THERMOECONOMIC FUNCTIONAL ANALYSIS: A METHOD FOR OPTIMAL DESIGN OR IMPROVEMENT OF COMPLEX THERMAL SYSTEMS

A new method called "Thermoeconomic Functional Analysis", (T.F.A.), is developed in this thesis for optimal design or improvement of complex thermal systems. The method is based on Second-Law Analysis and Optimization Theory.; The system is considered as made up of "units". Each unit has its own "function" (i.e. purpose or product), which is appropriately quantified by use of Second-Law concepts (entropy, essergy). The function of each unit is distributed to other units and/or to the environment. The representation of a system in terms of units and a function distribution network is called the "Functional Diagram of the System".; The objective of the optimization problem is to minimize the total cost of owning and operating the system subject to those constraints which are revealed by the Functional Diagram. The general formulation of the problem is presented and detailed equations for optimizing a four-unit thermal power plant are derived.; Special cases of T.F.A. are examined: Under certain conditions, the Decomposition Principle of Optimization Theory can be applied. Then, the system can be decomposed into smaller subsystems and corresponding subproblems which are solved much more easily. If additional requirements are satisfied, the system approaches a condition known as "Thermoeconomic Isolation", (T.I.).; The main advantages of the method are the following: (1) It establishes a rational basis for the performance evaluation of the complex system components. (2) It can be applied to systems of any size or degree of complexity. (3) By closely approaching T.I. the optimal design of a unit or of the whole complex system is greatly facilitated leaving time and means to investigate the effect of many new underlying variables and to deliberate on many more potential improvements than could otherwise be considered.; The applicability and the advantages of the new method are demonstrated by optimizing a four-unit thermal power plant using each one of the three versions (general, decomposition, T.I.), and comparing the results with those obtained by a more conventional approach presented in recent publications.