Paulo Ignácio Fonseca de Almeida - pignacio@power.ufscar.br
Universidade Federal de São Carlos, Departamento de Engenharia Química
13565-905 São Carlos , SP - Brasil

Carlos Henrique Novaga Alves - chna@hotmail.com
Universidade Federal de São Carlos, Departamento de Engenharia Química
13565-905 São Carlos , SP - Brasil

Natural drying by atmosphere evaporation is not efficient or convenient for industrial process. In alimentary production the tendency is to confine the products in stoves or in closed carriers for protect the product against atmosphere contamination and minimize its looses. In the present work an on line vision system supervises the product shrinkage (potato cubes) during drying process in a natural convective stove. A laser illumination system permitted three-dimensional images and its computer analysis. The results were correlated with date from an on-line strain gage specially mounted over the stove. The use of thee-dimensional images is adopted to overcome the error produced by two-dimensional area coincidence in the images obtained from an orderliness product drying process. The result show to be valid uses the laser illumination system for estimates the shadow dimension of the products together to the traditional two-dimensional image obtained by on line vision systems.
 
 

Sérgio R. Fontes - srfontss@fcav.unesp.br
UNESP - FCAV - Via Prof. Paulo Donato Castellane, s/n
14870-000 - Jaboticabal, SP, Brasil

Carlos A. Gasparetto - gasparetto@ceres.fea.unicamp.br
UNICAMP - FEA - Cx. P. 6121
13083-970 - Campinas, SP, Brasil

This is an investigation of non isothermal and non-Newtonian laminar flow in the entrance region of short tubes. The flow is steady, incompressible and tube wall has constant temperature with heating and cooling. Experimental work was conducted using water solutions of Xanthan and Guar gums which exhibited pseudoplastic behavior. Experiments lie in the ranges: 2x10 -04 < Gz -1 < 10 -02 , 300 < Pr < 1000, 30 < Re < 400 and 30,9 < L/D < 135,8. Results were reported as non-dimensional correlations allows practical calculations of Nusselt, Graetz, L/D, Stanton and the friction coefficients. The tendency of the results are compatible with the literature.

Keywords: Entrance region; Convective flow; Guar gum; Xanthan gum.
 
 

Sérgio R. Fontes - srfontss@fcav.unesp.br
UNESP/FCAV - Via Prof. Paulo Donato Castellane, s/n
14870-000 - Jaboticabal, SP, Brasil

Studies have been carried out on micro and ultrafiltration for macromolecular solutions. This complex flow in tubular geometry does not allow accurate analytical solutions to be developed. Approaches to the modelling of crossflow have been numerous highly varied in degree of complexity, and is of great interest in order to design the process and to reach the best transmembrane flux. In this work the fluid flow through a porous tube is modeled from the differential mathematical formulation presented by Zydney (1997), and the equation it approaches the fluid flow with an established velocities profiles, being an entrance region similar to Graetz problem. An analytical solution is presented for polinomial functions, and comparison is carried among experimental rate flux and analytical data, and good agreement is observed.

Keywords: Mathematical modeling; Crossflow; Mass transfer; Xanthan gum; Guar gum.
 
 

Schultz, E.L. - emersonleo@hotmail.com
Quadri, M.G.N. - mara@enq.ufsc.br
Universidade Federal de Santa Catarina, Departamento de Engenharia Química

Cx. P. 276 - 88040-900 - Florianópolis, SC, Brasil
Quadri, M.B. - m-quadri@enq.ufsc.br
Universidade Federal de Santa Catarina, Departamento de Engenharia Química
Cx. P. 276 - 88040-900 - Florianópolis, SC, Brasil

Drying rate is controlled by different factors that change during the drying process. The time of the process and energy costs can be reduced using variable conditions. Therefore, the influence of different air conditions on the drying rate has  been analysed in this work. It was found that shrinkage depends only on the material humidity content.

Keyword: Drying kinectics, Aplle slices, Shrinkage