Drying of Sisal Fiber: A Numerical Analysis by Finite-Volumes

Abstract

Vegetable fibers have inspired studies in academia and industry, because of their good characteristics appropriated for many technological applications. Sisal fibers (Agave sisalana variety), when extracted from the leaf, are wet and must be dried to reduce moisture content, minimizing deterioration and degradation for long time. The control of the drying process plays an important role to guarantee maximum quality of the fibers related to mechanical strength and color. In this sense, this research aims to evaluate the drying of sisal fibers in an oven with mechanical air circulation. For this purpose, a transient and 3D mathematical model has been developed to predict moisture removal and heating of a fiber porous bed, and drying experiments were carried out at different drying conditions. The advanced model considers bed porosity, fiber and bed moisture, simultaneous heat and mass transfer, and heat transport due to conduction, convection and evaporation. Simulated drying and heating curves and the hygroscopic equilibrium moisture content of the sisal fibers are presented and compared with the experimental data, and good concordance was obtained. Results of moisture content and temperature distribution within the fiber porous bed are presented and discussed in details. It was observed that the moisture removal and temperature kinetics of the sisal fibers were affected by the temperature and relative humidity of the drying air, being more accentuated at higher temperature and lower relative humidity, and the drying process occurred in a falling rate period.

Investigating the Drying Process of Ceramic Sanitary Ware at Low Temperature

“…In the final moments of the drying process, a curvilinear decay of the drying rate as a function of time is observed, tending to zero when approaching the hygroscopic equilibrium condition. The lack of a constant drying rate period was also reported in the literature for dr ceramic bricks [8,36], industrial ceramic blocks [5,35] and sisal fiber [40] with drying air peratures varying between 50 and 100 °C. However, for such cases, the most accentu decay of the drying rate with time occurred in the initial moments of the process.…”

“…However, for such cases, the most accentu decay of the drying rate with time occurred in the initial moments of the process. Rea Drying rate (kg/kg/h) The lack of a constant drying rate period was also reported in the literature for drying ceramic bricks [8,36], industrial ceramic blocks [5,35] and sisal fiber [40] with drying air temperatures varying between 50 and 100 • C. However, for such cases, the most accentuated decay of the drying rate with time occurred in the initial moments of the process. Reasons for this outcome are the lower values of initial moisture content of the samples and the higher values for drying air temperature, material composition, volumetric shrinkage behavior and part geometry, which are all factors that influence the effective mass diffusivity of the product.…”