卧式螺旋管内紊流传热

在宽广的参数范围内对卧式螺旋管内紊流换热特性进行了详细的试验研究, 试验结果表明,螺旋管内强化换热是紊流流动与二次流动共同作用的结果,Reynolds数越大,二次流对强化换热的贡献越小,平均换热系数也越接近于等条件下的直管换热;换热系数在圆截面上的分布很不均匀,最外侧换热系数可达最内侧的3～4倍,最内侧是平均换热系数的0.5倍,并得到了截面上局部换热系数的计算式;换热系数在流动方向的分布具有周期性。

TURBULENT HEAT TRANSFER IN HELICAL COILS

In this paper, the turbulent heat transfer in the horizontal helical coil is investigated in detail in a wide range of experimental parameters. The experiment shows that the enhancement of heat transfer in the coil results from the effect of turbulent flow and secondary flow. If the Reynolds number becomes larger, the secondary flow gives less contribution to the enhancement heat transfer, and then the average heat transfer coefficient of the coil is closer to that in straight tubes under the same condition. The cocal heat transfer coefficients on the cross section of the coil are not uniformly-distributed. The cocal heat transfer coefficient on the outside is three or four times period which is half of the average heat transfer coefficient. A correlation is proposed to calculate the heat transfer coefficient distribution on the cross section. The average heat transfer coefficients on the cross section change period along the direction of the fluid flow.