The measurement of the falling film thickness outside a horizontal tube of a falling film evaporator was performed with the laser induced fluorescence method and the image processing technique. The influences of feeder height

flow rate

and surface geometry configuration on the falling film thickness were explored during the subcooled liquid flowing outside a horizontal plain tube and a Turbo-CII tube at the ambient temperature and pressure. The two-dimension simulation on the water film flow around a plain tube was conducted with the Fluent

and the calculation results were compared with the experimental data. The results show that the film thickness at the upper semi-circular is greater than that at the lower semi-circular. Moreover

it decreases with the increase in the angle in the clockwise direction at the upper semi-circular

and changes slightly at the lower semi-circular. Further

the smallest value of the film thickness is near the 90° location at the lower semi-circular

and the film thickness increases with the increase in Re value and decreases with the increase in the feeder height. In addition

the film wave is stronger at the upper semi-circular

and the wave on the Turbo-CII tube is weaker than that on the plain tube.