Temperature Evolution in Liquid-Nitrogen Biobanks

Liquid-nitrogen biobanks require stable and spatially uniform vapor-phase temperatures for long-term biological-sample storage. Transient computational fluid dynamics models were developed for automated and non-automated configurations under empty-, half-, and full-load conditions. Loading was represented using different porosity settings for homogenized storage regions, and transient temperature evolution and monitoring-point temperature uniformity were evaluated. In the automated biobank, the final monitoring-point average temperature increased from −187.90 °C under an empty load to −183.21 °C under a full load, while the final monitoring-point temperature difference increased from 10.67 °C to 13.70 °C. In the non-automated biobank, the corresponding average temperature increased from −169.65 °C to −165.38 °C, and the temperature difference increased from 7.81 °C to 10.25 °C. In both configurations, the warmest monitoring locations were more responsive to loading than the coldest locations, indicating increased spatial non-uniformity. Under their respective modeled conditions, the automated configuration reached lower monitoring-point average temperatures but exhibited larger temperature differences, whereas the non-automated configuration showed higher average temperatures but smaller differences. Because the models differed in scale, internal arrangement, thermal boundaries, and monitoring layout, the cross-configuration comparison is descriptive rather than normalized. The results provide a model-based basis for structural screening, loading management, and functional temperature-monitoring strategies.