Drying Kinetics of Muscat Grapes in a Solar Drier with Evacuated Tube Collector

A solar drier assisted with evacuated tube collector is designed and developed to study and examine the drying Kinetics of muscat grapes in Thanjavur, Tamilnadu, India.  During the drying period, temperature at various places, relative humidity, wind velocity and mass of the sample are measured on hourly basis.  The outlet temperature of the collector and temperature within the chamber varies from 74-130 ºC and 50-87 ºC respectively, while the ambient temperature ranges from 29.5-33.2 ºC.  Solar insolation recorded during these days ranges from 155.6-1115 W/m2.  The designed drier takes 14 hours to lessen the moisture content of muscat grapes from 78% to 9.5% (wb) to ensure safe storage.  It is found that the whole drying process exists in falling-rate period.   The maximum drier efficiency for muscat grapes is found to be 29.92% during the drying period.  Six thin-layer drying models have been used to fit the experimental moisture ratio obtained for muscat grapes by nonlinear regression analysis using IBM SPSS 20 statistical package.  According to the results, Page model shows a good fit with highest correlation (R2 = 0.991), lowest reduced chi-square (χ2 = 0.001) and lowest root mean square error (RMSE = 0.0297).