Heated Air Circulate Drying Model And Saving Energy Technique Of Garlic Slices

As the largest garlic producer and consumer country, China has already played a pivotal role in the international garlic market. Garlic has become the largest amount exports of agricultural products in China. As the important processing products, the export volume of dehydrated garlic slice is increasing year by year. Heated air circulate drying is the most commonly employed commercial technique for drying biological products. However, the processing technique is short of systematic research, especially in the relationship between energy consumption and output. Knowledge of the dehydration characteristics of garlic slice is essential to the optimization and control of the dehydration processes. This study was carried out to investigate the effect factors of dehydration in heated air circulate drying. The dehydration process of garlic slices was optimized by quadratic orthogonal rotary design, and the minimum energy consumption of constant temperature is predicted. The experimental dehydration data of garlic slices obtained were fitted to the four drying models, and thin layer mathematical drying models were established to estimate drying process. Based on the model, the parameter of the mutative temperature drying was put forward.1. Dehydration characteristics The study was undertaken to investigate the dehydration characteristics of the garlic slice in heated-air circulate drying. The drying time decreased considerably with an increase in the air temperature and this trend was more obvious at the lower temperature. Although increase in sample thickness and loading density all caused an increase in drying time, the influence of sample thickness is more visible.2. The parameters of the constant temperature The dehydration process of garlic slices was optimized by quadratic orthogonal rotary design, and the quadratic regression equations were established and the predicted minimum energy consumption was 1.96kWh/kg. The optimum technique parameters of air temperature, sample thickness of garlic slice and forced filling rate were 62.3℃, 2.38mm and 2.69kg/m2 respectively. Under the controlled conditions, the energy consumption is 2.05kWh/kg, output is 4.11kg/h, and the equation was testified to be effective.3. The drying model Thin layer drying characteristics of garlic slices is experimentally investigated in a convective dryer and the mathematical modeling by using thin layer drying models in literature is performed. Four different thin layer mathematical drying models were compared according to their coefficient of correlation to estimate drying process, with the Henderson and Pabis and Two-term models giving better predictions than the Lewis and Page model. The constants and coefficients of this model could be explained by the effect of drying air temperature.4. Verification experiment and drying of mutative temperature According to the factory results, an approximation of the diffusion model could satisfactorily describe the drying process of garlic slices. The optimum technique parameter of mutative temperature drying is 60℃, 59.5min, 80℃, 43.5min and 60℃, 78.2min. Under the controlled conditions, the energy consumption is 1.729kWh/kg, output is 121kg/h, and the equations were testified to be effective.5. The comparison between constant temperature and mutative temperature drying Compared with constant temperature drying, the energy consumption of appropriate mutative temperature drying is less, and as a result of lower temperature in low moisture content drying stage, the browning is relatively lighten, mutative temperature drying is more available to produce quality products.