Abstract
This paper proposes an effective method for determining thermal stresses in structural elements with a three-dimensional transient temperature field. This is the situation in the case of pressure elements of complex shapes. When the thermal stresses are determined by the finite element method (FEM), the temperature of the fluid and the heat transfer coefficient on the internal surface must be known. Both values are very difficult to determine under industrial conditions. In this paper, an inverse space marching method was proposed for the determination of the heat transfer coefficient on the active surface of the thick-walled plate. The temperature and heat flux on the exposed surface were obtained by measuring the unsteady temperature in a small region on the insulated external surface of a pressure component that is easily accessible. Three different procedures for the determination of the heat transfer coefficient on the water-spray surface were presented, with the division of the plate into three or four finite volumes in the normal direction to the plate surface. Calculation and experimental tests were carried out in order to validate the method. The results of the measurements and calculations agreed very well. The computer calculation time is short, so the technique can be used for online stress determination. The proposed method can be applied to monitor thermal stresses in the components of the power unit in thermal power plants, both conventional and nuclear.
Highlights
In modern energy systems, wind farms have a significant share in the production of electricity, which is characterized by the high variability of the generated power over time
A thick-walled water-sprayed plate was selected as the construction element under test. Similar operating conditions such as during water spraying of the plate occur during the emergency cooling of a nuclear reactor pressure vessel and in conventional thermal power plants
In the first formula, the heat flux was calculated using a finite-difference of the first-order accuracy, using temperatures in the node located at the active surface and the adjacent node in the normal direction
Summary
Wind farms have a significant share in the production of electricity, which is characterized by the high variability of the generated power over time. It is not permitted to drill holes in the walls of pressure elements In such cases, the coefficient of heat transfer on the internal surface is determined based on the temperature measured on the insulated, accessible external surface of the element [19]. The. For all nodes located in the control volumes centers, the finite volume method can be used to lateral surfaces of the slab were thermally insulated, so their perfect insulation can be assumed: write the energy balance equations. To determine the heat transfer coefficient at node (4,4,3) (Figures 3c,d), located on the cooled plate surface, the normal component of the heat flux at the same point has been calculated as follows:.
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