect on Mixed Convection Heat Transfer and Flow of Carbon Nanotubes: Numerical Approach

Free convective heat flow from cold and heated conical shape bodies in Newtonian liquids

Investigation on the simulation effects of free convection flow from a cold and heated cone with a downward pointing tip in various stagnant fluids is presented in this study. Examining the steady-state isotherm patterns around the cone to determine heat transfer characteristics. Results are presented for friction factor and Nusselt number distributions Over the surface of the cone for distinct dimensionless quantities like Pr and Gr to deliver an extensive class of dimensionless numbers. The commercial program ANSYS CFX 16.0 was used to solve the regulating equations which governs the motion vis., momentum mass and energy were computed. The temperature as well as flow fields are coupled using the Boussinesq approximation in order to simplify the governing equations and capture natural convection. Heat transmission has a rather minimal influence on the local Nusselt number for low Grashof and Prandtl values, according to the findings. It gains strength as the Grashof and Prandtl numbers grow, because of the extreme curvature of the isotherms, the maximum value of the local Nusselt number may be found around the corner of the vertical cone in both cones. The current simulations closely match the numerical values provided in the printed matter.

Unsteady magnetohydrodynamic free convection and heat transfer flow of Al2O3‒Cu/water nanofluid over a non-linear stretching sheet in a porous medium

This article investigates the impact of time-dependent magnetohydrodynamics free convection flow of a nanofluid over a non-linear stretching sheet immersed in a porous medium. The combination of water as a base fluid and two different types of nanoparticles, namely aluminum oxide (Al2O3) and copper (Cu) is taken into account. The impacts of thermal radiation, viscous dissipation and heat source/sink are examined. The governing coupled non-linear partial differential equations are reduced to ordinary differential equations using suitable similarity transformations. The solutions of the prin-cipal equations are computed in closed form by applying the MATLAB bvp4c method. The velocity and temperature pro-files, as well as the skin friction coefficient and Nusselt number, are discussed through graphs and tables for various flow parameters. The current simulations are suitable for the thermal flow processing of magnetic nanomaterials in the chemical engineering and metallurgy industries. From the results, it is noticed that the results of copper nanofluid have a better impact than those of aluminium nanofluid.

Optimizing heat transfer efficiency with injection in ventilated cavity in the presence of internal thermal effects

Venturing into unexplored territory, the study explores the dynamics of mixed convection flow within a square cavity, influenced by a ventilated channel and an injection port. By conducting numerical simulations, the impact of internal heat generation/absorption and viscous dissipation on heat transfer efficiency is thoroughly examined. Employing a finite difference method alongside an alternate direction implicit scheme and iterative successive under-relaxation (SUR) technique, the study systematically solves the governing equations. The effect of physical parameters, namely the Reynolds number ( 50 ≤ Re ≤ 500 ), Richardson number ( 0.01 ≤ Ri ≤ 10 ), volumetric internal heat generation ( △ * > 0 )/absorption ( △ * < 0 ), Eckert number ( 0 ≤ Ec ≤ 0.3 ), and especially variation of injection strength, on the streamlines, isotherms, and average Nusselt number are discussed graphically. The findings demonstrate a significant improvement in heat transfer efficiency, ranging from 17% to 73% with injection, underscoring its substantial implications for advancing thermal management across diverse engineering domains.

Mathematical and statistical modeling of glucose permeation through ultrafiltration system

Membrane bioreactors (MBRs) have been recently proposed for enhancing enzymatic hydrolysis of lignocelluloses by simultaneously and selectively removing the produced sugars from the reaction system. An inverted dead-end MBR with polyethersulfone membrane was used to investigate glucose permeation. The effects of glucose concentration, water flowrate, and membrane molecular weight cut-offs (MWCO), were investigated. The developed diffusion-convective model predicted glucose permeation with R2 value of 0.96. The statistical analysis showed that the effects of glucose concentration and water flowrate were significant, with P-value less than 0.05 for both, whereas that of the MWCO was insignificant (P-value of 0.66). This is the first attempt to mathematically describe the behavior of glucose across ultrafiltration membrane, while taking into consideration both molecular diffusion and convective flow. The findings of this work are essential for understanding the behavior and enhancing the performance of solute permeation through ultrafiltration membrane, which is the heart of many processes.

Exact solutions of hydromagnetic convective flow in a microchannel with superhydrophobic slip and temperature jump: Microfluidics applications

AbstractThe researchers explored the free convective flow of a hybrid nanofluid in a vertical microchannel with a rectangular cross‐section. Notably, both channel walls were heated alternately, and a transverse magnetic field was applied across the channel. The channel walls had unique properties, one of which was nonslip and the other was exceedingly hydrophobic. The major purpose was to investigate the effects of magnetism and superhydrophobicity on important flow parameters. The differential equations in the investigation were solved, producing accurate results. The study yielded some significant discoveries. First, when heated, the magnetic parameter reduced skin friction on both sides. Second, in both heating conditions, the magnetic field reduced flow rate and velocity. The flow rates in the two reported situations were similar at a crucial temperature jump coefficient. Furthermore, for low‐temperature jump coefficients, heating the superhydrophobic side reduced the Nusselt number whereas heating the nonslip side had no magnetic effect. The percentage change in the value of Nusselt number and velocity decreases continuously with increase in nonlinear density variation with temperature (NDT) parameter and magnetic parameter. The percentage increases in the value of skin friction with increase in temperature jump and slip length but decrease in the percentage of skin friction for the effect of magnetic term and NDT parameter. As the NDT parameter increases, the velocity percentage rises to 50.59% when the superhydrophobic surface is heated and to 84.30% when the nonslip surface is heated. The temperature jump is statistically significant for the value of the Nusselt number and skin friction for the no‐slip surface condition. These discoveries have practical consequences for the design and management of both tiny and large‐scale systems, with possible applications in microfluidics, microelectronics, nanoscience, and nanotechnology.

Direct Numerical Simulation of Mixed Convection Flow in Lid-Driven Cavities

The mixed convection of heat transfer and fluid flow in a - lid drivencubical cavity filled with air is investigated numerically in this study. The computational procedure is based on the finite volume method and a full multigrid acceleration solver. The top wall of the cavity is maintained at a constant high temperature - Th, and it can move with a constant velocity U0. The bottom wall is immobile and maintained at a cold temperature Tc. While, the remaining boundary parts of the cavity are motionless and kept thermally insulated. Several numerical simulations were conducted to investigate mixed convection heat transfer in a sliding cubical cavity for a range of Reynolds numbers from 1000 to 5000 and Richardson numbers from 0.001 to 10. The influence of mixed convection parameters, Reynolds number, Richardson number, and heat transfer rate on the flow behavior was analyzed through parametric studies. The results include flow and heat transfer characteristics, iso-surfaces, and streamlines for the entire range of Richardson numbers and Reynolds numbers investigated. The study shows that as Reynolds number is increased beyond a critical value, the flow becomes unstable and bifurcates.

Inclined surface mixed convection flow of viscous fluid with porous medium and Soret effects

Abstract The combined heat and mass transfer phenomenon is a significant aspect of engineering and industrial processes. This phenomenon finds applications in various areas such as air conditioning, cooling and heating control of electronic devices, reactors, chemical systems, and emission processes. This research model focuses on the analysis of mixed convection flow of a viscous fluid with heat and mass transfer on an inclined surface with porous medium characteristics. The study also considers external heat transfer effects, radiation, Soret influence, and chemical reactions. A perturbation solution is derived in closed form, and the impact of various parameters on the thermal behavior is investigated. A comparative analysis of the heating and cooling regimes in plate flow is conducted, revealing a reduction in velocity in the heated plate regime with changes in the permeability parameter and an increase in concentration phase due to the Soret number.

Convective transport in a nanofluid-filled annulus with an eccentric hypocycloid within a square disk

Considering varying cusp numbers, we investigate the time-dependent, incompressible natural convective flow of an iron oxide-water nanofluid within an annulus formed between a square and a concentric hypocycloid. The vertical walls of the annulus are treated as relatively colder walls, while the bottom wall of the square disk and the inner hypocycloid wall act as heat sources. The outer upper wall of the square is considered adiabatic. We transform the dimensional, nonlinear, and strongly coupled fundamental equations of nanofluids in Cartesian coordinates into non-dimensional equations. We utilize the Galerkin finite element method to solve the governing equations. This study comprehensively explores the flow and heat transfer of nanofluids, considering the essential parameters relevant to the problem. The results highlight a remarkable observation, as the ferric oxide-water nanofluid exhibits significantly enhanced heat transfer compared to the conventional fluid. The precise positioning of the hypocycloid in the cusp configuration represents a critical phenomenon that substantially improves the flow and heat transfer rates of the nanofluid. The three cusped hypocycloids positioned on the inner wall of the annulus perpendicular to the horizontal axis result in a nanofluid flow configuration and heat transfer that surpasses other configurations and cusp numbers studied in the analysis. Notably, heat transfer exhibits a discernible increase with an increase in the nanoparticle volume fraction (maximum 3vol%), while it declines with an increase in the nanoparticle diameter. The intricate relationship between the nanoparticle diameter, volume fraction, cusp number, and hypocycloid configuration substantially influences the friction factor and particle-surface interactions. As the number of cusps on the inner surface increases, the velocity magnitude, Nusselt number, and concentration profiles near the boundary layer decrease, while the fluctuations of the middle annulus indicate the combined influence of nanoparticle dispersion and the formation of the annulus boundary layer due to the orientation of hypocycloidal cusps. Furthermore, an increase in the particle diameter and the sharpness of the corners of the hypocycloid lead to a proportional increase in the nanofluid flow resistance within the annulus.

Examination of convective heat transfer and entropy generation performance in twisted elliptical tubes using response surface method

In this paper, the convective heat transfer (CHT) and flow properties of twisted elliptical tubes (TETs) are numerically simulated within the range of Reynolds numbers (Re) 710 to 4790. The effects of design parameters such as twist ratio (P/D), aspect ratio (A/B), and Re on the CHT and flow resistance properties of TETs are highlighted. The response surface method (RSM) is used to research the effect of interaction between design parameters on the performance of CHT in TETs and establish the relationship between the objective function, i.e., Nusselt number (Nu), friction factor (f), and design parameters. The objective function fitted by RSM are optimized by the non-dominated sequential genetic algorithm (NSGA-II) to obtain the Pareto optimal solution. Besides, the entropy generation minimization principle explores entropy generation characteristics to reveal the mechanism of CHT enhancement in TETs. The results show that the CHT performance, flow resistance, and total entropy generation in TET increase, decrease, and increase with the growth of Re, respectively. They all increase with the reduction of P/D or the growth of A/B. The maximum values of Nu and pressure drop (ΔP) occur when A/B = 2.16 and P/D = 11.90; the minimum value of total entropy generation is reached when A/B = 1.34 and P/D = 26.33; and the Pareto optimal solution corresponds to the best combination of design parameters of Re = 3980, P/D = 13.32, and A/B = 1.82.

Comparative analysis of condensation heat transfer and pressure drop of low GWP near-Azeotropic mixture and R-290 in a plate heat exchanger

Downward condensation of a near-azeotropic low GWP refrigerant mixture of R290/R1270 (65%/35% wt.), named HC01, was investigated inside an offset strip-fin (OSF) flow-structured plate heat exchanger (PHE). This study tested the prototype heat exchanger with HC01 and compared the condensation heat transfer coefficient (CHTC) and pressure drop (CPD) with the pure R-290 for working conditions of refrigerant mass flux (G) = 20–50 kg/m2s, inlet vapor quality (xin) = 0.2–0.9, saturation temperature (Tsat) = 40–55 °C, and heat flux (q) = 4–13 kW/m2. It was observed that the condensation of HC01 occurred entirely within the forced convection condensation flow regime, despite a slight change in the CHTC at a lower xin as the G increased. The CHTC demonstrated an increase in response to higher values of G and q, but decreased with increasing Tsat. Similarly, the CPD exhibited an increase with higher G and a decrease with lower Tsat, whereas the q had minimal influence. Comparison results showed that the HC01 exhibited 14.2% higher average CHTC but 6.5% lower CPD than that of R-290 because of the differences in properties, such as liquid thermal conductivity, viscosity, surface tension, latent heat, and discrepancies in liquid and vapor phase densities. Correlations were generated to predict the values of the Nusselt number (Nu) and friction factor (FF) of HC01, with mean absolute errors of 12.1% and 12.7%, respectively.

A numerical study of MHD nonlinear mixed convection flow over a nonlinear vertical stretching sheet with the buoyancy and suction/injection effects

The current research has a primary focus on characterizing buoyancy-driven nonlinear mixed convection. This phenomenon is studied within the context of an MHD Newtonian flow over a vertically stretching sheet with nonlinear characteristics. Flow patterns resembling those studied in this context have practical applications in various industrial sectors. Such flow patterns have practical applications in several industrial sectors, including the article and pulp industry, polymer manufacturing, electronic device cooling, solar energy collection, gas turbine plants, and nuclear power generation. The governing partial differential equations (PDEs) for nonlinear mixed convection are transformed into higher-order nonlinear ordinary differential equations (ODEs) through appropriate transformations, and these transformed ODEs are subsequently solved numerically. The software MATHEMATICA is used to solve the boundary layer flow equations, employing the semi-analytical Galerkin weighted residual method (GWRM). This approach yielded simultaneous solutions for both cases suction and injection. For both the suction and injection situations, graphical results, such as velocity, concentration, and temperature profiles are included. An augmentation in the nonlinear stretching parameter results in a reduction in velocity near the surface of the sheet. Conversely, away from the sheet, velocity increases. Moreover, an increase in nonlinear stretching parameters corresponds to higher values for both temperature and concentration. An increase in the suction/injection parameter causes a decrease in the velocity, temperature, and concentration fields. In the scenario of assisting flow, an increase in the thermal buoyancy parameter leads to higher velocity but lower temperature. Conversely, in the case of opposing flow, an increase in the thermal buoyancy parameter results in higher values for both velocity and temperature. Furthermore, a numerical examination is conducted to analyze the values of skin friction, Sherwood number, and Nusselt number.

Philippine Sea plate and surrounding magmatism reveal the Antarctic-Zealandia, Pacific, and Indian mantle domain boundaries

Delineation of geochemically distinct domains in Earth’s mantle is essential for understanding large-scale mantle convective flow and dynamics. Previous studies identify possible long-lived (>60 million-year) mantle isotopic domains (i.e. Antarctic-Zealandia, Pacific and Indian) near the Philippine Sea and western Pacific. Here we compile published basalt geochemistry of the Philippine Sea and surroundings and add new Mo isotopic and water content data for Gagua Ridge lavas, northwestern Philippine Sea, to distinguish slab-derived components during subduction. The water content, trace element, and Mo-Sr-Nd isotope compositions of Gagua Ridge arc lavas suggest that slab fluids and sediment melts are responsible for element recycling to the arc. The Philippine Sea basalts show both Indian and Zealandia-Antarctic Pb isotopic signatures; restoration of the basalt locations within a plate reconstruction shows the far-travelled Philippine Sea traversed these mantle domains. We establish the Indian mantle domain eastern boundary at ~120°E under SE Asia and the Indian Ocean. The Antarctic-Zealandia mantle domain lies south of ~10°N within the SW Pacific and has mostly remained in oceanic realms since ~400 Ma with only limited continental material input.

Continuous flow membrane microextraction as a clean method for detecting codeine and papaverine in biological samples using HPLC-UV

In this study, continuous-flow membrane microextraction (CFMME) was connected online with a high-performance liquid chromatography-UV detector (HPLC-UV) for the pre-concentration and high clean-up of papaverine and codeine in biological samples. The extraction cell was designed with donor and acceptor chambers separated by a sheet membrane. By adjusting the pH of the donor phase (10 mL, pH 11), the analyte molecules were extracted into the supported liquid membrane (SLM) (15 μL of 1-octanol). The donor solution was circulated through the donor chamber using a peristaltic pump and magnetically agitated by a bar stirrer placed near the membrane, enhancing the diffusion and convection flow of the targeted drugs from the donor solution to the SLM. Subsequently, by adjusting the acceptor solution to an acidic pH of 2 (100 μL), the drugs in ionic form were reversely extracted into the acceptor phase. The procedure exhibited desirable relative standard deviation (RSD%) of less than 3.70%, linear ranges of 7-600 ng mL-1 for codeine and 2.0-600 ng mL-1 for papaverine, and limits of detection of 2.0 ng mL-1 for codeine and 0.6 ng mL-1 for papaverine. The design of the extraction cell significantly improved the performance for determining targeted drugs in complex matrices such as plasma and urine.

Double diffusive mixed convective flow over a wedge and cone in the presence of Brownian diffusion and thermophoresis parameter

The present article examines the double diffusion mixed convective nanofluid flow over a wedge and cone in which slip effects as Brownian motion and the thermophoretic parameter are considered. Mixed convective flow over wedges and cones is applied in different technical fields such as fiber technology, nuclear cooling systems, surface treatment, spray deposition techniques, and polymer production. Double diffusion is increasingly significant in scientific fields like astronomy, geosciences, oceanography, and chemical processes. Mixed convection occurs in several applications such as electric devices, solar panels, nuclear power plants, heat exchangers, radiators, and atmospheric boundary layer fluxes. The governing equations of the study are highly coupled nonlinear partial differential equations with surface constraints. The process of similarity transformation used to converts partial differential equations into nondimensional ordinary differential equations, which can be resolved using the MATLAB Bvp5c function. The graphical representation and detailed analysis of variations in velocity, temperature, and concentration distributions of nanofluids are presented. As the mixed convection parameter increases, the fluid’s velocity rises, with a more pronounced effect observed in the cone compared to the wedge. As the Brownian diffusion parameter grows, the fluid temperature increases, and velocity is more pronounced in the wedge scenario compared to the cone. Moreover, an increase in the thermophoresis parameter results in an elevation in the fluid’s temperature. Additionally, the wedge has a higher concentration of fluid and nanoparticles compared to the wedge. Fluid concentration falls with increasing Schmidt number, but fluid nanoparticle concentration decreases with increasing Lewis number.

Numerical investigation on mixed convection for laminar molten salt in horizontal square tubes

Molten salts are the key working media in nuclear and new energy fields. However, the mixed convection of molten salt is rarely investigated. The mixed convection of laminar flow in horizontal square tubes with constant heat flux is analyzed using Fluent software for the first time. The effects of heat flux, inlet temperature and Reynolds number on the flow and heat transfer performances are evaluated. It is found that as the buoyancy force increases, the friction factor, flow entropy generation rate, Nusselt number, and exergy efficiency increase, while the heat transfer entropy generation rate and exergy loss decrease. Compared to the forced convection, the maximum local friction factor, flow entropy generation rate, mean Nusselt number and mean exergy efficiency for mixed convection increase by 25.8%, 50.5%, 109.0% and 7.6%, respectively. Moreover, the maximum mean heat transfer entropy generation rate and exergy loss decrease by 56.1% and 57.3%, respectively. In addition, approximately 42% of the friction factor predicted by Fluent and 30% of the heat transfer predicted by Fluent exceed 20.0% uncertainties of conventional correlations. Therefore, an accurate friction factor correlation with 12.9% uncertainty and an accurate heat transfer correlation with 9.1% uncertainty are proposed.

Analysis of mixed convective thermal slip flow with nanofluid mixtures over a curved surface

Analysis of mixed convective thermal slip flow with nanofluid mixtures over a curved surface

Impact of chemical reaction on hybrid nanofluid (GO + MoS2) flow over an exponentially stretching sheet with Soret and Dufour effects

AbstractThe Soret and Dufour effects play a crucial role in various fields such as geosciences, groundwater pollutant migration, chemical reactor operations, binary alloy solidification, and isotope separation. This study focuses on examining the impact of mixed convective flow on hybrid nanofluid through an exponentially stretching sheet with Soret and Dufour effects. The flow is affected by factors like variable viscosity, radiation, viscous dissipation, and activation energy. Instead of the no‐slip condition at the boundary, velocity slip, thermal slip, and concentration slip are considered. The physical problem is modeled using boundary layer theory, and flow patterns are expressed using partial differential equations (PDEs). These governing fluid flow equations are transformed into non‐linearly coupled ordinary differential equations (ODEs) using exponential similarity transformations. These simplified ODEs are resolved using the MATLAB bvp4c package. The effects of physical parameters on velocity, temperature, and concentration are illustrated through figures. Additionally, the drag force coefficient and heat and mass transfer rates are calculated for various parameters and presented graphically and in tabular form. It is observed that compared to nanofluids, the drag force coefficient of hybrid nanofluids increases by up to 21.05% with various solute buoyancy parameters (δ). Also, the mass transfer rate of hybrid nanofluids can be increased by .96% by the chemical reaction rate (σm). A comparison of this work with previously published research has been reported.

Radiation absorption effect on MHD natural convective flow past an impulsively started infinite vertical plate with chemical reaction and thermal radiation

AbstractThe current work is interested on investigating the impacts of thermal radiation, chemical reaction, and absorption radiation of a hydromagnetic convection‐free mass and heat transfer flow in case of an electrically conducting fluid that passes through a vertical plate moving impulsively. The analytical solutions of the governing momentum, energy, and species concentration equations with the initial and boundary conditions are obtained by the Laplace transformation technique. Graphs for fluid characteristics are used to analyze the impact of changing parametric quantities such as M, N, Sc, Kc, Q, Gr, Gm, and t on the temperature, velocity, concentration, and Sherwood number. We derive the engineering curiosity expressions for the Nusselt number and stress, and at the end, we tabulate and discuss the consequences of new parameters. The magnetic field effect and the chemical reaction are seen to diminish the fluid velocity and concentration, respectively, but in contrast, the absorption radiation effect is seen to accelerate both velocity and temperature. It is closely studied that the Nusselt number and skin friction values for hydrogen consistently exceed those for carbon monoxide.

Frustrated-Laser-Induced Thermal Starting Plumes in Fresh and Salt Water

The results of a photothermal spectroscopy technique that effectively images convective and conductive heat flow in liquids via a thermal lensing effect are described. Pure water; sodium chloride solutions at salinities of approximately 5, 15, 25, and 35 g/kg; and an artificial seawater of 35 g/kg were studied across a range of temperatures. This system was studied because of the importance of thermal pluming in seawater. ‘Frustrated’ thermal starting plumes were observed near the temperature of maximum density. The physical characteristics of these thermal starting plumes are reported.