Simulation And Experimental Study On The Temperature-variable Drying Process With Heat Pump For Seeds

In order to study the model of heat and mass transfer and the vitality variation of cabbage during heat hump drying process, a lot of experiments in drying process of cabbage were carried out, the drying model in seed was researched.1. Empirical and semi-empirical model of moisture diffusionThe empirical model of moisture diffusion of the seed during drying process is different because of the difference in seeds'kind, drying condition. Through the research on the seed dried by the heat pump, the descending curve of its moisture content was fitted. The coefficients of the model were determined.2. Computer simulation of the heat pump drying systemThe system including compressor, condenser, expansion valve and evaporator was programmed by VB language. The result calculated by computer has low relative error with the result of research. So the power consumption and the SMER at any drying condition can be calculated expediently by using the simulation program.3. Research on the temperature variable drying methods of heat pump dryerSome feasible drying methods with temperature variable were discussed. And the drying process of the seed was simulated. After considering the power consumption and the drying time, the better drying method with variable temperature was found.4. Influences of drying parameters to seed vitalityThe paper uses the enzymatic activity of seeds inside to measure the seed vitality. Dried in high temperature, the value of the CAT, POD rise up at the beginning, and then descends. At the beginning, MDA increases slowly and then increases rapidly. The higher temperature and lower relative moisture content of the dry air have more influence on CAT, POD, MDA. The descent of the enzymatic activity was caused mainly by the uniformity of the moisture distribution during the drying process of the seed. When the moisture content of the inside still has a high level, the one outside was already below the safety value 5%. Though the study on the temperature variable methods, we found that those methods have the littler damage on the enzymatic activity of the seed.