采用两步法制备低浓度Al_2O_3(40 nm)-水纳米流体,其体积分数为0.1%～0.5%.制备过程中不加分散剂,采用超声振动,并对其进行Zeta电位、粒度和吸光度测试表征其悬浮稳定性,结果表明当超声时间为3 h时,Al_2O_3-水纳米流体悬浮稳定性最好.进一步测试其导热系数,结果表明Al_2O_3-水纳米流体的导热系数均高于水的导热系数;室温下(17 ℃)当体积分数从0.1%增加到0.5%时,其导热系数从5.40%增加到17.9%.对于体积分数为0.2%的Al_2O_3-水纳米流体,当温度从17 ℃增加到57 ℃时,相应的导热系数从7.23%增加到23%;实验还发现纳米流体导热系数与纳米粒子的体积分数和温度均呈非线性关系.
Al_2O_3-water nanofluid with 40 nm particle size was produced with various volume concentrations from 0.1% to 0.5% using a two-step method with ultrasonication and without any surfactant. The analysis of zeta potential, particle size and absorbancy indicates that 3 hours of ultrasonic vibration can uniformly disperse the Al_2O_3 nanoparticles in water. In this experimental process, thermal conductivities were mearsured.The results show that the thermal conductivities of Al_2O_3-water nanafluids are all higher than water. The enhancement of thermal conductivity is 5.40%-17.9% in the low volume concentration range of 0.1%-0.5%. Enhancement of thermal conductivity is 7.23%-23% in the temperature range of 17-57 ℃ at a volume fraction of 0.2%. Furthermore, the experimental results show the thermal conductivities of Al_2O_3-water nanofluids increased nonlinearly with the nanoparticle volume concentration and temperature increasing.
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