Modeling and simulation of water and PVP/water evaporating spray flows using the direct quadrature method of moments

The direct quadrature method of moments (DQMOM) in an axisymmetric, two-dimensional configuration is extended to model evaporating water as well as polyvinylpyrrolidone (PVP)/water solution spray flows, where the sprays are injected into a vertical spray chamber and carried by air. For model evaluation, the water/air spray is also simulated using the discrete droplet model (DDM). The droplet evaporation is described by Abramzon and Sirignano's model for the water spray, whereas for the PVP/water spray flow, the extended two-film convective bi-component model of Brenn is used with modifications to account for a bi-component spray with polymer presence and resistance due to solid layer formation. The variable liquid and film properties, convective droplet heating and evaporation, as well as droplet motion are included in the model. In the Euler−Lagrangian formulation (DDM), the spray is described by source terms in the gas phase equations. The DQMOM constitutes an Euler−Euler formulation, where the spray is modeled accounting for droplet size and velocity distribution. Droplet coalescence is considered in DQMOM and neglected in DDM. Appropriate initial and boundary conditions for the simulations are generated from experimental data. The droplet size and velocity distributions were measured with phase-Doppler anemometry (PDA). The DQMOM and DDM simulation results are compared with experimental data at various cross sections, and very good agreement is observed. In conclusion, DQMOM shows a much better performance with respect to computational costs and the ease to include droplet coalescence, and therefore, it is chosen to model the PVP/water spray flow in air, which results in similar good agreement with experimental data.