ABSTRACT
This chapter introduces the basic considerations in optimization and provides the general guidelines for the quantitative formulation of the problem. The main features of the optimization process, including the objective function, which is the quantity that is to be optimized, the design variables, the operating conditions, and the constraints are discussed. Commonly used objective functions for thermal systems such as cost, output/cost, efficiency, energy consumption per unit output, and environmental impact are considered. Several examples are given to illustrate the setting up of the optimization problem. Different optimization techniques, including calculus and search methods, and linear, dynamic, and geometric programming, are briefly presented. The range of application of these methods to thermal systems is discussed. Search methods are the most important optimization strategy for practical thermal systems because they converge to the optimum by iterating from one design to the next, keeping the number of iterations at a minimum. The chapter also discusses several important practical issues related to optimization and to the implementation of the optimal design obtained. These include sensitivity analysis, choice of dominant parameters, safety factors, and dependence of the optimal design on the objective function. Trade-offs are often needed to satisfy different desirable features or multiple objective functions. New optimization techniques are outlined. Optimization is presented as a step that follows the system design stage, which results in a feasible design, and is thus a part of the overall design process.
