Intercolumn two-phase flow patterns across falling film tube bundles

Abstract

Two-phase flow patterns are critical in falling film heat devices. Hydrodynamic characteristics of turbulent falling films across a horizontal triangular tube bundle were studied under a range of film Reynolds numbers and contact angles. A flow pattern map based on the k-means clustering approach was proposed after the intercolumn two-phase flow patterns were grouped. The results demonstrated that that the intercolumn liquid-vapor flow patterns in a horizontal tube bundle could be effectively and reasonably grouped using the k-means clustering approach according to the results of the void fraction and interface area. There are four intercolumn liquid-vapor flow patterns that were identified: bubbles flow, annular-slug-column flow, half-annular flow, and multi-bridges flow. The annular-slug-column flow pattern and the multi-bridges flow pattern are next to one another in the flow pattern map and are capable of transitioning one into the other. It is only through the two transitional flow patterns that the half-annular-column flow pattern and bubbles flow pattern can turn to one another. In the bubbles' flow pattern and half-annular-column flow pattern, respectively, the highest and least averaged heat transfer coefficients are attained. Simply raising the film Reynolds number or lowering the contact angle will not produce the best heat transfer results.