Egg-level temperature monitoring and CFD-guided structural optimization improve thermal uniformity and hatch performance in a single-stage tunnel incubator

Temperature uniformity inside commercial tunnel incubators is critical for hatchability and chick quality, but quantitative field data and validated engineering solutions remain limited. This study combined in situ EST measurements, hatch performance evaluation and computational fluid dynamics (CFD) modeling to characterize and improve the thermal environment in a single-stage tunnel incubator. In one tunnel incubator (capacity 90,720 eggs; operated under standard single-stage conditions), eggshell temperature (EST) was monitored at 15 locations (5 trolleys × 3 vertical tiers; 1-min logging for 12 h on embryonic day 1) during half-capacity (37,800 eggs) loading. Hatchability, hatch time, and chick weight uniformity were evaluated by tier using 5 replicate hatches, with trolley-within-tier as the experimental unit. A porous-medium CFD model was validated against the 15-point EST dataset and used to test transverse trolley orientation and a perforated flow-straightening plate. Under baseline conditions, maximum intra-trolley temperature differences reached 0.84°C and trolley-level non-uniformity indices approached 0.62±0.33%. Eggs on the middle tier, which experienced warmer and more stable temperatures, showed higher hatchability (p < 0.05), earlier mean hatch time (p < 0.05) and greater chick weight uniformity (p < 0.05) than upper and lower tiers. The CFD model reproduced measured temperatures with a maximum absolute deviation of 0.35°C and predicted that transverse trolley orientation could reduce non-uniformity indices to 0.29±0.12%, while the perforated plate reduced them to 0.38±0.14%. Field implementation of transverse trolley orientation confirmed improved temperature uniformity. These findings demonstrate that egg-level monitoring combined with CFD-guided structural optimization can substantially improve the thermal environment in commercial tunnel incubators and support more uniform broiler chick production.