The relationship between friction factor and Reynolds number is obtained by measuring the pressure drop and the flow rate when tetrachloromethane is used as working fluid and flows through the stainless steel microtubes with inner diameters 0.168 mm , 0.399 mm, 0.799 mm and the quartz glass microtubes with inner diameters 0.242 mm, 0.315 mm, and 0.520 mm. The experimental results show that the friction factors in microtubes, except for the stainless steel microtube with inner diameter 0.168 mm, are in rough...