不同换热管内超临界CO_(2)冷却换热的数值模拟

Numerical simulation of supercritical CO_(2) cooling heat transfer in different heat exchange tubes

为了研究不同换热管对超临界CO_(2)在螺旋槽管内的流动与换热特性,使用ANSYS Fluent 19.0软件建立了不同凹槽数螺旋槽管的三维实体模型,通过数值模拟得到了各个模型情况下的换热系数与摩擦系数。同时分析了湍流强度与浮升力对螺旋槽管内超临界CO_(2)的流动与换热产生的影响。结果表明:在相同的工况条件下,螺旋槽管凹槽数越多整体换热系数就越大,摩擦系数也越大。随着凹槽数的增加,螺旋槽管截面结构发生变化,截面面积增加,导致流体平均速度减小,湍流动能越大。随着凹槽数的增加,超临界CO_(2)径向密度差增大,导致浮升力作用增强,同时受离心力的作用形成的涡流也更为剧烈,湍流动能也随之增大。文中可以为超临界流体换热器的优化设计提供参考,从而提高换热效率和系统性能。

In order to study the flow and heat transfer characteristics of supercritical CO_(2)in spirally grooved tubes with different heat exchange tubes,three-dimensional solid models of spirally grooved tubes with different concave numbers were established by ANSYS Fluent 19.0,and the heat transfer coefficient and friction coefficient of each model were obtained by numerical simulation.At the same time,the effects of turbulence intensity and buoyancy on the flow and heat transfer of supercritical CO_(2)in spirally grooved tubes were analyzed.The results indicate that under the same working condition,the more the concaves,the greater the overall heat transfer coefficient and the greater the friction coefficient.With the increase of the number of grooves,the cross-section structure of the spirally grooved tube changes and the cross-section area increases,which lead to the decrease of the average velocity of the fluid and the increase of the turbulent kinetic energy.With the increase of the number of concaves,the radial density difference of supercritical CO_(2)increases,which lead to the increase of buoyancy force.At the same time,the vortex formed by centrifugal force is more intense,and the turbulent kinetic energy increases.This study can provide a reference for the optimization design of supercritical fluid heat exchanger,so as to improve the heat transfer efficiency and system performance.