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Date of Publication:2022-10-04

Journal:大连理工大学学报

Affiliation of Author(s):化工学院

Issue:1

Page Number:6-12

ISSN No.:1000-8608

Abstract:To improve the process economy ,freeze-drying of initially unsaturated frozen material from aqueous solution is put forward in the present investigation .A novel heat and mass transfer model of freeze-drying with hygroscopic effect was derived on the basis of a new adsorption-desorption relationship .The finite-volume method was adopted in solving the governing equations .Mannitol ,a typical pharmaceutical excipient , was selected as the solute in aqueous solution to be dried . Experimental results show that the freeze-drying process can be enhanced indeed using the initially unsaturated frozen material ,and drying time decreases with increase in the initial porosity ,ε0 (1 -S0 ) .There is the shortest drying time in correspondence with about 0 .30-0 .35 of initial saturation , S0 .According to the profiles of temperature and saturation ,heat and mass transfer mechanism was discussed and the drying rate-controlling factor was analyzed . Inspection on the effective mass diffusivity ,KS and the effective heat conductivity ,λ+ KTΔH displays that the rate-controlling factor would change from mass transfer to heat transfer with increase in instantaneous porosity ,ε0 (1-S) .

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