Energy and Thermal Performance of Vertical Heat-Source Arrangements in a Scaled Brick Tunnel-Kiln Cooling-Zone Model: A Validated CFD Study

Uniform and energy-efficient brick cooling is important for product quality, heat recovery, and tunnel-kiln performance. This study examines how vertical heat-source placement affects airflow, convective heat transfer, heated-surface temperature uniformity, pressure loss, and ideal air-side pumping demand in a 1:4-scale tunnel-kiln cooling-zone model. A three-dimensional CFD model was validated against published Nusselt-number measurements over Re = 15,938–30,890. The predicted average Nusselt numbers showed a mean absolute deviation of 6.55%. All configurations contained four complete thermally active brick units: two longitudinal sources (H1–H2) and two transverse sources (H3–H4). In Setting 1, the longitudinal and transverse sources occupied layers 3 and 2, respectively; in Setting 2, they occupied layers 1 and 2; and in Setting 3, layers 3 and 4. The configurations were compared over setting-specific Reynolds numbers of 16,829–30,641 while maintaining identical brick geometry, source number, and total imposed thermal input. Source placement affected thermal performance mainly by changing the exposure of heated surfaces to established high-velocity passages and wake regions. Setting 3 produced the highest average Nusselt number at the lowest and highest operating points, whereas Setting 1 was marginally higher at two intermediate points. At the highest point, where inlet velocities differed by less than 0.6%, Setting 3 increased the average Nusselt number by approximately 7–8% relative to Setting 2 while requiring about 4.5% less ideal pumping power. Under the investigated scaled, steady forced-convection conditions, Setting 3 provided the most favorable combined performance in terms of convective heat transfer, heated-surface temperature uniformity, and ideal air-side pumping demand.