Institute;
of;
Engineering;
Thermophysics,;
Chinese;
Academy;
of;
Sciences,;
Beijing;
100080,;
China;
Institute;
of;
Engineering;
Thermophysics,;
Chinese;
Academy;
of;
Sciences,;
Beijing;
100080,;
China;
visual ; experiment, ; microtube,; microscale; flow, ; friction ; factor, ; turbulent; transition. ;