2-PHASE FLOW PATTERNS AND TRANSITION CHARACTERISTICS FOR IN-TUBE CONDENSATION WITH DIFFERENT SURFACE INCLINATIONS

In-tube condensation of R-11 was experimentally investigated with vari ous surface inclination angle between the direction of the vapor flow and the gravitational force, phi. The two-phase flow patterns were obs erved visually and the transition locations between different flow pat terns were measured in a transparent test section. The vapor quality d istribution along the test tube and the measured transition locations were used to prepare a flow pattern map. The experimental results indi cated that the surface inclination, phi, strongly influenced the vapor and condensate distribution. Annular flow spanned the whole tube for phi = 0 degrees at various vapor flow rates. Annular flow and stratifi ed flow patterns were observed for phi = 45 degrees and 60 degrees. An nular flow, stratified flow, half-slug flow, and slug flow exist in se quence for phi = 90-120 degrees. Annular flow, churn flow and slug flo w occurred for phi = 180 degrees. The possible prediction of flow patt erns for in-tube condensation in a microgravity environment was discus sed briefly. (C) 1998 Elsevier Science Ltd. All rights reserved.