改性纳米碳粉芒硝基纳米流体强化传热

Enhanced Heat Transfer by Modified Nano-carbon Powder in Mirabilite-based Nanofluid

本工作以纳米碳粉为原料,浓酸及氨水、乙醇等为改性剂,制备了含有亲水性基团的改性纳米碳粉,并通过两步法制备出纳米碳粉芒硝基纳米流体。结果表明:与未改性纳米碳粉相比,改性纳米碳粉表面均含有亲水性基团,能稳定分散在芒硝基纳米流体中。芒硝基纳米流体温度越低,粘度对体积分数变化的感知能力越强;纳米碳粉体积分数越低,粘度对温度变化的感知能力越弱。40℃下,添加0.25%(体积分数)改性纳米碳粉的芒硝基纳米流体,相比于未添加纳米颗粒的芒硝基相变材料,其导热系数平均增长11.93%。通过H-C模型可知,改性纳米碳粉在芒硝基纳米流体中的分散稳定性优于未改性纳米碳粉。

The modified nano-carbon powder containing hydrophilic groups was prepared by utilizing the nano-carbon powder as raw material and the concentrated acid,ammonia and ethanol as modifiers.Then,the nano-carbon powder mirabilite-based nano fluid was obtained through a two-step strategy.The test results indicate that the surface of the modified nano-carbon powder contains hydrophilic groups as compared with the unmodified material,which ensures the stable dispersion in the Glauber’s salt-based nanofluid.In addition,it is found that the lower the temperature of Glauber’s salt-based nanofluid,the higher the sensitivity of viscosity to volume fraction changes.In contrast,the lower the volume fraction of nano-carbon powder,the lower the sensitivity of viscosity to temperature changes.As a result,the thermal conductivity of the mirabilite-based phase-change material increased by 11.93%on average after adding the 0.25vol%modified nano-carbon powder under 40℃.The H-C model revealed that the dispersion stability of the modified nano-carbon powder in mirabilite-based nanofluid is better than that of the unmodified sample.