André Luís Duarte Goneli

Modelagem matemática e determinação das propriedades termodinâmicas do café (Coffea arabica L.) durante o processo de secagem

The aim of the present work was to model the drying process and to obtain the thermodynamic parameters of coffee beans (Coffea arabica L.), cultivar Catuai Amarelo, for three different conditions of temperature and relative humidity (35 oC and 32.1 %; 45 oC and 15.7 %; 55 oC and 10.2 %). Coffee beans were hand picked with an initial moisture content of 1.25 (d.b.) and dried to a mean moisture content of 0.13 (d.b.). Six mathematical models commonly used to represent the drying process of agricultural products were fit to the experimental data. Fick’s second law was used to obtain the diffusion coefficients of coffee beans using the drying kinetics. The activation energy for the drying process of coffee beans, as well as the entropy, enthalpy and Gibbs free energy were determined. The modified Midili model best represented the drying phenomenon of coffee beans. The calculated diffusion coefficients were 2.99 x 10 -11 , 2.39 x 10 11 and 5.98 x 10 -11 m 2 s -1 , to the temperatures of 35, 45 and 55 oC, respectively. Enthalpy decreased with the increase in

Modelagem matemática e difusividade efetiva de folhas de aroeira durante a secagem

The drying process of agricultural products is extensively used worldwide for controlling and maintaining their quality. For medicinal and aromatic plants, this importance increases even more. Thus, this study aimed at evaluating the drying kinetics of Schinus terebinthifolius Raddi leaves, as well as adjusting different mathematical models to the experimental values of moisture ratio. The leaves were harvested with initial moisture content of approximately 65% (w.b.) and submitted to the drying process under controlled conditions of temperature (40oC, 50oC, 60oC and 70oC), up to the approximate moisture content of 10% (w.b.). Six mathematical models were adjusted to the experimental data cited at the specific literature and used to predict the drying process of agricultural products. According to the results obtained, it was concluded that the modified Henderson & Pabis and Midilli models were the ones that best represented the drying kinetics of S . terebinthifolius leaves. The temperature increase of the drying air promoted a higher rate of water removal from the product. The effective diffusion coefficient increased with the temperature elevation, and its relation to the drying temperature fitted the Arrhenius equation, which presented activation energy for the liquid diffusion, during the drying process, of 74.96 kJ mol -1 , for S . terebinthifolius leaves.

Cinética de secagem de folhas de erva baleeira (Cordia verbenacea DC.)

The objective of the present work was to evaluate the drying kinetics of Cordia verbanacea DC. leaves, as well to fit different mathematical models to the experimental data of the moisture ratio. The Cordia verbanacea Dc. leaves wers harvested with initial moisture content of approximately 75% w.b. and submitted to the drying process under controlled conditions of temperature (40, 50 60 and 70oC), until the approximate moisture content of 10% w.b. Eight mathematical models mentioned or the specific literature were fitted to the experimental data and used to predict the drying process of the agricultural products. Based on the results obtained,swe have concluded that the Midilli model was the one that best represents the drying kinetics of Cordia verbanacea leaves. The temperature increase of the drying air promotes higher removal rate of water from the product. The effective diffusion coefficient increases with temperature elevation,tand its relationship with the drying temperature can be described through the Arrhenius equation, which presents activation energy of 62.89 kJ mol-1 for the liquid diffusion during the drying of the Cordia verbanacea DC. leaves.

Thermodynamic properties of drying process and water absorption of rice grains

ABSTRACT This study aimed to obtain the drying and water absorption curves of husk rice grain (Oryza sativa L.), cv. Urucuia, as well as the thermodynamic properties. Five temperatures (35°C, 45°C, 55°C, 65°C and 75°C) were used. Two terms, logarithmic, modified Midilli, Page and Verma models were used to model the drying process, and the Peleg model was used to model the soaking process. The modified Midilli and Peleg models satisfactorily accounted for the processes of drying and absorption of water, respectively. The activation energy for the drying and soaking was 51.03 and 37.06 kJ mol−1, respectively. The enthalpy and entropy decreased with increasing temperature, regardless of the process. Their values ranged between −6.60 and 48.47 kJ mol−1 and between −0.1084 and −0.2464 kJ mol−1 K−1 for enthalpy and entropy, respectively. The Gibbs free energy increased with increasing temperature, with values between 69.36 and 86.22 kJ mol−1.

Modelagem matemática da secagem dos frutos de amendoim em camada delgada

Este trabalho teve por objetivo ajustar modelos matematicos aos dados experimentais da secagem dos frutos de amendoim em camada delgada, submetidos a diferentes temperaturas do ar de secagem. Foram utilizados frutos de amendoim da cultivar IAC 505. Os frutos de amendoim foram submetidos a secagem em estufa de ventilacao forcada com diferentes niveis de temperatura (40; 50; 60 e 70 oC). Aos dados experimentais foram ajustados dez modelos matematicos tradicionalmente utilizados para representacao da cinetica de secagem em camada delgada. Baseado nos resultados encontrados, conclui-se que dentre os modelos ajustados aos dados experimentais, o modelo de Page foi o escolhido para representar o fenomeno de secagem em camada delgada dos frutos de amendoim. O coeficiente de difusao efetivo aumenta com a elevacao da temperatura, e a sua relacao com a temperatura de secagem pode ser descrita pela equacao de Arrhenius. As propriedades termodinâmicas entalpia e entropia tiveram seus valores reduzidos com aumento da temperatura do ar de secagem, enquanto que os valores da energia livre de Gibbs aumentam com o aumento da temperatura.

Potencial fisiológico de sementes de amendoim submetidas à secagem e ao armazenamento

This study was performed to evaluate the immediate and latent effects of drying air temperature on the physiological potential of peanuts (Arachis hypogaea L.). The fruits were harvested at the physiological maturity stage, with 36 ± 2% water content (w.b.), and dried at temperatures of 40, 50, 60 and 70 oC, until 7 ± 1% (w.b.). Thereafter, the fruits were stored in an environment with non-controlled temperature and relative humidity for 150 days, and the water content, germination and vigor of seeds were immediately determined, as well as at every 30 days thereafter, through the first count, and the tetrazolium test, accelerated aging test, cold test with soil and electrical conductivity. According to the results, it was found that the physiological potential of peanut seeds is inversely related to the drying temperature and the storage time, due to the fact that the germination and vigor are reduced as both factors increase. The air temperature of 40 °C may be recommended for the drying of peanut seeds, and even associated with the storage time of 150 days under uncontrolled conditions.