齿带强化加热室自然循环蒸发器的优化设计

The Optimization Design of the Natural Circulation Evaporators with Strip-inserts of Oblique Teeth in Heating Transfer Tubes

自然循环蒸发器的结构设计以动力矩强化能够低流速自动清洗和以强化的自然循环推动力替代强制循环泵为优化目标.研究建立了进入管内斜齿扭带自转动力矩理论计算式,由此得到蒸发器加热室结构优化设计的原则是加热管Ф38×3×2000的立式短管加热室结构,管内安装宽度26mm、斜角35°、齿距60mm的斜齿扭带.以自然循环推动力计算式为理论基础,得到蒸发器自然循环推动力强化的沸腾室结构优化设计原则是较大深度、较大横截面、出口部形状逐渐扩大.按此原则结构设计的蒸发器的试验研究表明,齿带加热室传热系数提高了171%—91%、阻力在7000Pa以下、循环母液的进出口温度可以提高3℃左右,自然循环推动力可以达到12000Pa以上,显著地高于自然循环阻力;自然循环流速可以稳定在0.80m/s以上、甚至更高,斜齿扭带能够可靠地连续自转清洗防垢.因此,这种蒸发器能成功地解决传统蒸发器周期性停车清洗和强制循环泵高电耗两大难题,为蒸发生产企业创造很高的经济效益.

In the structure design of the new evaporators, the optimization purpose is to enlarge the force moment to realize the self-cleaning at low flowing velocity and enhance the driving force of natural circulation to replace the forced pumps. The theoretical equation is established to calculate the force moment of such inserts self-rotation in tubes. So in the structure design of heating chamber, the heat transfer tube is shortened and Ф38mm ×3mm ×2000mm and the optimal twisted strip with oblique teeth is 26 mm wide with the oblique angle of 35 degrees and the teeth interval of 60ram. Based on the driving force formula the of natural circulation, the height and the cross-section are greater and the outlet part is increased gradually in thestructure optimization of boiling chamber. The experiments show that the heat transfer coefficient is increased by 171%-91% in the heating chamber and the flowing resistance is less than 7000 Pa. The temperature difference of inlet and outlet of circulating solution is raised by 3℃. The driving force of natural circulation is as high as 12000 Pa, which is more than the circulation resistance significantly. The flowing velocity of natural circulation can be stable at the flowing velocity of more than 0. 80m/s. This kind of twisted strip with oblique teeth can remove and prevent fouling continuously and reliably. So, such reformation can successfully solve the problems of removing fouling periodically and consuming great power with forced pumps. The economic result is high using this technology in evaporating production.