A mathematical model of the water spray heat and mass transfer equipment with co-current flow of air and water droplets has been developed to investigate the effect of polydispersity of droplet size and the effect of spatial non-uniformity of the spray on evaporation performance. Our simulation results revealed that the simplifying assumption of constant droplet temperature led to significant errors when the droplet size distribution was strongly polydisperse. Numerous simulations showed that the average droplet diameter, droplet size distribution and the radial distribution of water spray significantly affected the changes in properties of air and water droplets. For polydisperse droplets with non-uniform spray, the case of a narrower droplet size distribution (sigma = 0.2) showed a faster decrease in the averaged diameter and temperature of the droplets, which were associated with a faster temperature decrease and humidity increase of the contacting air, than the case of broader droplet size distribution (sigma = 0.4) with the same volume-averaged diameter. (C) 2015 Elsevier Ltd. All rights reserved.