Abstract

This numerical study performed the three-dimensional simulations to explore the turbulent thermal flow characteristics over the heated blocks inside a square channel by a slotted ribbed plate through the RNG $\kappa -\epsilon$ turbulence model and SIMPLE-C algorithm. The influence of slotted ribbed plate on the enhancement of turbulent heat transfer from these heated block surfaces would be evaluated through varying the pitch ratio of rib (1.2, 0.8, and 0.6) and the streamwise locations of slotted ribbed plate (before the left side of first heated block, x = 130 mm; aligned with the left side of first heated block, x = 150 mm; after the left side of first heated block, x = 170 mm) under different Reynolds numbers (5000, 6500, 8000, and 9500). The results of numerical analyses reveal that the slotted ribbed plate placed above the heated blocks can effectually augment the heat transfer. In addition, these slots can induce the local fluid flow bursts along the surfaces of the blocks and modify flow interaction between the ribs and blocks on a channel. The slotted ribbed plate aligned with the left side of first heated block can lead to greater overall-mean Nusselt number than the other locations. As compared to C0 (without plate), C5 (the slotted ribbed plate of 0.8 pitch ratio located at x = 150 mm) brings the maximum enhancement ratio of the overall-mean Nusselt number about 1.57 at Re = 9500. Under considering the friction through the channel, C7 (the slotted ribbed plate of 0.6 pitch ratio located at x = 130 mm) gains the best thermal performance factor about 1.45 at Re = 5000.

摘要

这项数值研究进行了三维模拟，以探索通过RNG的开槽肋板在方形通道内加热块上的湍流热流特性。 $\kappa -\epsilon$湍流模型和SIMPLE-C算法。通过改变肋的螺距比（1.2、0.8和0.6）和开肋肋板的流向位置（在肋板左侧之前），可以评估开肋肋板对这些加热块表面湍流传热增强的影响。第一个加热块，x  = 130 mm；与第一个加热块的左侧对齐，x  = 150 mm；在第一个加热块的左侧之后，x = 170毫米）在不同的雷诺数（5000、6500、8000和9500）下。数值分析结果表明，放置在加热块上方的开槽肋板可以有效地增加热传递。另外，这些狭槽可引起沿块的表面的局部流体流动爆发，并改变通道上的肋与块之间的流动相互作用。与第一个加热块的左侧对齐的开槽肋板可导致比其他位置更大的总平均努塞尔数。与C0（无板）相比，C5（螺距比为0.8的开槽肋板位于x = 150 mm）在Re = 9500时使总平均Nusselt数的最大增强率约为1.57。在考虑通过通道的摩擦力时，C7（x 值为130 mm的0.6节距比的开槽肋板）获得Re = 5000时的最佳热性能系数约为1.45。