王维,陈墨,王威,潘艳秋,陈国华.初始非饱和多孔物料对冷冻干燥影响理论分析[J].,2014,54(1):6-12 |
初始非饱和多孔物料对冷冻干燥影响理论分析 |
Theoretical analysis for freeze-drying of initially unsaturated porous material |
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DOI:10.7511/dllgxb201401002 |
中文关键词: 初始非饱和 冷冻干燥 数值模拟 传热传质 多孔介质 |
英文关键词: initially unsaturated freeze-drying numerical simulation heat and mass transfer porous media |
基金项目:国家自然科学基金资助项目(21076042);中央高校基本科研业务费专项资金资助项目(DUT14RC(3)008). |
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摘要点击次数: 1901 |
全文下载次数: 1932 |
中文摘要: |
为提高过程的经济性,提出了液体物料初始非饱和冷冻干燥的技术思想.推导了冷冻干燥质、热耦合传递模型,模型采用了新的吸附-解吸平衡关系,并考虑了吸湿效应.控制方程用有限容积法进行数值求解.待干水溶液中的溶质选用典型的药物赋形剂——甘露醇.结果表明,初始非饱和多孔物料能够显著减少干燥时间,达到强化冷冻干燥的目的.随初始孔隙率 ε 0(1-S 0) 的不断增大,干燥时间逐渐缩短;在物料初始饱和度 S 0 为0.30~0.35时,干燥时间达到最短.依据干燥过程中饱和度和温度的分布,分析了物料内部质、热传递机理和干燥速率控制因素.对有效质量扩散系数 K S 和有效导热系数 λ+K T Δ H 的分析显示,随着冷冻干燥的进行,物料瞬时孔隙率 ε 0(1-S) 不断增大,过程将由传质控制逐渐变为传热控制. |
英文摘要: |
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, ε 0(1-S 0) . There is the shortest drying time in correspondence with about 0.30-0.35 of initial saturation, S 0. 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, K S and the effective heat conductivity, λ+K T Δ H displays that the rate-controlling factor would change from mass transfer to heat transfer with increase in instantaneous porosity, ε 0(1-S). |
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