The Heat Transfer Heterogeneities of Bends in Flow Boiling of Hairpin Tubes

A series of visual experiments were conducted for liquid-vapor two-phase flow in hairpin tubes, and it was observed that most of the nucleation sites were located at the outer tube wall of the bend. From the simulation, it was concluded that the uneven velocity distribution in the bend induced the heat transfer heterogeneity. Furthermore, the nucleation of both the inner and outer tube wall of the bend and the wall temperature distribution were discussed to understand the physical phenomena. (C) 2009 Wiley Periodicals, Inc.