The aim of the present study is to investigate experimentally the effect of the fluted surface tube
on the heat transfer and flow characteristics ofliquid falling fIlm. Experiments have been indicated
that, when a liquid falling film falls on a horizontal fluted surface tube, the transition starts at low
Reyno1d~ number than that of the plain tube. The value of the film thickness has been slightly
decreased by decreasing the fluted pitch. A reduction ofthe film thickness was observed at about
9% for the low fluted pitch tube, at Reynold's number of 485. A clear reduction of the
dimensionless wavelength, ), has been occuffed at low fluted pitch tube. The use of enhanced
surfaces can provide heat coefficients higher than those obtained from plain tube. Heat transfer
enhancement was noticed due to the use of fluted tube surface. An improvement of the Nusselt
number reached about 45% for low fluted pitch tube. However, the low values ofthe fluted pitch
increased the heat transfer enhancement that ofthe high values.