Author(s):
Guiné, Raquel 
; Barroca, Maria João ; Lopes, Paulo ; Silva, Vitor ; Santos, Mónica ; Ferreira, Dulcineia
Date: 2010
Persistent ID: http://hdl.handle.net/10400.19/1252
Origin: Repositório Científico do Instituto Politécnico de Viseu
Subject(s): mass transfer; drying; pear
Description
Traditionally, in Portugal pears of the variety S. Bartolomeu are dried through an open-air sun
exposure. However, this method of drying has some disadvantages, among which not being able to
fully guarantee the necessary quality and sanitary standards for commercialization. Hence, the
development of alternative drying methods to replace the traditional drying is of great importance
nowadays, and the knowledge of the transfer phenomena happening during drying helps to
understand these processes.
The present work aimed at determining the mass transfer properties of pears for air drying
performed in three drying systems: solar stove with forced air convection (STFC), solar stove with
natural air convection (STNC) and drying tunnel with hot air from a solar collector (DT). The
methodology used to determine the mass transfer properties was a diffusion model, which accounted
for shrinkage.
The values of the diffusion and mass transfer coefficients for the drying in the three systems were
estimated, and from them was possible to conclude that the values of D e in the STNC and DT systems
are similar to each other, whereas the STFC system gives a lower value of diffusivity, indicating that in
this system the internal moisture transfer is less efficient. As to h m , the system that presents the higher
values is STNC, demonstrating a higher efficiency of surface mass transfer.
