Investigation of performance and drying kinetics of the closed, partially open, and open heat pump drying systems

摘要

In this study, the slices of "starking delicious" apple were dried at 40 degrees C and an air velocity of 1 m/s in the heat pump drying system which was operated in three modes, that is, closed, open, and partially open. The model developed by Midilli and Kucuk was found to be the best model to explain the experimental data of apple slices drying. The effective moisture diffusivity values ranged from 2.33 x 10(-8)to 3.06 x 10(-8)m(2)/s. The evaporator and condenser side for open, partially open, and closed circuits are designed to operate with 100% fresh air or partial fresh air, which is controlled using dampers. Moisture content reduction of the apple slices from 4.631 to 0.126 g-water/g-dry matter moisture content took 404 min in the system operation with the condenser side partially open. Open heat pump drying system evaporator and condenser sides were completed in 27.4% less time than the open system application. The average performance coefficient (COPsys) of the entire system was found to be the highest in the closed system operation with 2.505. TheSMER(sys)average was 80.80 g/kWh and the minimum total energy consumption was 5.580 kWh in the open heat pump drying system with the condenser side open. Practical Applications In this study, a heat pump dryer has been developed that can be operated in both closed, partially open and as well as open loop modes to achieve the best drying performance with the help of dampers placed on the heat pump drying system. The innovation of this study is that the system works more efficiently and the drying time is completed in a shorter time by utilizing the external condenser heat. Drying was performed in five different applications depending on the position of the dampers. Another purpose of this study was to fit the experimental data to the eight thin-layer models and calculate the effective moisture diffusivity and activation energy. In addition, the color of the dried fruits was examined in terms of quality.