Finite element thermal analysis

For a wide variety of heat transfer problems, the calculation of temperature and heat flow is relatively straightforward. However, many practical situations exist where the geometry is so complex that an analytical solution either does not exist, or is so mathematically complex that it is impractical. For such situations, numerical methods, such as finite element analysis (FEA) are very useful. FEA consists of several steps. First, the geometry of the structure is modeled. Second, ''boundary conditions'' are applied to describe variables, such as heat flow to and from surfaces. Finally, the model is ''solved,'' producing a temperature profile and heat flows. The following is a description of one analysis, related to the postweld heat treatment (PWHT) of a first-of-a-kind feedwater nozzle modification at an East Coast nuclear power plant. Two critical components of the nozzle assembly (a sealing ring and spring) had a maximum allowable temperature of 750F, but were only inches from a weld that was required to be at 1150F during PWHT. Each step in the analysis is described below, including assumptions and simplifications made along the way