The Solar-Heat Pump Combined Drying Characteristics and Dynamic Model of Kelp Knots

For controlling the entire drying process of a material, it is crucial to understand the moisture ratio of the material in the drying process. In order to ascertain the moisture change rules of kelp knots in the solar-heat pump combined drying process, an analysis was made on the impacts of different drying temperatures, wind speeds and loading capacities on the drying rate in this research; meanwhile, three common drying dynamic models were selected and compared to know their applicability to the solar-heat pump combined drying of kelp knots. Further, the model coefficient was determined and the optimal model was obtained. The results reveal as follows: drying temperature, wind speed and loading capacity have significant impact on and significant correlation (P<0.05) with the drying rate of kelp knots; under different drying conditions, the drying rate is always high in the early stage, lowered and gradually moderate in the later stage. After fitting the drying dynamic model, it is found that among the experimental data, regression coefficient (R2) is the largest in the Verma model, and the sum of squares for error (SSE) and root mean square error (RMSE) are low. This indicates that the Verma model can be used to accurately express and predict the change rules of moisture in kelp knots during the solar-heat pump combined drying. According to Fick's second diffusion law, the effective diffusion coefficient Deff increases with the increase in drying temperature and wind speed, and decreases with the increase in loading capacity.