Estimation of drying parameters including moisture diffusivity by using temperature measurements

Abstract

This paper deals with the estimation of the moisture diffusivity, together with other thermophysical properties, as well as the heat and mass transfer coefficients of a convective drying body, on the basis of single thermocouple temperature measurements by using an inverse approach. Potato and apple slices have been chosen as representative drying bodies with significant shrinkage effects. A mathematical model of the drying process of shrinking bodies has been applied. The Levenberg-Marquardt method and a hybrid optimization method of minimization of a resulting least-squares norm were used to solve the present inverse problem. The experiments have been conducted on the experimental setup that is designed to simulate an industrial convective dryer. An analysis of the influence of the drying air speed, temperature and relative humidity, drying body dimensions, and drying time on the estimation of the unknown parameters enables the design of appropriate experiments that have been conducted as well. The estimated moisture diffusivities are compared with the results published by other authors. The experimental transient temperature and moisture content changes during the drying are compared with numerical solutions.