Theoretical analysis for freeze-drying of initially unsaturated porous material

Wei Wang, Mo Chen, Wei Wang, Yan Qiu Pan, Guohua Chen

Research output: Journal article publicationJournal articleAcademic researchpeer-review

2 Citations (Scopus)


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, KSand 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).
Original languageEnglish
Pages (from-to)6-12
Number of pages7
JournalDalian Ligong Daxue Xuebao/Journal of Dalian University of Technology
Issue number1
Publication statusPublished - 1 Jan 2014
Externally publishedYes


  • Freeze-drying
  • Heat and mass transfer
  • Initially unsaturated
  • Numerical simulation
  • Porous media

ASJC Scopus subject areas

  • General Engineering
  • General Physics and Astronomy
  • Applied Mathematics


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