论文标题
过渡流中石墨烯 - 水纳米流体的对流传热和压降特性
Convective Heat Transfer and Pressure Drop Characteristics of Graphene-Water Nanofluids in Transitional Flow
论文作者
论文摘要
通过专注于过渡流，对石墨烯 - 水纳米流体的对流传热和流动行为进行了实验研究。用两步方法产生具有不同颗粒质量级分（0.025、0.1和0.2％）的石墨烯 - 水纳米流体，并使用PVP作为表面活性剂。通过测量纳米流体的粘度和导热率来执行热体表征。从层流到湍流方案，对对流特征进行了实验研究。可以看出，随着纳米颗粒浓度的增加，压力下降会在过渡区域急剧增加，而层状向湍流过渡到较低的雷诺数。该过渡以2475的雷诺数启动，而纳米流体的粒子质量分数为2475，而纳米流体的启动为2315。在不同的雷诺数和轴向位置的平均传热系数和Nusselt数字的增加几乎相同，沿试管沿试管中的层流中的纳米流体和水的轴向位置增加，这是由于层状流量增强传导机制的优势，纳米流体和水。除了层流状态之外，还观察到努塞尔特数量的增强，表明嗜热和布朗运动是更有效的传热增强机制。对于3950的雷诺数，最大的传热增强为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.
