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Numerical investigation of air forced convection in channels with differently shaped transverse ribs

机译：横向肋肋形状不同的通道中空气对流的数值研究

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Purpose - The purpose of this paper is to investigate the flow and the heat transfer characteristics of a two-dimensional rib-roughned rectangular duct with the two principal walls subjected to uniform heat flux. In particular, the main goal is to generate friction and heat transfer data, for different values of p/e with square, rectangular, trapezoidal and triangular shape ribs for Reynolds numbers in the range between 20,000 and 60,000 and different heights and to describe the temperature and fluid-dynamic fields around the ribs. Design/methodology/approach - The model is constituted by a two-dimensional duct. On the duct wall square, rectangular, triangular and trapezoidal ribs are introduced by changing different geometry ratios. Governing equations are solved numerically by means of the finite-volume method. Findings - Simulations show that maximum Nusselt numbers are detected in correspondence with dimensionless pitch equal to 12 and 10 for the square, trapezoidal and rectangular ribs, and triangular ones, respectively. Heat transfer rate is at most 2.45 times higher than the smooth duct, when dimensionless height is equal to 0.05, and 1.85 at a dimensionless height equal to 0.02; furthermore, the friction factor is the highest at a pitch ratio of ten for the rectangular, trapezoidal and square ribs while the triangular ones show the maximum values at a dimensionless pitch equal to 8. For Re > 40,000 an asymptotic behavior is detected. Best thermal performances are provided by triangular ribs with w/e = 2.0 while the rectangular ribs with w/e = 2.0 present the lowest friction factor values. Local Nusselt number profiles reveal that the maximum values are detected from three to five times the rib height from the downstream turbulator. Finally, temperature fields and stream function contours are given in order to visualize the temperature distribution and flow pattern in presence of d-type and k-type roughness behavior also for triangular ribs. Originality/value - The paper investigates evaluation of temperature and velocity fields thermal and fluid-dynamic behaviors (in terms of average and local Nusselt number profiles and friction factors ones) of roughned ducts with different shapes, heights and aspect ratios of ribs in turbulent regime. The thermo-physical properties of fluid are assumed to be dependent on temperature. The paper is useful to thermal designers.
机译：目的-本文的目的是研究二维肋筋粗糙的矩形风管的流动和传热特性，其中两个主壁承受均匀的热通量。特别地，主要目标是生成摩擦和传热数据，对于雷诺数在20,000至60,000之间，高度不同的正方形，矩形，梯形和三角形肋的p / e值具有不同的值，并描述温度肋骨周围的流体动力场。设计/方法/方法-模型由二维管道组成。通过改变不同的几何比例，在风管壁上引入方形，矩形，三角形和梯形肋。控制方程通过有限体积法进行数值求解。结果-仿真显示，分别针对正方形，梯形和矩形肋和三角形肋，分别以等于12和10的无量纲间距检测到最大的Nusselt数。当无量纲高度等于0.05时，传热速率最多是光导管的2.45倍；在无量纲高度等于0.02时传热速率是1.85倍。此外，矩形，梯形和方形肋的螺距系数为十时摩擦系数最高，而三角形的梯形肋的无因次螺距则摩擦系数最大。对于Re> 40,000，可以检测到渐近行为。 w / e = 2.0的三角形肋可提供最佳的热性能，而w / e = 2.0的矩形肋可提供最低的摩擦系数值。局部Nusselt数曲线表明，从下游湍流器肋高的三到五倍检测到最大值。最后，给出了温度场和流函数等值线，以便可视化在存在三角形肋的d型和k型粗糙度行为的情况下的温度分布和流型。原创性/价值-本文研究了在湍流状态下肋的不同形状，高度和长宽比的粗糙管的温度和速度场的热和流体动力学行为（根据平均和局部Nusselt轮廓以及摩擦系数）的评估。假定流体的热物理性质取决于温度。本文对热设计人员很有用。

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