Expansion Study On Grain Storage Mechanical Ventilation

Storage mechanical ventilation has been used widely in grain storage company in China. Studies on cooling ventilation and decrease moisture ventilation in this article are supplements of storage mechanical ventilation theoretical and experimentation research. The main results of this paper are:1) According to the analysis on traditional formula, mended formula for calculating hours of cooling ventilation has been put forward in this paper which is based on grain being poor conductor of heat and the assumption of linear relationship between grain temperature and grain bulk height: The mended formula is more accurate than the traditional one.2) Investigation on relationship between cooling aeration hours andΔt(temperature difference of grain bulk and air) shows that cooling aeration hours decrease rapidly whenΔt≤8℃but decrease slowly whenΔt >8℃. The result verified the reliability of the"Technical regulation of aeration for grain storage"in theoretical respect.3) Ventilation uniformity is an important index of measuring the scientific characters, rationality and economic performance of the mechanical ventilation system. A convenient and effective method for evaluating the grain temperature or humidity data uniformity after mechanical ventilation was presented which based on linear regression and standard difference method. In the fitting equation y=ax+b. if a≤0.5,it shows that the data are in good uniform. Conversely, a≥0.5 means that data uniformity is not good enough. But This evaluation method is not suitable for evaluating the uniformity of drying aeration for high grain bulk beyond 4m.4) A software of in-store corn drying is been developed which is depended on the equilibrium equation raised by T.L.Thompson and is composed of two modules describing heat and mass transfer and deterioration. This software can be used to calculate the hours of drying ventilation and simulate the changes of some concrete state of grain bulk. Simulation result of the program is basically exact and reliable. This software can be extended to simulate in-store drying process of paddy and wheat.5) Conclusions can be summarized through an in-store drying contrast experiment of high corn bulk which contains about 15% moisture in ShangHai: Separate ventilation through cage on the ground caused moisture gradient too large in bulk. Separate vertical ventilation decreased grain moisture efficiently but with high cost. Decreasing grain bulk moisture is more efficient and cost lower when ventilation through cage on the ground is combined with vertical ventilation. Compared with Separate vertical ventilation, this ventilation mode decreased 61.9% labor cost, 87.5% equipment wear and 70.0% inserting pipe hours.