-The objective of this work is to investigate the production of hydrogen as an energy source by means of the reaction of aluminum with water. This reaction only occurs in the presence of NaOH and KOH, which behave as catalysts. The main advantages of using aluminum for indirect energy storage are: recyclability, nontoxicity and easiness to shape. Alkali concentrations varying from 1 to 3 mol . L -1 were applied to different metallic samples, either foil (0.02 mm thick) or plates (0.5 and 1 mm thick), and reaction temperatures between 295 and 345 K were tested. The results show that the reaction is strongly influenced by temperature, alkali concentration and metal shape. NaOH commonly promotes faster reactions and higher real yields than KOH.
Abstract. The search for new energy sources has been a great focus lately because of concerns about climate change caused mainly by fossil fuels gas emissions. The hydrogen is a promising energy source due its clean and high energy combustion. However, the major drawbacks to use hydrogen are the difficulty of formation, transportation and storage. The objective of this work is the study of hydrogen formation by aluminium reaction with water by using strong alkalis as catalysts (NaOH and KOH), and the development of a mathematical model that accounts the evolution of hydrogen at each time. Different alkali concentrations were used (1, 1.5, 2, 2.5 and 3 mol . L -1 ). The reactions were carried out with aluminum in different samples: foils, plates with 0.5 mm and 1 mm width each. The range of temperatures studied was: 295, 305, 315 and 325 K for foils and 0.5 mm plates; 315, 325, 335 and 345 K for 1 mm plates. The results show ed a strong dependence of the reaction rate on the temperature, alkali concentration and shape of the samples. The model predictions of hydrogen formation agreed with the experimental data of volume versus time, as well as the peaks observed in the reaction rates.
Existe um potencial significativo de economia de energia nos sistemas de climatização de salas limpas. Insufladores, os quais recirculam ar ultra-limpo, são ativos que demandam grandes custos de energia. Diversas publicações relatam que a vazão de ar para salas limpas costuma ser projetada acima do valor necessário. Paralelamente, estudos publicados propõem modelos de estimação da concentração de partículas em salas limpas, considerando diversas características operacionais. Neste trabalho é proposta uma nova abordagem, onde a taxa de trocas de ar por hora pode ser estimada e fornecida ao ambiente controlado conforme a necessidade, gerando uma economia de energia através da redução da velocidade do insuflador, por meio de um sensor por software, composto por um modelo de estimação de concentração de partículas no interior de uma sala limpa. Como estudo de caso, foi utilizada uma das salas limpas do instituto itt-Chip da Unisinos. Os resultados revelaram que é possível, sob certas condições e cenários de utilização da sala, uma redução de até 75,6% na energia consumida pelo insuflador do sistema HVAC.
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