Design And Simulation Of Constant Temperature Control System Of Drying Machine With Solar & Air-source Heat-pump

Dryer uses coal, electricity, natural gas and other fuel commonly, material drying is a huge energy-consuming process. It is not only energy saving but also affordable to develop and use industrial drying equipment with renewable energy, such as solar energy and air energy. Solar heat-pump dryer, which combines solar energy collection with air energy heat pump, can make full use of solar energy to achieve the best energy-saving effect. In addition, the dryer can ensure stable requirement of drying process. Crop seeds and other materials require higher temperature control and a constant temperature range in drying process, the temperature range can ensure the biological activity of crop seeds, besides, the stable and efficient drying process can be ensured. In view of the actual demand, this paper studies constant temperature control system for drying machine with solar and air-source heat-pump.The main researches are as follows:1. Design of a crop drying machine with solar energy and air-source heat pump:In the drying machine, closed-loop flowing pure water is used for heat transfer medium, and water storage tank is for storing thermal energy. Solar drying heat pump dryer has three operating modes:separate solar energy heating model、separate air heating model and solar air heat-pump heating mode at the same time. In a separate solar heating mode, the area of solar thermal collector is calculated and determined. Refering to geographical location of Guangzhou and sun’s radiation, slant angle of the solar thermal collector in different seasons is chosen. In a separate air heat-pump heating mode, heat pump computing power, type and other specific parameters are calculated. According to the demand of maximize storage and guaranteed dry heating, the volume of heat storage tank is calculated and determined.2. Research of control strategy and algorithm in constant temperature drying process: According to the requirements of efficiency, stability and constant temperature in drying process, the working process of drying control system in different working mode is determined. According to the demand of temperature control in solar heat pump dryer,such as stability, energy saving, the fuzzy PID control with Smith predictor is applied to the solar energy heat-pump drying control system, and the big mutation genetic algorithm is used for optimizing fuzzy control algorithm, and improving control performance of this system.3. Simulation and optimization of temperature control algorithm:According to the test model of drying room, transfer function between heat-pump compressor frequency and drying room’s temperature is established. By using Simulink module of MATLAB software, establishing conventional fuzzy PID control algorithm, joining Smith estimate of fuzzy PID control algorithm, and using genetic algorithm optimized fuzzy control algorithm, a simulation model is used for comparing the control effect of different control algorithm.4. Hardware design of control system in solar heat -pump drying machine:On the basis of the study above and using graphical programming tool Lab VIEW, the upper machine of the control system is designed to achieve the drying room temperature data in real-time monitoring and control. Lower machine chooses LPC2103 single chip processer as the core to complete the detection of controlled object, such as drying temperature, and the control of relevant executive device and function.