Control of Heat and Momentum Transport Process by a Reversible Transform Micelle of Polymer

众所周知，非牛顿流体中的索恩斯效应是减阻的原因。最近有报道称，添加少量的表面活性剂也能起到同样的减阻效果。减阻流动的特点能够以较低的能量损失输送长距离热介质。减阻机理一直没有得到深入的研究，尤其是在实际应用中出现的湍流条件下。本文对聚合物可逆转变胶束结构的行为进行了实验研究，并发展了一种利用表面活性剂控制热流体现象的技术。实验研究了稀相表面活性剂/水溶液在二维通道中的传热特性。还测量了热边界层内的温度分布。结果表明，在减阻热边界层中，壁面附近存在高扩散系数层，且随着壁面热流密度的增加，壁面附近温度波动的时间尺度变小。为了增加传热系数，利用网塞施加高剪应力破坏表面活性剂溶液中的胶束结构，从而产生湍流。网状塞表明，高换热区域具有与水流相同的湍流强度。网格有助于产生较高的壁面剪应力，从而破坏引入湍流的棒状胶束。结果表明，由于网塞只产生局部高剪应力，速度的湍动强度逐渐减小到与网眼下游减阻流动相同的强度。该技术可用于减阻流动中的有效强化换热。

It is well known that Thorns effect in non-Newtonian fluid causes the drag reduction. Recently it has been reported that an addition of small amounts of surfactants also provided the same effect on the drag reduction. The characteristics of drag reduction flow can transport the long distance thermal medium with low energy loss. The mechanism of drag reduction flow has been stilt unexplored, especially for the turbulent flow condition that appears in a practical application. In the present study, experimental study has been performed on the behavior of micelle structure with reversible transform of polymer, and a controlling technique for thermo-fluid phenomena has also developed by using surfactant.Heat transfer characteristics of a dilute surfactant/water solution in a two dimensional channel has been experimentally investigated. Temperature profile measurements in the thermal boundary layer were also made. It was found that high diffusivity layer exists near the wall in the drag reducing thermal boundary layer and that the time scale of temperature fluctuation in the layer becomes smaller as increased of wall heat flux. In order to increase the heat transfer coefficients, the mesh plug was used to exert high shear stress to destroy micelle structure in the surfactant solution so that turbulence could be produced. The mesh plug indicated that the high heat transfer region had the same turbulent intensity as that of water flow. The mesh helped to create high wall shear stress and therefore to destroy the rod-like micelles for introducing turbulent. It was found that the turbulent intensities of the velocity gradually decreased to the same as those of drag reduction flow downstream form the mesh because the mesh plug only produced a local high shear stress. This technique can be applied for effective heat transfer augmentation in a drag reduction flow.