SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2016, Vol. 24 ›› Issue (1): 116-125.DOI: 10.1016/j.cjche.2015.07.017

• 第25届中国过程控制会议专栏 • 上一篇    下一篇

Numerical investigation on freeze-drying of aqueous material frozen with pre-built pores

WeiWang1, DapengHu1, Yanqiu Pan2, Guohua Chen3   

  1. 1 Department of Chemical Machinery, Dalian University of Technology, Dalian 116024, China;
    2 Department of Chemical Engineering, Dalian University of Technology, Dalian 116024, China;
    3 Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Hong Kong, China
  • 收稿日期:2014-12-12 修回日期:2015-05-30 出版日期:2016-01-28 发布日期:2016-02-23
  • 通讯作者: WeiWang, Guohua Chen
  • 基金资助:

    Supported by the Fundamental Research Funds for the Central Universities (DUT14RC(3)008), the National Natural Science Foundation of China (21076042), and the Research Grants Council of Hong Kong SAR (HKUST600704).

Numerical investigation on freeze-drying of aqueous material frozen with pre-built pores

WeiWang1, DapengHu1, Yanqiu Pan2, Guohua Chen3   

  1. 1 Department of Chemical Machinery, Dalian University of Technology, Dalian 116024, China;
    2 Department of Chemical Engineering, Dalian University of Technology, Dalian 116024, China;
    3 Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Hong Kong, China
  • Received:2014-12-12 Revised:2015-05-30 Online:2016-01-28 Published:2016-02-23
  • Contact: WeiWang, Guohua Chen
  • Supported by:

    Supported by the Fundamental Research Funds for the Central Universities (DUT14RC(3)008), the National Natural Science Foundation of China (21076042), and the Research Grants Council of Hong Kong SAR (HKUST600704).

摘要: Freeze-drying of the initially porous frozen material with pre-built pores from liquid material was found experimentally to save drying time by over 30% with an initial saturation being 0.28 compared with the conventional operationwith the initial saturation being 1, usingmannitol as the solidmaterial. In order to understand themass and heat transfer phenomena of this novel process, a two-dimensional mathematical model of coupled mass and heat transfer was derived with reference to the cylindrical coordinate system. Three adsorption-desorption equilibrium relationships between the vapour pressure and saturation value namely, power-law, Redhead's style and Kelvin's style equation, were tested. Kelvin's style in exponential form of adsorption equilibrium relation gave an excellent agreement between the model prediction and experimental measurement when the equation parameter, γ, of 5000 was applied. Analyses of temperature and ice saturation profiles show that additional heat needs to be supplied to increase the sample temperature in order to promote the desorption process. Simulation also shows that there is a threshold initial porosity after which the drying time decreased with the increase in the initial porosity. Enhanced freeze-drying is expected to be achieved by simultaneously enhancing mass and heat transfer of the process.

关键词: Adsorption, Desorption, Drying time, Mass transfer, Porous material, Sublimation

Abstract: Freeze-drying of the initially porous frozen material with pre-built pores from liquid material was found experimentally to save drying time by over 30% with an initial saturation being 0.28 compared with the conventional operationwith the initial saturation being 1, usingmannitol as the solidmaterial. In order to understand themass and heat transfer phenomena of this novel process, a two-dimensional mathematical model of coupled mass and heat transfer was derived with reference to the cylindrical coordinate system. Three adsorption-desorption equilibrium relationships between the vapour pressure and saturation value namely, power-law, Redhead's style and Kelvin's style equation, were tested. Kelvin's style in exponential form of adsorption equilibrium relation gave an excellent agreement between the model prediction and experimental measurement when the equation parameter, γ, of 5000 was applied. Analyses of temperature and ice saturation profiles show that additional heat needs to be supplied to increase the sample temperature in order to promote the desorption process. Simulation also shows that there is a threshold initial porosity after which the drying time decreased with the increase in the initial porosity. Enhanced freeze-drying is expected to be achieved by simultaneously enhancing mass and heat transfer of the process.

Key words: Adsorption, Desorption, Drying time, Mass transfer, Porous material, Sublimation