Transport Processes and Separation Technologies

This chapter is devoted to study heat and mass transfer and dimension variations of arbitrary-shaped porous materials. The focus is on the drying process of clay ceramic materials. Here, different topics related to history, manufacturing, drying process, phenomenological lumped modeling, and parameters estimation are present and discussed. Emphasis is given to industrial clay bricks, with theoretical and experimental approaches.

This chapter aims to study the drying of sisal fibers. The interest in this type of material is related to its high mechanical performance. Several important topics such as theory, experiments, lumped and distributed mathematical modeling, and technological applications of fibers are presented and discussed. Emphasis is given to advanced distributed modeling that describes the heat and mass transfer in a wet fiber bed during drying. The model includes different effects such as bed porosity, fiber and bed moisture, coupling between heat and mass transport, and conduction, convection, and evaporation heat transfer. Results of fiber drying and heating kinetics, temperature distribution, and water vapor concentration in the fibrous bed are presented, compared with experimental data and analyzed.

The duck egg is an ideal product to increase human nutrition because it has a large amount of protein and vitamins. This chapter focuses on the foam-mat drying technique applied to duck egg white and yolk. The aim is to obtain powder of these materials after drying. Herein, different topics related to foundations, experiments, and lumped underling are presented and discussed. Drying experiments with and without emulsifiers to obtain stable foam were performed based on the complete factorial experimental design. The idea is to assist researchers, engineers, and academics in the understanding of this important topic related to food preservations.

This chapter presents the application of an analytical solution for the diffusion equation in cylindrical coordinates, considering a boundary condition of the third kind. This diffusive model was used to verify the influence of the presence of the seed coat in jackfruit seeds on the mass transfer at the product surface and on the drying time. For this, jackfruit seeds were dried with and without the seed coat at 60 and 70 °C. In order to obtain the optimal values of effective mass diffusivity and Biot number, the analytical solution was coupled to an optimizer developed from an inverse method. A program was developed in Fortran language to execute the optimizer coupled to the analytical solution. The results showed that the seed coat had a strong influence on the drying time and on the Biot number, indicating that the boundary condition of the third kind is the most suitable for the drying simulation of this type of product.

The spouted bed dryer with inert particles has been researched as an alternative for the drying fruit pulps in order to obtain powdered products. Depending on the composition and physical properties of the pulps, the dryer is subject to agglomeration and accumulation problems that can be minimized by the addition of drying adjuvants, especially carbohydrates, such as maltodextrin; sources of proteins, such as whey protein and milk itself. In this work, the advantages of the spouted bed dryer, regarding its mixing capacity, temperature uniformity, high heat and mass transfer rates, and reduced processing time are emphasized. A review of the fundamentals of the spouted bed is presented in this chapter, as well as the relevant and recent works related to drying fruit pulps in the spouted bed, addressing the use of adjuvants and the impact of the process on phytochemicals present in fruits and other vegetables. The chapter is concluded with the presentation of a case study on the drying of graviola fruit pulp with the addition of milk in the spouted bed dryer, where the results related to production, thermal efficiency, product characteristics, and process modeling are presented with intermittent pulp feeding.

This chapter focuses on the study of heat transfer in packed-bed elliptic cylindrical reactor. Based on the local thermal non-equilibrium, a heterogeneous mathematical model was developed. The transient model is composed for one solid phase and another fluid phase, in which the balance equation for each constituent, written in elliptic cylindrical coordinates, is applied separately, and the proposed model includes different phenomena such as geometry of the particles and reactor, bed porosity, fluid velocity, conduction, and convection heat transfer between the solid particles and fluid flowing inside the bed, and heat generations in the involved phases. Application has been done to a specific geometry of the reactor with aspect ratio 2.