Experimental study on the falling film thickness distribution on a horizontal tube under the cross airflow

Horizontal tube falling film evaporation technology has outstanding advantages such as high energy efficiency and easy operation. The purpose of this paper is to investigate the impact of cross airflow on the falling film thickness distribution outside the horizontal tube. The axial and circumferential film thickness distributions under inter-tube column flow mode are measured using the air-water system and the conductance probe method, and the mechanism of cross airflow on the falling film thickness distribution is analyzed. The results show that the axial film thickness between the two adjacent liquid columns has a wave crest region and is symmetric distributed, and the circumferential film thickness at the wave crest section does not symmetry about horizontal axis with a minimum value within the circumferential angle range of 100°~120° in the quiescent surroundings. When the cross airflow exists, the circumferential film thickness on the windward surface increases in the circumferential angle of 30°~90° and decreases in the circumferential angle of 90°~150°, while those on the leeward surface increases and becomes more uniform. The axial wave crest region and spreading region of the liquid film on the windward surface also increase, but those on the leeward surface change little.