Experimental Investigation of Heat Transfer in Cavities of Steam Turbine Casings Under Generic Test Rig Conditions

Abstract

This paper presents the first experimental results of the systematic investigation of forced convection heat transfer in scaled generic models of steam turbine casing side spaces with varied geometric dimensions under fully turbulent air flow. Data were obtained by two redundant low-heat measuring methods. The results from the steady-state inverse method are in good agreement with the data from the local overtemperature method, which was applied via a novel miniaturized heat transfer coefficient (HTC) sensor concept. All experiments were conducted at the new Side Space Test Rig “SiSTeR” at TU Dresden. The dependencies of the HTC distributions on the axial widths of the cavity and its inlet and on the eccentricity between them were investigated for Reynolds numbers from Re = 40,000 to 115,000 in the annular main flow passage. The measured HTC distributions showed a maximum at the stagnation point where the induced jet impinges on the wall surface, and decreasing values towards the cavity corners. Local values scaled roughly with the main flow Reynolds number. The HTC distributions thereby differed considerably depending on the dimensions and the form of the cavity, ranging from symmetric T-shape to asymmetric L-shape, with upstream or downstream shifted sidewalls.

Determination of heat transfer coefficient in a T-shaped cavity by means of solving the inverse heat conduction problem

“…For the application of the inverse method as described above, the symmetrical (T-shape) cavity in Figure 6 was considered in accordance to the experiment carried out at TU Dresden (Spura et al , 2018; Spura et al , 2018). The axial width of the cavity was 130 mm and the inlet width was 30 mm .…”

“…Comparison of heat transfer coefficients on the upper part of the cavity boundary determined from the inverse problem with results from gradient optimization method (Spura et al , 2018; Spura et al , 2018) and from the 2D analytic thermal network…”

“…they have a uniform temperature. Thus, they can be modelled as nodes in a thermal network (Figure 12; see also Spura et al , 2018). The heat input at the outer rings is represented as nodal heat source assuming perfect contact between the heating coil and the threaded groove.…”

“…1 and 12 in Figure 2) as well as the ambient temperature. A more detailed description of the test rig and the experimental procedure can be found in (Spura et al , 2018; Spura et al , 2018).…”

“…The generic side space test rig, “SiSTeR”, allows for the systematic investigation of the local forced convection heat transfer in scaled models of turbine side spaces with adjustable geometry using air as working medium (Spura et al , 2018; Spura et al , 2018) (Figure 2).…”