多效蒸发系统优化设计目标函数的建立与求解

Building and Solving of the Objection Function for Multi-Effect Evaporation Optimum Design

建立了带有冷凝水闪蒸的并流多效蒸发系统优化设计新模型。该模型以整个蒸发系统的年总费用 (包括加热蒸汽年费用、真空系统年费用以及蒸发器和各辅助设备的年折旧维修费用等 )最小为优化目标 ,以生蒸汽压力、冷凝器真空度及各效有效传热温度差为决策变量 ,提出一种新算法———复合形法嵌套拉格朗日乘子法和矩阵法求最优解。算例表明 ,生蒸汽压力、冷凝器真空度、价格参数和冷凝水闪蒸对优化结果影响显著 ,按新模型优化设计比常规设计可节省年费用 16 %左右。新算法对初值要求不高、收敛稳定性好、收敛速度快。

A new optimum design mathematical model of cocurrent multi-effect evaporation with condenser water flash is developed which aims at the minimum annual cost, including cost of fresh vapor, vacuum system, evaporator, maintenance and depreciation. The model based on decisive variables such as the pressure of fresh vapor, the pressure of condenser and effective heat transfer temperature difference of vary effect, is solved by the complex method, Lagrange multiplier method and matrix method. The practical example indicates that the effect of the pressure of vapor, the pressure of condenser, flash of condenser water and price parameters is substantial on the optimum results. The annual cost by the new optimum design is decreased by above 16% than that by the conventional design. The new algorithm increases the convergent speed and stability.