Desenvolvimento de um modelo matemático para o dimensionamento de coletores solares assistidos por termossifões

Abstract

Solar heaters may be utilized to heat water for domestic and industrial use. Among the variations of solar heaters, the evacuated tube heat pipe collector stands out due to his efficiency, because it is able to operate in higher temperatures than conventional collectors, since its operational principle is based on the working fluid phase change. In the present work, a theoretical and experimental study of evacuated tube heat pipe collectors was developed. First, two copper heat pipes, with diameters of 12,6mm and 9,45mm, were built and tested with different fill rates – 60% and 80% of the evaporator length. An experimental bench was developed to perform the tests in varied angulation compared to the horizontal plane. After, a mathematical model was developed based on the effectiveness-NTU method for heat exchangers. The model was initially proposed for one heat pipe, and after extended for the heat pipe array. It was implemented on the software EES, and its validation arose through the experimental data obtained by testing the aforementioned heat pipe. Finally, the model was evaluated for varied diameters, evaporator and condenser lengths and irradiation. The developed tool was able to assist projects of heat pipe solar collectors.