Experimental and unsteady CFD analyses of the heating process of large size forgings in a gas-fired furnace

Comprehensive unsteady analysis of large size forged blocks heating characteristics in a gas-fired heat treatment furnace was carried out employing experimentally measured temperatures and computational fluid dynamics (CFD) simulations. Heat and fluid flow interactions, consisting of turbulence, radiation and combustion, were simultaneously considered using k-ε, DO and EDM models in a three dimensional CFD model of the furnace, respectively. Applicability of the S2S radiation model was also evaluated to quantify the effect of participating medium and radiation view factor in the radiation heat transfer. Temperature measurements at several locations of an instrumented large size forged block and the furnace chamber were performed. A maximum deviation of about 7% was obtained between the model predictions and the experimental measurements. Results showed that despite the unloaded furnace had uniform temperature distribution, after loading, product surfaces experienced different heating rates, resulting in temperature differences up to 200 K. Findings were correlated with furnace geometry, vortical structures and flow circulations around the workpiece. Besides, S2S model demonstrating reliable results highlighted the importance of radiation view factor optimization in this application. The study could directly be employed for optimization of the heat treatment process of large size steel components. Keywords: Heat treatment, CFD simulation, Gas-fired furnace, Temperature measurement, Heating uniformity, Radiation modeling