Multiobjective optimization including design robustness objectives for the embodiment design of a two-stage flash evaporator

During the early phases of design processes, designers have to take the best decisions in order to converge quickly toward the most preferred design solution. More precisely, in a preliminary design context, the phase of embodiment design consists in determining the best values for the main dimensioning parameters of the system to improve its performances. In general, these performances must satisfy functional or technical requirements related to design objectives. The balancing act between the satisfaction of constraints and objectives can be treat as a multiobjective optimization problem. Although designers often face to a qualitative evaluation of design solutions, difficulty arises from his ability to express preferences and expectations throughout the objective function of the multiobjective optimization problem. Illustrated through the preliminary design of a two stage flash evaporator, the purpose of this article aims to develop a methodology to formulate both constraints and preferences into the optimization model. Thus design solutions are evaluated with a single global indicator of confidence. Flash evaporators are thermal systems which are mainly used for flash cooling and juice concentration applications. The design of such a system has to respect specific constraints related to these areas of applications and should meet multiple design objectives. Several goal-oriented design solutions are discussed, in particular when low design sensitivity is expected.