An Experimental Investigation on Indirect Solar Dryer for Drying Sliced Onions using Phase Change Materials (PCM)

The food industry primarily utilizes sun dryers to extract moisture in order to preserve edible items such as cereals, vegetables, fish, etc. The performance of an indirect, single-pass, forced convection solar dryer with and without paraffin, a phase change material (PCM), integrated into the solar collector, was assessed in this work. Improving the drying efficiency of sliced onions was the main goal, especially when there was little to no sunlight. In this design, the heating-and-drying chamber could hold 1.5 kg of vegetables. A glass cover with dimensions of 100 x 300 cm2 was used for the collector. A net served as the screen or tray inside the dryer. Three trays, each measuring 21 x 50 cm and framed with wooden edges. The findings showed that by prolonging the drying process past the sunlight period and sustaining high temperatures inside the drying chamber, adding lauric acid as a PCM greatly enhanced the dryer's performance. The current study carried out mathematical modeling with seven semi-empirical models and drying characteristics of onion slices. The study thoroughly examined important process variables for both dryer designs, moisture ratio (MR), and moisture removal rate. Tray 1 with PCM reached an MR of about 0.2 within 5 hours, while the same tray without PCM reached the same MR in approximately 6 hours. The Logarithmic model proved the best among all the different models fitted for onions dried with PCMs. Overall, the research results demonstrate the great potential of PCM integration to improve the efficacy and efficiency of solar dryers, especially in areas with fluctuating solar radiation.