Calviño Uxía, Vallejo Javier P, Buschmann Matthias H, Fernández-Seara José, Lugo Luis
Grupo GAME, Departamento de Física Aplicada, CINBIO, Universidade de Vigo, 36310 Vigo, Spain.
Área de Máquinas e Motores Térmicos, Escola de Enxeñería Industrial, Universidade de Vigo, 36310 Vigo, Spain.
Nanomaterials (Basel). 2021 Mar 25;11(4):844. doi: 10.3390/nano11040844.
The thermal properties of graphene have proved to be exceptional and are partly maintained in its multi-layered form, graphene nanoplatelets (GnP). Since these carbon-based nanostructures are hydrophobic, functionalization is needed in order to assess their long-term stability in aqueous suspensions. In this study, the convective heat transfer performance of a polycarboxylate chemically modified GnP dispersion in water at 0.50 wt% is experimentally analyzed. After designing the nanofluid, dynamic viscosity, thermal conductivity, isobaric heat capacity and density are measured using rotational rheometry, the transient hot-wire technique, differential scanning calorimetry and vibrating U-tube methods, respectively, in a wide temperature range. The whole analysis of thermophysical and rheological properties is validated by two laboratories. Afterward, an experimental facility is used to evaluate the heat transfer performance in a turbulent regime. Convective heat transfer coefficients are obtained using the thermal resistances method, reaching enhancements for the nanofluid of up to 13%. The reported improvements are achieved without clear enhancements in the nanofluid thermal conductivity. Finally, dimensionless analyses are carried out by employing the Nusselt and Péclet numbers and Darcy friction factor.
石墨烯的热性能已被证明非常出色，并且在其多层形式——石墨烯纳米片（GnP）中部分得以保留。由于这些碳基纳米结构具有疏水性，因此需要进行功能化处理，以评估它们在水悬浮液中的长期稳定性。在本研究中，对一种0.50 wt%的聚羧酸化学改性GnP水基分散液的对流换热性能进行了实验分析。设计好纳米流体后，分别在较宽的温度范围内，使用旋转流变仪、瞬态热线技术、差示扫描量热法和振动U型管法测量了其动态粘度、热导率、等压热容和密度。热物理和流变学性质的整体分析由两个实验室进行了验证。随后，使用一个实验装置来评估湍流状态下的传热性能。采用热阻法获得了对流换热系数，纳米流体的换热增强高达13%。所报道的改进是在纳米流体热导率没有明显提高的情况下实现的。最后，利用努塞尔数、佩克莱数和达西摩擦系数进行了无量纲分析。
