The feed water nozzle of the steam generator constitutes an area where exists a very high spatial thermal gradient, and also occasionally a temporal thermal gradient, for example during starting of the installation. In order to protect the vessel from thermal fatigue, the cold pipe is surrounded at the connection by an annular water layer to ensure thermal uncoupling. However the flow behavior remains unknown. In a first step, we improve our knowledge concerning the hydraulic behavior thanks to a model representing a simplified geometry of the nozzle environment. In a second step we confirm this behavior thanks to CFD parametric analysis of the geometry. These two first steps allowed us to identify the best geometrical dimensions, such as the depth and the thickness of the annular cavity, but also the curved or sharp junction. These parameters concern the mass transfer in the annular cavity. The current step concerns the thermal effects. The analysis is performed by both experimental and numerical approach. The experimental method to identify heat fluxes is presented, then the results are discussed and compared to numerical results.

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