Performance assessment of a heat pump assisted rotary desiccant dryer for low temperature peanut drying

Abstract

This study presents the investigation of a drying system in which both a desiccant wheel and a heat pump could be used together for low temperature agricultural food product drying. In the system, it was aimed to reduce the moisture content of the drying air to very low levels by using two dehumidification processes together, thus drying the product in a shorter time at low temperature. A model was formed to analyze the system according to different parameters. Peanuts, which are not suitable for high-temperature drying, were selected as the drying product. It has been observed that the system proposed in this study (System I) has a higher performance compared to other desiccant/heat pump drying systems with different configurations (System II-IV). The drying performance index (COP D ) increases by 23% in System I compared to System II, while specific energy consumption (SEC) decreases by 19%. In the case of drying air with low humidity (at 5.22 g w kg da −1 ), the drying performance parameters improve as drying time decreases, although the power consumed by the compressor increases. From the analysis, it has been determined that the optimum rotational speed of the solid desiccant wheel, which is one of the basic elements of the system, is 10 RPH under conditions considered in this study. The results show that COP D decreases as the SEC increases during the drying process, which is because the food product tends to dry at a decreasing rate. The proposed system is suitable for use in low-temperature food drying applications. • Investigation of a hybrid drying system for low temperature drying. • Determination of optimum desiccant wheel rotational speed. • The humidity of the drying air has a significant effect on the system performance. • The proposed system is suitable for low temperature drying applications. • ANN models of the desiccant wheel can be used in different system analyzes.