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Estimativa do coeficiente de transmissão térmica global em edifícios existentes com análise in situ
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Este trabalho consistiu na estimativa dos coeficientes de transferência de calor por transmissão e por ventilação em quatro soluções construtivas existentes. Realizou-se a análise de temperaturas interior e exterior durante o período de aquecimento dos espaços até que estes atingissem uma diferença de temperatura interior / exterior “quase” constante, a partir da qual se calculou a constante de proporcionalidade entre a potência de aquecimento introduzida no espaço e a diferença de temperatura daí resultante. Para determinar a componente de ventilação responsável pela determinação do coeficiente global de transferência de calor, estimou-se a taxa de renovação de ar, calculada a partir da análise do decaimento da concentração de CO2, gás indicador que foi introduzido nos espaços através do vazamento de duas cápsulas de enchimento de pneus de bicicletas. Os resultados obtidos foram comparados com valores calculados a partir da EN ISO 13789, que indica os princípios de cálculo para os coeficientes de transmissão de calor por transmissão térmica e por ventilação para soluções construtivas. Não foi possível concretizar o principal objetivo do trabalho, comprovar experimentalmente a existência de isolamento térmico de envolventes opacas. Dos três casos analisados, um teve um erro entre o modelo teórico e o modelo prático de 14 % enquanto os outros dois tiveram um erro inferior a 10 %. A estimativa experimental da taxa de renovação de ar para as perdas de calor por ventilação permitiu melhorar a estimativa do coeficiente de transmissão térmica por transmissão através das envolventes. As estimativas realizadas permitiram aferir existência de ventilação superior ao previsto pelo modelo teórico em 3 dos 4 casos de estudo.
This work consisted in the estimation of the heat transfer coefficient by transmission and ventilation in four buildings. A temperature analysis was performed for indoor and outdoor during a heating period of the spaces. The spaces were heated until they reached a "near" constant indoor / outdoor temperature difference. Then was calculated the proportionality constant between the heating power introduced in the space and the temperature difference. In order to determine the ventilation component responsible for the determination of the overall heat transfer coefficient, the air renewal rate was calculated from the analysis of measured CO2 concentration decay, this gas was introduced into the spaces through the leakage of two capsules for filling bicycle tires. The results were compared with the values calculated from ISO 13789, which are the calculation principles for heat transfer coefficients by thermal transfer and ventilation for buildings. The main objective of this work wasn´t reached. It was impossible to prove experimentally existence of thermal insulation of opaque surfaces. Of all 4 cases were an error between the theoretical model and the practical model 3 % to two study cases, 18 % for another and 41 % for the situation where we wanted to prove the existence o thermal insulation. The experimental estimative of the air transmission rate to heating loses by ventilation allowed to improve the thermal transmission coefficient research. The values calculated of air rate were higher than predicted by the theoretical model for 3 of the 4 case studies.
This work consisted in the estimation of the heat transfer coefficient by transmission and ventilation in four buildings. A temperature analysis was performed for indoor and outdoor during a heating period of the spaces. The spaces were heated until they reached a "near" constant indoor / outdoor temperature difference. Then was calculated the proportionality constant between the heating power introduced in the space and the temperature difference. In order to determine the ventilation component responsible for the determination of the overall heat transfer coefficient, the air renewal rate was calculated from the analysis of measured CO2 concentration decay, this gas was introduced into the spaces through the leakage of two capsules for filling bicycle tires. The results were compared with the values calculated from ISO 13789, which are the calculation principles for heat transfer coefficients by thermal transfer and ventilation for buildings. The main objective of this work wasn´t reached. It was impossible to prove experimentally existence of thermal insulation of opaque surfaces. Of all 4 cases were an error between the theoretical model and the practical model 3 % to two study cases, 18 % for another and 41 % for the situation where we wanted to prove the existence o thermal insulation. The experimental estimative of the air transmission rate to heating loses by ventilation allowed to improve the thermal transmission coefficient research. The values calculated of air rate were higher than predicted by the theoretical model for 3 of the 4 case studies.
Descrição
Tese de mestrado integrado, Engenharia da Energia e do Ambiente, Universidade de Lisboa, Faculdade de Ciências, 2019
Palavras-chave
Análise térmica Coeficiente global de transferência de calor EN ISO 9869 Certificação energética Teses de mestrado - 2019