Condensation Heat-increasing Grain Drying Test Device Based On Semiconductor Refrigeration Technology

No agricultural instability of the country,no food insecurity of the people.The grain industry is the foundation of rural revitalization,and ensuring food security is of far-reaching significance.In recent years,grain production has been above 600 million tons in China.While increasing grain production,further expansion of grain transportation,drying,storage and deep processing has become a problem that must be solved continuously.Grain drying is an important process before storage after production,and it is one of the processing units with high energy consumption in the field of grain circulation.Energy saving and environmental protection is the inevitable trend of grain dryer design.With the rapid development of industrial technology,the in-depth and popularization of research on new technologies,new ideas and new methods for grain drying technology have been proposed based on new energy and new materials.Semiconductor refrigeration technology is a new technology developed with the rise of semiconductor refrigeration materials in recent decades.It has the advantages such as no noise,no vibration,environmental friendliness,small size,light weight,flexible control,and convenient maintenance.In this study,the semiconductor refrigeration is first carried out in the grain drying fields.Thanks to semiconductor chilling plate has cold and hot sides,the tail gas with waste heat of the drying system can be cooled down by the cold side to produce dehumidify effect,and then the dehumidified gas would be heated by the hot side as a preheat process.The air can be recycled in the drying system.It provides an eco-friendly and energy saving new method for grain drying in the utilization of condensing and reheating.This paper is based on the demonstration research project of clean energy-based grain drying technology by the Jilin Provincial Department of Ecology and Environment.On the basis of the research of electric grain drying system drying system,a new drying technology method is proposed.With semiconductor refrigeration technology as the core of providing heat source and condensation and dehumidification,a set of basic experimental equipment for condensation heating is designed to reuse high temperature and high humidity drying exhaust gas,reduce energy consumption and improve energy utilization efficiently and environmental friendly.As we all know,semiconductors provides heat and cold sources through consuming clean energy and electricity.Semiconductor refrigeration technology is the first time used in grain drying technology,in which the cooling and heating functions of semiconductors are used at the same time.The main research contents of this paper are as follows:（1）Analysis of semiconductor refrigeration technical parameters and overall design plan of the device system.According to the principle of semiconductor refrigeration,its refrigeration efficiency was studied and analyzed,other parts were also carried out such as simulation of test data,analysis of the main work flow and control tasks of the entire control system,and design of the mechanical structure and control system software and hardware schemes.The temperature and flow rate of the drying medium inside the drying structure were uniform and controllable ensured by the whole test machine,including the start and stop of various electrical components according to the test conditions,precisely control of the temperature of the drying medium,the fan speed and the operating cycle of the semiconductor refrigeration chip,real-time collection and monitoring of temperature,humidity,wind speed,etc.In the warehouse,various parameter settings according to different test factors to ensure system control accuracy were operated.A basic experimental device for condensation heat increase based on semiconductor refrigeration technology was designed to simulate the process of fixed-bed grain drying.（2）The application of PLC electrical control system in condensing heat-increasing device.First,according to the control tasks,the control system was designed including determining the PLC host model,temperature and humidity sensor,I/O port distribution and electrical wiring,etc.Also the hardware construction of the control system and actuator was completed.The stable communication of the temperature and humidity sensor was realized,and each execution part can be started or stopped accurately.The stability and fluency of the electrical control system operation provided a guarantee for the success of the follow-up test and lay a solid foundation for the good operation of the whole machine.（3）LabVIEW human-computer interaction software system design.The host computer was designed with Lab VIEW software programming,and a friendly and simple information interaction interface was designed according to the work flow,which turns the complex process flow into a simple information processing process,and realized real-time data collection,processing,storage and interface presentation,and target display Alarms with abnormal information,etc.（4）Basic test plan design and overall machine performance analysis.Taking corn as the research object,a comprehensive test of the condensation heating system device was carried out according to the test purpose and requirements,and the unit energy consumption,drying rate and condensation intensity of the whole device were analyzed and processed.The control system monitored the total weight to predict the real-time water content of the corn,and there was a certain deviation from the actual measured water content.The actual measured water content was 1%～2.5%higher than the system measured water content.The condensation intensity increased with the number of cooling plates.It increased with the increase of the slow-supply ratio.It was confirmed that when a set of cooling fins have a wind speed of 1.6m/s,the overall unit energy consumption was the lowest.The lowest energy consumption of a set of cooling fins is 5255k J/kg·H₂O,which had the best energy saving effect.According to the requirements of the T/CAMDA6-2019 group standard promulgated by the China Agricultural Machinery Circulation Association:direct heating and circulating drying corn,the unit heat consumption is less than or equal to 7500k J/kg·H₂O,and the actual energy saving of this system is 30%.