Falling Film Transitions on Horizontal Enhanced Tubes: Effect of Tube Spacing

Abstract Horizontal falling film heat exchanger is widely applied to industrial area. In this work, falling film flow mode of tube bundles test bed was built for solving the basic problem of falling film heat transfer. Three tube spacing( s =6mm, 10mm, 15mm,) and three types of tube(smooth, two(2D) and three (3D) dimensional finned enhanced)were tested using water. Changing flow rate to obtain the effect of tube spacing on falling film Reynolds number(Re) at the same flow mode, the effect of tube spacing on flow mode transitions were investigated for three types tube. The result showed: (1)Increasing of tube spacing( s =6mm, 10mm, 15mm) has small effect for the Re of smooth, and lacking of enough surface tension appeared instable flow modes( s =20mm, 30mm). (2)For the Re of 2D enhanced tube, it decreased with tube spacing increased occurred in droplet and droplet-column modes, but for the column and column-sheet modes, Re was increasing (3)The tube spacing has great effect for the Re of 3D enhanced tube, and Re increased with tube spacing. The research gives guidelines to develop new efficient heat transfer equipment.