Abstract
Flanges with elliptical cross-section have extensive industrial application in hairpin heat exchangers, especially in large ones. Yet specified guidelines for their optimum design are not available in literature. This paper is dedicated to develop an optimized design method for elliptical weld neck (WN) flange with its closure under internal pressure. To minimize the weight of the WN-flange with its closure as main objective, optimization is implemented using Design Procedures No. 1 & 2 to obtain optimum geometric parameters. Design Procedure No. 1 is applied to meet requirements outlined in ASME and TEMA standards. The optimal values are extracted for geometric parameters of the structure. Among geometric parameters, the parameters such as flange thickness, hub height and closure thickness can be still optimized as per ASME Sec. VIII, Div. 2-Part 5. Protection against plastic collapse and local failure as Div.2's criteria, no leakage conditions and bolt integrity are considered as the constraints of Design Procedure No. 2. Along with the weight objective function, minimizing the stress in the bolts is also defined as a secondary objective function. This objective function enables the designer to use bolts made from alternative material. Design Procedure No. 2 is developed using modeFRONTIER software in conjunction with CATIA, ABAQUS, and EXCEL to minimize the weight and stress in bolts via a Non-dominated Sorting Genetic Algorithm (NSGA-II). The results shows that Design Procedure No. 2 is capable of achieving 22.57% weight reduction in comparison with Design Procedure No. 1.
