Magnitude Of Nusselt Number Research Articles

MHD nanofluid flow through Darcy medium with thermal radiation and heat source

In this analysis, we have considered heat transmission in two-dimensional steady laminar nanofluid flow past a wedge. Magnetohydrodynamic (MHD), Brownian motion, viscous dissipation and thermophoresis effects are considered over the porous surface. Similarity transformations have been used to change the governing partial differential equations (PDEs) into nonlinear higher-order ordinary differential equations (ODEs). Governing ODEs with boundary conditions are then converted to the system of first-order initial value problem. After that the modeled system is solved numerically by RK4 technique. Impact of the magnetic number, Eckert number, Prandtl number, Lewis number, Brownian motion, thermophoresis and permeability parameters on the flow domain is analyzed graphically as well as in tabular form. It is noted that magnitude of Nusselt number for the flow regime increases with the increase of nondimensional parameter [Formula: see text] while opposite behavior is observed in case of R.

Simulations for MHD mixed convection in a partially heated lid-driven chamfered enclosure

This study investigates the hydrodynamic convective heat transport mechanism in a chamfered square-shaped cavity filled with water. The upper edge of the cavity is presumed to be at low temperature and moving with constant speed. The mean position of the lower boundary is at higher temperature. The chamfered parts and the remaining edges of the enclosure are thermally isolated and fixed. The flow situation and heat distribution experience variations in response to different magnetic field orientations. This physical configuration exhibits mathematical translation via partial differential equations, which are solved numerically using the Galerkin finite element technique. The findings after simulation are visualized through contour plots and line graphs. The primary goal of this research is to examine the effects of Grashof number, Reynolds number, magnetic field strength, and inclination angle on the flow field and temperature distribution. Our findings provide valuable insights into the mechanisms of mixed convection and heat transfer in chamfered square-shaped cavities under the influence of magnetic fields. It is noted that magnitude of Nusselt number versus Reynolds number decrease from to as Hartmann number increases from to The enhancement in Nusselt number magnitude from upto is aloso observed when Reynolds number rises from upto

MHD mixed convection non-isothermal flow and heat transfer analysis of non-Newtonian fluid saturated in I-shaped cavity

The current numerical study comprises the MHD lid-driven flow of bi-viscosity fluid inside the I-shaped cavity with variable heated short side walls, uniformly heated bottom and the rest of the walls are supposed to be adiabatic. Physical problems are formulated mathematically by exhausting the Navier-stokes and energy balance equation with the help of bi-viscosity model. In governing equations, pressure terms are eliminated by using the Penalty method, and then Galerkin weighted-residual procedure with finite element technique is used to solve them. The obtained results establish that the fluid flow velocity and heat transfer rate have been increased by increasing the bi-viscosity parameter and Reynolds number respectively. The intensity of streamlines and circulation cells increases with an increasing Grashof number, due to enhanced convective flow. Furthermore, the magnitude of Nusselt number along the bottom lid decreases by with an increase in the value of from to The applications of the under-considered problem can be found in numerous heat transfer phenomena, such as in heat exchangers, solar collectors, polymer suspensions, cooling processes of devices, production of food, manufacturing float glass, chemical catalytic reactors, and high-performance boilers.

Irreversibility analysis in Darcy-Forchheimer flow of viscous fluid with Dufour and Soret effects via finite difference method

Background and objectiveHere irreversibility analysis in unsteady Darcy-Forchheimer flow of viscous fluid by a stretched sheet is examined. Lorentz force effect is considered. Energy attribution is discussed through thermodynamic first law with Joule heating, radiation and dissipation effects. Entropy generation is calculated. Thermo diffusion and diffusion-thermo characteristics are also examined. Furthermore binary chemical reaction is addressed. Significance of entropy generation and heat transfer rate is considered. Here our main aim is to discuss the entropy rate and heat transfer analysis. The recommended model is pertinent for heat exchangers, entropy optimization, biomedicine, two-phase flows, polymers, thermal and solutal transportation, fuel cells and geothermal energy system. MethodsPartial differential equations (PDEs) are altered into dimensionless form through appropriate variables. The resulting governing equations are then solved numerically by using finite difference method (FDM). ResultsInfluence of sundry variables on velocity, temperature, entropy optimization and concentration are deliberated. Skin friction coefficient and Sherwood and Nusselt numbers are scrutinized. An improvement in velocity field is noticed for Reynold number. An increment in magnetic parameter has reverse trend for temperature and velocity. Temperature is augmented against higher radiation and Dufour number. Concentration has opposite characteristics with variation of reaction parameter and Soret number. ConclusionsSignificance enhancement in velocity gradient is seen for higher magnetic and porosity variables. An increment in Forchheimer number improves the surface drag force. Magnitude of Nusselt number (heat transfer rate) reduces for higher Reynold number. An improvement in radiation declines the heat transfer rate. An augmentation in radiation parameter improves the temperature and entropy generation rate. Entropy generation rate is augmented versus Reynold number and radiation parameter. Entropy optimization and surface drag force have similar effects for magnetic parameter.

Analysis of Buongiorno’s nanofluid model in marangoni convective flow with gyrotactic microorganism and activation energy

This communication is to analyze the Marangoni convection MHD flow of nanofluid. Marangoni convection is very useful physical phenomena in presence of microgravity conditions which is generated by gradient of surface tension at interface. We have also studied the swimming of migratory gyrotactic microorganisms in nanofluid. Flow is due to rotation of disk. Heat and mass transfer equations are examined in detail in the presence of heat source sink and Joule heating. Nonlinear mixed convection effect is inserted in momentum equation. Appropriate transformations are applied to find system of equation. HAM technique is used for convergence of equations. Radial and axial velocities, concentration, temperature, motile microorganism profile, Nusselt number and Sherwood number are sketched against important parameters. Marangoni ratio parameter and Marangoni number are increasing functions of axial and radial velocities. Temperature rises for Marangoni number and heat source sink parameter. Activation energy and chemical reaction rate parameter have opposite impact on concentration profile. Motile density profile decays via Peclet number and Schmidt number. Magnitude of Nusselt number enhances via Marangoni ratio parameter.

Wall reabsorption effects on heat and mass transfer of viscous fluid in a narrow leaky tube

The steady heat and mass transfer problem of flow of an incompressible Newtonian fluid is investigated in this study. The axisymmetric flow of a non-isothermal and highly viscous fluid is considered through a narrow leaky tube of uniform cross-section with linear reabsorption across the wall. The Navier–Stokes equations are solved for axially symmetric and slow flow in the tube. The effects of linear reabsorption parameter on the dimensionless radial and axial velocities, temperature, concentration, shear stress, leakage flux, fractional reabsorption, pressure drop across the tube as well as the Nusselt and Sherwood numbers have been investigated analytically. For 50% fractional reabsorption, inlet radial velocity is half of the reabsorption velocity along the tube. It has been shown that increase in the strength of linear reabsorption parameter considerably reduces the radial velocity, while, axial velocity shows opposite behaviour. At the exit region (z=0.9), reverse flow phenomenon is observed for higher values of reabsorption parameter. The pressure, flow rate and wall shear stress decreases after entrance region (z=0.1) of the tube. Nusselt number and Sherwood number show opposite behaviour inside the tube. At z=0.1 the magnitude of Nusselt number is maximum, while the Sherwood number is minimum at the exit region with higher value of reabsorption parameter.

Numerical and experimental investigation of Aq. Sodium methoxide as a nanofluid

Nanofluid is a unique approach in increasing a medium’s heat transfer capacity by dispersing nano-particles into a solvent at definite volume fractions. Although there has been significant progress in developing nanofluids using inorganic and organic nano-particles, the use of sodium methoxide has rarely been investigated. The manuscript, therefore, investigates its potential of enhancement of the convective heat transfer coefficient in the turbulent flow regime of Reynolds numbers 30,000 and 40,000 and at a bulk fluid temperature at 40 ˚C. An increase in the magnitude of Nusselt number and heat transfer coefficient of aq. Sodium methoxide nanofluid by 10.1% and 12.4% respectively than water at 3% volume fraction were reported.

Effect of magnetized variable thermal conductivity on flow and heat transfer characteristics of unsteady Williamson fluid

AbstractA two-dimensional mathematical model of magnetized unsteady incompressible Williamson fluid flow over a sensor surface with variable thermal conductivity and exterior squeezing with viscous dissipation effect is investigated, numerically. Present flow model is developed based on the considered flow geometry. Effect of Lorentz forces on flow behaviour is described in terms of magnetic field and which is accounted in momentum equation. Influence of variable thermal conductivity on heat transfer is considered in the energy equation. Present investigated problem gives the highly complicated nonlinear, unsteady governing flow equations and which are coupled in nature. Owing to the failure of analytical/direct techniques, the considered physical problem is solved by using Runge-Kutta scheme (RK-4) via similarity transformations approach. Graphs and tables are presented to describe the physical behaviour of various control parameters on flow phenomenon. Temperature boundary layer thickens for the amplifying value of Weissenberg parameter and permeable velocity parameter. Velocity profile decreased for the increasing squeezed flow index and permeable velocity parameter. Increasing magnetic number increases the velocity profile. Magnifying squeezed flow index magnifies the magnitude of Nusselt number. Also, RK-4 efficiently solves the highly complicated nonlinear complex equations that are arising in the fluid flow problems. The present results in this article are significantly matching with the published results in the literature.

Magneto rotating flow of hybrid nanofluid with entropy generation

BackgroundStudy of nanofluids has been enormously increased for the last couple of years. Regardless of some irregularity in the revealed outcomes and lacking consistency, yet the mechanisms of heat transport have been emerged as highly efficient. In the continuation of nanomaterials research, the investigators and analyst have also attempted to utilize hybrid nanomaterial recently, which is designed by suspending unique nanomaterials (nanoparticles) either in mixture or composite structure. The theory of hybrid nanofluids can be further modified for heat transport and pressure drop attributes by trade-off between disadvantages and advantages of individual suspension, ascribed to great aspect ratio, better thermal system and synergistic impact of nanomaterials. Therefore, we have conducted a theoretical attempt on MHD entropy optimized viscous hybrid nanomaterial flow between two parallel plates. The boundaries of plates are fixed with velocity and thermal slip aspects. Chemical reaction with novel aspect of activation energy is accounted. Furthermore, thermal radiation, heat generation and Joule heating are examined. MethodThe modeled system is numerically simulated through bvp4c technique. ResultsBehaviors of pertinent variables on the velocity, skin friction, temperature, Nusselt number, entropy generation rate and concentration are presented and discussed through different graphs. Temperature field decays against higher values of Eckert number and thermal slip variable. ConclusionsIt is noticed that velocity of material particles increase against larger estimations of rotation parameter. Temperature declines versus larger Prandtl and Eckert numbers. Concentration decays when an enhancement is occurred in the Lewis number. Magnitude of surface drag force upsurges for rising values of Prandtl number and radiation parameter. Furthermore, magnitude of Nusselt number enhances through larger Eckert number, magnetic number and Prandtl number.

The effect of Total flowrate on the cooling performance of swirling coaxial impinging jets

Thermal management ability of swirling coaxial confined impinging air jets (SCCIAJ) are experimentally studied for different total flowrate. The coaxial structure of the jet is provided by a nozzle which is a cylindrical material having an inner round flow passage and three circumferential helical flow passages. Experiments are conducted for various values of dimensionless nozzle-to-plate distance (H / D = 0.5, 1.0, 1.5 and 2.0) and total flowrate (40, 50 and 60 LPM (liter per minute)). During the experiments, flowrate ratio (Q*) and heating power are set to constant values of 0.75 and 18.2 W, respectively. It is revealed that both the heat transfer rate and radial uniformity are improved by increasing total flowrate, while increasing spacing between the nozzle outlet and the target plate adversely affects the magnitude of Nusselt numbers. In this context, the condition of Qtot = 60 LPM with H / D = 0.5 presents the optimum case for heat transfer. The results obtained are also compared with the ones of the classical circular jet (Q* = 0) depending on the temperature distribution of the impingement surface. It is concluded that swirling coaxial jets with appreciate working conditions can be used as an effective tool for electronics cooling.

Natural convection of a chemically reacting fluid in a concentric annulus filled with non-Darcy porous medium

We investigate the natural convective flow in a reactor bounded by two concentric cylinders and filled with fluid-saturated porous media. The fluid is supposed to generate heat by an exothermic reaction. The problem is described using the non-Darcy model that includes the friction resulted from the macroscopic shear and the flow inertia. We solve the transformed equations using finite difference method. A detailed study of the flow and thermal fields and the heat transfer at the inner and outer walls of the annulus has been conducted for a wide range of the physical parameters, such as, the Darcy number, Forchheimer drag parameter, Frank-Kamenetskii number, Rayleigh number and outer radius of the annulus. Two counter-rotating vortices are generated in each half of the annulus. It is found from the variations of the streamlines and isotherms that for higher values of the physical parameters the outer vortices go upward and the maximum temperature is built up at the top of the annulus. However, for lower values of them the inner and outer vortices occur on the same line and the isotherms become nearly concentric. With the increase of the Darcy number and Rayleigh number, the maximum value of the magnitude of Nusselt number at the inner and outer walls increases whereas its minimum value decreases. As a result, the Nusselt number curves intersect each other. Besides the magnitude of Nusselt number at the inner and outer walls appreciably decreases due to the increase of the Frank-Kamenetskii number and outer radius of the annulus. These findings could be used for the advancement of the existing technology or the development of new technology, especially when an exothermic reaction plays a key role in the convection process in enclosed porous media.

Analytical investigation of a Maxwell fluid flow with radiation in an axisymmetric semi-porous channel by parameterized perturbation method

This analysis investigates the problem of heat transfer for steady flow in a two-dimensional Maxwell fluid between an axisymmetric channel having upper porous wall by incorporating thermal radiation impacts. An analytic solution is obtained for the resulting nonlinear equations using parameterized perturbation method (PPM). For studying the precision and strength of the present finding obtained by PPM, a comparison is presented along with the numerical findings (attained through shooting technique), and they were found to be in excellent agreement. The physical quantities of intersects are investigated including the Reynolds number, Nusselt number, power law index, radiation parameter and Prandtl number. It is observed from present investigation that the absolute value of skin friction coefficient is increased with an increase in Reynolds number. Also, it is evident from these results that magnitude of Nusselt number enhances by an increment in power law index, Prandtl number and Reynolds number. However, it has the reverse behavior for radiation parameter, as it decreases for higher values of radiation parameter.

Passive Control and Enhancement of Low Reynolds Number Slot Jets Through the Use of Tabs and Chevrons

Liquid microjets are emerging as candidate primary or secondary heat exchangers for the thermal management of next generation photonic integrated circuits (PICs). However, the thermal and hydrodynamic behavior of confined, low Reynolds number liquid slot jets is not yet comprehensively understood. This investigation experimentally examined jet outlet modifications—in the form of tabs and chevrons—as techniques for passive control and enhancement of single-phase convective heat transfer. The investigation was carried out for slot jets in the laminar flow regime, with a Reynolds number range, based on the slot jet hydraulic diameter, of 100–500. A slot jet with an aspect ratio of 4 and a fixed confinement height to hydraulic diameter ratio (H/Dh) of 1 was considered. The local surface heat transfer and velocity field characteristics were measured using infrared (IR) thermography and particle image velocimetry (PIV) techniques. It was found that increases in area-averaged Nusselt number of up to 29% compared to the baseline case could be achieved without incurring additional hydrodynamic losses. It was also determined that the location and magnitude of Nusselt number and velocity peaks within the slot jet stagnation region could be passively controlled and enhanced through the application of outlet tabs of varying geometries and locations.

Radiation effects on heat transfer of three dimensional nanofluid flow considering thermal interfacial resistance and micro mixing in suspensions

In this study, three dimensional Al2O3-Water nanofluid flow and heat transfer features between two horizontal parallel plates in the presence of magnetic field through porous medium is scrutinized. System under consideration is rotating. Effects of thermal interfacial resistance, nanoparticle volume fraction, Brownian motion, nanoparticle size, types of nanoparticle and base fluid on thermal conductivity are considered. Also micro mixing in suspensions is taken into account while calculating viscosity. Homotopy Analysis method is employed to solve the system of ordinary differential equations, obtained by reducing original system of partial differential equations using suitable change of variables. Effects of different prevailing parameters: Reynolds number, Radiation parameter, Magnetic parameter, nanoparticle volume fraction, Eckert number, Permeability parameter, Rotation parameter and Prandtl number on Heat transfer and fluid flow are discussed. Also it is observed that the skin friction increases with increase in Reynolds number and rotation parameter but trend is reversed for nanoparticle volume fraction. The magnitude of Nusselt number rises with Reynolds number and nanoparticle volume fraction but it declines with increase of rotation parameters and Eckert number.

Base fluids with CNTs as nanoparticles through non-Darcy porous medium in convectively heated flow: A comparative study

Comparative analysis for flow of CNTs nanofluids is discoursed in the presence of non-Darcy porous medium. The consequences of homogeneous/heterogeneous process and heat transfer through convection are employed. The flow induced is due to non-linear stretching sheet of variable thickness. The bottom of the variable thickness sheet is heated by convective processes from a heated fluid. The velocity, temperature and concentration functions are formulated for the stretched flow problem. Convergence control variables and square residual errors for series solutions are obtained through OHAM (Optimal Homotopy Analysis Method). Biot number corresponds to larger temperature distribution in case of MWCNT than SWCNT. Comparison of nanoparicles SWCNT and MWCNT for the CNTs nanofluid fluids is highlighted. Water and engine oil CNTs fluids have higher magnitude of Nusselt number when compared with kerosene oil CNT fluid. The heat transfer rate in the presence of MWCNT is higher than SWCNT. Comparison of present study with previous published data is made. The outcomes are found in favorable agreement.

Radiative flow due to stretchable rotating disk with variable thickness

Present article concerns with MHD flow of viscous fluid by a rotating disk with variable thickness. Heat transfer is examined in the presence of thermal radiation. Boundary layer approximation is applied to the partial differential equations. Governing equations are then transformed into ordinary differential equations by utilizing Von Karman transformations. Impact of physical parameters on velocity, temperature, skin friction coefficient and Nusselt number is presented and examined. It is observed that with an increase in disk thickness and stretching parameter the radial and axial velocities are enhanced. Prandtl number and radiation parameter have opposite behavior for temperature field. Skin friction decays for larger disk thickness index. Magnitude of Nusselt number enhances for larger Prandtl number.

Natural convection in a rectangular enclosure containing an oval-shaped heat source and filled with Fe3O4/water nanofluid

This work concerns with the study of natural convection heat transfer in rectangular cavities with an inside oval-shaped heat source filled with Fe3O4/water nanofluid. The finite element method is employed to solve the governing equations for this problem. Average Nusselt numbers are presented for a wide range of Rayleigh number (103≤Ra≤105), volume fraction of nanoparticles (0≤ϕ≤14%), and four different size and shapes of the heat source. Depending on concentration of the nanoparticle, geometry of the heat source, and the value of Rayleigh number different behaviors are monitored for average Nusselt numbers. Configuration of the heat source dictates a significant change on the behavior of the average Nusselt number, while addition of the nanoparticles has a negative effect on the magnitude of Nusselt number for this problem.

Prediction of turbulent heat transfer downstream of an abrupt pipe expansion

Turbulent flow and heat transfer characteristics downstream of a sudden circular pipe expansion are predicted by using the full Reynolds stress model. The uniform wall temperature condition is imposed to the downstream wall. The governing differential equations are discretized by finite volume method with power-law scheme. The results show that the precise inlet conditions taken from the experimental data improve the results, but that the overall magnitude of Nusselt number is still under-predicted due to the use of conventional wall functions.