A new method of measuring two-phase mass flow rates in a venturi

The metering of the individual flow rates of gas and liquid in a multi-component flow is of great importance for the oil industry. A convenient, non-intrusive way of measuring these is the registration and analyzing of pressure drops over parts of a venturi. The commercially available venturi-based measuring equipment is costly since they additionally measure the void fraction. This paper presents a method to deduce the individual mass flow rates of air and water from pressure drop ratios and fluctuations in pressure drops. Not one but two pressure drops are used and not only time-averaged values of pressure drops are utilized. As a proof-of-principle, prediction results for a horizontal and vertical venturi are compared with measurements for void fractions up to 80 %. Residual errors are quantified and the effect of variation of equipment and of slip correlation is shown to be negligible. At relatively low cost a good predictive capacity of individual mass flow rates is obtained

Modelagem termodinâmica de uma planta heliotérmica de calhas parabólicas utilizando sais fundidos como fluido de transferência de calor

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: O presente trabalho tem por foco a modelagem termodinâmica de uma planta heliotérmica de calhas parabólicas, com capacidade de 30 MWe, que utiliza sais fundidos como fluido de transferência de calor e armazenamento térmico. O modelo desenvolvido abarcou o funcionamento do campo solar, dos tanques de armazenamento direto e do bloco de potência. O desempenho da planta termossolar foi avaliado a partir da energia elétrica acumulada produzida, do fator de capacidade e da eficiência solar-elétrica mensal e anual. Os resultados obtidos mostram uma geração acumulada anual de 124 GWh, fator de capacidade anual de 47% e eficiência solar-elétrica anual de 20%. Os resultados foram também calculados através do software System Advisor Model (SAM) com diferenças inferiores a 2%, indicando a boa aderência dos resultados de simulação.ABSTRACT: The present work focuses on the thermodynamic modeling of a CSP plant of parabolic troughs, with a capacity of 30 MWe, which uses molten salts as heat transfer fluid and thermal storage. The model developed covered the operation of the solar field, the direct storage tanks and the power block. The performance of the thermosolar plant was evaluated based on the accumulated electric energy produced, the capacity factor and the monthly and annual solar-electric efficiency. The results obtained show an annual accumulated generation of about 124 GWh, annual capacity factor of 47% and annual solar-electric efficiency of 20%. The results were also calculated through the System Advisor Model (SAM) software with differences lower than 2%, thus indicating the proper compliance of the simulation results.info:eu-repo/semantics/publishedVersio

Modelo unidimensional de transferência de calor em um absorverdor trapezoidal multi-tubos para concentradores Fresnel lineares

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: Este artigo descreve o modelo matemático unidimensional de transferência de calor em um absorvedor multi-tubos com cavidade trapezoidal utilizado em um concentrador solar do tipo Fresnel Linear. Todas as taxas de transferência 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 m² de área localizados na cidade de Florianópolis. Nas condições analisadas, com diferenças de temperatura entre o fluido e o ambiente de até 200°C, aproximadamente 70% das perdas térmicas ocorrem por convecção das chapas metálicas 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 média de 10%, sendo superior no modelo. As trocas de calor pelo ar no interior da cavidade foram consideradas como por difusão apenas, desconsiderando efeitos advectivos e, esta consideração não 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 m² of area located in the city of Florianópolis. 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.info:eu-repo/semantics/publishedVersio