[en] 1 - Description of program or function: LDEF-SS solves the equations for the two-phase fluid flow in spray dryers. It calculates, by a particle method, the dynamics and vaporization of a single component liquid spray. The spray is fully-coupled to a two-component gas, consisting of an inert species and the vapor of the liquid. The effects of drop collisions and coalescence are included. The geometry is spatially two-dimensional and axisymmetric, and swirling motion is permitted about the dryer axis. A wide variety of dryer parameters, such as dryer size and geometry and atomizer size and speed, and operating conditions, such as gas-flow rates and temperatures, can be specified by user-supplied parameters. Program output includes contour, vector, and spray plots, supplemented by numerical results. 2 - Method of solution: The equations for a single-component liquid moving and evaporating in a two-component gas composed of air and the vapor of the liquid are solved by finite-difference methods. LDEF-SS incorporates the basic methodology of the stochastic parcel (SP) method, as well as many other features of the numerical solution procedure of Dukowicz, in conjunction with the Implicit Continuous-fluid Eulerian (ICE) method. An algorithm was added to calculate the effects of drop collisions. The ordinary differential equations governing the changes in drop properties are approximated by first-order methods. The finite-difference equations for the gas- phase properties are obtained by a control-volume derivation. An eddy diffusivity approximation is used to calculate the turbulent transport of mass, momentum, and energy in the gas. 3 - Restrictions on the complexity of the problem: LDEF-SS does not calculate the gas-phase transport of sulfur dioxide and its dissolution and reaction with the liquid