Abstract
The following paper presents the method for solving one-dimensional
inverse boundary heat conduction problems. The method is used to estimate
the unknown thermal boundary condition on inner surface of a thick-walled
Y-branch. Solution is based on measured temperature transients at two
points inside the element's wall thickness. Y-branch is installed in a
fresh steam pipeline in a power plant in Poland. Determination of an
unknown boundary condition allows for the calculation of transient
temperature distribution in the whole element. Next, stresses caused by
non-uniform transient temperature distribution and by steam pressure
inside a Y-branch are calculated using the finite element method. The
proposed algorithm can be used for thermal-strength state monitoring in
similar elements, when it is not possible to determine a 3-D thermal
boundary condition. The calculated temperature and stress transients can
be used for the calculation of element durability. More accurate
temperature and stress monitoring will contribute to a substantial
decrease of maximal stresses that occur during transient start-up and
shut-down processes.
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