Experimental and simulation studies of primary vacuum freeze-drying process of random solids at microwave heating

Nastaj, J.; Witkiewicz, K.; Wilczyńska, B.

doi:10.1016/j.icheatmasstransfer.2007.09.003

Cited by 16 publications

(7 citation statements)

References 8 publications

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“…[16][17][18]48] Microwave primary freeze drying of random solids is considered and a uniformly retreating ice front (URIF) one-dimensional model type is formulated in Cartesian geometry, as shown in Fig. 1.…”

Section: Mathematical Modelingmentioning

confidence: 99%

“…For this reason, Lambert's law, which assumes an exponential decay of the field intensity in a dielectric, does not need to be applied. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In this article, a representative of a granular adsorbent, Sorbonorit 4activated carbon, is investigated. Unlike typical freeze-dried products, it represents dielectric materials, which can be used to modify the dielectric properties of a dried system and in this way enhance process performance.…”

Section: Introductionmentioning

confidence: 99%

“…[16] Application of microwave energy in the freeze-drying process has been studied since the middle of the 20th century. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][23][24][25][26][27] Mathematical models of the microwave freeze-drying (MWFD) process are usually formulated with pseudo-steady-state assumption and derived on the basis of heat and mass transfer analysis. Ma and Peltre [2][3][4] described one of the first comprehensive mathematical models of the microwave freeze drying of foodstuff.…”

Section: Introductionmentioning

confidence: 99%

“…[28][29][30][31][32][33][34][35][36] Generation of volumetric heat sources by microwave energy is governed by the same mechanisms regardless of the type of microwave-assisted drying method. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][37][38][39][40][41][42][43][44] When liquid water is present in investigated material, the distribution of electric field strength in a sample is considered. [45][46][47] There are few papers strictly concerning optimization of MWFD [3,38] ; however, there are works dealing with optimal control of the freeze-drying process using conventional heating methods.…”

Section: Introductionmentioning

confidence: 99%

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Optimal Control Policy of the Microwave Primary Freeze Drying of Random Solids

Witkiewicz

Nastaj

2011

Drying Technology

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The optimal strategy of microwave energy input in freeze drying is proposed to keep the temperature of the material external surface, ice core, and sublimation interface as high as possible. This should ensure maximum process efficiency without violating the set constraints. The safety factors are introduced on electric field strength to avoid corona discharge. The microwave power is considered either constant or time variable during the process. A mathematical model of the microwave freeze-drying process is formulated with time-varying transport and dielectric properties of the frozen and dried layers. This model takes into account unknown a priori sublimation front temperature T S and mass concentration of water vapor C S at moving ice front. Comparative analysis of the various process operation conditions is performed to determine the optimal control policy for microwave freeze drying. It is demonstrated that applying an optimal control strategy for limiting process conditions significantly reduces the total microwave freeze-drying time in the primary stage.

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Section: Mathematical Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Optimal Control Policy of the Microwave Primary Freeze Drying of Random Solids

Witkiewicz

Nastaj

2011

Drying Technology

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“…Witkiewicz proposed mathematical modeling of the primary and secondary drying vacuum freeze drying of random solids at microwave heating [21,22] . In 2011, Cristiananalyzed the effect of drying room pressure, tray temperature, vial shape, initial solution temperature, nucleation temperature and phase transition on the heat transfer and temperature distribution of sample [23] .…”

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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