Islam A N M Fuhadul, Islam Riasat, Javed Sakib, Saha Sumon
Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh.
Heliyon. 2024 Jan 9;10(2):e24258. doi: 10.1016/j.heliyon.2024.e24258. eCollection 2024 Jan 30.
A computational analysis has been executed to analyze the combined conduction-mixed convection heat transfer of a rotationally oscillating solid cylinder in a differentially heated square box filled with air. The conjugate mixed convective flow initiates the heat transfer process, where the left-side boundary is isothermally kept to a higher temperature, and the right-side boundary is maintained at a lower temperature. Conduction heat transfer takes place inside the solid cylinder. Navier-Stokes and heat energy conservation equations model the system in the dimensionless pressure-velocity formulation. All these equations are solved via the Galerkin finite element approach. Three different combinations of Grashof (10-10), Reynolds (32-316), and Richardson (0.1-10) numbers are examined to systematically investigate the variations of governing parameters on instantaneous Nusselt numbers and the respective time-averaged values along the hot wall. In each combination, the impacts of the oscillating amplitude and frequency and the variation of cylinder diameter are examined to perform the optimization study. Power spectrum analysis is also done using the Fast Fourier Transform in the frequency domain to visualize the principal frequency of the system. The instantaneous values of the Nusselt number exhibit a wavering pattern over time owing to the recurrent waning and waxing of the thermal boundary layer. For all the cases, the maximum diameter and oscillating amplitude of the cylinder are found to maximize the heat transfer. However, the optimized frequency of the oscillation strongly depends on the selection of the governing parameters. In addition, the principal thermal frequency of the system is determined to be independent of the oscillation frequency.
已进行了一项计算分析，以研究在充满空气的差动加热方盒中旋转振荡实心圆柱体的传导 - 混合对流联合传热。共轭混合对流流动启动了传热过程，其中左侧边界等温保持在较高温度，右侧边界保持在较低温度。传导传热发生在实心圆柱体内。纳维 - 斯托克斯方程和热能守恒方程以无量纲压力 - 速度形式对方程组进行建模。所有这些方程都通过伽辽金有限元方法求解。研究了格拉晓夫数（10 - 10）、雷诺数（32 - 316）和理查森数（0.1 - 10）的三种不同组合，以系统地研究控制参数对沿热壁的瞬时努塞尔数及其各自时间平均值的变化。在每种组合中，研究了振荡幅度和频率以及圆柱直径变化的影响，以进行优化研究。还使用频域中的快速傅里叶变换进行功率谱分析，以可视化系统的主频。由于热边界层的反复减弱和增强，努塞尔数的瞬时值随时间呈现波动模式。对于所有情况，发现圆柱体的最大直径和振荡幅度可使传热最大化。然而，振荡的最佳频率强烈取决于控制参数的选择。此外，确定系统的主热频率与振荡频率无关。
