Modelos matemáticos para a secagem intermitente de arroz em casca

Abstract

R ESU M OPropôs-se, com este trabalho, ajustar modelos matemáticos aos valores experimentais em função do teor de água e estudar os efeitos das relações de intermitência na secagem de grãos de arroz na eficiência da operação. Utilizaram-se grãos de arroz com casca produzidos na Região Sul do Rio Grande do Sul. As amostras com teor de água próximo a 20% b.u. foram secadas sob três condições de relação de intermitência: 1:1, 1:2 e 1:4; em todas as condições foram utilizados os mesmos manejos térmicos em temperaturas graduais crescentes do ar: 70, 90, 110 ± 5 °C, respectivamente, na 1ª e na 2ª e a partir da 3ª hora. Para os ajustes dos modelos matemáticos foi realizada análise de regressão não-linear pelo método Simplex e Quasi-Newton, cujos valores são os parâmetros dos modelos estimados em função da temperatura do ar de secagem. Comparando-se os coeficientes de determinação ajustados (R 2 ajustado ), o erro médio relativo (P) e estimado (SE) e a distribuição de resíduos, os resultados obtidos permitem concluir que: a relação de intermitência altera o tempo de operação e a taxa horária de secagem dos grãos de arroz e, ainda, o modelo de Midilli foi o que melhor representou a secagem intermitente do arroz em casca. Palavras-chave: secador, Oryza sativa, curvas de secagem Mathematical models for intermittent drying of rice A B ST R A C TThis study aimed to adjust mathematical models to experimental values in function of the water content and study the effects of intermittent relations in drying of paddy grains in the efficiency of operation. Paddy grains produced in the southern region of Rio Grande do Sul were used. The samples with approximately 20% water content were dried under three intermittent relation conditions: 1:1, 1:2, 1:4. In all these conditions the same thermal procedures were utilized, gradual increase in air temperature 70, 90, 110 ± 5 ºC respectively, in the 1 st , 2 nd and 3 rd hour. For the adjustments of the mathematical models, a non linear regression analysis through the Simplex and Quasi-Newton methods was carried out. The values of the parameters of the models being estimated in function of the temperature of the drying air. A comparison was carried out of the adjusted coefficient of determination (R² adjusted ), the relative mean error (P), the estimated mean error (SE) and the distribution of residues. The results showed that the intermittent relation modifies the operating time and the hourly rate of drying of the rice grains and the Midilli model was the one which best represented the intermittent drying of paddy.

Drying kinetics of passion fruit seeds

“…These results agree with those found by Costa et al (2015), in which the Diffusion Approximation model presented R 2 above 99% for the drying of crambe fruits in thin layer. Meneghetti et al (2012) report the Wang and Singh model with R 2 above 99% for rice drying.…”

Infrared radiation drying of parboiled rice: Influence of temperature and grain bed depth in quality aspects

“…Initially, a large amount of water is removed from the grains to around 18 to 28% d.b., through rotary or fluidized-bed dryers (Prachayawarakorn, Prachayawasin, & Soponronnarit, 2006), followed by continuous or intermittent drying, until reach approximately 14% (d.b.) of moisture content (Meneghetti et al, 2012). However, these drying methods present high energy consumption and promote yellowish grains (Lamberts, Rombouts, Brijs, Gebruers, & Delcour, 2008).…”

Study on Drying of Black Rice (Oryza sativa L.) Grains: Physical-Chemical and Bioactive Quality

“…According to Silva et al (2018), through the drying kinetics it is possible to determine the behavior of the dried material, representing it by drying curves and drying rates (Menezes et al, 2013). Several mathematical models have been used to describe the drying process of agricultural products and to determine process information which can be used in future equipment designs (Meneghetti et al, 2012). Under certain conditions (spherical or cylindrical geometries, infinite slabs and constant thermal-physical parameters and volume), the diffusion equation has an analytical solution (Luikov, 1968;Crank, 1992).…”