Experimental inversion of the convective heat transfer coefficient of a vertical chord grid wire under transverse airflow

Wet chord grids have potential for dust removal, cooling, and condensation dehumidification of hot, humid mine return air, but their coupled models require a dry-wire gas-side baseline. This study applies a four-terminal electrothermal inversion protocol—constant-current Joule heating, resistance thermometry, radiation correction, and an explicit end-conduction bound—to a vertically tensioned 304 stainless-steel wire of diameter d = 0.35 mm and effective length L = 150 mm in transverse airflow. Eight retained operating-condition values cover u = 0.5–5.0 m/s ( Re = 10.5–104.6). The inferred h increases from 118.9 to 374.8 W/(m²·K), whereas Q rad / Q e decreases from 1.65% to 0.53%. A free log-linear fit gives Nu = 0.4709 Re 0.5044 (95% confidence intervals: C = 0.4392–0.5049 and m = 0.4860–0.5228; R² = 0.9987). A continuous broken-power-law test with a hinge at Re = 47 finds no significant change in slope ( F = 0.20, p = 0.67). A conservative one-dimensional fin estimate bounds end conduction at 4.5–6.1% of convection at the lowest velocity and 2.5–3.3% at the highest velocity; varying emissivity from 0.15 to 0.45 changes h by at most ±0.84%. Because the available dataset contains operating-condition values rather than run-level observations, repeatability intervals are not claimed. The resulting correlation is a geometry-specific dry-state benchmark for the stated wire, orientation, temperature range, and Reynolds-number range, rather than a universal diameter-independent correlation.