International Journal of Heat and Mass Transfer, Vol.113, 683-703, 2017
The defining factors of the phase change cycle of water droplets that are warming in humid gas
The heat and mass transfer processes of spraying water in humid gases are analyzed in the phase change cycle of water droplets. In the phase change cycle condensation, transit evaporation and equilibrium evaporation phase transformations regimes are distinguished. The variation of the phase transformation regimes is related with the surface temperature of warming droplet. The droplet surface temperature is defined according to the numerical iterative scheme, in which the model of the heat flux's balance on the droplet surface is applied. In this model the solutions of droplet external heat and mass transfer, as well as solution of droplet internal heat transfer are combined. The universal Spalding heat transfer number expression is applied for the phase change cycle and the convective heat flux for a droplet is described according to the classical empirical model. The heat flux of combined heat transfer in the droplet is determined according to the model of the heat transfer by radiation and conduction in the semi-transparent sphere. The radiation heat flux is defined according to the spectral radiation model. The influence of water circulation for the heat transfer in the droplet is evaluated by the effective heat conductivity parameter. The defining factors of the water droplets phase change cycle are: the temperature of sprayed water, temperature and humidity of the gas and the droplet's heating process. These factors influence is evaluated for combined heat and mass transfer processes in the phase change cycle of water droplet. (C) 2017 Elsevier Ltd. All rights reserved.