Study On The Mechanism Of Heat And Mass Transfer And Vitality Variation During Seed Heat Pump Drying Process

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. Model of heat and mass transfer:Not considering the influence of pressure and the temperature-moisture coupling effect, it got the simplified dynamic equations of heat and mass transfer. its parameter has clear physical meaning, and its boundary conditions are very exact.2. Influence of the drying medium parameter:If the beginning of drying process is ignored, the process is a falling-rate drying model. The drying-rate at beginning is maximal, and then decreased to zero gradually. The average drying-rate increased with the raises of drying temperature and with the decreases of the drying moisture. And the equilibrium moisture content decreased with the raises of drying temperature and increased with the raises of drying moisture.3. Researches on the whole heat hump system:The paper defines the high temperature side and low temperature side of the heat hump. It studies the influence of these two temperatures to drying air. Not only the temperature but also the moisture of drying air is decided by the high temperature and low temperature.4. Influences of drying parameters to seed vitality:The paper uses the enzymatic activity of seeds inside to measure the seed vitality. Dried in high temperature, the value of the CAT, POD rises 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.5. The micro-analysis about physiological destroy of seeds dried at high temperature:Because of the nonhomogeneity of moisture content inside the seed, moisture content of some parts of the seeds is under 5%. And monolayer water around the seed becomes discontinuous. Lipid is oxidized automatically, which lead to protein denaturizing and enzyme deactivation of the seeds.