Abstract:

Using water as the working fluid, the coupling characteristics of low Reynolds number pulsating flow and flexible wall in triangular channel were experimentally studied. Experiments of heat transfer and flow resistance were carried out in detail under the impacts of Womersley number (W), pulsating amplitude (A) and rigidity (K_b). Moreover, the dynamic response relation between flexible wall and pulsating flow was investigated to illuminate the effects of flexible wall deformation and vibration frequency on heat transfer and flow resistance. The results indicate that the dual effects of heat transfer enhancement and drag reduction are achieved by pulsating flow in the triangular channel with flexible wall, but heat transfer efficiency increasing by 0-50% is relatively weak. Besides, the reason why flow resistance and enhanced heat transfer efficiency decease is that deformed flexible wall results in increasing the cross-sectional area of the flexible wall (the fluid velocity decreases), and the pulsation energy is weakened with the increase of W and A. Furthermore, the reduction of enhanced heat transfer effect cased by flexible wall vibration and deformation gradually tends to be dominant with the increase of W . The reduction of flow resistance is mainly caused by the deformation of the flexible wall, and the flexible wall vibration frequency has less effect on the energy dissipation of pulsating flow.

Key words: pulsating flow, flexible wall, heat transfer, flow, drag reduction

摘要：

以水为工质对三角槽道低 Reynolds 数脉动流与柔性壁耦合特性进行了实验研究。通过传热与流动实验，分析了脉动频率(W)、脉动振幅(A)、柔性壁特性对脉动流传热及流动的影响。同时，通过可视化实验，研究了柔性壁与脉动流之间的响应特性，解析了柔性壁形变与振频对脉动流传热及流动的作用机制及分离贡献。研究结果表明，柔性流道脉动流可以实现强化传热与流动减阻双重效果，但强化传热效果相对较弱(传热效率提升0~50%)，适用于以减阻为主要目的的换热场合；柔性壁减阻与削弱强化传热效率，源于柔性壁形变造成时均流通截面积增大(流体流速下降)、W与A的增大减弱脉动能量；W的增加将使得柔性壁振动对脉动流强化传热效率的削减逐步趋于主导地位，而A的增加将使得柔性壁变形对脉动流强化传热效率的削减逐步趋于主导地位；脉动流阻力的削减主要来自于柔性壁的变形(D₁>70%)，而柔性壁振频对于脉动流能量耗散的抑制作用较为次要。

关键词: 脉动流, 柔性壁, 传热, 流动, 减阻