Convective heat transfer and pressure drop characteristics of graphene-water nanofluids in transitional flow
Convective heat transfer and pressure drop characteristics of graphene-water nanofluids in transitional flow
复制标题
过渡流中石墨烯-水纳米流体的对流传热和压降特性
DOI：
10.1016/j.icheatmasstransfer.2020.105092
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发表时间：
2021-01-07
影响因子：
7
通讯作者：
Erturk, Hakan
中科院分区：
文献类型：
--
作者：
Demirkir, Cayan;Erturk, Hakan
对石墨烯-水纳米流体的对流换热和流动行为进行了实验研究。以聚乙烯吡咯烷酮为表面活性剂，采用两步法制备了不同质量分数(0.025%、0.1%、0.2%)的石墨烯-水纳米流体。通过测量纳米流体的粘度和导热系数来进行热物理表征。实验研究了从层流到湍流区的对流特性。结果表明，随着纳米颗粒浓度的增加，过渡区的压降急剧增加，层流向湍流的转变向较低的雷诺数转变。水的雷诺数为2475，而粒子质量分数为0.2%的纳米流体的雷诺数为2315。在纳米流体和水的层流流动中，不同雷诺数和不同轴向位置的平均换热系数和努塞尔数的增加几乎相同，这是因为导热强化机制对层流换热的增加起主导作用。在层流区域以外，观察到Nusselt数的增大，说明热电渗流和布朗运动是更有效的强化换热机制。当雷诺数为3950时，换热强化最大可达36%。
The convective heat transfer and flow behavior of graphene-water nanofluids are studied experimentally by focusing on transitional flow. Graphene-water nanofluids with different particle mass fractions (0.025, 0.1 and 0.2%) are produced following two-step method and using PVP as a surfactant. Thermo-physical characterization is performed by measuring viscosity and thermal conductivity of the nanofluids. Convection characteristics are experimentally studied from laminar to turbulent flow regimes. It is seen that pressure drop increases dramatically in the transition region, and laminar to turbulent transition shifts to lower Reynolds numbers with increasing nanoparticle concentration. The transition initiates at a Reynolds number of 2475 for water, while it initiates at 2315 for the nanofluid with 0.2% particle mass fraction. Increase in mean heat transfer coefficient and Nusselt numbers are nearly identical at different Reynolds numbers and axial positions along the test tube in the laminar flow for nanofluids and water due to dominance of conduction enhancement mechanisms on the heat transfer increase in laminar flow. Beyond laminar flow regime, enhancement of Nusselt number is observed indicating that thermophoresis and Brownian motion are more effective heat transfer augmentation mechanisms. The maximum heat transfer enhancement is observed as 36% for a Reynolds number of 3950.