Modeling and simulation of the drying of thin sheets in a continuous infrared dryer

Abstract

The model gives the temperature and moisture distributions of the air, and of the moist sheet, as a function of time and distance in the dryer. The influence of the sheet's velocity and that of the radiant energy on the dryer performance as well as the effect of the moisture content of the entering sheet have been studied. A set of 27 experiments was carried out using the infrared dryer in order to calibrate the model. In these, the following three variables each had three operational levels: web velocity, initial web moisture and heating power. The model predictions agreed very well with the experimental data. Model predictions using arithmetic averages for the parameters, and parameters correlated with operational variables, are also presented and discussed. ~~~ ~Le modkle permet le calcul de la distribution de la temperature et de I'humidite de I'air ainsi que de la nappe en fonction du temps et de la position dans le sechoir. L'influence de la vitesse de defilement de la nappe, de I'energie radiante ainsi que de I'effet de I'humidite de la nappe a I'entrke sur le skchage a Cte etudik. Un ensemble de 27 exfiriences fut realise avec le stchoir B infrarouges afin d'obtenir les donnees nkcessaires a la calibration du modkle. Chacune des trois variables choisies, soit la vitesse de defilement de la nappe. I'humidite de la nappe a l'entree ainsi que la puissance de chauffe, furent operees a trois niveaux distincts. Les predictions du modkle rksultant de I'utilisation de ces paramktres correspondent relativement bien aux donnees. Les predictions du modkle utilisant la moyenne arithmttique des parametres ainsi que celles des parametres correlCs avec les variables opirationnelles sont egalement presentees et discutees.

Infrared Drying: From Process Modeling to Advanced Process Control

“…1 has been utilized in previous studies. [9,10] It is 144 cm long, 110 cm wide, and has an internal space of about 40 cm high in which the radiant elements can move away or get close to the material being dried. The dryer has a power capacity of 20 kW, for which the heating elements can reach a maximum temperature of about 800 C. The material to dry can travel inside the dryer at a velocity up to 25 cm=s.…”

“…The model was integrated and validated with experimental data. [10] Process Control and Optimization Even though most drying processes have been extensively studied over the last few years, the development and implementation of good control strategies to operate industrial dryers with high efficiency have not yet reached a satisfactory platform. Process control design with an optimizer is an imminent approach to handle the problem of energy saving and product quality encountered in pulp and paper or textile industries that heavily rely on drying.…”

“…Other important studies presented various models with different levels of complexity ranging from simple radiation equations to more comprehensive models depicting the dynamics of mass and energy transport caused by nonuniform radiant incidence in a polymer solution as a result of thermocapillary effects [15] or a dynamic model of a pilot-plant infrared dryer similar to an industrial setting. [10] Ranjan et al [17] solved numerically mass and heat transfer equations with a radiative power source that describe a two-way mass and temperature distribution inside a potato sample. Within a similar framework to and inspired by the theoretical approach of Whitaker, [20] Salagnac et al [21] presented a comprehensive model that integrates the dynamic evolution of moisture, temperature, and pressure during the drying of a porous material when the heating power is supplied by infrared and microwave radiations.…”

“…Several studies have concentrated on the drying by infrared radiation in pulp and paper industries, [4][5][6][7][8] textile industries, [9][10][11] in the drying of minerals, [12][13][14] polymer solution, [15] and the drying of food products and fruits, [16,17] and the list of applications and related research work is not exhaustive. The theoretical and experimental work of Lescanne [5] revealed that moisture in pulp paper plays a major role in the absorption of infrared radiation and it is much more important to use emitters of medium wavelengths than to use emitters of short or long wavelengths.…”

Derivation of a control oriented low order model of the dynamics of an infrared oven for the continuous drying of a thin sheet of material

“…The original distributed parameter model described by equations (1-3) with the initial and boundary conditions (410) was integrated numerically using the Lax-Wendroff and Donor-cell algorithms as described elsewhere (Dhib et al, 1994a). The outlet humidity and temperature of the web as a function of time were computed in response to separate 20% step changes [done at time zero] in the electrical power to the infrared emitters (Figure 4), the web velocity ( Figure 5) and finally the inlet web moisture content (Figure 6).…”