不同排列方式下水平降膜管束中的管束效应及传热特性

Falling Film Heat Transfer Performance and Bundle Effect in Horizontal Tube Bundles with Various Arrangements

管束效应普遍存在于水平管降膜蒸发管束中,表现为随着管束深度的增加,传热性能逐渐变差,严重影响着降膜蒸发器的运行效率.为了查明管束效应的产生机理,文中研究了46℃水在恒热流密度(47.3 kWm^(-2)K^(-1))条件下的管束降膜流动及传热特性.结果表明:(1)正方形排列管束传热性能最差,管束效应最明显;三角形排列管束传热性能最好,是正方形排列管束的1.3倍;(2)沿管束深度方向,传热系数波动幅度先增加后减小;(3)供液高度、竖直管间距的增加有利于上排管传热,对下排管影响较弱;(4)液膜分布对上排管传热影响较大,但随管束深度增加逐渐变弱.

The tube bundle effect generally exists in the horizontal tube falling film evaporator tube bundle.With the increase of tube bundle depth,the heat transfer performance deteriorates,which affects the efficiency of falling film evaporator seriously.In order to find out the mechanism of tube bundle effect,the falling film flow and heat transfer characteristics of 46℃water at constant heat flux(47.3 kWm^(-2)K^(-1))were studied.The results indicated that:(1)the square bundle provides the poorest heat transfer performance,behaving the most obvious bundle effect,and the heat transfer performance of triangular arranged tube bundle is the best,which is 1.3 times of that of square arranged tube bundle;(2)With the tube bundle depth,the fluctuation of the heat transfer coefficient goes through from strong to weak;(3)the increase in liquid feeder height and tube spacing is beneficial to the heat transfer of the upper tubes,but has little effect on the lower tubes;(4)the influence of liquid film distribution on the heat transfer of the upper tube is more obvious,but it becomes weaker with increasing tube bundle depth.