纳米流体导热系数影响因素分析

为了全面分析纳米流体的稳定性及导热系数影响因素，采用两步法配置了以去离子水和乙二醇为基液的氧化铝纳米流体，并添加了不同种类的分散剂.利用紫外可见分光光度计对纳米流体吸光度值进行测试，并基于Hot Disk热物性分析仪测试其导热系数.结果表明：吸光度法可有效评价纳米流体稳定性，但需要考虑分散剂对基液吸光度值的影响.超声波振荡可破坏粒子团聚，且当超声时间为1h时纳米流体稳定性最佳.分散剂、粒子体积分数、温度、基液等因素均会影响纳米流体的导热性能.当温度为50益时，添加质量分数0.2%的PVP分散剂，体积分数为0.5%的氧化铝-水纳米流体导热系数提高约20%.纳米流体可有效提供工质导热系数，提升系统散热性能.

Analysis of the Thermal Conductivity of Nanofluids

In order to analyze the stability and thermal conductivity of nanofluids, Al2 O3 nanofluids based on DI-water and EG were prepared by a two-step method, and different dispersant were added to avoid particle aggregation. The UV/VIS Spectrophotometer and Hot Disk thermal constant analyzer were used. The results reveal that absorbance can appraise the stability of nanofluids effectively, but the influence of dispersant should be considered. Ultrasonic oscillations can destroy the accumulation of nanoparticles, and it is 1h for the best effect. Moreover, dispersant, particle volume fraction, temperature and based fluids are all the influencing factors on thermal conductivity of nanofluids. When the temperature is 50℃, the thermal conductivity of 0. 5% Al2 O3-water nanofluids with 0. 2% PVP has been improved by about 20%. Nanofluids can enhance the thermal conductivity of working fluids effectively, and the heat transfer performance of system can also be improved.