Design and experimental analysis of a temperature-relative humidity controlled convective infrared dryer

The drying process is used extensively in the industry and has an important share in energy consumption. Drying is the process of removing the water applied to prevent the deterioration of food products. Walnuts are a popular nut due to their high antioxidant content. After the walnut is harvested, it must be dried thus, it can be stored without deterioration. Drying walnuts is a time-consuming and energy-intensive process. In the literature, it is seen that mostly hot air is used for drying nuts. However, there are a few studies on the use of infrared technology in drying nuts. No study was found on the energy and exergy analysis of an infrared convective dryer in the drying of nuts. Within the scope of this thesis, two different systems, open and closed cycle, were designed and manufactured in order to reduce energy consumption and drying time without sacrificing quality. The open cycle drying system was temperature controlled, the closed cycle drying system was temperature and relative humidity controlled. Bilecik region walnuts, which were harvested in 2019, were dried in the open cycle system, and the walnuts of the Bilecik region, which were harvested in 2020, were dried in open and closed cycle systems. The drying kinetics of the walnut were analyzed, energy-exergy analysis and performance calculations were performed. Ash and oil values, color properties, oil quality properties, fatty acid composition, total phenolic substance amount and antioxidant capacity of 2020 harvest walnuts dried in open and closed cycle drying system were examined. It has been concluded that infrared technology shortens the drying time, reduces energy consumption and improves food quality in open and closed cycle drying systems. The convective infrared closed cycle drying system with a product source distance of 20 cm has been determined as the most suitable system for the walnut drying process. In this thesis, the energy and exergy analysis, performance analysis, drying kinetics and food analysis results of a convective infrared dryer in walnut drying are introduced to the literature.