Method for Calibrating a Digital Model of Laminar-Turbulent Transition in Natural Convection Flows Around Steel Panel Radiators
Abstract
Method for Calibrating a Digital Model of Laminar-Turbulent Transition in Natural Convection Flows Around Steel Panel Radiators
Incoming article date: 13.07.2025Modeling natural convection from steel panel radiators presents a significant scientific and technical challenge. When heating the radiator's vertical surface, a boundary layer of warm air forms and ascends along the wall. Flow remains typically laminar in the lower section, but as the boundary layer develops, it becomes unstable and transitions to turbulence. Beyond temperature head, transition conditions depend critically on heater geometry. Height, panel count, and vertical finning elements directly impact convective flow formation, where optimized geometry promotes early laminar-turbulent transition and intensified convection. While heat transfer is conventionally evaluated through dimensionless correlations (with Grashof numbers near 10⁹ serving as critical transition thresholds for vertical surfaces, corresponding to ~70°C temperature head at 0.5–1 m height), real-world radiator operation maintains laminar flow in lower zones with upper-height transition to turbulence – a process indeterminable via correlation methods. This study proposes a CFD simulation methodology calibrated against laboratory tests conducted per GOST R 53583-2009, enhancing computational result reliability. The calibrated numerical model ensures high-precision prediction of integral heat emission characteristics. CFD implementation enables preliminary radiator behavior analysis without physical prototyping through parametric variation of geometry and thermal properties. The model is readily parameterized by panel dimensions, finning configuration, and material/medium properties, ensuring computational repeatability across configurations. The proposed calibration method (achieved by imposing experimentally measured heat flux values per GOST R 53583-2009) enhances accuracy in predicting radiator's integral performance metrics and improves model-experiment alignment. This approach guarantees computational reproducibility and flexibility in simulating diverse designs (panel sizes, fin arrangements, materials). Validation challenges persist: Absence of experimental temperature/velocity fields complicates mesh sensitivity analysis, while single-dataset calibration risks model overfitting. Nevertheless, this methodology proves strategically valuable for transitioning toward digital certification of heating devices, as it substitutes physical testing with numerically derived integral parameters of comparable accuracy.
Keywords: heating devices, natural convection, free air flow, heat transfer efficiency, laminar-turbulent transition