Desenvolvimento experimental de um sistema de secagem solar com unidade dessecante integrada.

Abstract

Studies on food drying have been developed around the world, since the traditional drying process in a greenhouse requires large investments and high electricity consumption, increasing the cost of the final product and making it difficult for local rural producers to access it. In this sense, solar drying in equipment built with low-cost materials, easily found in local businesses and whose operation and maintenance can be performed without the need for highly complex actions, becomes an appropriate technology for family farming. Thus, this work was carried out with the objective of analyzing the influence of pre-treatment of the drying air in an indirect solar drying system with an integrated desiccant unit, developed and tested in the production of dried bananas. Factorial experimental design was used to determine the optimized settings for the desiccant unit and for the solar collector. Drying tests were carried out in the drying system with desiccant unit and in the system without desiccant unit, in the cities of Campina Grande and Pombal, both located in the state of Paraíba, also contemplating the meteorological and climatic conditions of the periods of spring/summer and autumn/ Winter. The experimental results determined as the optimal configuration for the desiccant unit: internal volume of 24 liters, two trays for depositing the desiccant and air velocity by forced convection of 2 m/s. For the solar collector, the following were obtained: Transparent alveolar polycarbonate cover and use of a matte black painted zinc tile, used as a thermal capacitor. The average drying time, in the system with desiccant unit, was 712 minutes (12 hours); and, in the system without desiccant unit, it was 840 minutes (14 hours). The average thermal yields were 34% and 28% for the system with desiccant unit and without desiccant unit, respectively. The empirical models of Page and Midilli et al. to experimental data of drying kinetics. The average correlation coefficient of 99.73% and 99.76% was obtained, in the system with and without desiccant unit, respectively, for the Page model and average correction coefficient of 99.76% and 99.77%, in the system with and without desiccant unit, respectively, for the model by Midilli et al. It was possible to observe the protagonism of the use of silica gel as a drying air desiccant in environments with milder temperatures and higher relative humidity.