工质对微石英管内部流动特征的影响

为采用“两管法”以消除进出口压力降及入口效应对流动的影响,分别以蒸馏水、CCl_4及N_2为工质,测量其流过内径d分别为19．60、44．63、91．65及140．86μm微石英管的流量与进出口压降,得到微管内部充分发展流的摩擦阻力系数f与Re的关系．实验结果表明,除d=19．60μm的管外,其他管在Re较小时,微管内部的f值与Hagen-Poiseuille解几乎一致;当Re升高到1300时,f已开始偏离Hagen-Piseuille解．对于d=19．60μm的管,在Re＜500,工质为蒸馏水时,f比Hagen-Poiseuille解高10%～15%;工质为CCl_4时,f仍然约等于Hagen- Poiseulle解;工质为N_2时,f比Hagen-Poiseulle解低8%～10%．

The Influence of Working Fluid on Flow Characteristic in Microtubes

The double-tube method was used to eliminate the influence of the pressure drop of inlet and outlet of microtube and the entrance effect on flow in microtube.Distilled water,tetrachloromethane and nitrogen gas,used as the working fluid,flowed through the quartz glass microtubes with inner diameters 19.60μm, 44.63μm,91.65μm and 140.86μm,respectively.The relation between friction factor and Reynolds num- ber was studied by measuring the pressure drop and the flow rate.The experimental results show that the friction factors in microtubes,except the microtube with inner diameter of 19.60μm,are in rough agreement with those predicted by the Hagen-Poiseuille when Reynolds number is low.The friction factors depart from solution of Hagen-Poiseuille when Reynolds number is higher than 1300.For microtube with inner diameter 19.60μm,the values of the friction factor is 10%～15% higher.8%～10% less than those predicted by the Hagen-Poiseuille for the working fluids of distilled water,tetrachlormethane and nitrogen gas,respectively, when Reynolds number is less than 500.