ABSTRACT

The current paper reports the impact of variation of ribs’ pitch distance in the case of laminar flow and forced convection heat transfer upon flow characteristics in a rectangular channel experimentally and numerically. The thermal behavior of the ribbed channel with water as a working fluid was measured experimentally and compared to numerical simulations performed using Galerkin finite element method under the same operating and boundary conditions. Numerical analysis has been extended to investigate the entire ribbed channel with the presence of nano-particles in the base fluid to predict the performance of the heat transfer process with interaction with extended geometries. The analysis was done keeping heat flux constant at the bottom boundary condition. The impacts of the rib pitch-to-height ratio (p/e = 2.5, 3.125, 3.75, 4.375, and 5), nano-particle volume concentration (0% ≤ φ ≤ 4%), also Reynolds numbers (427.44 to 1282. 9), were all examined in the present study. The results show a good coincidence between the numerical and experimental study with a maximum deviation was nearly 3%. The main findings show that when the nano-fluid volume fraction increases from 0% to 4%, the average Nusselt number for all aspect ratios increases too. Meanwhile, the average skin friction decreases as the Reynolds number increase for different values of AR. Furthermore, the results revealed that the water – aluminum oxide nano-fluid with the concentration φ = 0.04 aid to improve the coefficient of heat transfer by 5% higher than the case of φ = 0.02, and up to 9.4% compared to pure water (φ = 0) due to an increase in viscosity. Finally, the current work shows that these extended surfaces with the use of nano-fluids can remarkably improve heat transfer properties with barely increased friction, making them suitable candidates for the development of efficient heat exchanger devices.

摘要

当前的论文报告了在层流和强制对流传热的情况下肋间距变化对矩形通道中流动特性的实验和数值影响。以水作为工作流体的带肋通道的热行为通过实验测量，并与在相同操作和边界条件下使用 Galerkin 有限元方法进行的数值模拟进行比较。数值分析已扩展到研究基液中存在纳米颗粒的整个肋状通道，以预测与扩展几何结构相互作用的传热过程的性能。分析是在底部边界条件下保持热通量恒定。肋骨间距与高度比的影响（p/e = 2.5、3.125、3.75、4.375 和 5），纳米颗粒体积浓度（0% ≤ φ ≤ 4%），还有雷诺数（427.44 到 1282. 9），都在本研究中进行了检查。结果表明数值研究与实验研究之间具有良好的一致性，最大偏差接近 3%。主要发现表明，当纳米流体体积分数从 0% 增加到 4% 时，所有纵横比的平均努塞尔数也会增加。同时，对于不同的 AR 值，平均表面摩擦随着雷诺数的增加而减小。此外，结果表明，浓度为 φ = 0.04 的水 - 氧化铝纳米流体有助于提高传热系数，比 φ = 0.02 的情况高 5%，与纯水相比高达 9.4%（ φ = 0) 由于粘度增加。最后，