Air cooling by evaporating droplets in the upward flow of a condenser

A numerical study has been carried out on a sprayed air flow. The droplet evaporation and the resulting balances for humidity and temperature of the air were investigated for various loadings, spray characteristics and injection solutions. An Eulerian-Lagrangian model simulating droplet motion in an air flow was used. Validation was achieved for the various sub-models, especially concerning the behavior of individual droplets in a given air flow. Numerical simulations were then performed on a geometry corresponding to an experimental device that will allow the study of the heat exchange in a real condenser. Even with low water flow rates (0.025 L/min), the use of very fine droplets with size between 25 and 50 mu m results in a significant air cooling (up to 10 degrees with local increase in humidity up to 5 g of water per kg of dry air). Optimal conditions have been sought regarding their size, as too small droplets were found to flow in a concentrated manner with a poor dispersion ability resulting in a less effective mixing, despite their better expected capacities when considered as individual particles. Strong coupling and non linear effects were observed and will require further studies. Effective cooling of the air before the condenser is achievable and can be used for the optimization of refrigerating systems. (C) 2011 Elsevier Masson SAS. All rights reserved.