圆柱形内肋强化换热数值模拟与火积耗散分析

对内肋管内部流体的湍流换热过程进行了数值模拟,讨论了肋高和肋的轴向夹角对换热的影响。相比于普通圆管,内肋圆管内的传热性能明显得到提高。无量纲肋高度和角度分别为0.8°和40°时传热效果最佳,而在0.1°和40°时换热与阻力的比值(Performance Evaluation Criteria,PEC)最大,综合换热性能最佳,可用于强化地源热泵地埋管换热。此外,本研究从火积耗散与传热效率的角度分析了内肋强化传热机理,得到管壁冷却管内流体的火积传递效率计算式,为内肋管强化换热的深入分析提供了依据。

Numerical Simulation of the Intensified Heat Exchange of Cylindrical Inner Ribs and Analysis of the Entransy Dissipation

Abstract:Numerically simulated was the turbulent heat exchange process of the fluid inside an internally ribbed tube and discussed was the influence of the two factors,i.e.height of ribs and angle of ribs included in the ribs and the axial centerline,on the heat exchanged.The research results show that compared with common round tubes,the heat exchange performance of internally ribbed tubes can be conspicuously improved.When the non dimensional rib height and angle are 0.8 and 40 degrees respectively,the heat transfer effectiveness will reach its optimum and when the said height and angle are 0.1 and 40 degrees respectively,the performance evaluation criteria (ratio of the amount of heat exchanged and the drag) will attain its maximum and the comprehensive heat exchange performance will be the optimum,which can be applicable for the enhanced heat exchange in embedded tubes by using geothermal heat pumps.In addition,the mechanism governing the enhanced heat exchange of the internal ribs was analyzed from the viewpoint of entransy dissipation and heat transfer efficiency and a formula for calculating the entransy transfer efficiency of fluids inside cooling tubes was obtained,thus providing an underlying basis for an in depth analysis of the heat exchange intensified by internally ribbed tubes.