THERMAL KINETICS OF THIN LAYER DRYING OF INDIAN GOOGEBERRY OR ANOLA FLAKS (PHYLLANTHUS EMBLICA)
The aonla flacks (Phyllanthusemblica), a fruit rich in vitamin-C, has very high medicinal importance in human life. Further, it is regarded as a highly perishable commodity due to its high moisture content. So it needs special attention for its preservation. Drying of aonla in the form of flacks and powder is one of the widely used methods of its preservation. Longer storage life, and substantial volume reduction are the main reasons of the popularity of its fruits and herbs in dried form. In
... in dried form. In thin layer drying model for drying a hygroscopic material the moisture ratio during the drying period is calculated by the Half Life Time Method, It is assumed that the material layer is thin enough and the air velocity is high so that the conditions of the drying air (humidity and temperature) are kept constant throughout the material at the average velocity of 0.48 m/s and relative humidity 35% of drying air and the drying air temperature in the range between 400 C to 750C. The drying models, namely Newton's Model, Page Model, Modified Page Model etc. were compared on the basis of to their statistical coefficients such as Root Mean Square Error RMSE, chi-square and Efficiency EF to see how close the predicted values were to experimental one. The results indicated that out of these models the values of RMSE and the reduced, chi-square 2 were found the lowest and values of EF highest with Henderson & Pabis model, defined by í± í± = í°´í± −í±í±¡ where í± and í± are the instantaneous and initial moisture contents respectively, The two constants namely shape factor and constant k were obtained using curve fitting for different drying air temperatures in the range í° ¶í° ¶. Using the experimental and predicted values, the resulting RMSE was found to lie between 0.0382 and 0.0094, reduced í¼ between 0.000132 and 0.00761 and EF between 0.9598 and 0.9985. Analysis of the effect of dryingair temperature at constant velocity and relative humidity, revealed the adopted Henderson and Pabis modelswas in good agreement with the experimental results for all drying conditions taken up in the present study of aonla flacks. This model, can therefore, used to predict the moisture content of the aonla at any time during thin layer of drying process, with reasonable accuracy.