A new solution approach for simultaneous heat and mass transfer during convective drying of mango E. Barati, J.A. Esfahani ⇑ Department of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, PO Box 91775-1111, Iran article info Article history: Received 20 July 2010 Received in revised form 6 September 2010 Accepted 9 September 2010 Available online 18 September 2010 Keywords: Coupled heat and mass transfer Analytical solution Mango Convective drying abstract The present investigation is contemplated to fill a gap in analytical modelling of coupled heat and mass transfer during convective drying process. A transport model to describe the temperature and moisture evolutions of mango slab is established. The main innovation introduced in this study is represented with the procedure of temperature and moisture predictions. Mango fruit dehydration can be easily simulated with implementation of the present advanced analytical technique at different operating conditions. Moreover, the temperature and moisture history of mango slice are presented for varying values of the drying air factors counting temperature, velocity, relative humidity and initial food temperature. This work confirms that notable time can be saved without sacrificing accuracy by applying proposed model. This method is expected to be useful for fast and accurate drying simulation. The agreement between published experimental results and model predictions is remarkable and an accurate simulation of exper- imental drying curves is obtained. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Food drying is one of the most used methods of preservation. Drying prevents occurrence of undesirable changes due to micro- bial activity. Knowledge of the transport processes is vital for the production of quality dried product and for energy preservation. Understanding and controlling the drying process is also important to improve the establishment of designed dryers. Although exper- imentation is an essential ingredient in the advancement of drying technology, fundamental research with the aid of mathematical modelling and analytical simulation provides an extremely power- ful tool for investigating the complicated physics that evolve dur- ing drying process. The drying is a complex process; hence, the modelling of the food drying is far from simple due to simulta- neous heat and mass transfer between the air and food. Numerical simulation is one of the possible solution strategies and the sub- stantial research has been preformed numerically (Kaya et al., 2007; Villa-Corrales et al., 2010; Mohan and Talukdar, 2010). Mod- elling of drying process brings mathematical as well as physical in- sight into the process; many studies have been devoted to analyze the different aspects of this phenomenon. Selected works include those from Janjai et al. (2010) which simulated drying of litchi fruit and they determined its diffusivity and shrinkage during drying process, Giner (2009) discussed about the effect of internal and external resistances to mass transfer for high-moisture content. Moreover, the dependence of physical and transport properties on food temperature and moisture has been investigated by Bon et al. (2010). In the past, analytical solutions of drying process were confined to simple drying configurations and were valid only under a very stringent set of assumptions. In recent years, the analytical proce- dure is frequently applied due to its ability for obtaining fast and accurate solutions to many of the previously intractable problems. Córdova-Quiroz et al. (1996) proposed a model with interfacial resistance to mass transfer to reproduce the experimental behav- iour of moisture evolution during carrot slab drying, but they did not solve heat transfer equation. Hernández et al. (2000) consid- ered the fruits drying process as isothermal, assuming drying tem- perature equal to the air temperature and accounting only for mass transfer. The aim of their work was to show and validate an analyt- ical solution of a mass transfer equation in which shrinkage was ta- ken into account. Ruiz-López and Garcia-Alvarado (2007) proposed a model that provides a simple mathematical description for food drying kinetics and considered both shrinkage and a moisture dependent diffusivity. They considered constant food temperature, which was also chosen by Simal et al. (2000), and Ben-Yoseph et al. (2000). Wu and Irudayaraj (1996) experimentally verified that dry- ing can be actually supposed as an isothermal process only if the Biot number is very low. When Biot number is high, internal trans- port resistances are also to be considered. It is worth noting that Barati and Esfahani (2008) introduced an analytical method describing simultaneous heat and mass transfer involved in 0260-8774/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2010.09.003 ⇑ Corresponding author. Tel.: +989358185400; fax: +985118763304. E-mail address: Abolfazl@um.ac.ir (J.A. Esfahani). Journal of Food Engineering 102 (2011) 302–309 Contents lists available at ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng