Studies on mechanism of outbreak and disappear of drag reduction by temperature change

为了寻找控制少量表面活性剂减阻作用的发生和消失的可行方法，本文从三个参数1.另外的表面活性剂的浓度，2.溶液的温度，和3.解决方案的速度。然而，在换热器的实际应用中，在操作中难以改变表面活性剂的浓度和溶液的速度。局部加热和局部冷却使管壁温度发生变化是唯一可能的，当管壁附近溶液温度超过或低于临界值时，减阻现象发生和消失。这些临界值取决于附加表面活性剂的浓度和溶液的流速。此外，临界温度的位置距离表面约0.1mm。 关于我们 在此范围内，温度几乎是恒定的，从减阻现象的爆发到消失的温度变化程度取决于外加表面活性剂的浓度、溶液的温度和溶液的剪切速度。温度对减阻现象从爆发到消失的变化过程不明显，存在滞后现象，特别是当表面活性剂浓度超过1000ppm时，粘度的变化依赖于温度。在这种情况下，阻力的减小和雷诺数的变化同时发生。本实验采用闭环流动通道，以十六烷基三甲基氯化铵（CTAC）为阳离子表面活性剂，加入等量的水杨酸钠作为反离子，研究了添加少量表面活性剂控制水流湍流摩擦阻力降低的可能性。少

The purpose is to find the practicable control method of the outbreak and disappear of drag reduction by the addition of small amount of surfactant.Control of the reduction in turbulent friction drag of water flow by the addition of small amount of surfactant has been done by three parameter, 1. the concentration of additional surfactant, 2. temperature of the solution, and 3. velocity of the solution. In practical applications to heat exchanger, however, it is difficult to change the concentration of surfactant and velocity of the solution in operation. Change of temperature of duct wall by heating and cooling locally has the only possibility.The outbreak and disappear of drag reduction phenomenon are observed on the condition that temperature of the solution near the wall go over or go down the critical value. These critical values depend on the concentration of additional surfactant and velocity of the solution. Furthermore, the place of critical temperature is about 0.1mm from the … More wall and within this range, temperature is almost constant.The extent of temperature from the outbreak to the disappear of drag reduction phenomenon depend on the concentration of additional surfactant, temperature of the solution, and shear velocity of the solution. The change process from the outbreak to disappear of drag reduction phenomenon due to temperature is not sharp and the hysteresis was observed.Specially, in the case of concentration of additional surfactant over about 1000ppm, change of viscosity depend on temperature. In this case, reduce of drag and change of Reynolds number occur at the same time. But, we need an in-depth survey and data.Possibility of control of the reduction in turbulent friction drag of water flow by the addition of small amount of surfactant made clear in this experiment using a closed loop flow channel and the cationic surfactant used was cetyltrimethyl ammonium chloride(CTAC),which was added with the same weight of sodium salicylate as the counter ion. Less