**5. Summary and conclusions**

A comprehensive experimental and computational study of the fluid dynamics of air-mist jets generated under conditions of interest in the cooling of surfaces found in metallurgical processes and in other high temperature processes was carried out. The work analyzes the variation of droplet velocity and water impact density as a function of droplet size and nozzle operating conditions.

The rigorous determination of statistically meaningful samples of droplet size allowed to establish that a relatively small numeric proportion (~0.17) of 'large´ drops (between ~25 m and 370 m) are responsible for transporting a large fraction of the water in the mist. The smaller drops transport only a small proportion of the liquid volume. This fact, which is typical of the different nozzles and operating conditions, suggested that the description of the drop sizes mainly responsible for carrying the water arriving at a given distance from the nozzle orifice would be crucial for formulating a 3-D turbulent Eulerian-Lagrangian model for simulating the dynamics of fan-shaped air-mists. Thus, the present model considers the volume frequency distribution of sizes, instead of the number frequency distribution, to prescribe the inlet ports assigned to the different sizes. This specification, together with those for the distributions of the velocity of the air and drops and of the water volume flux at the orifice, was critical in the results of the model.

The model predicts very well the correlation between drop velocity and size, indicating that the finest drops tend to decelerate rapidly when traveling in the periphery of the mist. Also, it gives an accurate description of the influence that the variation in water flow rate at constant air inlet pressure, and of the variation in air inlet pressure at constant water flow rate, has on the velocity of the drops and on the water impact density distribution. The results on the fluid dynamics of free mist jets are being very useful to develop models for simulating the interaction of dense mists with solid surfaces.
