Modeling of thin layer drying kinetics of Picrorhiza kurroa under different drying conditions

Abstract

This paper presents study of thin layer drying kinetics of \textit{Picrorhiza kurroa}, an important Himalayan medicinal herb based on several drying models and experiments conducted under convection or controlled drying conditions to simulate the thin layer drying processes. Eleven thin layer drying models, namely Diffusion, Jena and Das, Henderson and Pabis, Lewis, Logistic, Midilli, Modified Page, Page, Two Term exponential, Two term were used for simulating the drying behavior of \textit{Picrorhiza kurroa} rhizome during drying. Performance of all these models was compared.  Comparison was based on residual plots as well as different statistical parameters such as coefficient of determination ($R^2$), chi-square ($\chi^2$) and root mean square error (RMSE) between the experimental and predicted values. Jena and Das as well as Midilli models were found as the most versatile models to accurately describe the drying behavior in terms of moisture ratio-time relationship for drying of \textit{P. kurroa} rhizomes.