Phase distributions of boiling flow in helical coils in high gravity are investigated both experimentally and numerically. The study focuses on the boiling flow in helical coils of inner diameter 8.9 mm and coil diameter 150 mm at mass velocity 134 kg/(m(2) s), heat flux from 452 to 3164 W/m(2). The simulation uses the volume of fluid (VOF) multiphase model with user defined functions. Its results agree with the experimental visualization. In terrestrial gravity, the flow patterns in ascending and descending half-coils show differences. In high gravity, the phase distributions are different from those in terrestrial gravity and evolve highly depending on the high gravity direction and magnitude. An analysis on the acceleration calculation makes a prediction of the pressure gradient and the phase distribution. (C) 2014 Elsevier Ltd. All rights reserved.