Modeling the Impact of the Soluble Solids Content and Temperature on the Thermophysical Properties of Lime Juice (Mexican Lime)

It is necessary to determine the thermophysical properties of the various types of agricultural products in order to control thermal operations, as well as processes such as drying, freezing, cooling, and pasteurization. Moreover, most of the products' thermophysical properties vary by the temperature changes and the percentage of water content. Therefore, the mathematical models expressing the relationship of these properties serve as a beneficial tool for designing automatic processes and equipment. The present research entails the examination of the impact of four levels of soluble solid content 15, 20, 25, and 30 %, and nine levels of temperature 28.6, 35.4, 40.5, 47.6, 56.1, 63.3, 72.3, 83.2, and 90 °C on the thermophysical properties of lime juice including density, specific heat, thermal conductivity coefficient, and thermal diffusivity coefficient. Based on the results, soluble solid content and temperature had a significant impact (p≤ 0.05) on the thermophysical properties of lime juice. By increasing the percentage of the soluble solid content, the properties such as specific heat (from 3321 to 2897 J/kg°C), thermal conductivity coefficient (from 0.69 to 0.54 W/m°C), and thermal diffusivity coefficient (from 2.10×10-7 to 1.61×10-7 m2/s) decreased but the density was increased (from 1013 to 1057 kg/m3). Furthermore, by increasing the temperature, the values of specific heat, thermal conductivity coefficient, and thermal diffusivity coefficient increased but the density was decreased. Consequently, to model the thermophysical properties, the multivariable regression method and Matlab software were employed and the results of the examination were fitted. The coefficient of determination of linear models of density 0.94, specific heat 0.93, thermal conductivity, and thermal diffusivity 0.98. In accordance with the results, all thermophysical properties had a linear relationship with the independent variables such as temperature and soluble solid content.