Dry ice sublimation: A computational study with experimental validation for the effects of geometry.

Dry ice is one of the world's most in-demand commodities for cold-chain distribution of temperature-sensitive products. It offers an effective cooling solution without requiring mechanical refrigeration or specialized equipment. Dry ice is commonly produced as pellets and blocks. A widely used "rule of thumb" suggests that dry ice sublimates about 3%-8% per day. Mass of dry ice is typically the only packaging specification and/or regulatory limitation, even though sublimation rate is highly dependent on geometry. Therefore, the purpose of this study was to develop and validate a computational model for the sublimation process and to elucidate effects of geometry and orientation on dry ice sublimation. Experiments on sublimation of dry ice blocks were carried out and used to validate a multi-physics model involving radiation and convection heat transfer, computational fluid dynamics, and changes in the geometrical features. Following model validation, effects of dry ice geometry on sublimation rates were evaluated. Volume-to-surface area ratio was found to be a significant sublimation cooling performance parameter. Results showed that for the same mass, the rate of sublimation in the form of a sphere (high volume-to-surface area ratio) was almost half that of dry ice in the form of a block (lower volume-to-surface area ratio). This finding enhances our understanding of dry ice sublimation and cooling, which promises to help to improve practical cold-chain maintenance.