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

Abstract

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.