热容腔结构参数对近膜面流动的影响

Effect of heat cavity structure parameters on the flow field of membrane surface

应用粒子图像测速技术(PIV)对膜蒸馏系统热容腔结构参数影响近膜面处的流动情况进行正交试验,考察喷管前端距膜面的距离δ和喷管中心线与热容腔径向夹角β对流场的影响.试验结果表明,合理布置热容腔的结构参数组合可以使膜面冲刷速度增大,对膜面的有效冲刷面积也增大,更好的破坏温度极化和浓度极化,使系统的膜通量增加.对于试验中采用的膜蒸馏系统,最优的结构参数组合是第32组试验,δ1、δ2、δ3,β1、β2、β3的取值分别为4mm、3mm、4mm,50°、35°、25°.流量也是试验中一个重要的影响因素,随着流量的增加,膜面处切向速度增大,对膜面的作用力增大,但是在增大系统流量提高切向冲刷速度的同时,应该考虑膜的机械强度.试验为膜蒸馏系统内部流动的深入研究提供了试验数据和测试经验,可为膜蒸馏系统结构设计的改进和膜蒸馏系统效率的提高提供了参考.

The paper established a experimental system and investigated the flow field of membrane surface in heat cavity with a two-dimensional particle image velocimetry （PIV） system. The test results show that variable structural parameters--different gap between the membrane and nozzle and inlet nozzle＇s installa- tion angle make a significant impact on flow field and the best structural parameter of the experimental de- sign is δ1、δ2、δ3,β1、β2、β3 of the value 4 ram,3 mm,4 ram, 50°,35°,25°,respectively. Flow rate is also an im- portant factor in the test. Because the tangential velocity increases with increasing flow, and increasing the force on the membrane surface, it can be better to destroy the temperature polarization and concentration polarization and to increase membrane flux. The test provided valid data for optimization of the nozzle structure and test experience of the membrane distillation system.