Experimental and Numerical Investigation of Heat Transfer of a Side Space of a Steam Turbine Casing at Full and Partial Load

There is a significant demand for flexibility in steam turbines, including rapid cold starts and load changes, as well as operation at low partial loads. Both industrial plants and systems for electricity and heat generation are impacted. These new operating modes result in complex, asymmetric temperature fields and additional thermally induced stresses. These lead to casing deformations, that affects blade tip gap and casing flange sealing integrity.The exact progression of heat flux and heat transfer coefficients within the cavities of steam turbines remains unclear. The current methods used in calculation departments rely on simplified, averaged estimates, despite the presence of complex flow phenomena. These include swirling inflows, temperature gradients, impinging jets, unsteady turbulence, and vortex formation.This paper presents a novel sensor and its thermal measurements taken on a full-scale steam turbine test rig. Numerical calculations were performed concurrently. The results were validated by measurements. Additionally, the distribution of heat transfer coefficient along the cavity was analysed. The rule of L'Hôpital was applied at specific locations. A method for handling axial variation of heat transfer coefficient is also proposed. Measurements were taken under real-life conditions at a full-scale test rig at MAN Energy Solutions SE, Oberhausen, with steam parameters of 400 °C and 30 bar. Results for various operating points are presented.