Experimental investigation of thermal performance of indirect mode solar dryer with phase change material for banana slices

This paper presents an experimental investigation on a natural convection indirect mode solar dryer with phase change material (PCM) for drying of banana slices. The drying system consists of one collector with PCM and a drying chamber with two equally spaced trays. The paraffin wax was used as PCM in the dryer which release latent and sensible heat after sunset that make dryer operate effectively for the next 5 h. For the experimental investigations, 400 g of banana slices were dried from 73.2% (wb) to 20% (wb) of moisture content in 18 h (13 h day time operation + 5 h PCM) during April 2018 at Gorakhpur, Uttar Pradesh, India. Fourteen thin layer models for drying of banana slices, available in the either empirical or non-empirical form, were fitted using experimental data. A statistical analysis software, XL-stat was used to evaluate the values of constants of models and errors through non-linear regression analysis. Modified Henderson and Pabis model was found best suitable for the drying behavior of banana slices among all the models of thin-layer drying characteristics. The average drying rate for the lower tray and upper tray were 0.1316 and 0.1310 kg of water/kg of dried product/h respectively. The moisture content was reduced at a faster rate for the lower tray with moisture ratio from 100 to 28%. The maximum and average dryer efficiency were 9.88 and 2.98%, respectively, and the maximum and average collector efficiency were 85.46 and 66.32% respectively. This study showed that indirect type solar dryer with paraffin wax is suitable for drying of banana because it takes considerable time for drying and can be used for drying of other agricultural crops.