This paper develops a comprehensive numerical model of an industrial-scale walking-beam reheating furnace integrated with an improved oxidation model. The model demonstrates good agreement with experimental data, accurately predicting both temperature distribution and the oxidation process. Utilizing this model, the impact of mixed loading and swirl angles on the oxidation process is investigated. The average porosity of the scale, determined experimentally to be 0.25634, is used as a benchmark for the model. Comparisons of results with and without considering porosity highlight its significant impact on scale thickness distribution. This finding is crucial for the descaling process, allowing for a more accurate determination of descaling pressure and the reduction of production costs. Predicting scale distribution based solely on the temperature at a specific time is challenging due to the lag in scale accumulation. The temperature trend over an extended period is more consistent with the scale distribution. For the reheating furnace studied in this paper, the research results reveal that a swirl angle of 25° emerges as the optimal choice with industrial demands. These results underscore the importance of considering porosity and swirl angle effects on scale distribution and oxidation loss rate, offering valuable guidance for industrial processes.