Mathematical Model Suitability for Thin-Layer Drying of Chiangda Herbal Tea (Gymnema inodorum Lour) under Modified Greenhouse Dryer

Abstract

Chiangda or Gymnema is an herb from Thailand that has a long and varied history in traditional medicine. The objective of this study was to evaluate the influence of drying of gymnema with modified greenhouse dryer. Drying experiments were performed at an air temperature of 50°C was investigated in modified greenhouse dryer. The performance of the drying model was compared based on their correlation co-efficient (R 2 ), Root Mean Square Error (RMSE) and reduced Chi-Square (χ2) between the observed moisture ratios. The Wang and Singh models showed the best fit under modified greenhouse drying. The Wang and Singh equation was found to satisfactorily describe the drying behaviour of gymnema, with good agreement obtained with the experimental data the highest value of R 2 (0.9993) and the lowest values of MBE (-0.0007-0.00412), respectively. The moisture transfer from gymnema was describes by applied the Fick's diffusion model. The effective moisture diffusivity varied from 9.28×10 -11 to 2.606×10 -10 m 2 /s that increased with the temperature. An Arrhenius relation with an activation energy value of 24.91 kJ/mol expressed effect of temperature on the diffusivity.