Drying kinetics, mathematical modelling and colour analysis of an indirect solar dryer with latent heat storage unit for cucumber drying

Abstract

The industrial drying sector predominantly relies on fossil fuels and electricity to generate hot air for food drying applications, it leads to climate change. As an alternative, solar energy has emerged for producing hot air. This study focuses on developing an Indirect Solar Dryer (ISD) system equipped with a Corrugated Absorber-plate Solar Collector (CASC) integrated with a Lauric acid-filled Latent Heat Storage (LHS) unit to enhance the effectiveness of the food dehydration process. The drying kinetics of cucumber slices were investigated using Open Sun Drying (OSD) and the ISD system with two distinct solar collector configurations: CASC without LHS unit (System 1) and CASC with LHS unit (System 2) under spring and summer conditions. ISD System 2 during the summer season demonstrated superior performance, reducing cucumber moisture content 10.78 % in 12 h, while OSD took 17 h. Mathematical modelling using twelve different drying kinetics models were conducted to predict the drying behaviours. The results showed that the Midilli and Kucuk model provided predictions with high accuracy for all ISD systems with R² value of >99.5 %. The colour properties of cucumber were also assessed, with ISD system 2 during summer season resulting in minimal colour variation of 6.38, compared to other systems, which had colour parameters of 48.1 Lightness, −19.9 for intensity in red-green, and 21.3 for intensity in blue-yellow. Overall, the findings of this study highlight the effectiveness of the proposed ISD system 2 in dehydrating food items, offering a sustainable alternative to conventional methods.