Numerical and experimental study on a single cone saline water spray in a wind tunnel

Numerical and experimental study on a single cone saline water spray in a wind tunnel

Pre-cooling of inlet air using water sprays is a promising approach to enhance the performance of natural draft dry cooling towers. The present article investigates the usage of saline water in spray assisted natural draft dry cooling towers. A CFD model is developed to predict droplet evaporation, transport, and wet length (distance from the nozzle where all droplets are dry due to evaporation). This length is a key parameter when utilizing saline water in dry cooling tower designs as the risk of corrosion due to the existence of Cl− ions and deposition of salt should be minimized. Experimental tests are conducted in a wind tunnel at cooling tower representative conditions to validate the model. A good agreement is observed between numerical and experimental results. Once validated, results from a numerical experiment incorporating both non-uniform droplet distributions typical for sprays and spray half angle were used to develop a general dimensionless correlation for wet length in horizontal ducts, based on effective diameter and flow conditions. The dimensionless correlation presented in this work allows the influence of operating and ambient parameters on the wet length to be predicted. Air temperature has the strongest influence on wet length. A 4 °C increase in temperature leads to 11.4% reduction in wet length. Other operating parameter, such us droplet diameter and air velocity, have weaker effects.

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