Ricardo Salviano dos Santos

Transient Heat Transfer in a Packed-Bed Elliptic Cylindrical Reactor: A Finite-Volume Approach

This work aims to develop a transient three-dimensional mathematical model using the elliptic cylindrical coordinate system, to predict heat transfer in a elliptic cylindrical packed fixed bed reactor. The model considers variable thermo physical properties and a parabolic temperature profile at the fluid inlet. The governing equation is solved using the finite volume method. Results of temperature profile along the reactor are presented and discussed at different moments.It was verified that the maximum heat transfer rate inside the reactor occurs near the extreme region close to minor semi-axis of the ellipse; the higher temperatures at the reactor surface are also in this region, along the entire height of the bed; the steady-state regime is reached at t = 4.5 s of process, presenting after this time interval,small axial temperature gradients and high radial gradients along of the reactor bed; the parabolic temperature profile give to the bed a predominance of radial temperature gradients, and the radial porosity profile favours a higher heat transfer rate at reactor surface.

Drying of Industrial Hollow Ceramic Brick: Analysis of the Moisture Content and Temperature Parameters

The study of ceramic drying is theme of several researches today. In most case, this research is realized experimentally, making possible measurements errors that reverberating in data slightly out of the expected, or erroneous. Numerical simulation emerges like a tool that allows the reproduction of experiments using computers and suitable software’s. The use of numerical simulation enables fast changes in boundary conditions and help in the improvement of an unit operation. This paper aims to predict the drying process of an industrial hollow ceramic brick using the liquid diffusion model to describe the behavior of the temperature and moisture content inside the brick and drying kinetics along time, with the help of the Ansys® CFX commercial package. Predicted results of the average moisture content and temperature of the brick were compared with experimental results, and good agreements were obtained. It was verified that regions with smaller thickness dry and heat faster than the others.

A Mesoporous SiO2/γ-Fe2O3/KI Heterogeneous Magnetic Catalyst for the Green Synthesis of Biodiesel

A magnetic catalyst (sample MCat) consisting of KI supported on a mixture of silica and maghemite (γ-Fe2O3) was prepared and used in the transesterification reaction for the synthesis of biodiesel. The energy dispersive X-ray spectrum of the catalyst showed signals due to Si, Fe, K, and I. Powder X-ray diffraction data revealed the amorphous nature of the SiO2 and the duly impregnation of the support with KI. 57Fe Mossbauer spectroscopy and magnetization measurements confirmed the ferrimagnetic iron oxide in the catalyst to be maghemite. N2 adsorption-desorption data indicated that the silica is mesoporous with a specific area of 352 m2 g-1, enabling the impregnation of 40 and 11 wt.% of KI and maghemite, respectively, according to the chemical composition obtained by the X-ray fluorescence measurements. The MCat was found to be efficient in the transesterification reaction in the macauba and soybean oils. The MCat was easily removed from the reaction medium, with a hand magnet, and efficiently reused for more four consecutive reaction cycles. The good catalytic activity along with its magnetic behavior, high chemical stability and recyclability make the MCat a suitable material for the green synthesis of biodiesel.