封闭腔内纳米流体强化自然对流换热的数值模拟

Numerical simulation of natural convection and heat transfer of nanofluids in a two-dimensional enclosure

采用F luen软件对封闭腔内Cu-H2O纳米流体强化自然对流换热进行了数值模拟,重点分析Cu纳米粒子添加量和Gr数对换热性能的影响,并解释其换热机理。研究结果表明:在水基液中加入Cu纳米粒子可以显著提高基液的自然对流换热特性。对于一给定的Gr数,随着纳米粒子质量分数的增加,纳米流体的速度组成部分增加,纳米流体质量分数越大,x方向和y方向的速度峰越大,因此加速了流体中能量传输。另一方面,随着Gr数的增加,流线图中旋涡逐渐变大,流线间强度增加,说明换热效果逐渐增强。当Gr数较小时,传热主要是由热壁和冷壁之间的热传导引起的,随着Gr数的增大,换热逐渐变为由对流换热占主导地位。

The natural convection of nanofluids in a two -dimensional enclosure was numerically simulated with Fluent software. The effect of copper particle concentration and Grashof number on heat transfer properties was investigated. The results indicate that the suspended copper nanoparticles substantially increase the heat transfer rate at any given Grashof number. In addition, the heat transfer rate of Cu - H2O nanofluid increases remarkably with the mass fraction of nanoparticles. For a given initial Grashof number, as the mass fraction increases, the velocity components of nanofluid increase as a result of an increase in the energy transpertation through the fluid. On the other hand, the intensity of the streamline increase with the increases of the Grashof number, which indicate the heat transfer properties are enhanced. The heat transfer process is dominant with the heat exchange when the Grashof number is less, while the heat transfer process is dominant with the natural convection when the Grashof number increases.