Influencing factors of cooling performance of portable cold storage box for vaccine supply chain: An experimental study

The COVID-19 outbreak has presented new challenges for the cold chain logistics involved in vaccine distribution. To ensure the safe storage and transportation of vaccines while maintaining the required temperature range, this study focuses on investigating the cooling performance of vaccine cold storage boxes integrated with phase change material (PCM) bottles. The experiment is conducted within a controlled temperature range of 2–8 °C. Performance indexes are proposed to evaluate the performance of the vaccine storage box, including four basic performance evaluation indexes and two extended evaluation indexes. One of the key parameters used is the cold storage efficiency, which analyzes the relationship between the mass of vaccines and the mass of PCM. Initially, the study compares the performance of the storage box with four different layouts of PCM bottles. The results indicate that placing PCM bottles on all six walls of the box (layout 2) is the most effective pattern, yielding a total normalized value of 2.87. Furthermore, the study compares the performance of a cuboid box with that of a cubic box of equal volume. The findings demonstrate that the cubic box, which has a lower surface area to volume ratio, exhibits better performance. Finally, employing layout 2 and a cubic box, the study examines how vaccine loading and ambient temperature affect the performance of the box. The analysis reveals that at 100 % loading and an ambient temperature of 43 °C, the cooling time is 66.3 % shorter compared to an ambient temperature of 13 °C, and 11.4 % less compared to a scenario without any load. It is evident that ambient temperature has a more pronounced impact on the cooling performance than vaccine loading.