Camila Nicola Boeri

Equilibrium Moisture Content Isotherms of Codfish (Gadus morhua)

Industrial drying of salted fish is an extremely common practice in the Portuguese industry of codfish processing. The present study aims to obtain sorption isotherms of codfish, which will be useful in designing drying processes and prediction of storage conditions for this product. The equilibrium moisture contents (wet basis) were determined for salted codfish at 15, 18, 20, and 23ºC at relative humidities ranging from 40 to 70%. Experiments were also carried out for fresh codfish at the temperature of 20ºC for the same values of relative humidity. The sorption capacity of codfish decreased with an increase in temperature at constant relative humidity. Thirteen models were used to correlate the experimental data analysis of salted codfish: modified BET, Cauri, Chung-Pfost, modified Chung-Pfost, GAB, modified GAB, Halsey, modified Henderson, Kuhn, Oswin, modified Oswin, Smith, and modified Smith. Based on the mean relative percentage deviation, standard error of estimate, randomness of residual, and coefficient of determination, experimental data were well described by all the models. The equilibrium moisture content of salted codfish was best predicted using the modified GAB model, with a coefficient of determination of 0.99.

Bridging the gap between advanced control methods and industrial control applications: Shortcomings of the current nonlinear PID Method and new research lines to its enhancing

As the performance requirements become more demanding and the plants become more and more complex, control designers were naturally forced to look beyond traditional linear control theory and attempt to find more advanced nonlinear methods. However, it has been very difficult to overcome the huge gap between the current knowledge, researched by the scientific automatic control community, and its application in the industrial environment. In this paper, it is proposed to consider the nonlinear PID as the method to deal with this hitch. The current nonlinear PID methodologies were reviewed and their shortcomings presented. The main aim is to objectify new research lines that may enhance it, in order to ensure that the evolution of industrial control systems is strongly linked to that of the control techniques.

Modelling Codfish Drying: Comparison Between Artificial Neural Network, Diffusive and Semi-Empirical Models

Convective drying is of prime importance in the food conservation industry and has been constantly studied and improved to obtain products with higher quality and lower processing time. In this work, three different models were used to perform the codfish drying simulation: artificial neural network (ANN), diffusive and semi-empirical models. The simulation results were compared for the following experimental conditions: drying air temperature of 20 °C, air velocities of 2 and 3 m/s and drying air relative humidities comprise between 55 and 65 %. The simulations showed good results for the semi-empirical and ANN models, requiring improvements to the diffusion model.

Otimização dos parâmetros de secagem para minimização do custo energético num secador convectivo de alimentos

A viabilidade economica de um sistema de secagem e de extrema relevância, pois o custo final do produto colocado no mercado depende diretamente de todos os gastos necessarios para o seu processamento. Assim, a secagem e uma das etapas de grande importância do ponto de vista da conservacao e do custo final do produto. No que diz respeito a secagem de peixes, existem poucos trabalhos que tratam dos custos, apesar do elevado consumo de energia e da importância que a secagem representa apos a captura. Assim, este trabalho tem por objetivo apresentar os custos da secagem do bacalhau, mostrando o consumo energetico da instalacao experimental convectiva para diferentes condicoes operacionais, bem como realizar a otimizacao destas condicoes para reduzir o consumo energetico.

Controle dos parâmetros de secagem numa instalação experimental utilizando lógica difusa

A contribuicao deste artigo e a proposta de uma estrategia de controle nao linear, composto por quatro controladores difusos: Controladores difusos proporcionais e derivativos para um desumificador, um umidificador, um conjunto de resistencias eletricas e um ventilador utilizados na instalacao laboratorial de secagem convectiva. Os resultados foram comparados com os obtidos anteriormente atraves de um controlador linear PID otimizado. O objetivo desta pesquisa e encontrar as condicoes otimas para a secagem de bacalhau salgado verde. Os ensaios experimentais de secagem foram realizados para as seguintes condicoes operacionais: temperaturas do ar de 15, 18, 20 e 23°C; umidades relativas de 40, 45, 50, 55, 60, 65 e 70% e velocidades do ar iguais a 1,5 e 2,5m/s. As limitacoes da instalacao experimental restringem os valores de umidade relativa a um minimo de 40%. Os valores da velocidade do ar estao dentro do intervalo utilizado para a secagem de peixe. Foram parametrizados um grupo de conjuntos difusos, de forma a assegurar um alto desempenho do controlador, sem necessidade do desenvolvimento do modelo matematico do processo de secagem. A analise dos resultados mostrou um melhor desempenho para o controlador difuso quando comparado ao controle PID.