Avaliação do desempenho térmico de um coletor armazenador solar plano horizontal

Abstract

Solar energy is a type of clean energy that can be used as a source of thermal energy for heating air in convective dryers. As solar radiation in Brazil is abundant, almost all year round, solar drying becomes an adequate alternative, reducing processing costs and possible environmental impacts. Its use can be accomplished through the use of solar collectors, responsible for transforming the energy of solar radiation into thermal energy, aiming at the heating of the ambient air. The objective of this work was to evaluate the thermal performance of a horizontal flat solar collector. The solar collector built was of the horizontal flat plate type and to maximize the absorption of solar radiation, a zinc metal plate (CM) and a commercial steel wool (PA) were used separately. Tests 1, 2 and 3 were performed using the CM configuration, and for test 4 the PA configuration was used. Measurements of dry bulb and wet bulb temperatures and air velocities at the entrance and exit of the collector, at hourly intervals between 9 and 17 hours, were used to monitor the results of these experimental tests. To assess the equipment's instant efficiency, the useful energy gain, the useful area of the collector and the global irradiation were initially determined. The results showed that the highest temperature obtained at the collector outlet was 48 ° C, using the steel wool (PA) configuration. The average global irradiation obtained was in the range of 124 to 636 W / m2. It was observed that there was not a great variation between the air velocities at the entrance and exit of the collector, as well as between the mass flow rates. The configuration with the zinc metal plate showed an average efficiency of 52%, slightly lower than that with steel wool, which was 53%, and there were no significant differences (p ≤ 0.05) between them. Thus, the use of steel wool as an absorbent material has been shown to be more applicable than zinc metal sheet, as it has shown greater efficiency results and is more accessible and at a lower cost of acquisition.