In order to verify the rationality and applicability of mechanical ventilation in large warehouse warehouses, and explore the use of cold temperatures in winter to mechanically cool grain against pests in stored grain, etc., the Sanhe Direct Storage of the State Grain Reserve Bureau conducted a mechanical ventilation production test and achieved expectations. Effect, the experimental situation is introduced as follows: The mechanical ventilation system and the grain condition for the test warehouse are the large warehouse warehouses. The air duct is designed as a machine with a total of n air ducts. The cage is semi-circular and its cross-sectional area is lined.
Fan model with a wind volume of a full-pressure lining a power duct fabric as shown.
The average bulk moisture content of wheat in bulk in the test warehouse is as shown in the figure. As shown in the figure, each temperature measurement point is stratified from the bottom of the grain pile to the grain surface, and they are labeled as “Kunfanmin†and “Kun†layers respectively. The distance between each layer of the food surface layer and the adjacent layers at the bottom of the warehouse is the content of the experiment and the results. The measurement point of the grain surface wind speed is shown in the figure. The instrument measures the apparent wind speed of the grain surface. .
The measurement results show that the apparent wind speeds at all points of the grain surface are relatively uniform, all of which are in the right and left, and are all in line with the requirements of storage and mechanical ventilation design.
Since the ratio of the accessibility of the warehouse to the middle of the warehouse is such that the cooling rate is slower during the ventilation process, the surface of the trench is reduced before the measurement of t and the ventilation and cooling effect is significantly improved. The wind speed at the point corresponding to the canyon is comparable to that of the canyon. high.
The cooling effect of grain before and after ventilation was ventilated from the date of the year, to the end of the ventilation on the 3rd of the month, and the switch was totaled. The grain temperature was detected before the first power-on, and the grain temperature was measured at least once after each shutdown. The average grain of each layer The temperature table can be seen from the table. After the ventilation is conducted, the average grain temperature of the entire warehouse is about the average temperature of the grain layer between the gas and the cooked layer, and ventilation is carried out.
After that, the average food temperature in the entire warehouse was 13.
It is approximately equal to the average grain temperature of the island level.
After the ventilation was carried out for 19 hours, the average food temperature in the entire warehouse was slightly higher than the average grain temperature in the layer of Urumchi. After the ventilation was carried out, the average food temperature in the entire warehouse was in the middle of the Urumchi and S4 layers. After the ventilation was conducted, the average grain temperature in the entire warehouse was approximately equal to The average grain temperature in the civilian layer shows that in the process of ventilation of high-story houses, when the change in external temperature is small, the average grain temperature of the entire warehouse corresponds to the average grain temperature of different grain layers in different ventilation stages, and follows When the ventilation is carried out, the corresponding points move from the lower layer of the grain pile to the upper layer. When the average grain temperature of the entire grain is slightly lower than that of the Kunming layer, the ventilation can be ended.
Using trumpet wind hood with breeze attenuation to change the average time of change in sub-class before and after ventilation (monthly and daily single machine average average machine time temperature and humidity wet boot average grain deterrence before each layer (average grain temperature after shutdown) (Kunfan entire warehouse where After the entire warehouse ventilated the milk, the highest level of grain in each layer and the location, January Yin.
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The increase was large because the ground temperature under the grain piles was equivalent to the grain temperature of the Khumkow before ventilation. After the ventilation was completed, the grain temperature in the horse layer decreased sharply. The temperature difference between the ground and the mantle layer was obvious. The geothermal heat was from the warehouse floor to the Sl layer. Transmission, resulting in a gradual increase in grain temperature.
Therefore, when there is a large degree of cooling in a single ventilator, a compensating ventilation should be conducted at the appropriate time after the ventilation is completed to balance the grain temperature and ensure food security.
The change law of unit cooling effect in the ventilation process is based on the table to obtain the ventilation cooling effect and unit energy consumption of each layer of ventilation during each ventilation period. As shown in the table, the cooling effect curve of grain temperature per unit time during each period of ventilation can be drawn.
In the initial period of ventilation, the cooling rate of Fankun units sharply increased to a peak and then sharply decreased. The effect of ventilation and cooling was the best. The temperature reduction of every layer unit slowly increased, while the grain temperature in Renkun layer increased, and the cooling rate was negative in the middle period of ventilation. The cooling rate of the mature layer unit gradually decreased to a relatively low level and remained relatively unchanged, while the Wumin layer gradually increased after peaking, and the cooling rate of the Kunming unit gradually increased. During this period, the Pang S4 layer had the best ventilation cooling effect. At the end of the ventilation period, the cooling rate of the Kunming layer units gradually tended to zero, and the layer gradually increased after reaching its peak value. During this period, the Wei-Wei layer had the best ventilation and cooling effects.
It can be seen that during the ventilation of high-story warehouses, the grain temperature will decrease from the bottom layer to the top layer. The cooling rate of each layer unit in each period is different, and the temperature reduction rate of each grain temperature unit has risen to a peak. In the process of gradual decline, the peak occurs when the upper layer lags behind the lower layer, that is, the peak appears in turn from the bottom of the grain pile to the upper layer as the ventilation progresses, while the peak value gradually decreases.
The effect of fan power on cooling effect and unit energy consumption can be seen from the table. With the progress of ventilation, the cooling rate of the whole unit gradually rises to its peak and then gradually decreases, while the unit energy consumption gradually increases.
In order to further discuss the fan power on the mechanical ventilation unit, such as sand fire lu month Lun. l Selenium.
Lin Lun Sheng Jie Zhou Zhou Zuo Pu Zhoubin point maps J easy to measure point cloth 1 schematic natural ventilation in the mechanical ventilation in the supplementary role from the table shows that after the end of mechanical ventilation on the 13th, the average grain temperature in the Queensland is more than the atmosphere layer The high does not meet the conditions for the end of ventilation, but the average food temperature in the entire warehouse is the difference between the temperature and the air temperature, which is inconsistent with the continuous ventilation condition. At this time, the ventilation is suspended.
Due to entering the winter, the outside temperature gradually decreases and the air humidity is low. Therefore, natural night ventilation is performed using night low temperature windows. From the day and month to year and month, the temperature records and tables show that after natural ventilation, the average grain temperature of the Ss layer decreases. As far as the average grain temperature in the same layer as the average level, and close to the entire average grain temperature, the maximum grain temperature in the highest layer (the measurement point is the ventilation dead angle) has dropped from the previous level. Therefore, the mechanical ventilation in the large warehouse is performed because the grain layer is too thick and the grain temperature is too high. When the temperature difference is large, natural ventilation should be used to reduce the temperature of the surface layer of the grain, so that the temperature gradient of the entire grain pile meets the conditions for ending ventilation, and the cost of ventilation can be reduced.
It can be seen from the table that during the natural ventilation period, the grain temperature in the Kunming layer remained basically unchanged from the decline to the islander's level, while the grain temperature from the bottom layer of the grain piles rose from the grain temperature of the grain piles to the warehouse technology warehouse ventilation. Ventilation dew effect date (monthly stand-alone boot time (average grain temperature before ventilation (average grain temperature ventilation ventilation cooling effect unit drop decisive amplitude of eight units of energy consumption month 1-5 total energy consumption and unit cooling effect, the other The power is the wind turbine for ventilation and cooling of another steel bin of the same type (10 ducts, equipped with wheat, and the others are the same). The fan model is based on the total pressure of the wind and the ventilation cooling effect is as shown in the table test results. The energy consumption is the power of the fan. The unit energy consumption is better for the sub eight but the ventilation time is increased from visible to visible. When the mechanical ventilation of a ventilation network system and a specific large warehouse warehouse is cooled, if the air volume is equivalent, The fan power is changed within a certain range. When the power of the fan is significantly increased, the total pressure increases, the unit cooling rate is significantly increased, and the entire ventilation time is significantly shortened. But the impact on unit energy consumption is not significant.
The selection of the route ratio from the ventilation system of the large warehouse warehouse can be seen from the measured food temperature at the end of the daily ventilation. In addition to the higher grain temperature of the layers and the Kun layer, the remaining grain temperature is relatively uniform, basically consistent with The ventilation condition is ended, because the points are in the room of the warehouse, the ratio of the route is the ratio of the other points is less than the ratio of the two channels is not much difference, but the effect of the ventilation cooling effect on the upper layer of food, such as point, Kunfan The Kunhe layer grain temperature was 19.
The average grain temperature of each storey in each storey is the current cooling rate in the technical specifications of the mechanical ventilation store. The ratio of cooling routes to one can satisfy the following requirements for the ventilation of the grain piles, but it does not necessarily meet the above requirements for uniformity of ventilation and cooling in large warehouses.
For China's newly built large warehouses, because the grain piles are very thick (one storehouse span is larger than the layout of the air ducts is symmetrical or asymmetrical font type, it is recommended that the mechanical ventilation of the large warehouse warehouse is better than the alternative one, and the air duct installation requires each The point approach is as consistent as possible. In the wind grid shown in the figure, if the ventilation duct increases from long to long, the ratio of the M point to the narrower point is reduced from 4 to 31. The uniformity of ventilation will be reduced. better.
Before and after the ventilation, the moisture content of the grain changes uniformly along the duct. Each layer is sampled vertically to determine the moisture content. From the table, it can be seen that the moisture gradient of the grain pile after the ventilation is less than the thickness of the grain layer, which is consistent with the end of mechanical ventilation and cooling. conditions of.
The average moisture at the sampling point was 12.
Drop to the highest point of moisture by 13.
The decline will benefit food storage.
During the ventilation process, the temperature and wetness of the warehouse were changed. Before each start, the external temperature and humidity were recorded. After the start, the temperature and humidity of the warehouse were recorded. After that, the external temperature was recorded in a random manner. The results were recorded in the table before and after ventilation. (After ventilation, the grain moisture content of the grain water after ventilation is averaged and the average grain and oil storage technology and communication warehouse technology are wrapped in the process of ventilation and the warehouse is depleted.
Wet change Ventilation phase Ventilation time (exclusively when the moon is used, the wet tank is wet and the first temperature is the first 8 j fly 100 l, B, J J8 J, Shan Gong Wei j Wei J j, police month Forty-two from the table shows that the first time after the start of the warehouse hours wet to reach the second boot half an hour warehouse wet storage temperature shut down the warehouse wet warehouse temperature after the third boot for half an hour, the warehouse wet warehouse temperature 15 shutdown warehouse wet 31 warehouse temperature for the fourth time after the opening of the opening half an hour, warehouse wet 75 warehouse temperature 13 shutdown when the warehouse wet down to warehouse temperature 16 hours after the fifth boot, warehouse wet 35 warehouse temperature 10 shutdown when the warehouse wet down to warehouse temperature The average grain temperature of the whole warehouse is visible. In each stage of the ventilation, the humidity and temperature in the warehouse can rise rapidly due to the fact that the hot and humid air inside the warehouse cannot be discharged outside the warehouse in a timely manner. Especially during the early period of ventilation, this kind of high temperature and high humidity air and steel The beams are condensed into water droplets and fall into the heap of grain, which is not conducive to food security. We have added two exhaust fans at the window, and we have achieved very good results by expelling high temperature and humidity air from the warehouse as quickly as possible. With the progress of ventilation, this phenomenon It quickly disappeared. When checking the food situation, there was no evidence of condensation inside the grain piles.
The effect of mechanical ventilation on the prevention of pests in stored grain at a low temperature of 41.
Due to the large capacity of the warehouse and the long food intake period, and during the high temperature period in summer, the pests breed quickly and have many species. On a monthly inspection, it was found that there were pests such as the cymbals and cymbals in the valley of corn and valleys. Wax activity, before ventilation and temperature drop, choose a relatively serious part of the grain pest as a standard, and perform pest inspection every time after ventilation.
Ventilation was started from the beginning of the month to the end of the day, and the density of pests at various inspection sites was significantly reduced, and the trend was uniform.
However, during the ventilation process, it was found that the number of truncal saplings and wax insects on the surface of the grain increased sharply. This may be due to the fact that surface temperature and humidity were relatively high during the period of ventilation, which caused the eels and waxes to migrate to the surface.
After the end of the ventilation, it was found that some of the pests were paralyzed. Others were active, but their ability to move significantly weakened. They sunk to the minute paralyzed pests and gradually regained consciousness.
One month after ventilation, the pests were all in a cold coma and the recovery time at room temperature (approximately) was significantly longer.
Sampling inspections were carried out two months after ventilation, and no living pests were found at room temperature. The mortality rate of pests was up to 10 Tests showed that the death rate of pests gradually increased with the extension of low temperature time under certain low temperature conditions. Increase.
At the same time, the resistance to low temperature of each species is different, and the corn elephant valley is weaker, while the bookworms and locusts are stronger.
This experiment shows that the grain temperature has dropped to the left and right, and the time has remained for two months. All of Mae Shushu and Biangu Pirates have died.
Therefore, it is practically feasible to use low-temperature winter mechanical ventilation to control stored grain pests in large warehouses.
In summary, it can be considered that the design of the mechanical ventilation system of our warehouse is a reasonable application of mechanical ventilation and low temperature technology to prevent and control pests in stored grains. It is extremely promising to develop mechanical ventilation and low temperature pest control technology in suitable areas.
References Wu Deming Pu Haigen.
Valley basin biological characteristics and prevention methods.
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Wan Zhongmin.
New Trends in Mechanical Ventilation Storage Technology Research.
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Shen robe lin.
Stored grain is full of biological characteristics, hazards and prevention.
Grain and oil storage technology communication.
Shen Zonghai.
Grain and oil storage.
China Financial and Economic Publishing House National Grain Reserve Bureau Storage Division.
New grain storage tutorial.
Wang Dianyang Cao Yang editor.
Phosphorus nitrogen fumigation insecticidal technology.
Chengdu University of Science and Technology Press Date: January 18th Uguchii Inner Mongolian J1, Jigou, Jiqiu J, Jl, Jjjjj
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