This manuscript investigates the friction characteristics and the effective diameters of a capillary tube. Critical Reynolds number and resistance characteristic during the transformation from laminar flow to turbulence of capillary single tube was investigated by experiment to propose the transition critical Reynolds number from laminar flow to turbulence and verify if the flow resistance characteristic of capillary single tube meets typical normal tube. The experiment is carded out on water resistance test board with internal diameter of 2.3 mm capillary tubes. To get the friction characteristics, flow resistance coefficient was tested with Reynolds number varying from 400 up to 7500 and velocity varying in the range from 0.2m/s up to 3.2rn/s. Experiment results show that laminar-to-turbulent transition occurs for Reynolds number in the range 2100-2300 and the friction characteristics is consistent with typical normal circle tubes. It means normal tube friction theory may apply to capillary tubes. Above all, in this paper the transition critical Reynolds number from laminar flow to turbulence of capillary tube is proposed and indicates that the flow resistance characteristic of capillary single tube meets typical normal tube.
Building Energy ＆ Environment
capillary tube, Laminar-turbulent transition Reynolds number, frictional loss coefficient