EXPERIMENTS ON HEAT TRANSFER CHARACTERISTICS OF SHEAR-DRIVEN LIQUID FILM IN CO-CURRENT GAS FLOW

Experiments are performed to study the liquid film behavior and corresponding local heat transfer to shear-driven liquid film flow of water in the cocurrent nitrogen gas flow. The heated channel has a cross section of 30mm in width and 5mm in height, where the bottom is operated as a heating surface of 30mm in width and 100mm in length. The heated section is divided into segments to evaluate the local heat transfer coefficients. Under most gas Reynolds numbers, the local heat transfer coefficients are increased with increasing heat flux, where three mechanisms are important; (i) increase of areas along the three-phase interline around dried areas, (ii) rewetting of dried areas by the transverse liquid flow pushed by the generation of bubbles at the side edges of duct, (iii) microlayer evaporation during nucleate boiling in the film flow. The existence of duct corners makes the phenomena more unsteady and non-uniform in the transverse direction.