Theoretical models of vegetable drying by convection

Abstract

The results of experiments are often used to model empirical phenomena. However, the term model is applied in various meanings. A model is usually treated as an abstract formal structure that can replace a material system considered as original, in respect to the aim of modeling. Certain formal structures may be treated as theoretical models of empirical phenomena. On the other hand, a material system can also be referred to as a model of an abstract system, e.g., a set of equations or a hypothesis. Such a material system, if it is a distinct empirical interpretation of the language of a given theory, is then called a real model. Both kinds of models are applied in drying technology, but the second one is more inventive. The mathematical structures are treated as empirical formulae or as theoretical models properly derived from true or legitimated promises of a given theory. The advantages of some mathematical theoretical models of drying processes versus empirical formulae are discussed. The creation of new mathematical theoretical models of convection drying kinetics of some shrinking solids is presented and analyzed. One of the above models was also hypothetically suggested for modeling the drying of cut vegetables in a fluidized-bed. Despite its initial acceptance due to peer empirical justification on cut carrots and celery, it still requires further theoretical analysis. Other models indicated here are theoretical models of vegetable drying in a tunnel drier. These models are created by deduction from laws of heat and mass transfer theory and its basic equations.

Numerical analysis of drying kinetics for shrinkable products such as fruits and vegetables

“…Following the considerations of Pabis and Jaros (2002) and Pabis (2007), we make use of the measurements of volume shrinkage of dried vegetables expressed by the relation:…”

Numerical Investigation of the Deformable Porous Media Treated by the Intermittent Microwave

“…However, the setups of the experiments and the subsequent measuring instruments are costly in terms of time and money. Thus, as a supplement, physically based theoretical models provide the direct description of various thermal processes efficiently, which guide the optimization of the experiments in turn [20,21].…”

Desarrollo de geles deshidratados de rosa mosqueta: comparación de formulaciones con sacarosa y polidextrosa

“…La Tabla 1 muestra las temperaturas aplicadas usualmente en secado al vacío de alimentos, y los valores absolutos de presión correspondientes para lograr la ebullición del agua en el alimento. Mientras se produce la ebullición puede haber difusión de agua en fase vapor, cuando la dimensión característica de los espacios del aire libre es mayor a 10 -7 m, lo que corresponde a estructuras con macrocapilares (Pabis, 2007) Mediante el uso de una pinza amperométrica se observó la variación de la corriente durante el funcionamiento normal del equipo en dichos modos, comprobando que el magnetrón funciona en continuo para el modo P100 y en ciclos de 30 s que combinan los tiempos on/off para lograr el control de potencia en los modos P80 a P10 (ver Tabla 2). Es necesario aclarar que no se trata de un verdadero control de la potencia, ya que el magnetrón entrega una potencia fija de 900 W, valor que el equipo no permite modificar.…”