P IV application for the investigation of isothermal liquid film flow falling down an inclined plate

Falling liquid film is widely used in nuclear engineering, thermal engineering, chemical engineering, and electronics owing to its high efficiency of heat and mass transfer with small temperature difference, flow rate and power consumption, such as cooling towers, AP1000 passive containment cooling system (PCCS), and multiple-effect distillation (MED) for seawater desalination. To investigate the fluid dynamics of the falling liquid film, a simultaneous measurement technique with only one camera, which combined planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV), has been applied in the liquid film flow experiment. Image acquisition in this research utilizes a long distance microscope and provides high spatial resolution at a relative large working distance. With this experimental method, it becomes feasible to generate streamwise velocity evolution of film flow on an inclined plane. In addition, film thickness measurements are performed using a laser confocal displacement technique enabling investigation of the wave dynamics. Isothermal film flow with systematic variations of both Reynolds number (Re=11.5∼32.9) and the inclined angel (β=20deg) are investigated. Comparison between experimental results and previous published results is made to verify the measurement method. (author)