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Modelo unidimensional de transferĂȘncia de calor em um absorverdor trapezoidal multi-tubos para concentradores Fresnel lineares
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Abstract(s)
RESUMO: Este artigo descreve o modelo matemĂĄtico unidimensional de transferĂȘncia de calor em um absorvedor multi-tubos com cavidade trapezoidal utilizado em um concentrador solar do tipo Fresnel Linear. Todas as taxas de transferĂȘncia de calor foram modeladas analiticamente e o modelo foi validado experimentalmente. Os experimentos para a validação do modelo foram realizados em um Fresnel com 60 mÂČ de ĂĄrea localizados na cidade de FlorianĂłpolis. Nas condiçÔes analisadas, com diferenças de temperatura entre o fluido e o ambiente de atĂ© 200°C, aproximadamente 70% das perdas tĂ©rmicas ocorrem por convecção das chapas metĂĄlicas com o ar externo e 30% por radiação e convecção pela janela de vidro. Na comparação dos resultados do modelo com os dos testes experimentais foi observado uma diferença mĂ©dia de 10%, sendo superior no modelo. As trocas de calor pelo ar no interior da cavidade foram consideradas como por difusĂŁo apenas, desconsiderando efeitos advectivos e, esta consideração nĂŁo implicou em erros significativos.
ABSTRACT: This article describes the one-dimensional heat transfer mathematical model of a multi-tube trapezoidal cavity absorber used in a linear Fresnel concentrator. All heat transfer rates were modeled analytically and the model was experimentally validated. The experiments for the validation of the model were carried out in a Fresnel with 60 mÂČ of area located in the city of FlorianĂłpolis. Under the conditions analyzed, with temperature differences between the fluid and the environment of up to 200 ° C, approximately 70% of the thermal losses occur by convection of the metal plates with the external air and 30% by radiation and convection through the glass window. When comparing the results of the model with those of the experimental tests, an average difference of 10% was observed, being higher in the model. The heat exchanges for air inside the cavity were considered to be by diffusion only, disregarding advective effects and, this consideration did not imply significant errors.
ABSTRACT: This article describes the one-dimensional heat transfer mathematical model of a multi-tube trapezoidal cavity absorber used in a linear Fresnel concentrator. All heat transfer rates were modeled analytically and the model was experimentally validated. The experiments for the validation of the model were carried out in a Fresnel with 60 mÂČ of area located in the city of FlorianĂłpolis. Under the conditions analyzed, with temperature differences between the fluid and the environment of up to 200 ° C, approximately 70% of the thermal losses occur by convection of the metal plates with the external air and 30% by radiation and convection through the glass window. When comparing the results of the model with those of the experimental tests, an average difference of 10% was observed, being higher in the model. The heat exchanges for air inside the cavity were considered to be by diffusion only, disregarding advective effects and, this consideration did not imply significant errors.
Description
CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia Solar
Keywords
Solar energy Linear Fresnel concentrator Heat transfer
Pedagogical Context
Citation
Pigozzo, V.C.F... [et.al.] - Modelo unidimensional de transferĂȘncia de calor em um absorverdor trapezoidal multi-tubos para concentradores Fresnel lineares. In: CIES2020: As Energias RenovĂĄveis na Transição EnergĂ©tica: Livro de ComunicaçÔes do XVII Congresso IbĂ©rico e XIII Congresso Ibero-americano de Energia Solar. Helder Gonçalves, Manuel Romero (Ed.). Lisboa, Portugal: LNEG, 3-5 Novembro, 2020, p. 349-356
Publisher
LNEG - LaboratĂłrio Nacional de Energia e Geologia