The purpose of this work is to present a simple methodology which enables to size a thermosyphon system without always having to resort to a computational simulation. As a result of many system simulations using the TRNSYS software, whereby several project and equipment parameters were varied, a group of expressions were obtained which allow the determination of the system thermal daily efficiency (monthly average). The developed correlation includes geometric and thermal aspects related to the collector, the storage tank and the connecting pipes, as well as operational data such as thermal load, solar radiation and room temperature. This model is able to optimize several variables that comprise thermosyphon solar water-heating systems for the requirements of particular applications. The resulting correlation shows that the efficiency is a linear function of meteorological conditions, collector quality and parameters related to storage tank volume, volume load (consumption profile) and collector area. The correlation is very useful since it is a simple, fast alternative for the calculation of system efficiency without depending on experimental determination or numerical simulation results. The determination and sizing of the collector area and the volume storage tank that satisfy the required thermal load can be appropriately performed in a simple and fast way by using the proposed correlation.
Research on the design and operation of solar stills is relatively advanced, but many works have focused only on the description of the individual behavior and operation of experimental apparatus that can be operated under specific experimental or natural conditions. In any case, optimization of the systems requires the correlation of several parameters by means of mathematical modeling, which can be relatively complex. In this work, appropriate global normalization of governing mathematical equations employing dimensionless numbers has been successfully applied for the versatile operation of solar stills. In this novel approach, optimized conditions to design efficient solar stills are presented and discussed. The results also indicated that the generalized dimensionless model could be able of predicting the still performance. The reasons and processes behind the changing trends of the results depend on the simple analysis of the corresponding nondimensional number.
Os hábitos alimentares do brasileiro têm sido constantemente redefinidos, devido às mudanças culturais e sociais recentes, bem como o surgimento de uma grande variedade de produtos alimentícios dificultando uma alimentação consciente e segura. Assim, o objetivo desse relato de experiência, foi apresentar o projeto de formação educacional sobre os termos alimentares diet, light, probiótico, prebiótico, transgênico e irradiado com 72 alunos do oitavo ano do ensino fundamental de uma escola pública de Florestal-MG. Inicialmente, um questionário estruturado foi aplicado aos alunos para avaliar o conhecimento sobre os termos. Em seguida, o conhecimento sobre esses termos foi transmitido por meio de palestras. Posteriormente, os alunos participaram da Feira de Ciências para disseminar o conhecimento obtido no projeto. Por fim, o mesmo questionário foi reaplicado aos alunos para comparar o conhecimento prévio com o aprendizado adquirido. Uma cartilha, elaborada por um dos discentes voluntários do projeto, foi disponibilizada para consulta dos alunos da escola estadual, caso necessário. A análise dos resultados dos questionários foi realizada por estatística descritiva e teste de Wilcoxon pareado (P≤0,05). No questionário inicial, 80,6% dos alunos acertaram até três questões, enquanto 63,3% dos alunos acertaram quatro ou mais questões no questionário final. A média de 2,6 acertos no questionário inicial aumentou para 3,8 acertos no questionário final, com maiores aumentos de acertos para irradiado e probiótico. Apenas light e diet obtiveram maioria de acertos no questionário inicial, enquanto que todos os termos obtiveram maioria de acertos no questionário final. A transmissão de conhecimento foi efetiva, considerando o aumento do total de acertos geral após as palestras. Os resultados indicam que a ação de extensão contribuiu para a conscientização dos alunos do ensino fundamental e da comunidade sobre os termos alimentares, bem como para o aprimoramento do conhecimento dos estudantes universitários. Palavras-chave: Alimentação Saudável; Rótulo; Termos Alimentícios; Projeto de Extensão; Ensino Fundamental Awareness of food terminology in a state school Abstract: The eating habits of Brazilians have been constantly redefined due to recent cultural and social changes, as well as the emergence of a wide variety of food products, hindering conscious and safe eating. Thus, the objective of this experience report was to present the education training project on the food terms diet, light, probiotic, prebiotic, transgenic, and irradiated with 72 students from the eighth grade of elementary school at a public school in Florestal-MG. Initially, a structured questionnaire was provided to the students to assess their knowledge of the terms. Next, knowledge about these terms was conveyed through lectures. Afterward, the students participated in the Science Fair to spread their knowledge about the project. Finally, the same questionnaire was reapplied to the students to compare their previous knowledge with the acquired learning. A booklet, prepared by one of the school students of the project, was made available for consultation by state students, if necessary. An analysis of the results of the questionnaires was performed by descriptive statistics and paired Wilcoxon test (P≤0.05). In the initial questionnaire, 80.6% of the students got even question three right, while 63.3% of the students got all four or more questions right in the final questionnaire. The mean of 2.6 hits on the initial questionnaire increased to 3.8 hits on the final questionnaire, with more significant increases in hits for irradiated and probiotics. Only light and diet had a majority of correct answers in the initial questionnaire, while all terms had a majority of correct answers in the final questionnaire. The transmission of knowledge was effective considering the increase (P≤0.05) of the overall total hits after the lectures. The results indicated that the extension action contributed to the awareness of elementary school students and the community about food terms, as well as to the improvement of knowledge of university students. Keywords: Healthy Eating; Label; Food Terms; Extension Project; Elementary School
Various data reveals the potential of concentrated solar technologies for the electricity production. With global growing energy demand and green-house gas emission, concentrating solar power is considered as one of the promising options and has invited wide attention. In this work, a model for a 30 MW parabolic trough solar power plant system was developed for 31 different locations in Brazil, using TRNSYS simulation software, and TESS and STEC libraries. The power system consists of a parabolic trough solar collector loop connected to a power block by a series of heat exchangers. The solar collector loop consists of a field of parabolic trough collectors, stratified thermal storage tank, pump and heat exchangers to drive the power block and uses Therminol VP1 as heat transfer fluid. The results show that the cities of Recife (PE), Fortaleza (CE), Belterra (PA), Salvador (BA) and Petrolina (PE) stand out for their high monthly values of direct normal irradiation and, resulting the highest production of energy by the same configuration of Solar Central Power Plant.
The purpose of this study is to evaluate the main variables influencing the employability of young undergraduates alumni. The research comprehended the study of a database of 9753 young people, containing information on work styles, personal values, behavioral profile, logic level, proficiency in foreign languages, and also professional and extracurricular experiences. The analysis of this database shows is possible to identify the main variables adopted by organizations, as well as their relevance along the stages of the selection process. After such identification, a comparison was made between the profile of the successful candidates in a determined selection process and the students of the Chemical Engineering undergraduate course hosted by the
Several studies show that to the extent that the teacher knows the learning preferences of his students is able to promote quality in the teaching-learning process. However, the teacher must know and identify his own style of teaching. The aim of this study is to verify and analyze the diversity of teaching styles in a Brazilian federal public university, based on a widely known teaching model. The method of investigation used in this theoretical-empirical study is the quantitative, through the application of forms and statistical study of the data obtained, using the tool SPSS Statistics. It was observed that the Styles of Open Education and Functional Education are the most commonly found among the professors at the university analyzed. It can be observed that for a level of significance equal to 5%, the teaching styles do not vary significantly with the gender of the teacher, with his academic formation, with the time of activity in the university, that is, the styles presented independent of these factors. The results are different from those obtained in other studies, confirming that the educational environment, the strategies involved and the content of the subjects affect the teaching styles and what justifies the need for further investigation.
Este trabalho teve como objetivo contribuir com estudos sobre a elaboração e a implementação de propostas de atividade didática baseada em experimento de cunho investigativo. O trabalho descreve um experimento com fins acadêmicos para a determinação da massa específica e da viscosidade dinâmica de um fluido por meio do Método de Stokes, um procedimento experimental simples e de baixo custo e que possibilita o processo de ensino/aprendizagem de conceitos diversos da área de Mecânica dos Fluidos, aplicada ao campo da Engenharia. Os valores obtidos de massa específica - (899,60 ± 18,00) kg/m3, (996,00 ± 19,93) kg/m3 e (1.298,00 ± 25,97) kg/m3 - e da viscosidade dinâmica - (0,080 ± 0,001) Pa.s, (0,649 ± 0,007) Pa.s e (0,885 ± 0,015) Pa.s, respectivamente para os fluidos óleo vegetal refinado de soja, detergente e glicerina foram próximos dos valores encontrados na literatura e apresentaram baixo grau de incerteza propagada. O desenvolvimento desta implementação foi realizado com apoio do software EES e apresenta-se como uma proposta de atividade didática baseada em experimento de cunho investigativo em Mecânica dos Fluidos.
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