Convective Heat Transfer Flow Research Articles

Mixed convection Casson polymeric flow from a nonlinear stretching surface with radiative flux and non‐Fourier thermal relaxation effects: Computation with CSNIS

AbstractThermal non‐Newtonian polymer coating flows is growing as a major area in materials processing. Inspired by new developments in this field which require more sophisticated mathematical models, the current investigation examines the laminar viscoplastic boundary layer flow and mixed convective heat transfer over a power‐law nonlinear stretching surface. To simulate thermal relaxation effects the hyperbolic Cattaneo‐Christov heat flux model is deployed. The non‐Newtonian polymer characteristics are described by employing the Casson flow model. High temperature conditions invoke thermal radiation flux which is analyzed with an algebraic flux model. Via robust similarity transformations, the primitive partial differential conservation equations for momentum and energy equations are rendered into a system of coupled non‐linear ordinary differential equations with associated wall and free stream boundary conditions. The emerging boundary value problem is solved numerically with an efficient Chebyshev Spectral Newton Iterative scheme (CSNIS), in the MATLAB platform. The resulting solutions are discussed for different emerging parameters using graphs and tables. Validation is included with special cases from the literature. With increasing power law stretching index increases, the flow is decelerated, and temperatures are reduced. Increment in mixed convection parameter boosts the velocity but suppresses temperature and thermal boundary layer thickness. Increasing non‐Fourier Deborah number, temperatures are depleted whereas with increasing radiative flux parameter they are increased. With elevation in Casson non‐Newtonian parameter, velocity is decreased whereas temperature is enhanced and Nusselt number is suppressed.

Three-Dimensional Unsteady Mixed Convection Flow of Non-Newtonian Nanofluid with Consideration of Retardation Time Effects

The advances in nanotechnology led to the development of new kinds of engineered fluids called nanofluids. Nanofluids have several industrial and engineering applications, such as solar energy systems, heat conduction processes, nuclear systems, chemical processes, etc. The motivation of the present work is to analyze and explore the thermal and dynamic behaviors of a non-Newtonian fluid flow under time retardation effects. The flow is unsteady and caused by a bidirectional, periodically moving surface. In addition to the convective heat transfer and fluid flow, the radiation and chemical reactions have also been considered. The governing equations are established based on the modified Cattaneo–Christov heat flux formulation. It was found that the bidirectional velocities oscillate periodically, and that the magnitude of the oscillation increases with the retardation time. Higher temperatures occur when the porosity parameter is increased, and lower concentrations are encountered for higher values of the concentration relaxation parameter. The current results can be applied in thermal systems, heat transfer enhancement, chemical synthesis, solar systems, power generation, medical applications, the automotive industry, process industries, refrigeration, etc.

Activation Energy Impacts on Hydromagnetic Convective Heat Transfer Flow of Nanofluid Past a Surface of Vertical Wavy with Variable Properties

Activation Energy Impacts on Hydromagnetic Convective Heat Transfer Flow of Nanofluid Past a Surface of Vertical Wavy with Variable Properties

Experimental and numerical study of convective heat transfer in-line tube bundle by acoustic action

This paper proposes the acoustic properties acting on the in-line tube bundles heat exchanger and an analysis of the tube bundle gap flow characteristics and convective heat transfer. In contrast to the reported literature, the present study adds the effect of audible sound on the tube array gap flow, in which the Reynolds number for free flow is Re = 2000, sound frequency is f = 100–1000 Hz, and sound pressure level range is SPL = 127–145 dB. In this paper, a numerical calculated turbulence intensity and Reynolds shear stress of the fluid in the tube bundles gap for acoustic frequency and sound pressure level. Moreover, experiments revealed the effect of acoustic properties on convective heat transfer on the surface of the tube bundles. The results show that the average Nussle number increases by almost 1.8 when the acoustic frequency f = 100 Hz is added, and the sound pressure level reaches 145 dB, compared to no acoustic perturbation. The average Nussle number increases by almost 2.1 when the sound pressure level reaches 145 dB with frequency modulation of f = 1000 Hz. Since the relative error is less than 15% between experimental and numerical calculations, acoustic waves are able to enhance convective heat transfer through the tube array. At the same time, the present study serves as a reference for engineering applications.

Effect of thermal radiation on nonDarcy hydromagnetic convective heat and mass transfer flow of a water–SWCNT’s and MWCNT’s nanofluids in a cylindrical annulus with thermo-diffusion and chemical reaction

The examined through analysis of the movement of water-based single wall carbon nanotube (SWCNT) and multiwall carbon nanotube (MWCNT) nanofluids in a coordinate annulated zone under influence of non-uniform heat source/sink. By imposing the appropriate nondimensional variables, the governing partial differential equations are converted into a system of coupled nondimensional partial differential equations. By means of the usage of quadratic polynomials and the Galerkin finite element detail approach, the nonlinear equations have been executed. The expressions representing fluid velocity, temperature and concentration are discussed graphically. While skin friction, heat transfer and mass transfer are revealed in tabular structure. The proposed scheme is shown to have faster convergence than the existing scheme with excellent accuracy. Various parametric values have been analyzed and observed that higher temperatures and concentrations are produced with lower velocities with and bigger velocities with higher radiative heat flux or nanoparticle volume fraction.

Effect of Hall Currents on Transient Convective Heat and Mass Transfer Flow of a Viscous Fluid in a Vertical Wavy Channel with Tranveling Thermal Waves

Effect of Hall Currents on Transient Convective Heat and Mass Transfer Flow of a Viscous Fluid in a Vertical Wavy Channel with Tranveling Thermal Waves

Flame Dynamics in the Combustion Chamber of Hybrid Rocket Using Multiangle Chemiluminescence

The flame dynamics in the combustion chamber of a hybrid rocket motor were visualized using novel chemiluminescence imaging. A multidirectional visualization system employing endoscopes generated images based on methylidyne chemiluminescence (CH*), with one endoscope in the precombustion chamber and two in the postcombustion chamber. Images were collected with a high-speed camera using a 1 ms exposure and a 1 kHz frame rate. Fuel grains having a helical or a conventional circular port structures were assessed, and combustion trials were conducted using a laboratory-scale hybrid rocket motor with oxygen as the oxidizer at mass flow rates from 10.43 to : equivalent to combustion chamber pressures ranging from 0.7 to 1.24 MPa. Flame structures were observed during the ignition, combustion, and shutdown stages; and the helical grain generated a larger, more intense flame zone. A proper orthogonal decomposition analysis showed that the helical grains also produced a greater degree of turbulence and stronger oscillations. These results confirm that a helical structure increases the flow turbulence and convective heat transfer in the combustion chamber. These effects lead to higher regression rates and better mixing efficiency that may, in turn, provide greater combustion efficiency at optimized oxidizer/fuel ratios.

Impact of porosity and radiation on two‐dimensional unsteady magnetohydrodynamics heat transfer stagnation point flow with viscous dissipation

AbstractThe current study aims to investigate the influence of porosity in the presence of radiation, and viscous dissipation on two‐dimensional unsteady magnetohydrodynamics mixed convection heat and mass transfer flow at the stagnation point. The governing time‐dependent nonlinear partial differential equations are converted into a nonlinear ordinary differential equation by utilizing similarity transformations. The transformed equations are solved by employing the bvp4c technique, a well‐known numerical approach. The influence of nondimensional factors on fluid velocity, temperature, and species concentration profiles is explored and graphically represented. For varied values of the Prandtl number, magnetic field, and Schmidt number, the friction factor, Nusselt, and Sherwood numbers are also explored and provided in tabular format. As increasing the porosity parameter, the temperature profile, concentration profile is growing, and velocity profile diminishes. The conclusions of this study are widely accepted by the scientific community.

A numerical study on boundary layer flow of Carreau fluid and forced convection heat transfer with viscous dissipation and generalized thermal conductivity

Forced convective heat transfer and boundary layer flow of non-Newtonian fluid over a moving wedge is numerically studied. The non-Newtonian fluid is represented by Carreau fluid which is inelastic and characterizes shear-thinning and shear-thickening fluid. The thermal conductivity of fluid is no longer constant during heat transfer but is a function of temperature. The motion of the wedge surface is considered in the direction of mainstream or opposite. Both wedge and mainstream flows are assumed as a power of distance from the origin. Upon using similarity transformations, resultant equations are analyzed numerically using Chebyshev collocation and shooting methods for simulations of solutions. Most of the general features of solutions are identical to Newtonian fluid, the effects of Carreau fluid are to increase the velocity and heat transfer rate, and decrease the thicknesses. The present results of Carreau fluid and heat transfer unveil single and double solutions for the same system parameters and are shown to be a continuation of the Newtonian fluid. Also, the non-uniqueness of the solutions for the same set of parameters is classified as first and second solutions. Thus, there is a critical point beyond which no solution exists to model. In order to identify which of these solutions can be simulated practically, we perform linear stability analysis on velocity and temperature solutions. The eigenvalue analysis shows that the first solutions are always stable and the second solutions are amplified in time. Other interesting flows and heat transfer features are discussed in detail.

Diffusion Thermo and Chemical Reaction Effects on Magnetohydrodynamic Jeffrey Nanofluid Over an Inclined Vertical Plate in the Presence of Radiation Absorption and Constant Heat Source

This article investigates the Diffusion thermo and chemical reaction effects on the free convection heat and mass transfer flow of Jeffrey nanofluids (Cu and TiO2) over an inclined porous vertical plate embedded in a porous medium in the presence of radiation absorption and constant heat source under fluctuating boundary conditions. The plate is moved with a constant velocity U0, temperature and the concentration are assumed to be fluctuating with time harmonically from a constant mean at the plate. Perturbation technique is applied to solve the governing equations of the flow and pointed out the variations in velocity, temperature and concentration with the use of graphical presentations. The impact of several parameters on local skin friction, Nusselt number and Sherwood number is also noticed and discussed. It is concluded that the resultant velocity reduces with increasing Jeffrey parameter and Suction parameter, velocity and Temperature enhances with increasing Radiation absorption parameter. Also it is noticed that the solutal boundary layer thickness decreases with an increase in chemical reaction parameter. It is because chemical molecular diffusivity reduces for higher values of Kr.

Convective heat transfer and MHD flow through semi-porous cylindrical filters embedded in an impermeable region

• Magnetic field dominate the flow field and suppresses the flow rate. • Maximize the effect of Hartmann number leads to rise in temperature distribution for the flow. • Heat transfer in the flow is enhanced as the Darcy number increased. • A negative pressure gradient influences the flow immensely. In the present study, profound applications of agriculture, industries and engineering have motivated to report an exact solution for steady incompressible axisymmetric electrically conducting fluid flow through a semi-porous media surrounded by an impervious cylinder. The uniqueness of this paper is to propose the effect of Joule heating by incorporating convection terms which allows to improve the flow model. Further, the non-dimensional parameters applied on equations governing the flow, takes the form of non-linear differential equations. A Differential Transform Method (DTM) is employed directly to the non-linear differential equations. A succinct solution for velocity and temperature is obtained and its variation on the fluid flow is observed for different dimensionless parameters. This is an interesting phenomenon graphically revealed by Skin-friction and Nusselt number. A good agreement is found in the current paper with certain added features by making the equations compatible and well matched with the previous work of research investigators.

Impacts of Maxwell-Cattaneo effects on the convective heat transfer flow inside a square enclosure filled with a porous medium

Impacts of Maxwell-Cattaneo effects on the convective heat transfer flow inside a square enclosure filled with a porous medium

Mixed convection heat transfer and transient flow of high-pressure gas in a large-scale cavity with rotating blade

Mixed convection heat transfer phenomenon, incorporating natural and forced convection process, occurs widely in natural and industrial fields. Nevertheless, few works have investigated numerically the turbulent mixed convection heat transfer within the large-scale structure under high-pressure condition. In this study, a three-dimensional numerical model of a large-scale closed cavity with two rotating blades and reactor has been built on account of the finite volume method, aiming to explore the mixed convection heat transfer and turbulent flow of internal high-pressure gas. Compressible gas with varying thermophysical properties was chosen as the heat transfer medium and the numerical model was solved by Unsteady Reynolds-Averaged Navier-Stokes (URANS). Turbulent flow and heat transfer, inside the enclosure and reactor, were compared through the variation of the Reynolds number (Re), gas pressure (P) and heating surface temperature (Th). The results signify that for given P and Th, varying Re has a consistent impact on the transient flow and heat transfer process inside the enclosure and reactor. The turbulent flow and thermal transport are enhanced as increasing the Re. When the Re = 900,000, an enhanced forced convection effect is found inside the reactor. Dissimilar impacts on the flow field and thermal transport inside the enclosure and reactor are found with changing gas pressure owing to the interaction of natural and forced convection. The flow field attenuates gradually as the increment in P, and thereby larger high-temperature zone is achieved at a smaller pressure inside the enclosure, whilst inside the reactor, faster heat conduction is attained at a bigger pressure. Changing heating surface temperature has a more significant influence on the flow field and heat transfer inside the reactor compared to the enclosure. Additionally, increasing the Re and Th has a smaller effect on the average Nusselt number (Nuavg) while a positive correlation between the Nuavg and P is obtained.

Numerical investigation, environmental consideration, and the use of machine learning in optimizing the dimensions of a rectangular blade between two blades in the presence of a magnetic field (Two-phase method)

Human life is being impacted by nanotechnology in many ways, including economics, production, and the environment. The present study has numerically investigated the laminar flow and natural convection heat transfer (NACHT) in a square enclosure filled with nanofluids (NFs), considering the entropy generation (ETG) and Be. The 2D enclosure includes two rectangular fins attached to the left hot wall and a single fin of very high temperature positioned in the middle of the enclosure. A constant magnetic field (MCF) has been applied to the enclosure. The average Nu, maximum value of stream function (MXSF), generated entropy, and Be have been examined by changing the length and thickness of the middle fin and the distance between heated fins (fin spacing). Finally, these parameters have been optimized through machine learning methods to determine the best case with the highest HT rate and lowest ETG rate. A two-phase model based on control volume has been used for NFs flow simulation. Results indicated that increasing fin length (w) increases Be and decreases the MXSF. Also, by increasing the w, the Nu and generated entropy initially decrease and then increase. Increasing the fin thickness (b) and fin spacing lead to a decrease in the MXSF. Increasing thickness for the fin increases the Nu but decreases it for larger fin spacing.Furthermore, the studied model is less harmful to the environment than existing models.

Physically plausible and conservative solutions to Navier–Stokes equations using physics-informed CNNs

The physics-informed neural network (PINN) is an emerging approach for efficiently solving partial differential equations (PDEs) using neural networks. The physics-informed convolutional neural network (PICNN), a variant of PINN enhanced by convolutional neural networks (CNNs), has achieved better results on a series of PDEs since the parameter-sharing property of CNNs is effective in learning spatial dependencies. However, applying existing PICNN-based methods to solve Navier–Stokes equations can generate oscillating predictions, which are inconsistent with the laws of physics and the conservation properties. To address this issue, we propose a novel method that combines PICNN with the finite volume method to obtain physically plausible and conservative solutions to Navier–Stokes equations. We derive the second-order upwind difference scheme of Navier–Stokes equations using the finite volume method. Then we use the derived scheme to calculate the partial derivatives and construct the physics-informed loss function. The proposed method is assessed by experiments on steady-state Navier–Stokes equations under different scenarios, including convective heat transfer and lid-driven cavity flow. The experimental results demonstrate that our method can effectively improve the plausibility and accuracy of the predicted solutions from PICNN.

Effect of interior venetian blinds on natural convective heat exchange at a full-scale window glazing

• The setting of the louver enhances the convection heat transfer from the window. • The space of the louver from the window has a great influence on the heat transfer. • Differences in louver angles result in up to 45% difference in heat transfer. • Differences in flow types will result in a deviation of 70% in the heat transfer. • Correlations are proposed for the convective heat transfer from the louvered surface. The indoor venetian blinds are commonly used to block the solar radiation, which will also have an impact on the convective heat transfer from windows. The existing research on this phenomenon is almost based on reduced-scale experiments or simulations, which do not reflect the natural convection of actual windows. In this work, the natural convection near a full-scale window when louver close to the window ( n ≤ 10 mm) is firstly investigated by CFD simulation. Research indicates that the convective heat transfer from the full-scale window will be enhanced when the louver is closer to the window. The cause for the increased heat transfer is not only related to the thermal bridge effect of the aluminum louvers, but also to the type of flow near the window. Three different flow types will be generated along the window surface with venetian blinds during our simulation, which are named as Duct-directed flow (DDF), Transition flow (TF) and Louver-directed flow (LDF). The difference between the flow types will result in a discrepancy of approximately 70% in the convective heat transfer from the window. In addition, the influence of the slat angle φ , space from slats to window n and temperature difference between air and window Δ T on flow development and convective heat transfer has been investigated in this study. The correlation obtained from this work allows to accurately calculate the convective heat transfer from the full-scale window covered with venetian blinds, and the average error of the correlation is within 8.2%.

Numerical Analysis of Lid Driven Convective Heat Transfer and Fluid Flow around a Tilted Elliptical Cylinder

A study of the heat transport and fluid flow behaviour around a tilted elliptical cylinder that is located concentrically in a square enclosure whose top horizontal wall is driven by a lid in the positive x-direction is presented. Due to the disparities in the results of convective heat transfer in square cavities in the literature, this study seeks to investigate the combined effects of the Grashof number, Aspect ratio of the geometry, and Elliptical cylinder inclination angle on the dynamics of thermal and flow fields within the geometry investigated. COMSOL Multiphysics 5.5 version was used to resolve the non-dimensional transport equations, while simulations were performed to examine the implications of salient parameters such as the elliptical inclination angle , Grashof number and aspect ratio . The simulation outcomes are displayed as average Nusselt numbers, velocity streamlines, and isothermal contours. Findings from this study show that an increase in aspect ratio resulted in increased heat transfer at the elliptical cylinder wall, with the highest rate of heat transfer occurring when .0. Furthermore, the inclination angle increments when Gr= and led to a reduction in the average Nusselt number of the elliptical cylinder wall. At and AR ranges of , the value of the elliptical cylinder wall increased as the ellipse's inclination angle increased. The findings of this study have found use in heat transfer systems, particularly electronic cooling and nuclear technologies.

Effect of sound excitation on the flow field and convection heat transfer around a cylinder

The combination of experiment and numerical simulation, sound frequency and sound pressure level on the flow field, and heat transfer around a cylinder with two flow patterns are investigated. Flow patterns are periodic laminar flow (L3, Re0 = 100) and wake transition (TrW2, Re0 = 300), respectively. Sound frequency range f = 100–1000 Hz, and sound pressure level range SPL = 127–145 dB. Based on the influence of acoustic characteristics on the viscous boundary layer and thermal boundary layer of cylindrical wall, constructed a functional relationship between convection heat transfer and sound wave frequency and sound pressure level. Influenced by the acoustic action, the flow field force around the cylinder, the vortex street structure, the vortex size, and the length of the wake area may be changed. Acoustic action flow field excitation fluid particle velocity amplitude increased. As the sound pressure level increased, the amplitude of the fluid mass vibration velocity increased. From the experimental results, it can be seen that for the acoustic frequency effect, the heat transfer coefficient increases with increasing sound frequency. For the particle velocity amplitude effect, as the acoustic Reynolds number increases, the heat transfer coefficient increases and is 2.3 times higher than that without acoustic disturbance in the wake turning flow regime. In comparison with numerical and experimental results, the error is less than 15%, which meets the actual requirements of the project. It has been shown that sound waves can enhance the convective heat transfer around a cylinder in the cross-flow.

Pore-scale analysis of two-phase nanofluid flow and heat transfer in open-cell metal foams considering Brownian motion

Simultaneous use of porous media and nanofluids will increase the convective heat transfer multiple times compared to non-porous and pure fluid conditions. Heat transfer and flow transport of nanofluids inside porous media are usually simulated in large-scale with average properties, which are typically highly uncertain. Pore-scale simulation as an alternative approach can capture the characteristics of flow and heat transfer more accurately. Only few studies have been conducted to study nanofluid flow through porous media in pore-scale, and most of them employed single-phase approach without focus on different affective forces. This paper uses a pore-scale approach to investigate the flow characteristics and convective heat transfer of two-phase nanofluid flow in open-cell metal foams (OCMFs). Simulation of fluid flow and heat transfer is achieved by Buongiorno’s model. Therefore, a computational code through the OpenFOAM library that operates by a direct numerical simulation (DNS) approach and the finite volume method (FVM) is used. The momentum, energy, continuity, and nanoparticle distribution equations are discretized, and the SIMPLE algorithm is utilized for pressure and velocity coupling. In the present study, three OCMFs with a constant porosity (0.86) and various pore densities are investigated. Also, variations of pressure gradient, Nusselt number, and Darcy velocity are investigated as a function of pore density (as a geometric parameter), nanoparticle diameter, concentration, and Brownian motion force. The results indicate that the Brownian force enhances the heat transfer in OCMFs from 2% by up to 14% for the nanofluid flowing with 3% nanoparticle concentration. Also, increasing the diameter of nanoparticles reduces the Darcy velocity and heat transfer by up to 4%. On the other hand, increasing particle concentration from 3% to 5%, increases heat transfer by up to 10% and reduces the Darcy velocity by up to 9%. Finally, doubling the pore density demonstrates the complex behavior of the flow patterns, in which the heat transfer increases by up to 30% and permeability and velocity are reduced by up to 70%.

MHD natural convection heat and mass transfer flow over an inclined porous plate with thermophoresis and nonlinear thermal radiation effects

AbstractThis study examined magnetohydrodynamic natural convection mass and heat transfer flow of an electrically conducting and viscous incompressible fluid over an inclined porous plate with thermophoresis, suction/injection, and uniform magnetic field. The mathematical model governing the fluid behavior surrounding an inclined plate is solved through the Runge–Kutta–Fehlberg fourth–fifth order after utilizing the shooting method. The implication of active dimensionless parameters in the governing equations is fully discussed in detail. The results obtained show that, in the existence of nonlinear thermal radiation and suction/injection, the heat transfer rises with the increase in the angle of inclination but it decreases with the mass transfer and plate shear stress. Furthermore, the heat transfer rate experiences a serious setback due to the increase in the buoyancy force but improves the plate shear stress. The mass transfer is directly proportional to the thermophoresis effect. In addition, Particle suction increases the velocity and temperature curves while it declines the concentration profile, but the opposite is valid for injection. Nonlinear thermal radiation positively affects the temperature, velocity, and concentration profiles. The Lorentz force suppresses the fluid transport and retard the rate of particle concentration, but promotes the fluid temperature distribution. It is also deduced that increasing the rate of particle suction from 0 to 1, accounts for over 76% increase in the particle deposition at the plate surface. However, increasing the rate of particle injection from 0.004 to 0.250 accounts for an over 83% decrease in the particle deposition at the plate surface.