导　　师： 骆仲泱;程乐鸣

学科专业： 080702

授予学位： 硕士

作　　者： ;

机构地区： 浙江大学

摘　　要： 纳米流体是指将纳米级/(10-9 m/)的金属或非金属颗粒按一定比例加入到液体中形成的特殊悬浮液。由于纳米颗粒具有常规微细颗粒不具备的特殊理化效应,如表面效应、量子尺寸效应、宏观量子隧道效应等,使纳米流体具有导热系数高,对设备磨损小等优点,可作为良好的传热工质。 纳米流体的制备按步骤可分为：一步法和两步法。一步法制备的纳米流体分散性和稳定性较好,但两步法在纳米流体的工业化制备上具有明显的工艺和经济优势。为研究纳米流体导热和辐射等特性,本文利用高压微射流法/(两步法/)制备了多种纳米流体,并通过Zeta电位和分散率的测量分析了流体的稳定性。 本文利用乌氏粘度计测量了不同纳米流体的粘度,研究了纳米颗粒种类、形状、粒径、体积浓度及流体温度对粘度的影响。实验结果表明：相同体积浓度的纳米流体,颗粒长径比的增大和粒径的减小都会增加流体的粘度；流体粘度随体积浓度的增大而线性增长,随流体温度的增加而降低,变化趋势与基液相似 本文搭建了单瞬态热线法试验台,用蒸发法真空镀膜技术及透明聚氨酯绝缘喷漆对铂丝表面进行了绝缘处理,使该试验台能满足pH值为1～11的纳米流体导热系数的测试要求。首先用乙二醇和去离子水对试验台进行了校正,表明该试验台具有较高的精度,可将误差控制在土2/%。通过测试不同工况下纳米流体的导热系数,研究了纳米颗粒种类、形状、粒径、体积浓度、流体温度对导热系数的影响。实验表明：纳米颗粒自身导热系数越高,相同条件下其对应的纳米流体导热系数亦越大；相同体积浓度下,粒径越小,导热系数越大；导热系数随体积浓度增大而增大,随温度升高而升高。在导热系数计算模型研究上,由于目前的预测模型一般只考虑了部分影响因素或建立在特定 Nanofluid is a new kind of suspension which is prepared by adding nanoscaled metallic or nonmetallic particles with definite proportions in base fluid. Nanoparticles have some special characters, such as surface effect, quantum size effect and macroscopic quantum tunnel effect, which enable the improvement of heat transfer coefficient without clogging flow channels or eroding pipelines, therefore nanofluid is also a favorable working fluid for heat transfer. There are two classified processes used to produce nanofluids:one-step and two-step methods. Nanofliud made by one-step method has better stability and dispersion, while two-step method has advantages in manufacture and cost. To investigate the characteristics of nanofluids on thermal conductivity and the radiation. high performance nanofluids were prepared by high shear homogenizer, and the stability of the nanofluids were analyzed by monitoring the size distribution and zeta potential. In this thesis, to investigate the effects of several key factors on viscosity, including particle type, size, shape, and fluid temperature, we detected the viscosity of the nanofluids by Ubbelohde viscometer. Experimental results indicate that the reduction of particle size will enhance the viscosity. Meanwhile, the viscosity increases linearly with the rising of volume concentration of particles, and declines with the drop of fluid temperature, which is similar with that of the base fluid. Hot-wire method was customized and the surface of platinum wire was insulated by evaporation vacuum coating technology and transparent polyurethane insulation spray, so that the thermal conductivity of nanofluids with a pH value in a range of 1-11 can be tested accurately. Ethylene glycol and deionized water were used to calibrate the testing system, showing that the test method has a very high accuracy within 2/% error. The thermal conductivity of nanofluids was measured under different conditions. Experimental results demonstrate that the thermal conductivity of nanofluid in

关 键 词： 纳米流体 粘度 导热系数 辐射特性 值 团聚 分形维数

领　　域： [一般工业技术]