Simulation Research On Low-temperature Grain Storage System With Seasonal Natural Energy In Severe Cold Climates

Under the current grain storage system in China,grain storage cycle is generally 3 to 5 years.Respiration of grain during storage can cause a lot of loss of nutrients due to aging,meanwhile the grain is prone to mildew.This will lead to 20%~30% loss of the total reserves of grain in one year,which means the direct economic losses amount to tens of billions of yuan.This kind of situation will seriously endanger the strategic national food security.The decrease of temperature in granary will greatly increase the efficiency of grain storage.Two low-temperature grain storage methods are widely used--mechanical ventilation storage and mechanical refrigeration storage.But those two methods both have some limitations.The former requires a lot of ventilation for a long time,which consumes large amounts of energy and is not suit for long-term high-temperature and high-humidity climate;The latter has larger energy consumption and the expense is too high for large-scale applications.Therefore,by extensively reading relevant domestic and foreign literature,this paper presents a new method of grain storage using seasonal cold resources,which is suitable for severe cold climates.This method is based on the idea of relocating cold air resources that widely present in nature.During winter,cold resources will be stored in soil,grain,and the exterior-protected construction.The exterior envelope is insulated to store the cold for use in the spring,autumn and summer months.This method can more than double the grain storage cycle,and it has the advantages of energy saving and reduction of construction and operating costs.This article uses softwares such as Fluent and De ST to assist theoretical research.Based on the actual project,a new type of grain storage system suitable for the research was designed.By analysing the theoretical process of the seasonal cold storage,a mathematical model was established and simplified,and the model was verified based on the local experimental data in Shuangyashan.The three-dimensional model of the granary was established and meshed by using the Gambit software.The porous media model in CFD was used to perform numerical simulations by compiling and importing the UDF function.The grain temperature and soil temperature in the cold storage process were obtained,the time to reach the target temperature of the cold storage is 41 days and 28.5 days,respectively.Under the condition of local climate,the granary can be cooled to-20°C in the winter.After changing the working conditions,the influence of different wind speeds of ventilated cage on the granary temperature field was obtained.Through calculation in the De ST software,the granary's full-time hourly release of cold was obtained.Compared with the entire granary cold storage capacity,the feasibility of the technology is verified.At the same time,the annual temperature change table of the granary was obtained,and the highest average temperature in the granary was found to be-3.01°C,which met the expected goal of low-temperature grain storage.The research further studied based on the climatic conditions of other cities,obtained full-time hourly release of cold and temperature change of the granary of other cities in severe cold climates,and put forward some views and prospects for the popularization and application of this technology.The research results of this article can play a role in guiding the design of lowtemperature granary using seasonal cold in the actual projects in severe cold climates.