Abstract

Forced convection heat transfer in power-law fluids has been investigated numerically around four identical circular cylinders in a diamond array in a square enclosure. For the laminar flow, the governing equations have been solved numerically over the following ranges of parameters: Reynolds number (5 − 200), Prandtl number (0.7 − 100), power-law index (0.2 − 2) and center-to center gap between cylinders (0.3 − 0.7) to elucidate their influence. The detailed kinematics and engineering parameters are influenced by the gap between the cylinders via the development of multiple secondary flow regions and/or the splitting of incoming fluid stream. The drag on the trailing cylinders with reference to the lead cylinder can be up to ± ∼ 80% higher or lower depending upon the gap between the cylinders, power-law index and Reynolds numbers. In compact arrays, the drag becomes slightly negative due to the reverse flow for certain combinations of power-law index (< 1) and high Reynolds numbers (100 and 200). Similarly, the heat transfer affected by the subsequent cylinders ranges from 50-60% for the second cylinder which drops to ∼10% for the last cylinder. Finally, the functional dependence of the Nusselt number has been consolidated in terms of Reynolds number, Prandtl number, power-law index and the gap ratio.

摘要

幂律流体中的强制对流传热已在方形外壳中的菱形阵列中的四个相同圆柱体周围进行了数值研究。对于层流，控制方程已在以下参数范围内进行了数值求解：雷诺数 (5 − 200)、普朗特数 (0.7 − 100)、幂律指数 (0.2 − 2) 和中心到中心的间隙圆柱体之间 (0.3 - 0.7) 以阐明它们的影响。详细的运动学和工程参数受气缸之间间隙的影响，通过多个二次流动区域的发展和/或进入流体流的分裂。根据气缸之间的间隙、幂律指数和雷诺数，拖曳气缸相对于引导气缸的阻力可高达 ± 80% 或更高或更低。在紧凑阵列中，由于幂律指数 (< 1) 和高雷诺数 (100 和 200) 的某些组合的反向流动，阻力变得略微为负。同样，受后续气缸影响的传热范围为第二个气缸的 50-60%，最后一个气缸下降到 10%。最后，努塞尔数的函数依赖性在雷诺数、普朗特数、幂律指数和间隙比方面得到了巩固。