Design optimization of radiant enclosures
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Design problems involving radiant enclosures are encountered in many different industrial applications. Examples include the design of annealing furnaces used in materials processing, ovens that bake food or cure coated surfaces, and rapid-thermalprocessing chambers used to manufacture semiconductor wafers. In each of these applications, the objective of the design problems is to find the enclosure geometry and heater settings that produce the desired temperature and heat flux distribution over the product. Traditionally, this has been done using a forward “trialand-error” design methodology, which is a time-consuming process that results in a solution of limited quality. More recently, inverse design methodologies have been developed that require far less time than the forward methodology, and produce solutions that better satisfy the desired conditions over the product surface. It is difficult to enforce design constraints, however, which often limits the usefulness and applicability of solutions obtained by this approach. This dissertation describes several optimization methodologies that can be used to solve several types radiant enclosure design problems. In this approach, an objective function is first defined that quantifies the “goodness” of a particular design, in such a way that its minimum corresponds with the ideal design outcome. The objective function is dependent on a set of design parameters that control the enclosure configuration. Once this is done, the optimal set of design parameters is found by minimizing the objective function through nonlinear programming. Far less design time is required compared to the forward methodology, and the final solution is near-optimal. Furthermore, unlike the inverse methodology, it is possible to implement constraints by restricting the domain of the design parameters, which ensures that the solution can be easily implemented in a practical setting. Design methodologies are presented for design the heater settings and geometry of both diffuse-walled enclosures and enclosures containing surfaces with directionally dependent properties, and for solving the heater settings in problems involving transient and multimode heat transfer effects.