Angle Of Enclosure Research Articles

Experimental Investigation into Natural Convection Heat Transfer inside Triangular Enclosure with Internal Hot Cylinder

Natural convection air heat transfer and fluid movement currents around a hot circular cylinder inside an inclined triangular enclosure has been analyzed experimentally. Three different sizes of an enclosure with a long side of 20, 25, and 30 cm, the thickness of 1 mm, and depth of 50 cm were used in the present work to give three radius ratios. The effect of Rayleigh number, radius ratio, the rotation angle of triangle enclosure, and the inclination angle of the apparatus with horizontal axis ? on the heat transfer process was investigated. The ranges of these parameters were: Rayleigh number from 5×106 to 2.5×108, radius ratio (0.345, 0.455, and 0.618), rotation angle (0o, 45o, and 90o), and inclination angle (0o, 45o and 90o). The results show that the heat transfer rates increase with increase in Rayleigh number and as the rotation angle of enclosure is changed from 0o to 90o. Moreover, the heat transfer rate increases linearly with Rayleigh number at higher radius at rotation angle 0o, 90o only. While, it increases slightly with Rayleigh number at rotation angle 45o. Additionally, the higher heat transfer rates occur at vertical position of enclosure inclination angle 90o and rotation angle 0o (the base of triangle at the bottom) and it decreases as inclination angle deviates from 90o to 0o. This behavior is reverse completely at higher radius ratio 0.618. Empirical correlations for the average Nusselt number has been found to depend on Rayleigh number., radius ratio, rotation angle and inclination angle.

RETRACTED: Utilization of machine learning and neural networks to optimize the enclosure angle, magnetic field, and radiation parameter for mixed convection of hybrid nanofluid flow next to assess environmental impact

This paper examines the mixed convective heat transfer (HTR) of nanofluid (NFD) flow in a rectangular enclosure with the upper moving wall numerically. The lower wall has a high temperature and a number of semi-circular obstacles with the same temperature are installed on it. The upper moving wall has a low temperature and the other two walls are insulated. The enclosure can change from horizontal to vertical. Radiation HTR is considered in the enclosure and there is a magnetic field (MGF) that can change the angle from horizontal to vertical affecting the NFD. This study is carried out for different angles of the enclosure and MGF from horizontal to vertical for radiation parameters (RDP) of 0 to 3 and a constant MGF with Hartmann number of 20 and Richardson number of 10. The aim is to estimate the Nusselt number (Nu), entropy generation (ETG), and Bejan number (Be). The SIMPLE algorithm is utilized using FORTRAN software, and optimization is done using artificial intelligence to find the maximum and minimum output values. The results demonstrate that the maximum value of Nu and Bes corresponds to the MGF angle and enclosure angle of 90°. The minimum value of the Nu and the maximum amount of ETG corresponds to the horizontal MGF and horizontal enclosure when the RDP is 1.5. An increment in the RDP enhances the amount of Nu. The maximum amount of ETG, i.e. 12.87, corresponds to the enclosure with an angle of 45° for the horizontal MGF and the absence of RDP. corresponds to the enclosure with an angle of 45° for the horizontal MGF and the absence of RDP. It was also found that most environmental impacts, and hence values for different environmental factors, arise from the production of nanoparticles; thus, it is a significant contributor to environmental impacts.

Use of neural network and machine learning in optimizing heat transfer and entropy generated in a cavity filled with nanofluid under the influence of magnetic field: A numerical study

The current research was conducted with the aim of numerical simulation of the natural convection heat transfer and the radiation heat transfer (RHT) of a nanofluid (NF) in a square enclosure under the effect of a magnetic field (MF). The enclosure can rotate and have various angles. The left-hand wall is warm while the opposite wall is cold. Moreover, the upper and lower walls are insulted and there are two blades on the warm wall. In this study, the Lattice Boltzmann Method (LBM), which was written manually in the Fortran software, were used to solve the partial differential equations and simulate the problem, respectively. The radiation parameter, Rayleigh number (Ra), volume percentage of nanoparticles (VNPs), and enclosure angle were among the parameters studied for both rectangular and triangular blades. By evaluating the results of Nu (Nu), generated entropy (GE), and Bejan number (Be), it was found that the highest value of heat transfer (HTR) and GE is in enclosure 90 with rectangular blades, although the Be is minimal in this case. Finally, the addition of radiation to the enclosure increases HTR for rectangular and triangular blades by 91 and 98%, and decreases GE by 4.2 and 2.6%, respectively.

Magnetohydrodynamic Natural Convection in a Quadrantal Enclosure

The present paper investigates the magnetohydrodynamic natural convection thermal transport and entropy generation characteristics inside a quadrantal enclosure filled with an electrically conducting fluid, silicon. Both uniform temperature heating and nonuniform temperature heating at the bottom wall are considered along with adjacent left cold wall and insulated curved wall. The results are enumerated for a broad range of Hartmann number () and Rayleigh number (), in terms of streamlines and isotherms, local and average Nusselt number, and local entropy generation. The results reveal that considering lesser , the heat transfer rate remains invariable even with the change in . Considering a larger , the effect of the magnetic field is sufficiently distinguishable, signifying that the abatement in the rate of heat transfer on considering the intensification in magnetic field strength is definitely compelling. The results also reveal that the entropy generation due to heat transfer intensifies with the increase in for the case with nonuniform heating although it remains practically constant for all values of investigated with uniform heating. Interestingly the heat transport rate is augmented by decreasing the sector angle of enclosure and vice versa for the uniform heating situation but not with the nonuniform heating considering and 20.

Numerical analysis of magnetohydrodynamic natural convection in a nanofluid filled quadrantal enclosure

The present numerical work investigates the magnetohydrodynamic buoyancy driven thermal energy transport inside a copper-water nanofluid filled quadrantal enclosure. The base of the enclosure is subjected to constant temperature heating, while the vertical wall is maintained at a uniform cold temperature and the curved wall is insulated. The results are enumerated for the following range of parameters: 103 ≤ Rayleigh number (Ra) ≤ 106, 0 ≤ Hartmann number (Ha) ≤ 100 and 0 ≤ volume fraction of nanoparticles (ϕ) ≤ 0.05. It reveals that the average Nusselt number is a function of ϕ and it shows an increase with ϕ. Further, it is also observed that the average Nusselt number decreases with Ha and the change is more profound at higher Ra (105 and 106) values. The heat transfer rate is increased by decreasing the sector angle of enclosure and vice versa. In this way not only Ra, ϕ, Ha influence the heat transfer rate but a geometry variation has an equal role to play in the alteration of heat transfer.

Natural Convection and Entropy Generation of MgO/Water Nanofluids in the Enclosure under a Magnetic Field and Radiation Effects

The authors of the present paper sought to conduct a numerical study on the convection heat transfer, along with the radiation and entropy generation (EGE) of a nanofluids (NFs) in a two and three-dimensional square enclosure, by using the FVM. The enclosure contained a high-temperature blade in the form of a vertical elliptical quadrant in the lower corner of the enclosure. The right edge of the enclosure was kept at low temperature, while the other edges were insulated. The enclosure was subjected to a magnetic field (MGF) and could be adjusted to different angles. In this research, two laboratory relationships dependent on temperature and volume fraction were used to simulate thermal conductivity and viscosity. The variables of this problem were Ra, Ha, RAP, nanoparticle (NP) volume fraction, blade aspect ratio, enclosure angles, and MGF. Evaluating the effects of these variables on heat transfer rate (HTR), EGE, and Be revealed that increasing the Ra and reducing the Ha could increase the HTR and EGE. On the other hand, adding radiation HTR to the enclosure increased the overall HTR. Moreover, an augmentation of the volume fraction of magnesium oxide NPs led to an increased amount of HTR and EGE. Furthermore, any changes to the MGF and the enclosure angle imposed various effects on the HTR. The results indicated that an augmentation of the size of the blade increased and then decreased the HTR and the generated entropy. Finally, increasing the blade always increased the Be.

Natural convection in an L-shape cavity equipped with heating blocks and porous layers

In the current study, a comprehensive validated numerical simulation is carried out to reveal the significance of porous layers in the improvement of natural convection of L-shape enclosure and secondly nondimensionally optimize the location of blocks and porous layer (along the walls of the cavity) to achieve the maximum heat transfer rate. Besides, many other effective parameters i.e. Darcy number, Rayleigh number, relative thermal conductivity ratio and enclosure angle of inclination are considered. According to the findings of present research, application of porous layer enhances the convective heat transfer performance especially in higher values of Rayleigh number. Furthermore, heating block location is a crucial factor in enhancing heat transfer throughout the cavity, and in this case, case “a” obtains higher convective heat transfer. Triangular heating blocks illustrate a slightly better convective heat transfer performance and Da = 10−5 was found a vital point for the efficient utilization of porous layers.

Numerical Investigation of Natural Convection and Irreversibilities between Two Inclined Concentric Cylinders in Presence of Uniform Magnetic Field and Radiation

In this study, the free convection with volumetric radiation in a water–alumina nanofluid flowing between two inclined concentric cylinders was simulated. The enclosure, or the cavity between the two circular quadrants in which the inner and outer pipes were respectively at high and low temperatures, was exposed to a magnetic field, and the remaining walls were insulated. Simulations were performed using control volume and the SIMPLE algorithm. The effects of the Rayleigh and Hartmann numbers, cavity or enclosure angle, magnetic field angle, nanopowder volume fraction, radiation intensity, and aspect ratio were investigated on the Nusselt number, irreversibilities and the Bejan number. According to the results, the Rayleigh number, hot pipe diameter, and adding more nanopowder have increasing and the Hartmann number has decreasing effect on the thermal performance and irreversibilities. Adding more nanopowder and increasing the enclosure angle also improved heat transfer. Increasing the magnetic field angle first increased and then decreased irreversibilities. In fact, increasing the magnetic field angle increased up to 15 ̊, the heat transfer rate increased, and further increase of the magnetic field angle from 15 to 90 ̊ decreased the heat transfer rate.

Using artificial neural network to optimize the flow and natural heat transfer of a magnetic nanofluid in a square enclosure with a fin on its vertical wall: a lattice Boltzmann simulation

The heat transfer of a nanofluid in a square enclosure is numerically simulated using FORTRAN software in this paper, by considering the radiation (Rad) effect. The enclosure is under a magnetic field (MaF) and can also deviate from the horizontal axis. The enclosure has insulated top and bottom walls, as well as hot and cold right and left walls. There is a fin (0.1 × 0.4) with constant thermal conductivity on its hot wall. Entropy generation (EnG) is investigated as one of the important results in this paper. The lattice Boltzmann method is used for the simulations. A sensitivity analysis is performed on three parameters; including Rayleigh (Ra), Hartmann (Ha), and enclosure angle are introduced as the most effective parameters. Finally, based on these parameters, the performance of the cavity was simulated using an artificial neural network. The results show that the Nusselt (Nu) and EnG increase with the Ra and decrease with the Ha. The parameters mentioned above are subjected to optimization, indicating that the maximum Nu which is equal to 22.24 corresponds to the Ra of 992,409, the Ha of 0.004, and the inclination angle of 34.74°.

Latent Heat Thermal Storage of Nano-Enhanced Phase Change Material Filled by Copper Foam with Linear Porosity Variation in Vertical Direction

The melting flow and heat transfer of copper-oxide coconut oil in thermal energy storage filled with a nonlinear copper metal foam are addressed. The porosity of the copper foam changes linearly from bottom to top. The phase change material (PCM) is filled into the metal foam pores, which form a composite PCM. The natural convection effect is also taken into account. The effect of average porosity; porosity distribution; pore size density; the inclination angle of enclosure; and nanoparticles’ concentration on the isotherms, melting maps, and the melting rate are investigated. The results show that the average porosity is the most important parameter on the melting behavior. The variation in porosity from 0.825 to 0.9 changes the melting time by about 116%. The natural convection flows are weak in the metal foam, and hence, the impact of each of the other parameters on the melting time is insignificant (less than 5%).

Entropy generation and natural convection flow of a suspension containing nano-encapsulated phase change particles in a semi-annular cavity

Abstract The natural phase change convection of a new type of hybrid nanofluids, suspensions of Nano-Encapsulated Phase Change Materials (NEPCM), was addressed in a semi-annular inclined enclosure. The nanoparticles consist of a polymer shell and a nonadecane shell, in which the nonadecane core can change phase at its melting temperature and absorb/release a significant quantity of latent heat. The NEPCM-suspension circulates in the enclosure due to the natural convection, and the NEPCM particles contribute to heat transfer by phase change. The equations governing the movement and heat transfer of the suspension and nanoparticles were inserted in the form of partial differential equations. The finite element method was used to numerically solve the equations. Then, the entropy generation of NEPCM suspension in the attendance of the phase change was examined. The influence of the fusion temperature and volume fraction of nanoparticles, Stefan number, Rayleigh number, and inclination angle of enclosure on the thermal behavior and entropy generation of the suspension was explored. The results showed that the contribution of phase change core of nanoparticles was significant, and the heat transfer was enhanced by the presence of NEPCM particles. The fusion temperature of particles controls the Bejan number (entropy generation) behavior of the NEPCM suspension. There is an optimum phase change temperature for nanoparticles, which results in maximum heat transfer. For a horizontal enclosure, the optimum fusion temperature is the average temperature of the active walls. This optimum phase change temperature is a function of the tilting angle of the enclosure.

Modeling natural convective heat transfer within an inclined enclosure in the presence of copper oxide/water nanofluid

In this study, the effects of adding CuO nanoparticles (NPs) on natural convection heat transfer within an enclosure by considering Brownian motions and thermophoresis were discussed. For this purpose, copper oxide NPs were inserted to water at 1, 3, and 5 vol.%. Using two‐phase model, at constant Grashof (104) and Richardson numbers (102), the enclosure angularity efficacy on the heat transfer was examined at 30°, 45°, and 60°. Adding NPs has one positive effect (thermal conductivity enhancement) and one negative point (viscosity augmentation). It was found that up to 1 vol.%, the addition of NPs improves (due to the superiority of the positive effect on the negative effect) the thermal conductivity but upon 1%, the negative effect is preferred to the positive effect, and hence heat transfer is diminished. At Ri = 100, only adding 1% of the NPs enhanced the Nusselt number (Nu) and adding more NPs diminished the Nu. The angle of the enclosure affects the concentration distribution of the NPs and diminishes eases the NP homogeneity as well. As the enclosure angle augmented from 30° to 60°, the Nu improved by 47%. Note that at the best conditions, adding NPs improved the Nu up to 2%.

Free convection/radiation and entropy generation analyses for nanofluid of inclined square enclosure with uniform magnetic field

This paper studies the generation of entropy and free convective heat transfer of Al2O3/water nanofluid in an inclined enclosure affected by a magnetic field considering radiation effects. There is a circular quadrant at temperature $$T_{\text{h}}$$ in the bottom section of the left wall of the enclosure. The right wall of enclosure is kept at a fixed temperature $$T_{\text{c}}$$. The other walls are insulated. The governing equations for fluid flow are resolved using the algorithm of SIMPLE. The effect of variations of Rayleigh number (Ra), Hartmann number (Ha), the enclosure angle and concentration of nanoparticles ($$\varphi$$) on the flow field, isothermal field, entropy field, Nusselt number (Nu), Bejan number (Be) and total generation of entropy is investigated. The results indicate that the Nu enhances by 160% and 40% by augmenting the Ra and decreasing the Ha, respectively. Be diminishes by enhancing the Ra and reducing the Ha. The maximum generation of entropy intensifies by 288% and 39% by augmenting the Ra and reducing the Ha, respectively. The highest average Nusselt umber ($${\text{Nu}}_{\text{M}}$$) and an overall generation of entropy occur at the inclination angle of 30°.

Free convection and entropy generation of a nanofluid in a tilted triangular cavity exposed to a magnetic field with sinusoidal wall temperature distribution considering radiation effects

Abstract In this research, free convective heat transfer and entropy production of alumina/water nanofluid in a tilted triangular enclosure are studied considering radiation impacts and inclined constant magnetic field (MF). SIMPLE algorithm is used to solve the governing equations. The impact of effective parameters consist of Ra, Ha, MF angle, enclosure angle, radiation parameter and concentration of alumina nano-materials on the convective heat transfer, the entropy production and the Bejan number (Be) are examined. The findings reveal that the heat transfer rate (HTR) increased 2.32 times and the entropy production augmented 14.17 times with growing the Ra. The HTR and total entropy production (TEG) diminish by augmenting the Ha. The Be enhances by decreasing the Ra and growing the Ha. The maximum HTR takes place at MF angle of 90° and also at the enclosure angle of 60°. The HTR enhances 7.3% and the TEG rises by 9.3% when 6% of the nano-materials was added to the water.

Effect of an inclined partition with constant thermal conductivity on natural convection and entropy generation of a nanofluid under magnetic field inside an inclined enclosure: Applicable for electronic cooling

Free convection heat transfer of Al2O3/water nanofluid in an inclined closed enclosure is investigated numerically considering radiation effects. A horizontal and constant magnetic field is applied to the chamber. The chamber also has an angle with the horizontal axis. A partition with constant thermal conductivity is positioned on the horizontal diameter of the enclosure and divides the fluid inside it into two parts. Parts of the left and lower walls of the chamber are kept at high temperature, and the right wall is kept at low temperature. The rest of the walls are also insulated. In the present work, in addition of investigation of the heat transfer rate (HTR), total entropy generation (TEG) and Bejan number (Be) are also evaluated. The results show that as the Hartmann number intensifies from 0 to 40, heat transfer and entropy generation decrease by 35% and 46%, respectively. An intensification of the Rayleigh number results in an intensification of the HTR by 39% and the entropy generation by 90%. The Bejan number decreases by augmenting the Rayleigh number and intensifies with the Hartmann number. The addition of radiation heat transfer results in an intensification of the entropy generation and a reduction in the Bejan number. The enclosure angle changes have different effects on the vortices formed at the top and bottom of the partition. As the hot wall length intensifies from 0.1 to 0.9, the Nusselt number and entropy generation become 3.77 and 2.8 times, respectively.

SECOND LAW ANALYSIS OF MIXED CONVECTION OF MAGNETOHYDRODYNAMIC FLOW IN AN INCLINED SQUARE LID-DRIVEN ENCLOSURE

Second law of thermodynamics analysis is formulated for the case of laminar mixed convection in an inclined square lid-driven enclosure in the presence of magnetic field. Vertical sides of the enclosure moves upward when inclination angle is zero. Governing equations of flow and temperature in the form of stream function-vorticity formulation were solved numerically using the differential quadrature method. Governing parameters are: Richardson number (from 0.01 to 100), Prandtl number (from 0.1 to 1.0), inclination angle of enclosure (from 0 to 180), Hartmann number (from 0 to 100) and magnetic field direction (0). It is found that the inclination angle of enclosure is effective parameter on entropy generation especially for higher Richardson number (Ri > 1) due to domination of natural convection. However, Hartmann number is effective on both heat transfer and entropy generation for all values of Richardson and Prandtl numbers and it decreases the convective fluid flow and entropy generation.

Magnetic field effects on natural convection flow of a non-Newtonian fluid in an L-shaped enclosure

The effect of magnetic field on natural convection heat transfer in an L-shaped enclosure filled with a non-Newtonian fluid is investigated numerically. The governing equations are solved by finite-volume method using the SIMPLE algorithm. The power-law rheological model is used to characterize the non-Newtonian fluid behavior. It is revealed that heat transfer rate decreases for shear-thinning fluids (of power-law index, n 1) in comparison with the Newtonian ones. Thermal behavior of shear-thinning and shear-thickening fluids is similar to that of Newtonian fluids for the angle of enclosure α 60°, respectively.

Natural convection heat transfer in an inclined square enclosure filled with a porous medium saturated by nanofluid using Buongiorno’s mathematical model

This paper presents numerical study of nanofluid free convection in a porous enclosure. Two vertical walls are maintained at constant but different temperatures. (Th>Tc), while the remaining walls are insulated Two-phase Buongiorno nanofluid model is employed in this work considering Brownian diffusion and thermophoresis effects. Governing equations are solved using a Simple-based finite volume method. Two different nanofluids are considered in this study, i.e. Al2O3/water and Cu/water. Numerical simulations are conducted for different porous Rayleigh numbers (Rap=102, 103 and 104), porosities (ɛ=0.5, 0.7 and 0.9), particle volume fractions (0⩽φAve⩽0.04) and inclination angle of enclosure ranging from 0° to 60°. Numerical results indicate that porosity plays an important role on the heat transfer rate especially at high porous Rayleigh numbers. Compared to Al2O3, Cu nanoparticles show more uniform distribution inside the enclosure. Numerical results demonstrate that there is mass boundary layer adjacent to enclosure walls and its thickness decreases by reducing porosity or increasing porous Rayleigh number.

A numerical study of natural convection in an inclined square enclosure with an elliptic cylinder using variational multiscale element free Galerkin method

In this paper, a numerical study for steady-state natural convection in a cold outer square enclosure containing a hot inner elliptic cylinder is investigated using the variational multiscale element free Galerkin method (VMEFG). The VMEFG method is a meshless method which coupled element free Galerkin method and variational multiscale method, it allows equal order basis for the velocity and the pressure field. The numerical calculations are performed for various Rayleigh numbers ranging from 103 to 106, the inclination angle of the outer square enclosure from 0° to 45° and major axis of the inner cylinder from 0.2L to 0.4L. The results show that the Rayleigh number, the size of the inner cylinder and the inclination angle of the outer square enclosure have remarkable effects on the streamlines and temperature contours in the enclosure, but the inclination angle of the enclosure has a small effect on average Nusselt number on the inner elliptic cylinder.

Thermo-dynamic irreversibility induced by natural convection in square enclosure with inner cylinder. Part-I: Effect of tilted angle of enclosure

Two-dimensional numerical simulations were conducted to investigate the natural convection heat transfer induced by the temperature difference between cold walls of the tilted square enclosure and a hot inner circular cylinder for different Prandtl numbers (10−2⩽Pr⩽102) and Rayleigh numbers (103⩽Ra⩽106). The numerical solutions are obtained using an accurate and efficient immersed boundary method. The outer square enclosure is tilted from γ=0° to γ=45° by each 5°. Detailed analysis results including the distribution of streamlines, isotherms and Nusselt numbers are presented. The entropy generation and corresponding Bejan number in the enclosure are analyzed to estimate the thermo-dynamic irreversibility accompanied by the natural convection in the system.