Studies on drying characteristics of Thompson seedless grapes using mixed mode forced convection solar dryer

Solar drying is the most cost-effective and energy-efficient way to preserve grapes and agricultural goods. Many of the post-drying quality analysis tests are not reported in the literature however they are essential to ensure hygienity of the dried grapes in view of health issues of the consumers of the dried grapes. Hence all kind of quality analysis tests were conducted on the fresh and dried grapes. It is observed that dried grapes using mixed mode forced convection (MMFC) solar dryer gives better quality over the open sun based dried samples. Various mathematical models available in the literature were compared to predict the most suitable model for the present study. However, these mathematical models have few limitations since they are only time dependent and constants used in these models are unknown. Hence a novel empirical correlation was developed using Buckingham Pi theorem and Mathematica to predict the final weight of the dried grapes which is the function of temperature and relative humidity. This novel correlation had a prediction accuracy ±17 % which will be useful to predict the final weight of the dried grapes those were dried using various types of the dryers such as indirect dryers, hybrid dryers, and MMFC solar dryers.