Concept development for the experimental investigation of forced convection heat transfer in circumferential cavities with variable geometry

Abstract

Cavities of various geometries occur in several technical applications and the knowledge about the heat transfer inside them is limited. For industrial steam turbines, this becomes critical since thermal casing distortion needs to be predicted reliably in the development process. A test rig concept is presented in this paper to investigate the forced convection heat transfer in cavities with various geometries where the enclosed fluid is driven indirectly by an external turbulent air flow. The dimensions are chosen to achieve similarity with side spaces in steam turbines. For estimating the flow conditions in the side spaces, a computational fluid dynamics analysis and experiments at a shallow water duct were conducted. Two different methods will be used to determine the heat transfer coefficient along the outer cavity wall of the compressed air test rig: the overtemperature method and the steady-state inverse method. In order to eliminate flow disturbances due to natural convection in the cavity and interference among the measurement systems, a parametrical finite element analysis was performed to determine an appropriate concept for the sensor arrangement.