Computational investigation of annular flow condensation in microgravity with two-phase inlet conditions

摘要

Condensation heat exchangers contribute significantly to the size of the thermal management system, and their implementation in future spacecraft will require a better understanding of the underlying heat transfer phenomena. In this study, we computationally investigate flow condensation in microgravity with two-phase inlet conditions utilizing the VOF multi-phase model and a 2-dimensional axisymmetric domain. The model is validated utilizing experiments from prior microgravity flow condensation tests conducted onboard a parabolic flight. A control-volume-based theoretical model is utilized to estimate the inlet vapor fraction and inlet phase velocity boundary conditions. The computational model predicts complex flow behavior occurring at the two-phase interface during condensation, but the model suffers from some liquid accumulation in the vapor region. Local condensation heat transfer is under-estimated in the inlet section, and over-estimated in the exit section, compared with the experimental measurements. Mean condensation heat transfer coefficients compare well to experiments. Results show a need for full 3D simulations of flow condensation to improve predictions of liquid entrainment and liquid deposition phenomena that significantly influence local heat transfer coefficients predictions.