超临界R134a水平圆管内冷却换热模拟研究

采用增强壁面函数的标准k-ε模型对超临界R134a水平圆管内冷却换热进行了模拟研究.分析了管内不同截面上流体温度、速度和湍动能的分布情况及对应关系。研究了质量流量和浮升力对换热系数的影响。结果表明,流体速度随着温度的降低而减小,并且最大速度处对应着最高温度和最小湍动能.换热系数随着质量流量的增加而增大,其峰值出现在准临界温度附近。浮升力在似液体区的影响较大,对流体换热起到增强的效果。

Numerical Study of Cooling Heat Transfer of Supercritical R134a in a Horizontal Circular Tube

Cooling heat transfer of supercritical R134 a in a horizontal circular tube is studied numerically using standard k-ε model with enhanced wall treatment.the distribution and corresponding relationships of fluid temperature,velocity and turbulence kinetic energy at different axial locations along the tube are analyzed.Influences of mass flow rate and buoyancy on heat transfer of supercritical R134 a are investigated.Results show that velocity gradually decrease with decreasing temperature along the flow direction,the maximal of the velocity corresponds to the maximal fluid temperature and the minimal turbulence kinetic energy.The heat transfer coefficient of supercritical R134 a increases with increasing mass flow rate,and reaches the peak point near the pseudo-critical temperature.The buoyancy enhances the heat transfer of supercritical R134 a especially in the liquid-like region.