Natural Convection Solar Dryers for Agricultural Products — A Comprehensive Exploration

Abstract

Objectives: To make review on passive solar dryers and its performance of drying agricultural products. Methods: This article focuses on the development in various categories of passive solar dryers in last six years. The different studies carried out in direct, indirect and mixed mode types of passive dryers for drying agricultural products in the year of 2014 to 2020 have been considered this review. Investigations on forced convection solar dryers have not been included in the current paper. The various experimental setups of solar dryers, specimens used for experimentation, measured output parameters and performance have been illustrated. The changes made in construction of solar dryers for improving the performance have also been reviewed. Findings:The mixed mode passive solar dryer is found to be superior in terms of drying time, better utilization of solar energy and efficiency compared to other passive dryers. Novelty: Several review articles have been published in solar dryers. Nevertheless, no comprehensive reviews have hitherto been published on passive dryers in particular. Hence, our current review article focuses on development in passive dryers and its advancements with emphasis on dryer design features, specimen and measured output parameters. Keywords: Passive solar dryers; Natural convection solar dryers; Direct solar dryers; Indirect solar dryers; Mixed mode solar dryers