On the Influence of Flows in Clearances for Thermal Shocks in a Globe Valve
In a nuclear power plant, the functionality of valves must be proven under severe operating conditions. Thermal shocks of approximately 225°C are part of the qualification tests, that fulfill this demonstration. Such shocks are studied here on a large globe valve (nominal diameter: 150 mm), experimentally and numerically. The experimental campaign is carried out on the testing loop “CYTHERE” of EDF. 14 thermal shocks are performed successively in pressurized cold and hot water. The tested valve is equipped with 37 thermocouples distributed over its entire height. The 12 studs of the body-bonnet flange are instrumented with strain gauges, which allow the tracking of the clamping forces evolution in the flange. A 3D numerical simulation of such a shock in the valve is performed. It is carried out by a chained multiphysics simulation: fluid, heat conduction and finally mechanics. The mechanical simulation models around 40 different parts with numerous contacts. Two versions of this simulation are presented, the second one takes into account a heat transfer taking place in clearances. A good agreement between simulation and experiment is shown for temperature in the studs. For clamping forces, only the second simulation manage to reproduce tightening variations observed experimentally at the beginning of cold and hot shocks.