Drying Model

Convection Drying Modeling. Models of the drying process have been developed to estimate whether a particular coating can dry under the conditions of an available dryer. These models can be mn on desktop personal computers (see Computer technology). 

We will cover a simple drying model to examine the radiation drier of coated paper. We assume there are no major temperature or humidity variations in the direction of the paper web thickness, and that temperature T and humidity u are constant in the direction of thickness. This assumption requires that the capillary action be ignored, and the pressure gradient of water is zero on the assumption hu/dx = dT/dx = 0. How is it possible that the humidity distribution remains uniform ... 

BisHov s J, MASUOKA Y and KAPSALis J G (1977) Antioxidant effect of spices, herbs and protein Hydrolyzates in freeze-dried model systems Synergistic action with synthetic phenolic antioxidants, J Foot/ Processing Preservation, 1, 153-66. 

Mulct, A., Bema, A., Rossello, C. (1989). Drying of carrots. 1. Drying models. Drying Technology, 7(3), 537-557. Navas, J.A. (2005). Optimizacion y control de la calidad y estabilidad de aceites y productos de fritura. Ph.D. thesis. Universitat de Barcelona, Espaiia. 

On standing in air, surfaces covered with aminopolysiloxanes become coated with a strongly adhering white powder that has been shown to be the product of the interaction of the amine with C02 in the air. Similar products are isolated from reactions of neat, dry model amines with dry ice [2]. 

Fig. 1. Comparison between the predictions of the present pneumatic drying model, DryPak model, Rocha in [20] and Levy and Borde [8] models and the experimental data for (a) gas temperature, (b) solid temperature, (c) gas humidity and (d) particle s moisture content along the dryer length.

The pneumatic drying model was solved numerically for the drying processes of sand particles. The numerical procedure includes discretization of the calculation domain into torus-shaped final volumes, and solving the model equations by implementation of the semi-implicit method for pressure-linked equations (SIMPLE) algorithm [16]. The numerical procedure also implemented the Interphase Slip Algorithm (IPSA) of [17] in order to account the various coupling between the phases. The simulation stopped when the moisture content of a particle falls to a predefined value or when the flow reaches the exit of the pneumatic dryer. 

Fig. 2. The predictions of the pneumatic drying model for (a) gas phase velocity, (b) dispersed phase velocity, (c) gas phase temperature, (d) dispersed phase temperature, (e) gas humidity, (f) particle s moisture content and (g) particle s diameter along stream lines and the dryer length.

E. Machnow, M. Ihlow, M. Henneberg, et ah, Fluidized bed steam drying -modelling and experimental studies, Chem. Eng. Technol.,... 

Farag, R.S., Osman, S.A., Hallabo, S.A.S., Nasr, A.A. 1978. Linoleic acid oxidation catalysed by various amino acids and cupric ions in freeze-dried model systems. J. Am. Oil Chem. Soc. 55, 703-710. 

A change in composition or a commercial food product s formulation is most likely to affect its cellular stmcture, especially if formed by extrusion or puffing. Thus, studying the effect of stmcture or composition in isolation may not be an easy task. However, there are ways to investigate their effects. For example, freezing at different rates usually produces ice crystals of different sizes, which upon dehydration can produce foams with almost identical composition but different cellular stmcture. Freeze-dried model foams, based on food gums with and without additives can be used to study the effect of the cell wall material in foams that have a similar stmcture (see, e.g., Nussinovitch et al. 2000, 2001). Whether this kind of study will generate wide interest, however, is uncertain. 

The Kossovich (Ko) and Posnov (Pn and PUp) numbers [(6.23), (6.28)] defined by Eqs. (6.188)-(6.190) are obtained from the drying model (Eqs. (6.178)-(6.183) completed with specific initial and boundary conditions). Moreover, they are converted into a dimensionless form by applying the pi theo-... 

Dynamic Rotational Isomeric State (DRIS) Model... 

During the falling rate phase of drying, models based on rate-limiting diffusion within the particles and also from external vapor diffusion on the particles have been proposed, but the primary energy transfer mechanisms remain the same. 

To carry out the objective of this paper, we consider a one-dimensional freeze drying model based on the work of Liapis and Sadikoglu [8]. During the primary drying, the vial contains two regions a dry layer, in which the majority of water was sublimated and a frozen layer. These two areas are separated by a moving interface called the sublimation front. In this work, it is assumed that [5] ... 

TABLE 12-8 Mass-Balance Equations for Drying Modeling When Diffusion Is Mass-Transfer Mechanism of Moisture Transport... 

Waananen et al. (1993), in their review of drying models, note that most models in their final form express the driving force for moisture movement in terms of a moisture concentration gradient. However, the true potential for transfer may be different, namely, differences in chemical potential, as explored in greater detail by Keey et al. (2000). In theory, the diffusion coefficient will be independent of moisture concentration only if the moisture is unbound) but concentration-independent diffusion coefficients have been successfully used in some cases over a wide range of moisture contents. 

Waananan, Litchfield, and Okos, Classification of Drying Models for Porous... 

In contrast realistic, functional drying models provide the basis for optimizing kiln schedules that then can be automated. They need at least three close-coupled modular elements the airflow around the kiln the boundary layer above the lumber surface and the processes of moisture movement within the wood itself In turn each of these has subsidiary complexities. Here, the intention is to reiterate the ideas and features that must be incorporated in these models - and to emphasize the importance for managers of getting quality technical advice before investing in drying facilities. 

Some time ago Kamke and Vanek (1994) compared the performance of a number of within-the-timber drying models, representing mainly diffusion-like and multiple-transport mechanism approaches, for predicting average moisture contents and moisture-content profiles. Four data sets were used, with three sets representing idealised problems. The fourth data set was the experimental results of drying 40 mm boards of Norway spruce, Picea abies, from initial moisture contents of 29-66% at a dry-bulb temperature of 60°C, wet-bulb depressions of 8-25°C, and an air velocity of 6 m s. The required inputs for the models, including physical properties... 

Prediction results from drying models are only as good as the input data supplied. The more sophisticated models do not perform any better than the simple models if the physical property data is inadequate...A simple model will work quite well if good physical property data is available for the species and the drying conditions are within the range for which the model was developed. For research purposes where detailed heat and mass transfer information is required (such as predicting stress and strain behaviour) the models that separate the transport mechanisms may prove more useful. 

The model for batch drying is shown in Table 39.1 (continuous drying model not shown). 

Numerical simulation results of batch and continuous drying models for slices of peppers in packed beds were presented in this work. The reported models were based on differential mass and energy balances in the dryer along with kinetic equations describing transport phenomena in individual particles and product quality deterioration. The shrinkage problem was... 

Three amorphous food model systems consisting of lactose, trehalose, and lactose/trehalose (1 1) as matrix materials, and L-lysine and D-xylose (1 1, 5% w/w) as reactants were prepared by freeze-drying. Aliquots (1 g) of the powdered freeze-dried model materials were transferred into 20-ml glass vials, which were stored in desiccators over four relative vapor pressures (RVP) of 33.2,44.1,54.5, and 65.6%. Triplicate samples were removed at 10- to 24-h intervals depending on the RVP, and the extent of browning was determined spectrophotometrically at 280 and 420 nm. 

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