Numerical study of the falling film thickness around the tube bundle with different spacings between spray holes and tubes under tilt and sloshing conditions

Abstract

The shell-side flow patterns and liquid film thickness (δ) distribution of the falling film are extremely important for the comprehensive performance of the spiral-wound heat exchangers. In this paper, 3-D simulations calculated with volume of fluid (VOF) method are performed to study the inter-tube flow modes and the distribution characteristics of δ around the tube. At first, the effects of different spray densities, longitudinal inter-tube spacings (St) and spray holes arrangements (Sh) on the δ distribution are studied to determine the appropriate values. After that, the influence of tilt and sloshing conditions are examined based on the selected geometric parameters. The results show that although the value of St has a significant influence on the fluctuation range of δ in stable zone, the average δ in stable zone could remain in the same level. For the spray holes arrangement, the decrease of Sh does not thicken the δ in stable zone but promotes a 46% axial length expansion for the crest zone with a thicker δ. The tilt conditions significantly deteriorate the inter-tube flow modes transitions, which makes the column flow much easier convert to sheet flow. Under roll motion, a secondary crest zone emerges nearby the original main crest zone and its δ is 30%–40% thinner than that of the original main crest zone.