Partially Heated Research Articles

Thermal management optimization of natural convection in a triangular chamber: Role of heating positions and ternary hybrid nanofluid

In this paper, we used the multi-relaxation time lattice Boltzmann method to investigate natural convection in a triangular-shaped cavity filled with a tri-hybrid nanofluid. The cavity is partially heated by a chip of fixed size (l=L/2), the position of which varies on the left and bottom walls in order to find the optimal positions. The inclined side is maintained at a cool temperature, while the other parts are adiabatic. A detailed analysis is carried out on the impact of four essential parameters on the optimization of heat transfer: the Rayleigh number, ranging between Ra = 103 and Ra = 106; the partial heating position, showing the cavity in six different configurations; the fluid type, including pure water, nanofluid, hybrid nanofluid, and tri-hybrid nanofluid; and finally, the volume concentration of the nanoparticles for three values, ϕ = 0%, 3%, and 6%. Results are presented in the form of isotherms, streamlines, temperature and velocity profiles, and the mean Nusselt number values. As the results show, the position of the partial heater plays a crucial role, influencing natural convection heat transfer significantly in certain positions at all values of the Rayleigh number. The type of fluid has a remarkable impact on the amplification of natural convection at large values of the Rayleigh number, where the buoyancy force becomes strong. Notably, the use of tri-hybrid nanofluid shows a clear improvement in natural convection heat transfer. Furthermore, a substantial increase in thermal transmittance is observed with an increasing nanoparticle volume fraction. The validation results agree well with both numerical results and experimental data published in the literature.

Hybrid Nanofluid Unsteady MHD Natural Convection in an Inclined Wavy Porous Enclosure with Radiation Effect, Partial Heater and Heat Generation/Absorption

Hybrid Nanofluid Unsteady MHD Natural Convection in an Inclined Wavy Porous Enclosure with Radiation Effect, Partial Heater and Heat Generation/Absorption

Entropy generation in a partially heated hybrid nanofluid saturated wavy porous cavity

PurposeA porous cavity flow field generates entropy owing to energy and momentum exchange within the fluid and at solid barriers. The heat transport and viscosity effects on fluid and solid walls irreversibly generate entropy. This numerical study aims to investigate convective heat transfer together with entropy generation in a partially heated wavy porous cavity filled with a hybrid nanofluid.Design/methodology/approachThe governing equations are nondimensionalized and the domain is transformed into a unit square. A second-order finite difference method is used to have numerical solutions to nondimensional unknowns such as stream function and temperature. This numerical computation is conducted to explore a wide range of regulating parameters, e.g. hybrid nano-particle volume fraction (σ = 0.1%, 0.33%, 0.75%, 1%, 2%), Rayleigh–Darcy number (Ra = 10, 102, 103), dimensionless length of the heat source (ϵ = 0.25, 0.50,1.0) and amplitude of the wave (a = 0.05, 0.10, 0.15) for a number of undulations (N = 1, 3) per unit length.FindingsA thorough analysis is conducted to analyze the effect of multiple factors such as thermal convective forces, heat source, surface corrugation factors, nanofluid volume fraction and other parameters on entropy generation. The flow and temperature fields are studied through streamlines and isotherms. The average Bejan number suggested that entropy generation is entirely dominated by irreversibility due to heat transport at Ra = 10, and the irreversibility due to the viscosity effect is severe at Ra = 103, but the increment in s augments irreversibility due to the viscosity effect over the heat transport at Ra = 102.Originality/valueTo the best of the authors’ knowledge, this numerical study, for the first time, analyzes the influence of surface corrugation on the entropy generation related to the cooling of a partial heat source by the convection of a hybrid nanofluid.

Partial magnetic field and segmental heating effects on hybrid nanofluidic convection in a tilted porous wavy cavity

The present study investigates the magneto-thermal convective process in an oriented porous wavy-walled geometry filled with Cu–Al2O3/water hybrid nanofluid, which is partially heated from the upper and lower walls under a partially active magnetic field. The sidewalls are cooled, while heating is carried out from the upper or lower walls or both. The flow-physics are greatly affected by the segmental heating and their positions, sidewall curvature, spatially active partial magnetic field, and all the flow-controlling variables. The transport equations are solved using the finite volume technique with SIMPLE and TDMA solver-based computing code. The hydro-thermal behavior of the thermal system is evaluated for several important variables, such as the Darcy-Rayleigh number, Hartmann number, Darcy number, concentration of hybrid nanofluid, partially active magnetic field strength, inclination and positions, geometry orientation, length of segmented heaters, and their position. It is revealed that the overall thermal transport phenomena can be precisely controlled by adjusting the position and dimension of segmented heaters, the active zone and direction of the imposed magnetizing field, and the cavity angle. Both the cavity angle and magnetic field angle of 90° enhance heat transfer. Top wall heating produces weak circulation. In the case of position study for segmental heating, the sidewall position is the best location for maximum heat transfer. The circulation strength and heat transfer are maximum for the bottom heated scenario, and the transfer enhancement goes up to 132.91%. In addition, an entropy generation analysis is conducted to understand the order of thermal, viscous, and magnetic effects on irreversibility production. The results demonstrate the effectiveness of the proposed approach in optimizing the system's performance.

Simulation of magneto mixed convective flow and thermal behavior of hybrid nanofluid in a partially heated wavy cavity

This study is an attempt to address numerically the thermal performance of magneto mixed convection in a wavy cavity filled with Cu-Al2O3(50%–50%) hybrid nanoparticles suspended in water under the influence of magnetic field dependent viscosity. A focus is made on the nonuniform partial heating from the left. The role of geometric parameters on the thermal performance is scrutinized thoroughly by changing surface waviness of the right wall, heating location and the direction of motion of the top and bottom walls. Based on these lid motion, the analysis is conducted by considering four geometrical set up. The transformed governing Navier–Stokes equations in dimensionless form are written in stream function-vorticity and energy transport equations. These equations are solved by using an inhouse computing code written in the compact finite difference approach. This study encompasses the effects of different physical pertinent parameters such as Richardson number, Hartmann number, magnetic orientation, solid concentrations, magnetic number. Simulations show the significant enhancement of thermal performance with the increase of magnetic orientation, undulation of the waviness and solid concentration of nanoparticles while it decreases with the increase in magnetic intensity. It is also seen that Case-I (single wall motion) and Case-III (parallel wall motion) can be an optimal configuration to get the strongest heat transfer inside the partially heated wavy enclosure.

Natural Convection Instabilities Using the Lattice Boltzmann Method: Cavity Aspect Ratio Effect

In this paper, the natural convection instability flows in a partial heating cavity filled with air and cooled by the top wall are numerically investigated using the lattice Boltzmann method; and the cavity is partially heated and contains a heat source from below that is presented as an electronic component. To track the cavity aspect ratio effect on the heat transfer over time, first, a series of numerical simulations is completed by varying the aspect ratio of the cavity from to . The results show that the change in aspect ratio has a noticeable impact on the heat transfer behavior, specifically on the temperature distribution in the cavity, and the numerical results obtained indicate two different temperature distribution regimes: a stable steady regime, and a stable oscillatory regime. In the second step, a numerical simulation is done to study the natural convection instability into the cavity for the aspect ratio configuration of . The results show that the cavity structure has an important effect on the heat transfer in the cavity. The lattice Boltzmann method choice as a numerical simulation approach is due to its considerable result in fluid flow simulation and also to its simplicity of implementation, and it has become a suitable alternative method for solving fluid dynamics and thermal problems, as well as challenged traditional methods in many sectors by its simplicity of implementation.

Warping and springback reduction in bending of U-profiles through partial heating over the cross-section

Bending of profiles is challenging due to the high stiffness and possible deformations in the process. Especially bending of profiles with asymmetric cross-section regarding the force initiation axis leads to unwanted warping of the bent profile. This warping results from the position difference between the force initiation axis and the shear center, implying torsion moments on the profile. To prevent profile warping the use of shape-bound tools or a change of the force initiation axis position are common practices, though these methods reduce the flexibility of the process. A new method to prevent profile warping during bending is the use of partial, cross-sectional heating. Due to thermal softening in one profile area a quasi-symmetric bending case is achieved, which changes the position of the stress-free fiber and thus reduces the torsion moment. In this work, the warping and springback behavior of partially heated U-profiles consisting of S500MC steel after a three-roll push bending process is investigated using experimental methods. Through partial heating of one profile area to up to 600°C, a warping reduction of 83 % and a springback reduction of 69 % were achieved.

Local thermal non-equilibrium condition on mixed convection of a nanofluid-filled undulating cavity containing obstacle and saturated by porous media

The paper is aiming to examine the magnetic impacts on the mixed convection of a nanofluid contained by an undulating porous cavity with the help of radiative and heat generation. The condition of the local thermal non-equilibrium (LTNE) is considered. The partial heater is in the corrugated bottom partition and the top corrugated partition has T c . The vertical walls are adiabatic with a lid-velocity in the right wall. The regulating equations are worked out by the finite volume method (FVM). The involved parameters are the heater length B (between 0.2 and 0.8 ), heat generation/absorption coefficient Q (between −2 and 2), modified conductivity ratio (between k r = 0 - 10 ), thermal radiation parameter R d (between 0 and 5), a porosity parameter ε (between 0.4 and 0.9), heater position D (between 0.3 and 0.7), thermal conductivity ratio k fs (between 4 and 0.25), an undulating number λ (between 1 and 5), Darcy parameter Da (between 1 0 - 1 and 1 0 - 5 ), an inclination angle of a cavity α (between 0 ° and 90 ° ), nanoparticles parameter ϕ (between 0 and 0.1), and coefficient of an inter-phase heat transfer H ∗ (between 0 and 5000). The results indicated that the growth in nanoparticles parameter augments the profiles of average Nu of a fluid phase. The heat transfer is influenced by the variations in the length/position of the heater source. The maximum of the streamlines decreases by 97.55% as Da decreases from 1 0 - 1 to 1 0 - 5 and increases by 42.86% as an undulating number λ raises from 1 to 5.

Entropy generation minimization E.G.M. analysis of free convective hybrid nanofluid flow in a corrugated triangular annulus with a central triangular heater

All heat transfer phenomena are always escorted with entropy production and hence destruct the available work and energy resources. One way to minimize valuable energy rescores, especially in convective heat transfer augmentation situations, is to develop a thermal design that reduces the temperature differences inside the system and thus the entropy generation. This study analyzes an optimal thermal design for an augmented free convective situation considering a hybrid nanofluid flow in a corrugated triangular annulus heated by an underneath partial heater. Three approaches are applied to reduce entropy production: the corrugated walls, an inner heater at a lower non-uniform temperature, and the magnetic field effects. A numerical solution is presented for the normalized governing equations by a finite element method. A comparison with previously published investigation confirms the validity of results. The study reveals the influential role of the presented design in reducing entropy production due to the higher thermal conductivity of hybrid nanofluid. It is noticed that if the inner triangular body is heated at uniform or non-uniform temperature, keeping the magnitude of temperature lesser than the bottom heat source, the overall entropy significantly reduces. Moreover, overall, entropy is minimized if, instead of flat walls, corrugated walls are considered.

Interaction of mixed convection with non-gray gas radiation in a partially heated horizontal pipe: entropy generation analysis

PurposeThis paper aims to numerically analyze the effect of non-gray gas radiation on mixed convection in a horizontal circular duct with isothermal partial heating from the sidewall. The influence of heater location on heat transfer, fluid flow and entropy generation is given and discussed in this study.Design/methodology/approachThe numerical computation of heat transfer and fluid flow has been developed by the commercial finite element software COMSOL Multiphysics. Radiation code is developed based on the T10 Ray-Tracing method, and the radiative properties of the medium are computed based on the statistical narrow band correlated-k model.FindingsThe obtained results depicted that the radiation considerably contributes to the temperature homogenization of the gas. The findings highlight the impact of the heater location on swirling flow. It is also shown that the laterally heating process provides better energy efficiency than heating from the top of the enclosure.Originality/valueThis study is performed to improve heat transfer and to minimize entropy generation. Therefore, it is conceivable to improve the model design of industrial applications.

Lattice Boltzmann Simulation for Flow Inside Open-Ended Porous Medium With Partially Thermally Active Walls

Abstract Free convection heat transfer and flow characteristics in an open-ended enclosure occupied with fluid saturated porous media are highlighted in this paper. All numerical investigations are achieved using the mesoscopic approach thermal Lattice Boltzmann Method (LBM) by using the Darcy-Forchheimer model. The bottom and the top sides of the porous enclosure is thermally isolated with complete or partially heated vertical wall facing the opening sidewall. The partial slice of left wall of the enclosure with a fixed heating length as (H/3) is isothermally heated at the middle, top and bottom locations. However, right side is open to the ambient physical conditions. The influences of partial heating location on free convection characteristics, namely, isotherms, streamlines, centerline variations of horizontal and vertical, average and local Nusselt numbers are explored for Darcy number of 0.01, porosity of 0.4, Rayleigh number of 106 and unity Prandtl number.

MIXED CONVECTION IN A SINGLE-WALLED CARBON NANOTUBE-WATER NANOFLUID FILLED PARTIALLY HEATED TRIANGULAR LID-DRIVEN CAVITY HAVING AN ELASTIC BOTTOM WALL

In this study, mixed convection of nanofluid filled triangular cavity with a partial heater and having an elastic bottom wall is analyzed with finite element method. Left vertical wall is partially heated while the inclined wall is kept at constant lower temperature. The bottom wall is flexible and inclined wall is moving at constant speed. Influences of Richardson number, elastic modulus of flexible wall, solid nanoparticle volume fraction on the convective heat transfer characteristics are analyzed. It was observed that, lower values of Richardson number, elastic modulus of the flexible wall and higher values of nano-particle volume fraction resulted in higher local and average heat transfer enhancements. Average heat transfer enhanced significantly when solid particle volume fraction of nanoparticle was increased. Enhancements up to 121% were obtained at solid volume fraction of 0.04 as compared to pure water at Richardson number of 1. Effects of elastic modulus of the bottom wall were found to be marginal and at Ri=1, enhancements up to 2% were achieved by using a more flexible wall.

MHD natural convection in a cavity in the presence of cross partial magnetic fields and Al[formula omitted]O[formula omitted]-water nanofluid

In this study, a numerical investigation on nanofluid flow and heat transfer is presented in a cavity under the effects of cross partial magnetic fields and a partial heater. The governing stream function–vorticity equations are solved by thin plate spline radial basis functions (Rbfs) in space derivatives and backward Euler method in time derivatives. The vorticity transport equation involves either only buoyancy force or both buoyancy and cross partial magnetic field force. The results are depicted as streamlines, isotherms and vorticity contours as well as mean Nusselt number. The convective heat transfer increases with the rise in the length of the partial heater, in the concentration of nanoparticles and in Rayleigh number while it decreases with the augmentation of the Lorentz force.

MHD mixed convection in a chamfered lid-driven cavity with partial heating

In this study, MHD mixed convection lid-driven cavity problem is investigated to find thermal effects of chamfer on the corner of the cavity. For this purpose, open source CFD software, OpenFOAM's existing solver is modified to add Lorentz Force to the momentum equation. Simulation parameters consist of different Richardson numbers (0.01 ≤ Ri ≤ 100), Hartmann numbers (0 ≤ Ha ≤ 75), magnetic field angle values (0° ≤ γ ≤ 90°), different chamfer radii (0.1 ≤ r * ≤ 0.3) and Lid Motion Direction (LMD) as positive and negative. The square cavity is partially heated from the bottom plate covering 40% of its length and the rest of the bottom plate is considered as adiabatic along with the side walls. Top plate an isothermal moving lid and its temperature is lower than the bottom plate. It is observed that chamfer presence can increase the heat transfer but effectiveness of chamfer is limited and dependent on the size of corner vortices and chamfer radius. For a square cavity, only 0.39% increase in the average Nusselt number is obtained at maximum. If there is no corner vortex, chamfer can also block the main stream and decrease heat transfer up to 11%. Lid motion direction can increase the effectiveness of the chamfer, depending on the corner vortex size and at γ = 45 °, reverse lid motion direction increases average Nusselt number up to 57.2% compared to the positive lid motion direction.

An Analytic Formulation of the 21 cm Signal from the Early Phase of the Epoch of Reionization

Abstract We present an analytic formulation to model the fluctuating component of the H i signal from the epoch of reionization during the phase of partial heating. During this phase, we assume self-ionized regions, whose size distribution can be computed using excursion set formalism, to be surrounded by heated regions. We model the evolution of the heating profile around these regions (near zone) and their merger into the time-dependent background (far zone). We develop a formalism to compute the two-point correlation function for this topology, taking into account the heating autocorrelation and heating-ionization cross-correlation. We model the ionization and X-ray heating using four parameters: efficiency of ionization, ζ; number of X-ray photons per stellar baryon, N heat; spectral index of X-ray photons, α; and minimum frequency of X-ray photons, ν min. We compute the H i signal in the redshift range 10 < z < 20 for the ΛCDM model for a set of these parameters. We show that the H i signal for a range of scales 1–8 Mpc shows a peak strength of 100–1000 (mK)2 during the partially heated era. The redshift at which the signal makes a transition to a uniformly heated universe depends on the modeling parameters; e.g., if ν min is changed from 100 eV to 1 keV, this transition moves from z ≃ 15 to z ≃ 12. This result, along with the dependence of the H i signal on the modeling parameters, is in reasonable agreement with existing results from N-body simulations.

Thermal performance improvement based on the partial heating position of a heat sink

The thermal performance of a heat sink is analyzed according to the position of the partially heated surface. Numerical models for simulating forced convection were used to analyze the heat transfer between the heat sink and ambient air. The optimal partial heating position was discussed in terms of the effects of total heat transfer rate, air velocity, the ratio of total heat sink length to partially heated surface width, the thermal conductivity of the heat sink, and the thickness of the heat sink base. Finally, a correlation was suggested to determine the partial heating position that maximizes thermal performance by using the experimental design method. It was thus possible to reduce the thermal resistance of the heat sink by up to approximately 30% by finding the optimal partial heating position.

Study of heat transfer by natural convection of nanofluids in a partially heated cylindrical enclosure

In this research, a numerical study was carried out on heat transfer by natural convection of two nanofluids in a partially heated horizontal cylindrical enclosure. The partial heating occurs through the lower side of the enclosure at a constant temperature. The length of the heat source is changed from 5% to 25% of the total perimeter of the enclosure. The two side parts of the enclosure are maintained at a low constant temperature, each one of them has a length of 25% of the total perimeter. The top part of the enclosure is considered as adiabatic, it has a length of 25% of the total perimeter. The two nanofluids used are Cu-water and TiO2-water with a volume fraction of nanoparticles being varied in the range of 0–0.05. The Rayleigh number was varied in the interval 103 to 106. The results obtained were summarized in the form of correlation equations of the average Nusselt number as a function of the heated length, the Rayleigh number and volume fraction for both types of nanofluids.

Computational analysis of magneto-hydrodynamic natural convection in partially differentially heated cavity: Effect of cooler size

This work presents thermal lattice Boltzmann method simulation of magneto-hydrodynamic, buoyancy-driven convection in a partially differentially heated cavity (aspect ratio = 1) subjected to a magnetic field along the vertical direction, i.e. at 90°. Lattice Boltzmann method simulations are performed for three different cooler lengths (Lc = H/4, H/2, H) placed along the middle of one vertical wall for a wide range of Rayleigh and Hartmann numbers (103 ≤ Ra ≤ 105; Ha = 0, 60, 120) at fixed Prandtl number (Pr = 0.71, air). A partial heater is placed at the center of other vertical walls and its size is kept as half of the characteristic length (H/2). The physical insights of the systems are delineated by systematic analysis of stream function and temperature contours. Heat transfer characteristics of the cavity are elucidated by using averaged values of the Nusselt number. It is noted that average Nusselt number has a proportional dependence with cooler length and Rayleigh number, while it varied inversely with Hartmann number. Further, the functional dependence of average Nusselt number with cooler size, Rayleigh number, and Hartmann number is established for possible use in engineering design purpose.

Hot stamping of titanium alloy sheets using partial contact heating

Hot stamping of titanium alloy sheets using partial contact heating by contact heating was developed, and cylindrical deep drawing was performed. An outer portion of a 6Al-4V titanium alloy disc blank was heated with a hot stainless-steel ring by thermal conduction. The partially heated blank was drawn just after contact heating. The limiting drawing ratio in partial contact heating was higher than that of whole heating with a furnace. The concentration in deformation at a corner was prevented by the difference in flow stress between the outer portion and punch portion of the blank. A small distortion of the bottom of the cup was observed for the result of partial contact heating because of the non-uniform thermal shrinking.

Numerical study of three-dimensional natural convection and entropy generation in a cubical cavity with partially active vertical walls

Natural convection and entropy generation due to the heat transfer and fluid friction irreversibilities in a three-dimensional cubical cavity with partially heated and cooled vertical walls has been investigated numerically using the finite volume method. Four different arrangements of partially active vertical sidewalls of the cubical cavity are considered. Numerical calculations are carried out for Rayleigh numbers from (103 ≤ Ra ≤ 106), various locations of the partial heating and cooling vertical sidewalls, while the Prandtl number of air is considered constant as Pr=0.7) and the irreversibility coefficient is taken as (φ=10−4). The results explain that the total entropy generation rate increases when the Rayleigh number increases. While, the Bejan number decreases as the Rayleigh number increases. Also, it is found that the arrangements of heating and cooling regions have a significant effect on the fluid flow and heat transfer characteristics of natural convection and entropy generation in a cubical cavity. The Middle-Middle arrangement produces higher values of average Nusselt numbers.