Multiobjective optimization of the design of two-stage flash evaporators: Part 1. Process modeling

In recent years, flash evaporation processes have received increased attention in particular areas such as the wine industry where evaporators are mainly used for flash-cooling or concentration. Faced with specific constraints relating to these new areas of application, the design of flash evaporators must now take into account multiple design objectives. Based on an experimental pilot carried out with industrial developments, physical, economical and environmental models have been developed to analyze the performances of this process. Physical models take into account mass and thermal balances at the steady state inside of the evaporation chambers and condensers through a Number of Transfer Unit – Efficiency model. The dimensioning of the chambers is bounded to the flash phenomenon and the size of the droplets carried-over by the vapor flowing out of the chambers to the condensers. The flash evaporator model also takes into account the dimensioning of components such as a mist eliminator, a vacuum pump and an eccentric rotor pump of the Archimedes screw type. The global performance variables of the system are computed from environmental and economical performances. Environmental performances are derived from an eco-indicator related to the environmental impact of the materials and fluid consumptions of the system. The economical performances are computed from the investment and operative costs of every component.