Analyzing Heat Transfer Characteristics of Pulsating Shear Layer under Eddy Motion
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摘要: 基于自激振荡的脉冲效应,分析了自激振荡换热管的传热效果。利用大涡模拟数值计算方法,分析了自振管瞬时涡量变化对管道流场的影响,分析了随下游流道管径比L*=d3/d2变化流向涡与法向涡的瞬时结构及其换热特性与阻力特性,并以综合性能评价系数评价管道的换热特性。结果表明:自振腔内剪切层中的离散涡与碰撞壁碰撞分散出的小涡随边向下游运动,并在下游流道近壁面处诱发新漩涡;L*变化可以控制脉动剪切层的发展,随着L*的增大流向涡的强度先增大后减小,法向涡逐渐向管道轴心发展;通过调节L*可以控制管道的换热与阻力,当1.4 ≤ L* ≤ 1.8时其传热效率提高45.1%~56.5%,综合性能系数最高可提高45.4%。Abstract: Based on the impulse effect of self-excited oscillation, the heat transfer effect of the heat exchanger tube is analyzed. The influence of changes in instantaneous vorticity on the flow field of the downstream flow channel is analyzed with the large eddy simulation numerical calculation method. The transient structure, heat transfer characteristics and resistance characteristics of the downstream flow channel with L*=d3/d2 are analyzed and evaluated with the comprehensive performance evaluation coefficient. The results show that the small vortices dispersed by the collision of the discrete vortex in the shear layer of the vibration cavity move downstream with the edge, thus inducing the new vortex generation. The change of L* can control the development of the pulsating shear layer. With the increase of L*, the strength of the stream-wise vortex first increases and then decreases, and the normal vortex gradually develops towards the pipe axis. By regulating L*, the heat transfer and resistance can be controlled. When 1.4 ≤ L* ≤ 1.8, the heat transfer efficiency is improved by 45.1% to 56.5%, and the comprehensive performance coefficient is up to 45.4%.
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Key words:
- self-excited oscillation /
- shear layer /
- heat transfer characteristics
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表 1 自激振荡脉冲射流喷嘴主要参数
mm 参数名称 数值 上游入口管径d0 12 下游出口管径d3 6~14 上游入口流道长度l1 40 下游入口流道长度l2 12 下游入口流道长度l3 200 自振腔入口直径d1 5 自振腔出口直径d2 6 自振腔室直径D 40 自振腔室长度L 12 表 2 下游换热管道的ENu, Ef和η
L* ENu Ef η 1.0 0.672 0.572 0.811 1.4 1.451 1.713 1.376 1.8 1.562 1.241 1.454 2.2 0.326 0.857 0.343 2.6 0.287 0.487 0.365 -
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