Thermodynamic properties of water desorption in Buchenavia capitata (Vahl) Eichler

ABSTRACT Thermodynamic properties provide information on energy demand and kinetic parameters in water sorption processes in agricultural products. Such information is essential to analyze and scale drying and storage equipment. The objective of this study was to determine the thermodynamic properties involved in the water desorption process in Buchenavia capitata (Vahl) Eichler seeds with moisture contents ranging from 13.31 to 7.21% dry basis (d.b.), obtained by the indirect static method, at temperatures of 10, 20, 30 and 40 °C. The latent heat of vaporization, differential entropy and Gibbs free energy increase with the reduction of the moisture content of the seeds. The enthalpy-entropy compensation theory is valid for the desorption process, which is controlled by the enthalpy. The desorption of water in the seeds is not a spontaneous process.

摘要 热力学性质可为农产品的吸水过程提供能量需求与动力学参数相关信息，此类信息对干燥与储存设备的分析与规模化应用至关重要。本研究旨在采用间接静态法，在10、20、30与40 ℃的温度条件下，测定含水率范围为13.31%~7.21%干基（d.b.）的比奇纳维亚（Buchenavia capitata (Vahl) Eichler）种子的水分解吸过程相关热力学性质。研究结果表明，随着种子含水率降低，其汽化潜热（latent heat of vaporization）、微分熵（differential entropy）与吉布斯自由能（Gibbs free energy）均呈升高趋势。焓-熵补偿理论（enthalpy-entropy compensation theory）适用于该水分解吸过程，且该过程受焓驱动。此外，该种子的水分解吸并非自发过程。