Method for routine density measurement of sublimating solid carbon dioxide (dry ice) for cold-chain quality control

Abstract

With recent development of vaccines and biologics, interest in dry ice for cold chain shipping has increased. However, understanding of how dry ice properties relate to performance is not well understood. This study introduces a simple method for measuring a key property of dry ice that has been shown to correlate to performance. The method involves a variant of the water displacement method for determining volume, where dense solid particles are used in place of water for volume determination. Three particle types (sieved sand, glass beads, and stainless-steel shot) were tested for suitability with the particle displacement method. Items of known mass and volume were used to validate the method. Direct volume measurements of dry ice cut samples using digital calipers were conducted in parallel for relative comparison. Results showed that the proposed particle displacement method using sieved sand produced density readings with an accuracy of 97-99%, whereas digital calipers underestimated density values. The sand and glass particles were less successful due to high thermal conductivity (stainless-steel shot), which led to errors due to condensation, and particles that were too fine and not sufficiently dense to prevent fluidization doe to sublimation gas flow. Sieved sand provided a good combination of particle size, density, thermal conductivity, and heat capacity for routine measurement of density of dry ice regardless of shape

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