Simulation of refrigerant flow boiling in serpentine tubes

Numerical simulations were conducted to investigate the refrigerant flow boiling in a horizontal serpentine round tube with the Eulerian multiphase flow model and a phase-change model for the mass transfer. Correspondingly, an experimental investigation was conducted to provide validation and data for the simulations. The liquid/vapor phase distributions show stratification in horizontal tubes, indicating the buoyancy force caused by gravity acceleration is dominant, especially when the vapor void fraction is sufficiently high. The adiabatic bend sections served to redistribute the vapor phase, which was induced by the centrifugal force and re-condensation of the vapor (due to thermal non-equilibrium of two phases). The phase distributions in the bend sections showed the competitive influence of buoyancy force and centrifugal force at different operating conditions. In all cases, the numerical simulations appear reasonably consistent with the experimental observations. In particular, the simulation very well explains the bend effects on flow reconstruction and thermal non-equilibrium release observed in the experiments.