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

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 60mm.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 the structure 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.