椭圆管内对流换热与流动阻力特性研究

通过CFD技术,分别对5种长短轴之比的椭圆管管内湍流和层流状态时的换热与流动进行数值研究,分析了流体流动状态和椭圆管长短轴之比对换热系数与流动阻力的影响,并根据数值计算结果拟合出湍流区椭圆管管内换热系数的准则关系式,最后绘制每种类型椭圆管的局部换热系数曲线。研究结果表明:数值计算结果与实验值吻合良好;采用当量直径的方法计算椭圆管内换热系数误差较大;随着雷诺数的增加,每种类型的椭圆管管内阻力系数逐渐减小;而在相同的雷诺数下,随着长短轴之比K的增大,管内阻力系数逐渐增加;每种类型的椭圆管具有类似的局部换热特性,即长半轴两端点处局部换热系数最低,而短半轴两端点处具有最大局部换热系数。

A Study on Heat Transfer and Flow Resistance Characteristics in Elliptical Tubes

The heat transfer and flow in elliptical tubes with different axis radio K are investigated in this paper. Computational Fluid Dynamics （CFD） was used to analyse flow state and axis radio K influence on the heat transfer and flow, a correlation equations ofNu （Nusselt） =f （Re） is given. At last, five types of elliptical tubes＇ local convective heat transfer characteristics are showed. The results show that the experiment basically tallies with the value of numerical calculation. Equivalent diameter may lead to a great error when calculating heat transfer coefficient of different types of elliptical tubes. With the increase of axis radio K, convective heat transfer coefficients increases, while flow resistance coefficients also increases in the same reynolds number. It is found the local convective heat transfer coefficients are similar for five types of elliptical, that is heat transfer coefficient is lowest at the point of semi-major axis, and it has greatest heat transfer coefficient in the center of tube.