Three-dimensional CFD simulation of geyser boiling in a two-phase closed thermosyphon

This paper examines the application of CFD modelling to simulate the complex multiphase characteristics inside a wickless heat pipe (thermosyphon). Water and refrigerant R134a were selected as working fluids. A novel and comprehensive three-dimensional CFD model of a wickless heat pipe was developed to simulate both the complex multiphase heat and mass transfer characteristics of boiling and condensation and the heat transfer characteristics of the cooling fluid in the condenser - heat exchanger. The CFD simulation has successfully predicted, for the first time, a boiling regime and two phase flow pattern that takes place with water at low power throughput, known as geyser boiling. The effects of the power throughput on the characteristics of the geyser boiling were investigated. The CFD simulation was also successful in modelling and visualising the multiphase flow characteristics, emphasising the difference in pool boiling behaviour between these working fluids. Temperature profiles and visual validation of the resulting 3D CDF findings were conducted using two experimental facilities.