A Comprehensive Experimental Database and Novel Onset Criterion for Heat Transfer Deterioration in Vertical Upward Supercritical CO₂

This study systematically evaluates and advances methods for identifying heat transfer deterioration (HTD) and its onset in vertical upward flow of supercritical carbon dioxide (sCO₂). We compiled and rigorously curated the largest experimental dataset to date, comprising 47338 data points from 41 publications and covering pressure, inlet temperature, heat flux, mass flux, pipe diameter, material and lengths of heated and insulated sections; uniform screening, calibration and categorization produced 1095 directly comparable cases spanning the complete q-G and q/G-d operating space. A systematic assessment of existing identification techniques motivated the development of an improved temperature fluctuation approach, which achieves 89.2% accuracy. Comprehensive evaluation of buoyancy and thermal acceleration dimensionless groups demonstrated that no single effect parameter maintains a stable HTD threshold across all conditions, highlighting the need for multi effect coupled modeling. Finally, after reviewing nineteen classical onset criterion correlations, we introduce a data driven framework based on Buckingham Pi analysis and active subspace methods to select dominant dimensionless groups and formulate a novel onset criterion with adjustable probability thresholds that outperforms existing methods in accuracy. This work provides a high quality experimental database, refines HTD identification techniques and proposes an advanced onset criterion, thereby laying the groundwork for future standardization, online monitoring, mechanistic insight and practical engineering applications in sCO₂ heat transfer systems.