Condensation modeling of the unsteady processes in two phase gas-water droplets systems

Abstract

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.

A thermal state variation of water droplets carried by a gas flow during unsteady phase transformations at their surface, with a purpose to explore optimum conditions for utilization of phase transformation heat accumulated in humid flue gas has been modeled. The importance of the case of phase transformations of a “single droplet”, during conductive heating, for a comparative evaluation of warming droplet heating in different heat and mass transfer condition conditions, has been shown. It has been confirmed that the thermal state variation of droplets presented in the time scale expressed in Fourier number is not dependant on water spray dispersity if droplets are heated conductively. Intensity and duration of the process of water vapor condensation on droplet surface is significantly influenced by water temperature and spray dispersity as well as flue gas temperature and its humidity. The radiation flow absorbed by droplets depends on water spray dispersity. It determines formation of a negative gradient temperature field and can shorten duration of the condensation mode.