A Statistical Comparison of Various Fluids for a Drift Flux Model in Reduced Gravity Two‐Phase Slug Flow

The desire to utilize enabling, two‐phase (gas‐liquid) systems for advanced life support and thermal management are driven by NASA’s exploration initiative and the early development of commercial space interests. Two‐phase flow heat transfer is highly advantageous over single‐phase systems. Two‐phase fluid loops provide significant thermal transport advantages over their single‐phase counterparts and are able to carry more energy per unit mass than single‐phase systems at reduced pumping power per unit mass. These advantages alone offer great reductions in both mass and volume, as well as power requirements; unfortunately, the ability to predict two‐phase phenomena such as flow regime transitions and void fraction at microgravity conditions is greatly limited and its development will facilitate the utilization of two‐phase systems. The drift flux model is a useful tool to predict the void fraction and thus, the pressure drop. Results of a statistical analysis indicate that for water/air and water‐Zonyl/air fluids, the drift velocity, U_gj, is −0.070 and the distribution parameter, C₀, is 1.269. These results indicate that the surfactant used had little effect on the model compared to the liquid density difference from the water‐glycerin mixture as well as the liquid density and vapor density differences from the refrigerants R12 and R134a.