螺旋折流板换热器壳程流动特性研究

Flow characteristics in shell side of heat exchanger with helical baffles

利用激光粒子图像测速(PIV)技术在有机玻璃模型上对螺旋折流板换热器的壳程流动特性进行了实验研究。结果表明,螺旋折流板换热器管间流体斜向冲刷管束。管间流场中非稳定区的流体由于接近换热器的轴心,受三角区漏流的影响,流速沿轴线方向呈上升趋势,且具有较强的轴向速度。稳定区内的流体流动较为平稳,其切向速度较高,具有明显的旋流特征,是换热效果较好的区域。管间流场的流体具有沿轴线方向波动的径向速度,可以增加流体的扰动,有利于传热。在管束外围,折流板与筒体之间的漏流会增加流体的轴向速度,而搭接区的漏流则使得流体的切向速度增加而轴向速度减小。漏流对流体流速的影响会沿着轴线方向不断减小,流体流速趋于稳定。

The shell-side flow field in the sing PIV technique. The experimental results the tubes. Because the unstable flow field in heat exchanger with helical baffles was measured ushow that the fluid flow in tube bundles is angled to tube bundles is near the heat exchanger＇s axes and the fluid is affected by the leakage flow from the triangular area, the flow velocity in this field rise along the axial direction and exhibits high axial velocity. There is strong spiral flow character for high tangential velocity in the stable flow field in tube bundles, where the heat transfer effect is better. The fluid in tube bundles has the radial velocity which is fluetuant along the axial direction. The radial velocity could enhance fluid＇s disturbance and is helpful to heat transfer. Out of the tube bundles,the leakage flow between the shell and baffle could raise the fluid＇s axial velocity. The leakage flow from the lapping area could raise the fluid＇s tangential velocity and decrease the axial velocity. The effect of the leakage flow will weaken along axial direction and the flow velocity of the fluid tends to steady.