Parametric CFD and reduced order modelling of wavy-finned flattened tube thermohydraulic performance in laminar and transitional flow

• A parametric CFD model of a wavy-finned flat air-cooled condenser tube is presented. • Geometric and flow parameter ranges are specific to large air-cooled condensers. • New parametric correlations are provided for thermal and hydraulic performance. • Correlations apply to both laminar and transitional flow. Wavy-finned flattened tube heat exchangers are used in large-scale industrial direct dry cooling systems (air-cooled condensers, or ACCs) due to their relatively high air-side heat transfer and low pressure drop characteristics. Attempts at optimizing these tubes through geometry manipulation, for specific applications (e.g. in natural draft systems), requires careful consideration of the typical trade-off between enhancing heat transfer (benefit) and increasing pressure loss (detriment) across a range of relevant flow conditions. A validated parametric numerical (CFD) model is developed Ansys Fluent 2023 R1 . The model employs the transitional k − ω SST turbulence model along with common tube modelling approaches from literature. The numerical model is used to generate thermal and hydraulic performance data, in the form of Colburn j-factor and apparent friction factor, as a function of relevant fin geometric parameters (fin spacing, fin thickness, wavy wavelength and amplitude) and flow conditions covering laminar and transitional flow ( 500 ≤ R e ≤ 4000 ). A sensitivity analysis identifies fin spacing and wavy amplitude as the most important geometric parameters. A reduced order model is generated using a response surface analysis of the numerical data. Conditioned geometric power law correlations are presented for quantifying the thermohydraulic behaviour of a wavy-finned flattened air-cooled condenser tube as a function of fin spacing and wavy amplitude over a relevant flow range. Good accuracy is achieved with RMSE / R 2 of 7.38 / 95.9 ░ % and 9.01 / 96.6 ░ % for Colburn j-factor and apparent friction factor respectively.