非清洁水换热器管内振荡流动除垢性能研究

Study of Descaling Performance of Oscillation in Unclear Water Heat Exchanger Tube

为了得到非清洁水换热管内振荡流动的除垢性能,研究了有无振荡干预下非清洁水源热泵换热器管内的流动和传热情况。建立恒热流条件下圆管内振荡流动的物理模型,针对不同工况进行数值模拟。模拟结果显示,振荡流动能够明显增大流体对于壁面的剪切力,在5Hz和10Hz情况下能够增大流体和壁面间的平均表面换热系数,1Hz情况下平均表面换热系数变化不明显。在1Hz实验工况下搭建了试验台进行实验研究,实验结果表明,实验工况条件下,振荡对于换热器管内表面换热系数的影响较小,但是剪切力的增大造成部分污垢沉积物脱落,减小了污垢热阻从而使换热器的传热系数增加了22.2%,因此振荡可以作为换热管内除垢的一种有效方式。

To obtain the defouling performance of oscillation flow in heat transfer tube with unclear water as fluid, the flow and heat transfer mechanism are investigated under conditions of oscillation and no oscil- lation. Firstly, a physical model is set up under constant heat flux condition and simulations are carried out in different conditions. The simulation shows that oscillation flow can obviously increase shear forces act- ing on the wall, and can also increase average surface convective heat transfer coefficient under frequency conditions of 5Hz and 10 Hz. An experiment is carried out under conditions of 1Hz and 1m/s, which has little influence on average surface convective heat transfer coefficient. It is shown that the increased shear forces can peel off the fouling so that heat transfer coefficient is increased by 22.2 %. It is concluded that oscillation flow is an effective way of defouling in heat transfer wall.