Effect of moving stretching sheets on natural convection in partially heated square cavity filled with nanofluid

This article deals with the heat transfer enhancement due to buoyancy force in a partially heated square enclosure filled with nanofluids. The model is developed to analyse the behaviour of nanofluids taking into account of volume fraction and stretching parameter, when square horizontal walls are moving in opposite directions to each other. Implicit alternate direct finite difference method has been used to solve the governing equations of vorticity, energy, and kinematics. Graphically investigated the effect of physical pertinent controlling parameters on the dimensionless velocity, streamlines, isothermal, and Nusselt number. The obtained numerical solution achieves the best configuration for Rayleigh number 103 ≤ Ra ≤ 105, stretching parameter 0 ≤ τ ≤ 2.5, and volume fraction 0 ≤ ϕ ≤ 0.2. It is found that the stretching parameter and direction of moving walls affect the fluid flow, flow strength, and heat transfer in the cavity.

Thermal Transport in Radiative Nanofluids by Considering the Influence of Convective Heat Condition

The analysis of nanofluid dynamics in a bounded domain attained much attention of the researchers, engineers, and industrialists. These fluids became much popular in the researcher’s community due to their broad uses regarding the heat transfer in various industries and fluid flowing in engine and in aerodynamics as well. Therefore, the analysis of Cu-kerosene oil and Cu-water is organized between two Riga plates with the novel effects of thermal radiations and surface convection. The problem reduced in the form of dimensionless system and then solved by employing variational iteration and variation of parameter methods. For the sake of validity, the results checked with numerical scheme and found to be excellent. Further, it is examined that the nanofluids move slowly by strengthen Cu fraction factor. The temperature of Cu-kerosene oil and Cu-water significantly rises due to inducing thermal radiations and surface convection. The behaviour of shear stresses is in reverse proportion with the primitive parameters, and local Nusselt number increases due to varying thermal radiations, Biot number, and fraction factor, respectively.

Effects of different thermal modes of obstacles on the natural convective Al2O3-water nanofluidic transport inside a triangular cavity

This study investigates the Al2O3-water nanofluidic transport within an isosceles triangular compartment with top vertex downwards. The top wall is maintained isothermally cooled and left as well as right inclined walls are made uniformly heated. Two diamond-shaped obstacles are positioned inside the enclosure. The nanofluidic motion is supposed to be magnetically influenced. This investigation includes a fine analysis of how various thermal modes of obstacles affect the velocity and thermal profiles of the nanofluid. Appropriate similarity conversion leads to having a non-dimensional flow profile and is treated with Galerkin finite element scheme. The grid independency, experimental verification, and comparison assessments are directed to explore the model accuracy. The dynamic parameters like Rayleigh number [Formula: see text], nanoparticle volume fraction [Formula: see text], and Hartmann number [Formula: see text] are varied to perceive the noteworthy changes in isotherms, velocity, streamlines, and Nusselt number. The consequences specify average Nusselt number deteriorates for Hartmann number but escalates for nanoparticle concentration and Rayleigh number. Both heated and adiabatic obstacles exhibit high heat transport, while cold obstacles reveal the lowest magnitude in heat transmission. For Rayleigh number, cold obstacles reveal 34.51% heat transport enhancement, whereas it is 52.72% for heated obstacles compared to cold one. mathematics subject classification: 76W05

EFFECT OF HEAT AND MASS TRANSFER AND THERMAL RADIATION ON A STEADY MHD CONVECTIVE FLOW WITH VISCOUS DISSIPATION AND SUCTION/INJECTION

Our motive is to examine the impact of thermal radiation and suction or injection with viscous dissipation on an MHD boundary layer flow past a vertical porous stretched sheet immersed in a porous medium. The set of the flow equations is converted into a set of non-linear ordinary differential equations by using similarity transformation. We use Runge Kutta method and shooting technique in MATLAB Package to solve the set of equations. The impact of non-dimensional physical parameters on flow profiles is analysed and depicted in graphs. We observe the influence of non-dimensional physical quantities on the Nusselt number, the Sherwood number, and skin friction and presented in tables. A comparison of the obtained numerical results with existing results in a limiting sense is also presented. We enhance radiation to observe the deceleration of fluid velocity and temperature profile for both suction and injection. While enhancing porosity parameter accelerates velocity whereas decelerates temperature profile. As the heat source parameter increases, the temperature of the fluid decreases for both suction and injection, it has been found. With the increasing values of the radiation parameter, the skin friction and heat transfer rate decreases. Increasing magnetic parameter decelerates the skin friction, Nusselt number, and Sherwood number.

EFFECT OF CAVITY RATIO ON HEAT TRANSFER BY FREE LOAD FROM HEATED PLATES UPWARD WITH CONSTANT HEAT FLUX

Many engineering and industrial applications always seek to find ways to dissipate heat from heated surfaces used in these industries. As it is involved in the cooling of electronic parts and electrical transformers, as well as the design of solar collectors, in addition to being a process of heat exchange between hot surfaces and the fluids in contact with them. Since most electronic devices or their parts are cooled by removing the heat generated inside them by using air as a heat transfer medium and in a free convection way, and the fact that heat transfer by free convection occurs in many fields, so there were many studies that dealt with this topic. The free load is generated by the buoyant force (Bouncy force) As a result of the difference in the density of the fluid adjacent to the heated surface due to the difference in temperatures between the fluid and the surface. The laminar flow along surfaces has been extensively studied analytically [1,2,3,4] In the horizontal, inclined and vertical case, whether by constant heat flux or constant surface temperature, there are also many experimental studies of heat transfer by free convection from horizontal, inclined and vertical surfaces with constant heat flux or constant surface temperature [5,6,7,8]. Some experimental studies have also been conducted on heat transfer by convection from heated surfaces in the form of a disk (ring)The outcome of these studies was to extract an exponential mathematical relationship between the average of Nusselt number and the Kirchhoff number or Rayleigh number and the following formula: (Nu=C(Ra) n It is one of the most suitable formulas for heat transfer by free convection from heated surfaces in all its forms and over a wide range of Rayleigh number . It is noted that not all of these studies dealt with the study of the effect of the cavity ratio on heat transfer by free convection from square-shaped surfaces, which is the form that is more applied in electronic devices. Therefore, the current research means studying the rate of change in the average of Nusselt number, which represents a function of the rate of change in the rate of heat transfer by convection, as well as studying the thermal gradient above the surface, and this was done through using three hollow surfaces in proportions (0.25,0.5,0.75) of the total area.

Nusselt Number and Friction Factor Correlations Development for Arc-Shape Apex Upstream Artificial Roughness in Solar Air Heater

In the present work an outdoor experimental investigation for solar air heater with arc-shaped apex-upstream flow by the use of circular cross section wires as roughness elements has been carried out. The roughness-element have been expressed in non-dimensionalizing geometric parameters as relative roughness-pitch (P/e), relative roughness-height (e/D) and flow attack-angle (α/60), and the range of these parameters varies from 8 to 15, 0.0454, and 0.75 to 1.25, respectively. For evaluation of performance of the roughened SAH, a novel parameter has been proposed and introduced in the present investigation which is Thermo-Hydraulic Improvement Parameter (THIP). With the use of present roughness geometry, considerably Nusselt number enhancement ratio (NNER) and friction factor enhancement ratio (FFER) have been observed. The maximum NNER and FFER values obtained experimentally is about 2.83 and 1.79 times, respectively. While, the maximum THIP has been obtained 157.49% higher than the smooth SAH. Using the experimental results correlations for the output parameters (Nusselt number and friction factor) as a function of input parameters (flow and roughness) have been developed.

Numerical investigations of heat transfer around a hot block subject to a cross-flow and an extended jet hole using ternary hybrid nanofluids

In the last few years, modern heat transfer technologies significantly improved to provide more efficient systems in industries. One of those technologies is cooling electronic components in laminar flow using water nanofluids, which is interesting. This research used a ternary hybrid nanofluid with various nanoparticle forms to conduct a numerical investigation of three-dimensional heat transfer and fluid flow over a heated block exposed to a horizontal flow and an impinging jet. The effects of several variables such as the Reynolds number ratio [Formula: see text], volume fraction of nanoparticles [Formula: see text], length of extended jet hole [Formula: see text], and the influence of the inclination angle of the impinging jet inlet [Formula: see text] on the fluid flow and heat transfer were examined. Using the Ansys-Fluent 14.5 program and under laminar flow conditions, the finite-volume method was applied with the help of the SIMPLE algorithm to solve continuity, momentum, and energy equations. Several characteristics are assessed, including velocity streamline, isotherm contours, Nusselt number contours, the average Nusselt number ([Formula: see text]), the friction factor [Formula: see text], and drop pressure [Formula: see text]. The findings of the current analysis revealed that adding an impinging jet can boost the heat transfer rate up to [Formula: see text] better than a non-impingement jet. Also, a significant enhancement in the heat transfer rate was obtained when growing one of these parameters α, [Formula: see text], and E. Moreover, the ternary hybrid nanofluid with different nanoparticle forms significantly boosts the heat transfer rate compared to the traditional nanofluid. The maximum heat transfer is reached as the velocity of the impinging jet rises. Inclining the angle of the impinging jet inlet with [Formula: see text] toward the channel inlet boosted the rate of heat transfer up to [Formula: see text] compared to the perpendicular impinging jet [Formula: see text]. A strong consensus has been reached with the theoretical and experimental findings found in the literature.

Forced and mixed convection experiments in a confined vertical backward facing step at low-Prandtl number

In this paper, we present experimental results for a non-isothermal vertical confined backward facing step conducted with a low-Prandtl number fluid. The eutectic alloy gallium–indium–tin is used as the working fluid. We conducted experiments for different Reynolds and Richardson numbers covering both forced and mixed convection regimes. Time-averaged velocity profiles were measured at six streamwise positions along the test section center-plane with so-called permanent magnet probes. The local Nusselt number was measured in streamwise and spanwise directions along the heating plate mounted right after the step. We further ran RANS simulations of the experiment to study the qualitative influence of assuming a constant specific heat flux thermal boundary condition for the experiment heating plate. The measured velocity profiles show the expected behavior for both studied convection regimes, while the measured streamwise local Nusselt number profiles do not. This is explained by how the heating plate thermal boundary condition is defined. We performed an order of magnitude estimate to estimate the forced- to mixed convection transition onset. The estimate shows good agreement with the experimental data, although further measurements are needed to further validate the estimated transition threshold. The measurement of fluctuating quantities remains an open task to be addressed in future experiments, since the permanent magnet probe measurement equation needs further adjustments. Graphical Abstract

Transient Fluid-Solid Interaction and Heat Transfer in a Cavity with Elastic Baffles Mounted on the Sidewalls

Fluid-solid interaction phenomenon study is necessary for the analysis of several engineering systems such as structures and vessels that interact with wind and blood flow, respectively. In this study, the interactions between buoyancy-driven airflow and elastic baffle(s) inside a square enclosure were modeled numerically. While the two sidewalls of the enclosure were insulated, the lower and upper walls were kept at hot and cold temperatures, respectively. The heat transfer rate through the hot wall by calculating the Nusselt number and von Mises stress at the baffles’ root for various configurations of baffle(s) was considered. The domain was modeled in ANSYS Workbench, and the k-ε model was employed to solve the turbulent convective flow (Ra > 107). A two-way algorithm along with the finite element method was employed to simultaneously solve the equations governing the fluid flow and the solid phase. The dynamic mesh method was employed to account for the change in the location of the fluid domain at a new time step. The results show the elastic baffle, in comparison to solid baffle, intensifies the heat transfer rate by 15%. The results also indicate that the Nusselt number in the single-baffle case is higher than in double-baffle cases. The fact that the amount of von Mises is a function of the baffles’ configuration is another point obtained from the results. It was found that the von Mises stress at the baffles’ root represents more unsteady fluctuations in the asymmetric case, while it approaches a constant value in the symmetric case.