Effect of Liquid Nitrogen Flushing on O_2 Concentration of CA Storage

摘要

Liquid nitrogen (LN_2) is a colourless, odourless, low boiling point cryogenic liquid. Due to its inertness and high expansion ratio (646 between liquid and gaseous N_2) it is an excellent means for rapid purging of the initial O_2 gas from the Controlled Atmosphere (CA) storage. Simulations were carried out for predicting the amount of LN_2 required for flushing at different conditions like free volume of storage chamber, purity level of LN_2 and set point for O_2 concentration. It was found that LN_2 consumption decreased with decrease in free volume of the C A chamber. It was also found that the higher the O_2 present in LN_2 (low LN_2 purity), higher is the LN_2 consumption. At a set point of 2.5% of O_2 concentration, the consumption was 126 g at the highest level of LN_2 purity (0.1% O_2 in LN_2), which increased to 215 g at the lowest level of LN_2 purity (2% O_2 in LN_2). Higher level of O_2 set point was found to consume less amount of LN_2. The simulation results were validated using the laboratory scale CA storage having storage capacity of 10 kg of apples.