Simulating And Anticipating The Technology Process During Vacuum Freeze-drying

Owing to vacuum freeze drying keeps amply the nutrition and the live material of the dried substance, and keeps the natural colors,flavor and shape, vacuum freeze drying has a comprehensive apply in food,medicine and creature produce. But the high cost of energy consumption limits the development in the agricultural product process. So it is very important to study the process of lower energy consumption freeze-drying. The paper mainly searches the way to simulate and anticipate the technology process during vacuum freeze-drying. On the basis of summarizing the way and apply of neutral network, the paper elaborates the feasibility that the neutral network is used to simulate analyze. The theory of neutral network system is applied to study the mold and process anticipation during vacuum freeze-drying. Through the MATLAB method, BP artificial neutral network model is established using toolbox and the model was used to simulate the freeze-drying. The paper adopts the neutral network to anticipate the effects of factors such as material thickness, radiant temperature and pressure of drying chamber on vacuum freeze-drying. Analysis to the data suggests it is feasible to anticipate the vacuum freeze-drying process through the neutral network. Using carrots as the model material, the effects of operation parameters on the drying process are studies deeply in the experiment. The results indicate that drying thickness, radiant temperature and pressure of drying chamber are the most three significant factors. The material thickness is the key factor that influences the freeze-drying process. The freeze-drying time of mixing heating is obviously shorter than that of pure radiation heating. Based on proper assumptions, a transient-state mathematical model to describe the heat and mass transfer during freeze-drying is deduced. The quasi-steady state model that is simplified from the partial differential equation above is developed and analyzed. The results show that the simulation of neutral network can substitute for mathematical model to analyze the freeze-drying process under certain conditions. The predicted drying time is found to fits the experimental results.