摘要
DN(double notched)型波纹板传热元件在回转式空气预热器中应用广泛,为了揭示DN板波纹通道内的微观流动形态和强化传热机理,本文采用LBKE(Lam and Bremhorst k-ε model)湍流模型和计算流体动力学(CFD)数值模拟技术对DN板的传热、阻力特性展开研究,预测DN板的传热和阻力系数,分析DN板通道内的流场和温度场。模拟计算发现:DN板通道内的流动可分为波纹通道流动和平直通道流动两大类;DN板斜波纹段、凹槽段迎风面努塞尔数(Nu)较大,背风面Nu较小;Nu随着雷诺数(Re)的增大而增大,DN板上的Nu分布随着Re的增大而更趋均匀;增加DN板上斜波纹结构比例可提升其传热能力,但阻力损失也会相应增加;DN板在中等Re水平(Re≈5000)下运行时效果最佳,此时既能保证DN板上Nu均匀分布又控制了阻力损失大小。
The double notched(DN) type corrugated plate heat transfer element is commonly used in rotary air preheaters. To reveal the micro-flow morphology and strengthening heat transfer mechanism in the corrugated channel of the DN plate, the LBKE(Lam and Bremhorst k-ε model) turbulence model and CFD numerical simulation technology are applied to investigate the heat transfer and flow resistance characteristics of the DN plate, including predicting the heat transfer and flow resistance coefficient, and analyzing the flow field and temperature field inside the channel of the DN plate. The results show that, two types of flow are observed in the predicted velocity fields, wavy channel flow and pipe flow. The Nusselt number Nu in upwind surface of the DN plate is larger while that at the leeward side is lower. As the Reynolds number Re increases, the Nu increases and its distribution on the DN plate becomes more uniform. Increasing the proportion of the corrugated structure can enhance the heat transfer capacity of the DN plate, but will also increase the resistance loss simultaneously. It suggests that the DN plate operate at moderate Re values(≈5 000), to obtain the best effect and ensure the uniform distribution of Nu and control the resistance loss.
引文
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