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Experimental investigation of passive flow destabilization and heat transfer enhancement in grooved channels.

机译：槽形通道中被动流动失稳和传热增强的实验研究。

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摘要

An experimental investigation of passive flow destabilization and heat transfer enhancement in grooved channels is performed. The channel geometry is designed to excite normally-damped Tollmien-Schlichting modes resulting in early transition to three-dimensional unsteady flow. In this experiment, a hydrodynamically fully developed flow encounters an isolated section where one channel boundary is a saw-tooth series of periodic, transverse grooves. Attention is given to both the grooved section, where unsteadiness appears, and a flat recovery region downstream of the grooves, where unsteadiness eventually decays. The experimental measurements are made for a range of Reynolds numbers, 300 {dollar}le{dollar} Re {dollar}le{dollar} 15,000. These results are compared to measurements in the same test section with the grooved wall replaced by a flat surface. Both air and water are used as working fluids.; Flow visualizations at Re = 1000 in long, grooved channels show that unsteadiness appears within a few hydraulic diameters of the first groove. The onset point for unsteadiness is closely correlated with locations where measurable increases in heat transfer and pressure drop are observed. Fully developed results indicate that heat transfer is enhanced by as much as a factor of 4.6 at equal Reynolds numbers and 3.5 at equal pumping powers relative to flat passages.; The local heat transfer coefficient and pressure gradient drop off from the grooved channel values at different rates in the flat, downstream recovery passage. In the Reynolds number range, 1500 {dollar}le{dollar} Re {dollar}le{dollar} 3000, the pressure gradient relaxes to within 10% of the flat channel value in roughly ten hydraulic diameters. The heat transfer decay length is approximately twice that distance. Intermittently grooved channels may, therefore, offer even greater practical improvement in the heat transfer/pumping power performance of exchange passages.
机译：进行了沟槽通道中的被动流动失稳和传热增强的实验研究。通道的几何形状设计成激发正常阻尼的Tollmien-Schlichting模式，从而导致早期过渡到三维非定常流动。在该实验中，流体动力学充分发展的流动遇到一个孤立的部分，其中一个通道边界是一系列周期性横向槽的锯齿形。注意出现不稳定的开槽部分和最终导致不稳定消失的沟槽下游的平坦恢复区域。对一系列雷诺数进行了实验测量，雷诺数为300 15,000 Re。将这些结果与同一测试部分中的测量结果进行比较，但用平的表面代替开槽的壁。空气和水都用作工作流体。在Re = 1000的长沟槽通道中的流动可视化显示，在第一个沟槽的几个水力直径内出现了不稳定。不稳定的起点与观察到的传热和压降明显增加的位置密切相关。充分发展的结果表明，相对于平坦通道，在相同的雷诺数下，传热提高了4.6倍，在相同的泵浦功率下，传热提高了3.5倍。在平坦的下游恢复通道中，局部传热系数和压力梯度以不同的速率从开槽的通道值下降。在雷诺数范围1500 {Releolds范围内，在大约10个水力直径中，压力梯度松弛到平坦通道值的10％以内。传热衰减长度大约是该距离的两倍。因此，间歇地开槽的通道可以在交换通道的传热/泵送功率性能方面提供更大的实际改进。

著录项

  • 作者

    Chen, Ruey-Feng.;

  • 作者单位

    University of Nevada, Reno.;

  • 授予单位 University of Nevada, Reno.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 1993
  • 页码 170 p.
  • 总页数 170
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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