减阻型纳米流体在圆管内的流动和换热特性

Heat transfer and flow resistance characteristics with drag reducing nanofluids in circular tube

实验测定了在Reynolds数4000～16000范围内，质量分数0～0.5%的石墨、多壁碳纳米管、Al2O3、Cu、Al、Fe2O3、Zn纳米粒子加入到100～400 mg·kg-1浓度的十六烷基三甲基氯化铵（CTAC）减阻剂中所制备的减阻型纳米流体的摩擦阻力系数和对流传热系数。结果表明：在 CTAC 中加入水杨酸钠（NaSal）与去离子水所配制的减阻剂具有一定的稳定性和很强的减阻特性，当减阻剂浓度为200 mg·kg-1时其减阻特性最优。石墨纳米粒子在增强对流换热和减少流动阻力方面具有较佳的综合性能，当石墨纳米颗粒质量分数为0.4%时，其综合性能因子K是去离子水的5倍。最后给出了减阻型石墨纳米流体在圆管内的流动阻力和换热关联式，其计算值和实验值吻合良好。

Drag reducing nanofluids can reduce flow resistance and enhance fluid convective heat transfer. In this study, the convective heat transfer coefficient and flow resistance coefficient were determined experimentally at the Reynolds number of 4000—16000, with 0—0.5% mass fraction of graphite multi-walled carbon nanotubes, A12O3, Cu, Al, Fe2O3, and Zn nanoparticles added into a concentration of 100—400 mg·kg-1 cetyl trimethyl ammonium chloride （CTAC） drag reducing fluid. The ratio of the two fluids and preparation method were examined and the overall performance on convective heat transfer and flow characteristics was evaluated. The results show that the drag reducing fluid forming by sodium salicylate, CTAC and deionized water presents certain stability and significant drag reduction characteristic. At the drag reducing fluid concentration of 200 mg·kg-1, the drag reduction performance is the best. Graphite nanoparticles give better overall performance in enhancing convective heat transfer and reducing flow resistance among the nanoparticles. At 0.4%（mass） of graphite nanoparticles, the overall performance factorK is five times that with deionized water, presenting the best heat transfer and drag reduction characteristics, so it has good application prospects. Finally, a correlation is obtained by fitting the heat transfer and flow resistance of the drag reducing graphite nanofluid in circular tube, which is in good agreement with the experimental values.