A model for the conceptual design of thermal systems; concurrent decisions in designing for concept

A systems approach to engineering design called the Decision Support Problem (DSP) Technique is being developed in the Systems Design Laboratory in the Department of Mechanical Engineering at the University of Houston. As part of this effort, a decision-based model of the conceptual design process has been developed. In this dissertation the model is particularized for the conceptual design of thermal systems. The design process is characterized by a series of events, for example: (1) the selection of a solution principle or implementation concept to satisfy a set of problem requirements (i.e., type of thermodynamic cycle for power generation), (2) the selection of components associated with the implementation concept, and (3) the determination of the best operating conditions for the overall system with respect to a set of constraints and conflicting goals.; An approach to the integration of information from these events is proposed and demonstrated. The advantages of addressing these events concurrently over the traditional iterative approach are established. The concurrency within design events is achieved by modeling the interaction by means of hierarchies of decisions. Three case studies are formulated and solved to illustrate these concepts: (1) The coupled selection of a heat exchanger concept and coolant. This problem illustrates the process of designing from catalogs. (2) The design of a solar powered irrigation system. In this case the selection of the type of solar collector and working fluid is performed concurrently with the determination of the operating conditions of the entire system. (3) The design of an active thermal control system for spacecraft. In addition to the heat transport fluid selection and determination of operating conditions, the selection between a compressed vapor cycle and a two-phase pumped fluid cycle is incorporated in the formulation.; The modeling of the case studies, the development of the mathematical formulations to model the interactions and the development of the solution methodology are done concurrently. The contributions of this dissertation include the development of the constructs and mathematical models that facilitate making hierarchical decisions in designing for concept and the development of a set of expandable computer-based tools needed for implementation and solution of these formulations.