几何因素对U型管内超临界甲烷流动换热影响

Effect of Geometric Factors on Fluid Flow and Heat Transfer of Supercritical Methane in U-type Tube

超临界甲烷换热器广泛存在于工程实际中,由于超临界甲烷在拟临界温度附近物性变化剧烈,使得其流动与传热规律十分特殊而复杂。基于计算流体动力学(compautational fluid dynamics,CFD)原理,采用有限体积法对超临界甲烷湍流流动与传热特性进行数值模拟,在验证模型可靠性的基础上,分析了弯管曲率半径、U型管立式与水平布置形式对传热特性的影响。结果表明:在管壁边界热流密度q=80 kW/m^(2)、入口质量流量G=75 kg/(m^(2)·s)、入口温度T in=180 K的条件下,迪恩涡强度随弯管曲率半径的增大而减弱,弯管处的对流传热系数随曲率半径增大而增大;此外,与水平布置相比,U型管立式布置时,超临界甲烷流体与壁面间的对流换热效果更强。本文研究结果对超临界甲烷换热器性能优化具有指导意义。

Supercritical methane heat exchangers are widely used in engineering practice.The heat transfer law of supercritical methane is special and compalicated due to the drastic change of physical properties near the pseudo-critical tempaerature.Based on the principle of Compautational Fluid Dynamics(CFD),the finite volume method is used to simulate the turbulent flow and heat transfer characteristics of supercritical methane.On the basis of verifying the reliability of the model,the influences of curvature radius of bent tube,vertical and horizontal arrangement of U-type tube on the heat transfer characteristics are analyzed.The results show that:when heat flux q=80 kW/m^(2),mass flow G=75 kg(m^(2)·s),and inlet tempaerature T in=180 K,the dean vortex strength decreases with the increase of curvature radius of the bent pipe.The convective heat transfer coefficient at the bent tube increases with the increase of the curvature radius.In addition,compared with the horizontal arrangement,the vertical arrangement of U-type tube has a stronger supercritical methane heat transfer capacity.The results of this paper provide guidance for the performance optimization of supercritical methane heat exchanger.