人工粗糙度对矩形弯曲管道流动与传热数值模拟

人工粗糙度作为一种局部强化换热技术,对提高再生冷却效率有重要意义。为了研究人工粗糙度对矩形冷却通道三维流动与传热特性的影响,以及在弯曲段与二次流的耦合作用,对有人工粗糙度的三维弯曲矩形通道进行了建模,并应用Fluent软件进行了数值仿真计算,采用了能够有效准确地求解受强曲率影响的管道内及近壁区域湍流流动的RNG k-ε湍流模型。结果表明:在冷却通道底面添加人工粗糙度会使底部流动受到干扰进而导致流速中心上移,因此在弯曲段,有人工粗糙度的冷却通道中所产生迪恩涡的范围相对较小且距离底面较远,而随着二次流的产生,流速中心会向底部移动,使得该处的换热得到改善,整体对流传热系数上升;当入口质量流量分别为0.1 kg/s,0.2 kg/s,0.3 kg/s时,有人工粗糙度工况下弯曲段加热面平均对流传热系数分别增加了11.86%,13.11%,16.14%,表明添加人工粗糙度可以显著提高换热,且随着入口质量流量的增加其对换热的提高作用也变得越来越明显。

Numerical simulation of flow and heat transfer in a curved rectangular channel with artificial roughness

As a local heat transfer enhancement technology, artificial roughness is of great significance to improve the regenerative cooling efficiency. In order to study the influence of artificial roughness on the three-dimensional flow and heat transfer characteristics of the rectangular cooling channel, and the coupling effect with the secondary flow in the curved section, a three-dimensional curved rectangular channel with artificial roughness was modeled and simulated by Fluent software in this paper. RNG k-ε turbulence model was used to effectively and accurately solve the turbulent flow in the pipeline and near-wall flow affected by the strong curvature. The results show that adding artificial roughness to the bottom of the cooling channel will disturb the bottom flow and cause the velocity center to move up. Therefore, in the curved section, the range of Dean vortices generated in the cooling passage with artificial roughness is relatively small and far from the bottom. With the generation of the secondary flow, the flow velocity center moves to the bottom, so that the heat transfer is enhanced and the overall convective heat transfer coefficient is increased. When the inlet mass flow rate is 0.1 kg/s, 0.2 kg/s and 0.3 kg/s, the average convective heat transfer coefficients of the heating surface in the curved section under artificial roughness conditions increase by 11.86%, 13.11% and 16.14%, respectively. It is shown that the heat transfer can be improved obviously by adding artificial roughness, and its effect on heat transfer becomes more and more obvious with the increase of mass flow rate.