Annular gas-liquid flows have been extensively studied over the years. However, the nonlinear behavior of the interface is still currently the subject of study by multiple researchers worldwide. The appearance of a liquid layer on the wall and its turbulent behavior support the heat exchange of multiple systems in the industrial field. Research in this area allows the optimization of these installations as well as the analysis of possible safety problems if the liquid film disappears. This study first shows some of the most important findings obtained in the GEPELON experimental facility (GEneración de PElícula ONdulatoria or Wavy Film Generator). The facility was built in order to analyze the behavior of the liquid film in annular downward air-water flow. The experimental range of the inlet conditions is 800-8000 for the Re L and 0-110,000 for the Re g . Measurements for the mean film thickness show a fairly good agreement with the empirical correlations and the measurements of other authors. One of the most demanded applications of this type of measurements is the validation of computational dynamics or CFD codes. Therefore, the experiment has been modeled using Ansys CFX software, and the simulation results have been compared with the experimental ones. This article outlines some of the reasons why two-phase flow simulations are currently challenging and how the codes are able to overcome them. Simulation predictions are fairly close to the experimental measurements, and the mean film thickness evolution when changing the boundary conditions also shows a good agreement.

A very efficient method of condensing the steam in various industrial applications is the steam direct discharge into pools with subcooled water. This kind of condensation is known as Direct Contact Condensation (DCC), by providing high heat transfer and mass exchange capacity, the steam condenses quickly. In the past few decades, many experiments have been carried out on the submerged jets of non-condensable gases and pure steam in pools, supplying much information of interest, but efforts are still being made to obtain more information. In particular, the research of steam and non-condensable gas mixtures is of great interest to the chemical, energy, and nuclear industry. Consequently, this study investigates the discharge behavior of air-steam mixtures in a pool with subcooled water by direct visualization techniques using a high-speed camera. To know the behavior of the dimensionless momentum length, tests were carried out considering several initial discharge conditions such as nozzle diameter, percentage of mixture, and flow rates. After image acquisition, a series of complex processing, filtering, and post-processing procedures are applied using a subroutine in MATLAB. The momentum length of the jet was measured and found to be heavily influenced by the nozzle diameter, the jet velocity, and the mixture percentage. A correlation is obtained for the dimensionless momentum length of the horizontal jet that depends on the Froude and Mach numbers.

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