Analysis of drying of melon in a solar-heat recovery assisted infrared dryer

Abstract

Infrared drying systems are popular in terms of high heat and mass transfer. By using an infrared dryer, it is possible to catch fast heating and short drying time in comparison to the other drying methods. But it consumes a high amount of energy. Therefore, a new type solar air collector (SAC) and air to air heat recovery unit were added to the infrared dryer to reduce specific energy consumption. The general aim of this study is to analyze heat and mass transfer characteristics of the dryer and three-dimensional (3-D) computational fluid dynamic (CFD) simulation and to investigate drying kinetics of melon slices. Experiments were performed at 50 °C and 60 °C melon’s surface temperature and 0.5 m/s air velocity. Melon slices were dried from 9 g water/g dry matter to 0.044 g water/g dry matter moisture content. The effective moisture diffusivity (De) values varied from 8.25 × 10−10 to 1.24 × 10−9 m2/s. The average mass transfer coefficient (hm) values increase from 8.53 × 10−8 m/s at 50 °C to 1.47 × 10−7 m/s at 60 °C. Heat recovery unit has a key role in this system and it provides 23–28% of total input energy. Average solar air collector efficiency was calculated as 50.6%. Obtained theoretical and experimental results are in line with each other. This study shows the successful and efficient combination of solar energy, infrared energy and heat recovery in food processing.