Desenvolvimento experimental de um secador solar multienergético para secagem de frutas.

Abstract

This work represents the development of a solar dryer focusing on the appropriate technologies for the Brazilian agriculture, spreading the culture of renewable energies and contributing to the promotion of the sustainable development. It is about an indirect solar exposition dryer with the solar collector and drying chamber merged and represents numerous innovations, which are a thermal capacitor inside the solar collector and a movement system of the drying air (cooler), energized by photovoltaic solar energy. The innovations used allowed the system to obtain air temperatures inside the drying chamber around 50ºC ±5ºC, the drying air relative humidity about 30ºC ±5ºC. With these characteristics, the drying process operated in the traditional dryers with an average efficiency around 87%. The experimental tests were realized by drying silver bananas (Musa spp.). For the experimental tests realized, the solar dryer shown itself trustworthy, because the necessary time required for the bananas to reach humidity level in wet basis of about 25% was 840 minutes (14 h), being compatible with the catalogued time in the equivalent equipment literature. The drying kinetics was adjusted by the empirical method of Page and the results were representative with high values of determination coefficients approached 0.99. The temperature and relative air humidity measurement system of the drying air using Arduino, ensured the measurement of the temperature and relative air humidity in the intakes and outlets of the solar collector and drying chamber, allowing the solar dryer energy balance realization, resulting in the thermal efficiency calculation of the solar dryer and other thermodynamics properties of the drying air. The results obtained by the thermal efficiency of the drying system were around 19.60%, which are compatible with the ones described in the literature for equivalent solar dryer that used only solar energy as energy provider. The investments with the maintenance and operation of the drying system are only related to the natural degradation of its components. Its economic viability was demonstrated in a short term investment return of about six months.