An adsorption-sublimation model for a freeze dryer

Litchfield, R.J.; Liapis, Athanasios I.

doi:10.1016/0009-2509(79)85013-7

Cited by 63 publications

(32 citation statements)

References 7 publications

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“…2, 14, and 15, and are discussed by King (1971), Meo (1972), Liapis and Litchfield (1979a), Liapis (1979), andMillman (1984). …”

Section: The Sorption-sublimation Modelmentioning

confidence: 95%

“…However, in a well-designed freeze-dryer, the external mass and heat transfer resistances are not significant (King, 1971;Mellor, 1978). The sorption-sublimation model has been shown by comparison with experimental data (Litchfield and Liapis, 1979;Liapis andMarchello, 1982, 1983a) to predict the drying rates and times quite accurately.…”

Section: The Sorption-sublimation Modelmentioning

confidence: 95%

“…Although the bound water constitutes a rather small portion of the total, its effect is significant as it frequently takes as long to remove as the free water (Men, 1972;Mellor, 1978;Litchfield and Liapis, 1979). It has been found by comparison with experimental data (Liapis and Litchfield, 197913;Liapis, 1980b) that the "sublimation" model of Liapis and Litchfield (1979a) describes the removal of the free water more accurately than the commonly nsed "uniformly retreating ice front" model (King, 1971).…”

Section: The Sorption-sublimation Modelmentioning

confidence: 98%

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An analysis of the lyophilization process using a sorption‐sublimation model and various operational policies

1985

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The freeze-drying process is studied under various operational policies through the use of a sorption-sublimation model. The operational policy that provides the shortest drying times keeps the pressure at its lowest value. The upper and lower heating plates are independently controlled so that the material constraints are encountered and held throughout the free water removal phase.Under certain conditions, and for the case of samples of small thickness, the sorbed water profiles may have segments whose bound water concentrations are higher than those at the start of the free water removal phase. It is shown that the criterion used in terminating the freeze-drying process is of extreme importance, since it may lead to an undesirable sorbed water profile which may deteriorate the quality of the dried product. M. J. MILLMAN, SCOPECertain biological materials, pharmaceuticals, biochemical products, and foodstuffs which may not be heated even to moderate temperatures in ordinary drying, are freeze-dried. Recent developments in biotechnology and biochemical engineering (Hill and Hirtenstein, 1983) have established the importance of lyophilization-freeze-drying-in biochemical processing.As a rule, freeze-drying produces the highest quality product obtainable by any drying method (Goldblith et al., 1975;Mellor, 1978). Prominent factors are the structural rigidity of the product, which facilitates rapid and almost complete rehydration at a later time, little loss of flavor and aroma, and minimization of degradative reactions which normally occur in ordinary drying processes, such as nonenzymatic browning, protein denaturation, and enzymatic reactions.However, freeze-drying is an expensive form of drying because of the slow drying rates and the use of vacuum. Thus, it is essential to develop operational policies which would reduce the drying times by improving the drying rates.The interactions in the variables of the freeze-drying process are complex, and an experimental approach of examining the various operational policies is tedious, expensive, and timeconsuming. But the experiment will finally confirm or disprove the validity of operational policies suggested by theoretical work, and which are supposed to improve or minimize the drying times. A mathematical model which can predict known freezedrying experimental results accurately, can be used in the analysis of the freezedrying process and in the examination of various operational policies which may maximize the drying rates. This work develops a sorption-sublimation model which is used to study operational policies that may significantly reduce the drying times. This model is also used to examine the effects on the bound water profiles of the criteria employed to end the terminal drying phase. Skim milk was used as a model material.The development of bound water profiles incorporates an important factor for optimization policies for quality retention in freeze-drying. CONCLUSIONS AND SIGNIFICANCEA sorption-sublimation model is presented and used to simulate the fr...

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“…2, 14, and 15, and are discussed by King (1971), Meo (1972), Liapis and Litchfield (1979a), Liapis (1979), andMillman (1984). …”

Section: The Sorption-sublimation Modelmentioning

confidence: 95%

Section: The Sorption-sublimation Modelmentioning

confidence: 95%

Section: The Sorption-sublimation Modelmentioning

confidence: 98%

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An analysis of the lyophilization process using a sorption‐sublimation model and various operational policies

1985

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“…Most of the new models only make some changes, in consideration of some specific situations. In 1979, Lichtfield made deep research on the optimization of freeze-drying process, and established the unsteady heat transfer mathematical model under the condition of radiation heating [8] . He analyzed the vacuum freeze-drying by this model.…”

Section: Research Status At Home and Abroadmentioning

confidence: 99%

Analysis of heat and mass transfer mechanism of vacuum freeze-drying in the primary drying

Jiao

et al. 2007

JAC

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The freeze-drying process is a complex heat and mass transfer process virtually. The drying process of freeze-drying is not only the key stage which decides the success of freeze-drying, but also the most difficult stage to control. There are lots of papers about heat and mass transfer in vacuum freeze drying at home and abroad. The present status of research on heat and mass transfer during vacuum freeze drying in the primary drying is summed up and analyzed, the trend of research in this field is discussed in this paper.

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“…Mathematical model describing the unsteady state heat and mass transport during the freeze-drying process has been reported by Trifonova and Arora [3]. The pioneering work in this line appeared from the research group of Liapis and co-workers [4][5][6][7][8][9][10] when they reported a series of mathematical models each successively improving the previous one describing the unsteady state heat and mass transport during the freeze-drying process. These models are complex in nature; however, in spite of the difficulty in the experimental determination of some of their simulation parameters like bulk diffusivity, Knudsen diffusivity, structural constants, etc., the novelty of these model equations lies in the fact that these are practiced in food and pharmaceutical industries in routine basis for the last two decades.…”

Section: Introductionmentioning

confidence: 96%

Modeling and simulation of parametric sensitivity in primary freeze-drying of foodstuffs

Chakraborty

Saha

Bhattacharya

2006

Separation and Purification Technology

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An adsorption-sublimation model for a freeze dryer

Cited by 63 publications

References 7 publications

An analysis of the lyophilization process using a sorption‐sublimation model and various operational policies

An analysis of the lyophilization process using a sorption‐sublimation model and various operational policies

Analysis of heat and mass transfer mechanism of vacuum freeze-drying in the primary drying

Modeling and simulation of parametric sensitivity in primary freeze-drying of foodstuffs

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