Desempenho térmico do colector solar de tubos evacuados para cozinha solar

Abstract

Evacuated tube solar collectors are still little known in Mozambique, however in some regions such as China and Europe they are widely used because they have greater heating capacity even on cloudy days (diffuse radiation). This technology can be used for different domestic and industrial purposes. In this work we intend to experimentally evaluate the thermal performance of evacuated tubes solar collector installed at the top of the Faculty of science, department of Physics of Eduardo Mondlane University for heating a thermal fluid to be used in a solar cooker. The evacuated tube solar collector consists of 15 borosilicate tubes with an aperture area of 1.39 m2 and an absorption area of 1.21 m 2 . A methodology based on a thermal energy balance between the collector and the thermal fluid was used. K-type thermocouples and a photovoltaic cell were used to measure temperature and solar radiation, and a NI 9213 datalogger was used for data acquisition. For data automation, software based on the object-oriented programming language LabVIEW was developed. The temperature profiles at the inlet and outlet of the thermal fluid were analyzed for a set of mass flows, as well as the efficiency was calculated. The results showed for an average radiation of 889.32 W/m 2 a stagnation temperature of 186.54 o C. For mass flows of 1,62×10 -³ kg · s-¹ , 6,45×10-³ kg · s-¹ e 1,51×10 -² kg · s-¹ the average temperatures were 133.87±28.87 o C, 90.18±15.24 o C, 69.51±9.22 o C, the efficiencies were 23%, 55.28% and 57.41% respectively