Time Optimal Control Operation of Bulk Lyophilisation of Materials on Trays Reduces the Exergy Losses and Increases the Efficiency of Energy Utilisation
Exergy represents a measure of quality of energy and because exergy is destroyed due to process irreversibilities within a system to produce entropy, the exergy expressions and analysis developed in this work could be used to operate the intrinsically unsteady-state lyophilisation processes more efficiently. It is shown that the time optimal control operation of a freeze dryer with respect to heat input to the trays and total pressure in the drying chamber, reduces the duration times of the primary and secondary drying stages by 42.43% and 41.17%, respectively, and this leads to a reduction of 38.19% in the magnitude of the total exergy losses of the lyophilisation system studied in this work. Also, the potential for reducing further the exergy losses when organic co-solvents and water forming non-ideal mixtures of solvents with positive deviations from Raoult's law are used in a lyophilisation system operated under time optimal control, is discussed.
A. I. Liapis et al., "Time Optimal Control Operation of Bulk Lyophilisation of Materials on Trays Reduces the Exergy Losses and Increases the Efficiency of Energy Utilisation," International Journal of Exergy, vol. 32, no. 4, pp. 329-355, Inderscience Enterprises Ltd, Aug 2020.
The definitive version is available at https://doi.org/10.1504/IJEX.2020.108945
Chemical and Biochemical Engineering
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10 Aug 2020