Abstract:

To enhance the heat transfer on shell side of a double-pipe heat exchanger with helical fins on the outer wall of the inner tube, some pin fins were installed along the centerline of the helical channel formed by helical fins. The heat transfer enhanced by these fins was investigated experimentally and the enhancement mechanism was analyzed by applying the field coordination theory. The heat transfer coefficient in the exchanger with helical fins and pin fins was 1.53—2.53 times as much as that with helical fins only at the same pitch and was 3.08—4.87 times that without the fins for Reynolds number ranging from 4000 to 14000. The performance of the exchanger with pin fins and helical fins was much better at the same mass flow rate, pressure drop and pumping power. Reducing the pitch of pin fins by half, the heat transfer was much better. At the same pressure drop and pumping power, the heat transfer in the exchanger with odd-numbered pin fins within one pitch was a little better than that with even-numbered pin fins. The pin fins increased the radical velocity. Accordingly, the resultant effect of temperature field and velocity field improved the heat transfer.

摘要：

对于内管外壁安装有螺旋片的套管换热器的壳侧，在螺旋片所形成的螺旋通道中心，沿螺旋方向周期性地布置扰流柱以进一步提高其换热性能，对这种扰流柱协同螺旋片强化的换热器的换热特性进行了实验研究，应用场协同理论分析了其强化机理。结果表明，在Re=4000～14000范围内，扰流柱协同螺旋片强化的换热器的传热系数为相同螺距下只安装螺旋片的换热器的1.53～2.53倍，为光滑内管换热器的3.08～4.87倍。在相同质量流量、相同压降及相同泵功条件下，扰流柱协同螺旋片强化的换热器的综合换热性能明显好于相同螺距下只安装螺旋片的换热器及光滑内管换热器；在相同压降及相同泵功条件下，保持螺距不变，安装扰流柱比螺距减小一半的综合换热性能更好；单位螺距内安装奇数个扰流柱比安装偶数个扰流柱略好。扰流柱的安装增大了径向速度，使温度场与速度场的协同效果更好，从而提高了换热效果。