Design and Performance Evaluation of Solar Dryer for Agricultural Products

Abstract

In this study performance of three solar dryers, namely indirect natural convection solar dryer (INCSD), solar cabinet dryer (SCD), and forced convection solar dryer (FCSD), is evaluated theoretically and experimentally. This research work has been carried out to identify an appropriate solar dryer for drying different agricultural products. The turmeric drying and blanching is processed using solar thermal energy. Red chilli is also dried in the SCD with and without steam. newlineIn INCSD, experiments are conducted by connecting it to Scheffler system and compound parabolic concentrator. The variation of moisture ratio kept in each tray in the dryers is evaluated and analyzed. The analysis is performed in the INCSD when operated at different temperatures. SCD is used to dry turmeric and red chilli with and without steam generated from the Scheffler system. The FCSD is operated at the different air velocities, and the optimum air velocity is evaluated by performing experimentations. newlineThe steam generated from the Scheffler system and compound parabolic concentrator is used for turmeric blanching, turmeric, and red chilli drying. The average efficiency of the Scheffler concentrator for turmeric blanching is found higher than compound parabolic concentrator, which makes it an attractive solar concentrator. From the experiments conducted it is observed that Scheffler concentrator is an efficient solar thermal technology for the post-harvesting heat treatment of turmeric and is recommended for seasonal applications. newlineThe moisture content reduction is computed from the experimental data and compared with open Sun-drying process. The moisture ratio is evaluated using a mathematical models and Minitab 17TM software and analysed. Different drying kinetics models are checked to predict the moisture reduction of turmeric and red chilli. From the analysis, best-suited models were found out. Page model and Wangh and Singh are found to best suited to predict the moisture ratio of turmeric and red chilli drying. newlineThe heat transfer coeffi