Abstract
Shippers of healthcare and food products, in most cases, have regulatory responsibility to ensure quality by maintaining product’s temperature during transportation. Dry ice is commonly used as cold source inside the insulated cold-storage packages which are often transported via air freights. But dry ice sublimation can lead to asphyxiation of crew members or passengers due to which, several regulatory bodies have recommended safe limits of dry ice aboard aircraft mainly based on rule-of-thumb. Prior to establishing the limits, understanding dry ice sublimation is of paramount importance. Therefore the current research, experimentally and numerically explores dry ice sublimation packed in commonly encountered containers made of polystyrene foam. A three dimensional quasi-steady model is developed to predict variation of dry ice mass inside the insulation packages. The model is validated against mass and temperature measurements performed on two types of insulation packages made of different material and geometry. The model is able to fairly predict the reduction in dry ice mass over time and the end-of-sublimation time. Both experimental and numerical results show that the sublimation rate of dry ice can be reduced by covering the inner walls of insulation package with a reflective layer like aluminized mylar foil. The good agreement between model and experimental data of dry ice mass variation makes it possible for the shippers to use the modeling approach in estimating sublimation rates of dry ice.
Highlights
Since the beginning of twentieth century, the developments in transport of temperature controlled goods has given rise to a cold chain ecosystem which contributes significantly to the global economy
Mass and temperature measurements were carried out for insulation packages of two different geometries, namely cuboid and cylinder made of expanded polystyrene and graphite filled expanded polystyrene, respectively
Based on the first estimate, it is shown that the expected sublimation rate of dry ice in the insulation package is low
Summary
Since the beginning of twentieth century, the developments in transport of temperature controlled goods has given rise to a cold chain ecosystem which contributes significantly to the global economy. Bio-pharmaceuticals and perishable food products require controlled temperature conditions to maintain quality during their transport. As a result of the regulatory requirements set by the governing bodies like FDA, ICH and ATP, the distributors are required to transport the tem perature sensitive product without braking the cold chain. Temperature sensitive shipments of air cargo often utilizes dry ice as a cold source due to its high sublimation enthalpy (571*103 J kg− 1) which helps in maintaining the desired temperature for longer period of time. The products along with dry ice are commonly transported into insulated container consisting of expanded polystyrene (EPS) foam box and an outer cardboard covering, see Fig. 1. The main purpose of the cardboard covering is to carry safety labels and provide protection to the foam box
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