Simulation of Bulk Condensation in a Flow of a Vapor–Gas Mixture through a Nozzle by CFD-Methods Using a Special Computational Module

— Bulk condensation belongs to the most widely used thermodynamic processes. However, the complexity of its simulation often reduces numerical studies to a one-dimensional formulation of the problem and simple channel shapes. This work presents a bulk condensation computational module based on the solution to the kinetic equation by the method of moments for the droplet size distribution function. The module has been upgraded considering the user-defined scalars (UDS) and integrated into the CFD-package. This module upgrading has considerably improved the stability and accuracy of the solution and also has cut down the computational time. The developed condensation model and its implementation using the module have been verified for one-, two-, and three-dimensional formulations in steady state and unsteady approximations against two sets of third-party experimental data by an example of a solution to the problem of bulk condensation during supersonic expansion of a vapor–gas mixture in a nozzle. This yielded the distributions of pressure, temperature, density, degree of supersaturation, mass fraction of condensate, number density, and average droplet size both in cross sections and along the centerline of the examined nozzles. An important conclusion has been confirmed that we should consider not only the formation of droplets but also their growth since it is this process that has the main effect on the thermogasdynamics of the process. The solutions of the 2D and 3D problems are almost identical, which allows us to conclude that 2D formulations may be employed for solving similar problems with a simple channel geometry.