Thermodynamic analysis of experimental sorption isotherms of loquat and quince fruits

Moreira, Ramón; Chenlo, F.; Torres, M.D.; Vallejo, Nicolau

doi:10.1016/j.jfoodeng.2008.03.011

Cited by 144 publications

(168 citation statements)

References 34 publications

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“…With the increase in the drying air temperature and consequent increase in the partial vapor pressure of the water in the product, there is also an increase in the excitation of the molecules and reduction of the water viscosity, factors that when are combined provide the increase of the water diffusion velocity and the reduction of the entropy in the process. The negative entropy values may be attributed to the existence of chemical adsorption and/or structural modifications of the adsorbent (Moreira et al, 2008). Table 4, there was an increase in the Gibbs free energy values, in proportion to the increase of the drying air temperature, for the peanut kernels.…”

Section: Resultsmentioning

confidence: 94%

Drying Kinetics of Peanut Kernels in Thin Layers

et al. 2017

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The aim of this study was to adjust mathematical models to the experimental data on the peanut kernels drying in thin layer, as well as to determine the effective diffusion coefficient and the main thermodynamic properties involved in drying of the grains under different air conditions. The peanut kernels, with a water content of 0.59 ± 0.002 (dry basis, d.b.), were dried in a forced air ventilation oven with different temperature levels (40, 50, 60 and 70 ºC) until reaching a water content of 0.04 ± 0.001 (d.b.). For the experimental data, eight mathematical models traditionally used to represent the drying kinetics of thin layer of agricultural products were adjusted, also being determined the effective diffusion coefficient and the thermodynamic properties, specific enthalpy and entropy and Gibbs free energy. The Diffusion Approximation, Two Terms, Midilli, Page and Thompson models represent the drying kinetics of peanut kernels in thin layers. The effective diffusivity increases with the increase of temperature, being the relation with the drying temperature described by the Arrhenius' equation. The increase in temperature promotes the decrease of the enthalpy and entropy values and the increase of the Gibbs free energy.

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Section: Resultsmentioning

confidence: 94%

Drying Kinetics of Peanut Kernels in Thin Layers

et al. 2017

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“…Segundo Goneli et al (2010), a entropia é uma grandeza termodinâmica ligada ao grau de desordem cujos valores se elevam durante o processo natural em um sistema isolado. Os valores negativos de entropia podem estar atribuídos à existência de adsorção química e/ou modificações estruturais do adsorvente (Moreira et al, 2008).…”

Section: Resultsunclassified

Cinética de secagem de folhas de timbó (Serjania marginata Casar)

Martins

Lage

Goneli

et al. 2015

Rev. bras. eng. agríc. ambient.

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R E S U M OPropôs-se, neste trabalho, avaliar a cinética de secagem de folhas de timbó (Serjania marginata Casar) e ajustar diferentes modelos matemáticos aos valores experimentais de razão de umidade. As folhas de timbó foram colhidas com teor de água inicial de 2,03 ± 0,10 decimal b.s., sendo submetidas à secagem sob condições controladas de temperatura (40, 50, 60 e 70 °C), até o teor de água de 0,08 ± 0,02 decimal b.s. Aos dados experimentais foram ajustados dez modelos matemáticos utilizados para representação da secagem de produtos agrícolas. Com base nos resultados obtidos o modelo matemático de Midilli é o que melhor representa a cinética de secagem para as folhas de timbó. O aumento da temperatura promove: uma taxa maior de remoção de água nas folhas de timbó durante a secagem; aumento do coeficiente de difusão efetivo sendo que esta relação pode ser descrita pela equação de Arrhenius que apresenta uma energia de ativação para a difusão líquida durante a secagem de 81,39 kJ mol -1 para as folhas de timbó; aumento da energia livre de Gibbs, enquanto a entalpia e a entropia decrescem. Drying kinetics of Serjania marginata Casar leaves A B S T R A C TThis study aimed to evaluate the kinetics of drying of Serjania marginata leaves, as well as to adjust different mathematical models to the experimental values of the moisture ratio. The Serjania marginata Casar leaves were harvested with initial moisture content of 2.03 ± 0,10 decimal dry basis., and submitted to drying process under controlled conditions of temperature (40, 50, 60 and 70 ºC), until the moisture content of 0.08 ± 0,02. Ten mathematical models were fitted to the experimental data and utilized to predict the drying process of agricultural products. Based on the obtained results, the mathematical model of Midilli best represented the kinetics of drying leaves of Serjania marginata. The increase in temperature promotes: an increased rate of water removal in Serjania marginata leaves during drying; the increase of the effective diffusion coefficient, and this relationship can be described through the Arrhenius equation, which presents an activation energy for the liquid diffusion during drying of 81.39 kJ mol -1 for Serjania marginata leaves; an increase in Gibbs free energy, while the enthalpy and entropy decrease.Palavras-chave: modelo de Midilli coeficiente de difusão propriedades termodinâmicas razão de umidade

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“…In the GAB model the constants Xm, C and K are dependent on the temperature; Xm represents the moisture of the molecular monolayer on the inner surface (Blahovec, 2004), C is the constant related to the heat of sorption of the monolayer and K is the heat of sorption of the multilayer compared to pure water (Moreira et al, 2008). In Table 1 (Eqs.…”

Section: Modeling Of Sorption Isothermsmentioning

confidence: 99%

Isotherms and isosteric heat of sorption of two varieties of Peruvian quinoa

Ramos¹,

Vieira²,

Telis‐Romero³

et al. 2016

Sc.Agropec

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The isosteric heats of sorption of two varieties of quinoa (Chenopodium quinoa Willd.) grain were determined by the static gravimetric method at four temperatures (40, 50, 60 and 70 °C) and in relative humidity environments provided by six saturated salt solutions. Six mathematical equations were used to model the experimental data: GAB, Oswin, Henderson, Peleg, Smith and Halsey. The isosteric heat of sorption was determined using the parameters of the GAB model. All the equations were shown to be appropriate by the coefficients of determination (R 2 ) and the mean absolute error (MA%E). The influence of temperature was observed because the adsorption of water by the grains was lower at higher temperatures. The equilibrium moisture contents for security of storage, for long periods of time at water activity lower than 0.65, were 12 -13%. The effect of temperature on the parameters of the GAB model was analysed using the exponential Arrhenius equation. The isosteric heats of sorption were determined by applying the Clausius-Clapeyron equation as a function of humidity. The isosteric heat at 5% moisture for grains of the Blanca de Juli variety was 3663 kJ/kg and for the Pasankalla variety it was 3393 kJ/kg. The experimental data for isosteric heat as a function of humidity were satisfactorily modelled using three mathematical equations.

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Thermodynamic analysis of experimental sorption isotherms of loquat and quince fruits

Cited by 144 publications

References 34 publications

Drying Kinetics of Peanut Kernels in Thin Layers

Drying Kinetics of Peanut Kernels in Thin Layers

Cinética de secagem de folhas de timbó (Serjania marginata Casar)

Isotherms and isosteric heat of sorption of two varieties of Peruvian quinoa

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