Interaction of heat and mass transfer processes of water droplets slipping in humid gas

Abstract

This paper presents the transformation cycle of condensation and transit evaporation regimes of sprayed water droplet phase in humid gas in the context of heat utilization from removed biofuel combustion products. A mathematical model based on the heat flow balance on the droplet surface was applied. It combines droplet internal heat transfer and external heat transfer and phase transformation problem solutions. The unsteady temperature field gradient of the droplet is described according to analytical model of heat spread by conduction and radiation in a droplet, while the influence of heat convection is evaluated by the effective heat conductivity parameter. In the droplet, local radiation flow is defined based on spectral radiation absorption in a semitransparent sphere model. Variation of droplet heat and mass transfer parameters is defined by droplet surface instantaneous temperature that is selected according to iterative numerical scheme operated by the fastest descent method. For this scheme, the requirement is raised that relative error between instantaneous calculated heat flows that flow in and from the surface should not exceed five-hundredths percent. The essential role of the droplet slipping factor upon interaction of transfer processes in transformation regime of the condensation phase in gas flow was highlighted.