MODELLING OF THE THERMOPHYSICAL LACTIC ACID AQUEOUS SOLUTIONS. DENSITY AND VISCOSITY

Abstract

Lactic acid is an industrially important product with a large and rapidly expanding market due to its attractive and valuable multi-function properties. It is widely used in various fields such as food industry, in pharmaceuticals and cosmetics etc. and knowing and predicting the evolution of its thermophysical properties at any moment may be very useful. In this paper various mathematical relations between lactic acid concentrations and temperature with density and dynamic viscosity were established. The known data were fitted in different equations in order to assess and select a suitable mathematical model. Taking in consideration the level of precision and the simplicity of formulation several equations were generated for each thermophysical property. For density, two equations were formulated with average relative errors (absolute value) of 0.062% and respectively R² = 0.9999 and average relative errors of 0.055% for intervals of temperature of 298.15 to 353.15 K and dry matter concentration range between 9.16 to 85.32%. For the dynamic viscosity an equation based on Arrhenius mathematical model with average relative errors of 1.11% and an equation with other mathematical formulation with R² = 0.9997 were generated in the same range of temperature and citric acid concentration. The obtained equations can be uploaded in computer software for storing, organizing and manipulating data available both for industrial and academic users and so facilitating the sizing and optimization calculations of various technological processes and equipments.