New Perspectives for Optimal Control of Drying Processes

Quirijns, E.J.; Willigenburg, L.G. van; Boxtel, A.J.B. van

doi:10.1016/s1474-6670(17)38578-6

Cited by 9 publications

(5 citation statements)

References 11 publications

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“…This model boundary plays a crucial role in the diffusion-sorption model. 5 The moisture content at which the heat of sorption approaches the heat of vaporisation of water (ie H is ≈ 0 J mol −1 ) is generally taken as indicative of the amount of bound water existing in the material. 17,20,27,29,34 In view of the localised sorption theory, this point corresponds with the level of moisture content where the multilayer molecules behave like liquid water molecules.…”

Section: Model Boundary Between Bound and Free Watermentioning

confidence: 99%

“…Since the distinction between the different classes is not sharp, 3 the term boundary is mainly an operational term, required for the model. 5 Third, the thermodynamics corresponding to this boundary are derived from the sorption isotherm. Both the boundary and the corresponding thermodynamics are used to model the conversion between bound and free water.…”

Section: Introductionmentioning

confidence: 99%

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Sorption isotherms, GAB parameters and isosteric heat of sorption

et al. 2005

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The diffusion-sorption drying model has been developed as a physics-based way to model the decreasing drying rate at low moisture contents. This new model is founded on the existence of different classes of water: free and bound water. The transition between these classes and the corresponding thermodynamics form distinct components of the drying model. This paper shows that the characteristics of the different classes of water and of the transition between them can be deduced from the GAB sorption isotherm. The parameters in the GAB sorption isotherm support the theory of localised sorption, establishing the existence of different classes of water. Moreover, the sorption mechanism retrieved from the GAB parameters is in accordance with the sorption mechanism, which is obtained from the moisture dependence of the net isosteric heat of sorption. This holds for experimental sorption data of corn and starch as well as for literature data on five vegetables and four fortified cassava products. An extremum in the net isosteric heat of sorption coincides with the transition between bound and free water, and the partition moisture content corresponds with the monolayer value derived from the GAB equation. This confirms that the GAB monolayer value can be chosen as model boundary between bound and free water. Moreover, it reveals that this method can be developed into a technique to estimate the bound water content in foods.

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Section: Model Boundary Between Bound and Free Watermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sorption isotherms, GAB parameters and isosteric heat of sorption

et al. 2005

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“…A typical example of such a goal is to reach a specific final moisture content with maximum preservation of quality. 15,16 The role of the sorption isotherm during this application is twofold.…”

Section: Introductionmentioning

confidence: 99%

An improved experimental and regression methodology for sorption isotherms

et al. 2004

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Sorption isotherms of corn and starch cylinders with immobilised catalase are experimentally determined at different temperatures for use in drying models in optimal control studies. This application of the sorption isotherm requires an accurate prediction of the sorption data at different temperatures for the low water activity range. The GAB equation is used for the prediction of the sorption isotherms. Two major problems are encountered by employing standard procedures, ie prediction of sorption at a w < 0.11 and sensitivity of the GAB parameters to the applied data range. An improved methodology is developed, consisting of extending the standard experimental procedure with additional data points in the low water activity range and changing the criterion in the regression procedure in the sum of squares, which is weighed by the variance of the experimental data. The new methodology leads to accurate, consistent and physically relevant parameters of the GAB equation, which are independent of the applied data range in the regression analysis and which result in accurate predictions of the sorption behaviour at low water activity. The sorption data at different temperatures at low water activity can be predicted in the best way with parameters obtained after direct regression based on weighed SSQ.

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“…Goldberg and Tröltzsch, Kleis and Sachs, Mittelman and Maurer, and Biegler et al, among others, illustrate the use of the complete parametrization approach. Banga et al, , Petzold et al, Blatt and Schittkowski, Quirijns et al, and Saa et al., again among others, illustrate the use of the control vector parametrization approach. More recently Serban et al presented the application of a modified multiple shooting approach to an optimal control problem associated with a modified Burgers' equation.…”

Section: Dynamic Optimization Solution Methodsmentioning

confidence: 99%

“…However, there is still much work to do in terms of automating the generation of these reduced-order models. Therefore, methods of the second type are still the ones generally used by the dynamic optimization community − and are also the methods to be used in this work.…”

Section: Solution Of An Initial Boundary Value Problem (Ibvp)mentioning

confidence: 99%

Dynamic Optimization of Distributed Parameter Systems Using Second-Order Directional Derivatives

Balsa‐Canto

Banga²,

Alonso³

et al. 2004

Ind. Eng. Chem. Res.

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The dynamic optimization of combined lumped and distributed process systems, governed by nonlinear ordinary and partial differential equations (ODEs and PDEs), is considered in this work. The application of a recently developed method based on the combination of the control vector parametrization approach with the calculation of exact gradients and projected Hessians (Hp's), is presented as an alternative for the efficient computation of the control policies needed to optimize a specific performance criterion. The exact first-and second-order information is calculated by means of the solution of an extended initial value problem (IVP) whose particular time-varying Jacobian structure is exploited by a sparse implicit solver to increase efficiency. Finally, the applicability of this method is shown through the solution of a number of case studies demonstrating that a significant speed-up can be obtained through the use of exact secondorder information.

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New Perspectives for Optimal Control of Drying Processes

Cited by 9 publications

References 11 publications

Sorption isotherms, GAB parameters and isosteric heat of sorption

Sorption isotherms, GAB parameters and isosteric heat of sorption

An improved experimental and regression methodology for sorption isotherms

Dynamic Optimization of Distributed Parameter Systems Using Second-Order Directional Derivatives

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