Concentric evaporating spray jets in dilute gas–solids pipe flows

Abstract

Hydrodynamic mixing of evaporating spray jets in dilute gas–solids pipe flows was investigated both experimentally and analytically. An analytical model was developed for the field description of each phase while an experimental system with a thermocouple matrix was set up to assist the modeling development and validation. A mechanistic model of thermocouple measurements in a general gas–solid–droplet three-phase flow was further established for building up the linkage between the averaged mixture temperature and the temperature of each phase as well as for the measurement interpretation. Phase transfer and interactions between the spray and the ambient flow such as entrainment and turbulent transfer across the jet boundary were delineated in the analytical model. The histogram of spray droplet evaporation, the jet boundary expansion, and the phase distributions of velocity, temperature and concentration were predicted. Effects of the ambient flow velocity, solids loading and spray jet mass flow rate on both the jet structure and temperature profiles were illustrated. Unique phenomena such as the shortening of the spray penetration, the ambient temperature reduction, and the ambient gas acceleration were explored and interpreted. The comparison between the modeling predictions and measurements on the mixture temperature profiles suggests that the proposed analytical approach is reasonably correct.