Desenvolvimento e análise experimental de um sistema de secagem solar em regiões com condições meteorológicas distintas.

Abstract

The Brazilian Northeast stands out, among other aspects, for its fruit production and the availability of solar energy. However, the production of dried fruits in this region of the country is still not expressive. In the search to align these potentialities, the objective of this work was to develop and test experimentally, in the cities of Campina Grande - PB and Petrolina - PE, a solar drying system for fruits that meets different meteorological and climatic conditions to obtain maximum thermal efficiency. The drying system was experimentally tested in pineapple drying. As a methodology, factorial experimental design was used to determine the best configuration of the drying system for the meteorological conditions of Petrolina and Campina Grande in different seasons of the year. The type of coverage and the use of desiccant were delineated as independent variables. The drying time for the pineapple to reach a moisture content of 25% on a wet basis was adopted as the response variable. The analysis of drying kinetics was performed using two-term mathematical models, Lewis and Page. The solar drying system developed was built with low-cost materials, easily found in local commerce, as a way of guaranteeing equipment that can have its technology disseminated and that meets the demand of producers in the region. The main results obtained, after carrying out the experimental tests in autumn/winter and spring/summer, pointed to the flat cover and the use of the desiccant unit as the most statistically significant variables in the reduction of drying time, in the experiments carried out in the two cities, with an average reduction of 60 min in pineapple drying time. In autumn/winter, the average drying time in the system with flat roof and desiccant unit was approximately 490 min (8 h and 15 min) in Petrolina and 660 min (11 h) in Campina Grande. In the drying system with convex cover and desiccant unit, the average drying time was 720 min (12 h) in Petrolina and 630 min (10 h and 30 min) in Campina Grande. In spring/summer, the average drying time in the system with flat roof and desiccant unit was 420 min (7 h) in Petrolina and 600 min (10 h) in Campina Grande. In turn, in the drying system with convex cover and desiccant unit, it took 480 min (8 h) in Petrolina and 660 min (11 h) in Campina Grande, for the pineapple samples to reach the desired moisture content. Page's model presented, in general, the best fit to the experimental data; an average correlation coefficient (R²) higher than 97,37% was obtained in all drying systems in both locations. From the calculation of the thermal yield, it was possible to conclude that the highest values for the thermal yield, in general, are obtained in the period between 11 am and 2 pm in all drying systems, regardless of the place where the experiments were carried out. the highest averages for the thermal efficiency were observed in the drying system with flat cover and with desiccant unit, being 47,73% in Campina Grande (in autumn/winter); 46,19% in Petrolina (in spring/summer); and 43,73% in Campina Grande (in spring/summer).