Abstract: To solve the problems of severe fouling and high energy consumption of forced circulation in evaporators, a hydrodynamic reciprocating-spiral cleaning technology used for natural circulation evaporator was demonstrated. Its cleaning mechanism consists of a reciprocating spring with small elasticity coefficient and fouling removal spiral inserted in each heating tube. Relying on the pulsation of vapor-liquid flow, the fouling removal spiral generates reciprocating vibration for uniform descaling purpose. Atmospheric evaporation test rig with 6 heating tubes is designed to study the spring and spiral of different structure parameters, in which water and steam flow through heating tubes. The optimized parameters of the spring and spiral and the correlation charts between the reciprocating stroke of fouling removal spiral, circulation velocity and heat transfer temperature difference are obtained. The experimental results show that when the elasticity coefficient of the reciprocating spring is 7.0~8.0 N/mm, and ratio between the pith of fouling removal spiral and inner diameter of the tube 0.676~0.764, and heat transfer temperature difference greater than 18℃ under atmospheric evaporation with the heating tube with the outer diameter of 38 mm, wall thickness 2 mm and tube length 2 m, the circulation velocity is not lower than 0.57 m/s, and the reciprocating stroke of the fouling removal spiral is greater than a pith, which meets the needs of uniform scale removal.

Key words: evaporator, natural circulation, reciprocating spiral, fouling removal

摘要： 针对蒸发器结垢严重及强制循环泵能耗高的问题，提出了一种用于自然循环蒸发器加热管内往复螺旋在线清洗技术，依靠气液两相流速度场的脉动实现工作螺旋轴向往复振动实现均匀防、除垢. 以水为实验介质，设计了6根加热管的常压蒸发实验台，用不同往复弹簧和工作螺旋组成的清洗装置进行了实验，并在优化参数下得到了工作螺旋轴向往复行程、循环流速与传热温差的关系. 结果表明，加热管规格为外径38 mm、壁厚2 mm、管长2 m的常压蒸发条件下，往复弹簧弹性系数K=7.0~8.0 N/m、工作螺旋螺距与管内径比为0.676~0.764且传热温差大于18℃时，系统循环流速不低于0.57 m/s，工作螺旋往复行程稳定大于一个螺距，满足均匀除垢需求.

关键词: 蒸发器, 自然循环, 往复螺旋, 除垢清洗