An evaluation of force term in the lattice Boltzmann method for mixed convection with large Richardson numbers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sayed Mahdi Naghavi ◽  
Ghanbar Ali Sheikhzadeh
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Richardson Number ◽  
Body Force ◽  
Convection Heat Transfer ◽  
The Body ◽  
Convection Heat ◽  
Content Type ◽  
Mixed Convection Heat Transfer ◽  
Boltzmann Method

Purpose The purpose of this study is the identification of the best method to apply the body force in the lattice Boltzmann method (LBM). In the simulation of mixed convection, especially for large Richardson number flows in a square cavity. Design/methodology/approach First, three methods for applying the body force were compared to each other in the LBM. Then, an LBM-based code was written in the FORTRAN language using these three methods. Next, that code was used to simulate natural/mixed convection in a two-dimensional cavity to evaluate the methods for applying the body force. Finally, the optimum way for applying the body force was used for the simulation of free convection heat transfer in a concentric annulus with Rayleigh number in a range of 1,000 to 50,000, and mixed convection heat transfer in a concentric annulus with Rayleigh number in a range of 10,000 to 50,000 and Reynolds number in a range of 100 to 400. Findings Mixed convection heat transfer was simulated in a two-dimensional cavity with Richardson number in a range of 0.0001 to 100. The results which were obtained in low Richardson number flows have shown good adaptation to the available data. However, the results of large Richardson number flows, for example, Ri = 100, have shown a significant difference to the available data. Investigations revealed that this difference was due to the method of applying the body force. Therefore, the choice of the best way to apply the body force was investigated. Finally, for the large Richardson number flows, the best method to apply the body force has been identified among the several techniques. Originality/value To the authors’ knowledge, the effects of methods for applying the body force were not investigated in the cavities mixed convection, even though there are numerous investigations conducted on mixed convection with the LBM. In this study, the effects of techniques to apply the body force were investigated in large Richardson number flows. Finally, the best method to apply the body force is distinguished between several techniques for the large Richardson number mixed convection flows.

Laminar entry region mixed convection heat transfer from an inclined rectangular fin array

2020 ◽  
Vol 30 (6) ◽  
pp. 3283-3305
Author(s):  
Krishna Roy ◽  
Asis Giri ◽  
Biplab Das
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Thermal Field ◽  
Computational Study ◽  
Convection Heat Transfer ◽  
Solar Thermal ◽  
Convection Heat ◽  
Content Type ◽  
Mixed Convection Heat Transfer ◽  
Practical Implications

Purpose The paper aims to investigate the influence of the angle of inclination on mixed convection heat transfer from rectangular plated shrouded fin array computationally. This study has got applications in the various thermal field such as cooling, solar thermal and so on. Design/methodology/approach A computational study is made to evaluate the thermal performance in an inclined channel. Findings Increase in clearance from 0.01 to 0.25 results in an increase of local Nusselt number by is as high as 15% near the exit. At a higher value of Gr with an increase in C* from 0.10, Nu is found to increase by 5.5%. Increase in Gr by 1.37 times results in enhancement of Nu by a maximum of 25-30%. Around 10% increase in overall Nu value is observed with an increase in inclination (i.e. from 30° to 60°). Practical implications This study has got applications in the various thermal field such as cooling, solar thermal and so on. Originality/value Entry region mixed convection in a shrouded inclined finned channel is performed.

Manninen’s mixture model for conjugate conduction and mixed convection heat transfer of a nanofluid in a rotational/stationary circular enclosure

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Faraz Hoseininejad ◽  
Saeed Dinarvand ◽  
Mohammad Eftekhari Yazdi
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Content Type ◽  
Mixed Convection Heat Transfer ◽  
Conjugate Conduction

Purpose This study aims to investigate numerically the problem of conjugate conduction and mixed convection heat transfer of a nanofluid in a rotational/stationary circular enclosure using a two-phase mixture model. Design/methodology/approach Hot and cold surfaces on the wall or inside the enclosure (heater and cooler) are maintained at constant temperature of Th and Tc, respectively, whereas other parts are thermally insulated. To examine the effects of various parameters such as Richardson number (0.01 = Ri =100), thermal conductivity ratio of solid to base fluid (1 = Kr = 100), volume fraction of nanoparticle (0 = φ = 0.05), insertion of conductive covers (C.Cs) around the heater in a different shape (triangular, circular or square), segmentation and arrangement of the conductive blocks (C.Bs) and rotation direction of the enclosure on the flow structure and heat transfer rate, two-dimensional equations of mass, momentum and energy conservation, as well as volume fraction, are solved using finite volume method and Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm. Findings The results show that inserting C.C around heater can increase or decrease heat transfer rate, and it depends on thermal conductivity ratio of solid to pure fluid. Also, it is found that by the division of C.B and location of its portions in a horizontal configuration, heat transfer rate reduces. Moreover, it is observed that external heating and cooling of the enclosure causes enhancement of heat transfer relative to that of internal heating and cooling. Finally, results illustrate that under the condition that cylinders rotate in the same direction, the heat transfer rate increases as compared to those that rotate in the opposite direction. Hence rotation direction of cylinders can be used as a desired parameter for controlling heat transfer rate. Originality/value A comprehensive report of results for the problem of conjugate conduction and mixed convection heat transfer in a circular cylinder containing different shapes of C.C, conducting obstacle and heater and cooler has been presented. An efficient numerical technique has been developed to solve this problem. The achievements of this paper are purely original, and the numerical results were never published by any researcher.

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