Vertical warehouse grain pile cooling and ventilation system, ventilation method and fan selection method

Abstract

The application discloses a vertical silo grain pile cooling and ventilation system, a ventilation method and a fan selection method, to solve the problems of large fan noise, more fan compression heat and poor grain pile cooling and ventilation permeability in the existing vertical silo using large centrifugal fan for pressure type uplink grain pile cooling and ventilation. The ventilation system comprises a vertical reinforced concrete silo and four small-power fans, and four longitudinally distributed air ducts are uniformly arranged on the inner wall of the cylinder of the silo along the height direction. The application adopts cross-flow ventilation, which is based on the fact that the long axis of the grain is mainly arranged along the horizontal direction when the grain enters the silo, and the airflow resistance in the horizontal direction is 0.6 times that in the vertical direction, so that a ventilation fan with smaller power is used, thereby reducing the equipment cost and operation cost. The total ventilation volume is larger, the grain pile cooling and ventilation time is shorter, and the energy consumption is lower. Meanwhile, a ventilation method of alternating airflow is provided, which effectively solves the problem of the central dead zone of the grain pile. A ventilation fan selection method is also provided.

Description

Technical Field

[0001] This application relates to the field of grain storage and distribution technology, specifically to a cooling and ventilation system for vertical grain piles in a warehouse, a ventilation method, and a fan selection method. Background Technology

[0002] During natural grain storage, the combined effects of the external environment and the respiration of grain particles within the grain pile can lead to localized increases in temperature and moisture, resulting in insect infestation and mold growth. This deteriorates grain quality and jeopardizes safe storage. Therefore, temperature and moisture content within the grain pile are two parameters that require close monitoring during natural storage. To ensure safe grain storage, a grain ventilation system is used to reduce internal temperature and moisture levels.

[0003] Grain storage involves controlling the moisture content and temperature of stored grains to inhibit the growth of insects and molds, maintain grain viability, delay quality deterioration, and improve processing quality. In temperate and subtropical grain storage areas, based on the two major physical characteristics of grain piles—porosity of 0.35–0.55 and poor thermal conductivity—the base temperature of the dry grain pile is lowered by utilizing natural cool air for ventilation in autumn and winter, while surface temperature control and chemical fumigation of the grain pile are employed in summer and autumn to control the growth and development of stored grain pests and maintain grain quality. This application proposes a method for cooling and ventilating a vertical, tall, concrete circular silo. Summary of the Invention

[0004] Therefore, this application provides a vertical grain pile cooling and ventilation system, ventilation method, and fan selection method for constructing grain silos and shallow circular silos with a height of 28 to 50 meters. At the same time, it solves the problems of high fan noise, high fan compression heat, and high energy consumption in existing vertical grain pile cooling and ventilation systems that use large centrifugal fans for forced upward cooling and ventilation.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] In a first aspect, a vertical grain storage cooling and ventilation system includes a vertical storage silo, a first fan, a second fan, a third fan, and a fourth fan. The storage silo is a reinforced concrete silo. Four longitudinally distributed air ducts are evenly arranged along the height direction on the inner wall of the cylindrical part of the storage silo, and are respectively labeled as air duct A, air duct B, air duct C, and air duct D in a clockwise direction along the circumference. Air duct A and air duct C are two opposing air intake ducts, and air duct B and air duct D are two opposing air exhaust ducts. The first fan and the second fan are located at the outer bottom of the storage silo, and the third fan and the fourth fan are located at the top of the storage silo. The first fan, the second fan, the third fan, and the fourth fan are respectively connected to air duct A, air duct B, air duct C, and air duct D.

[0007] The air intake duct and the air exhaust duct are perforated plates, and the diameter of the perforations is smaller than the minimum particle size of the grain.

[0008] Optionally, the diameter of the warehouse is 6 to 12 meters, and the height of the grain pile inside the warehouse is 26 to 50 meters;

[0009] The straight-line distance between the centers of the two air intake ducts is 1.0 times the diameter of the warehouse; the distance from the air intake duct to the two exhaust ducts is 0.7 times the diameter of the warehouse.

[0010] Optionally, the intake duct and the exhaust duct have the same duct size;

[0011] The cross-sectional shape of the air intake duct and the air exhaust duct is a semi-circular duct with a radius of 0.3 to 0.5 m. The material is a 1.5 to 2 mm thick cold-rolled perforated plate, and the hole type is a bridge-type double hole with an opening rate of 25% to 30%.

[0012] Optionally, the first fan, the second fan, the third fan, and the fourth fan are centrifugal fans.

[0013] Optionally, the first fan, the second fan, the third fan, and the fourth fan are axial flow fans.

[0014] Optionally, a vent and a cover are respectively provided on the side of the air duct A and the air duct C near the first fan and the third fan;

[0015] The air ducts A, B, C and D are all composed of multiple air duct units, which are fixedly connected to each other, and each air duct unit is 1m long.

[0016] Optionally, the ventilation system is an exhaust airflow system, with negative pressure set on air duct A or air duct C, and the other three air ducts serving as air intake supply ducts.

[0017] Secondly, a method for cooling and ventilating a vertical grain pile in a warehouse, employing the aforementioned vertical grain pile cooling and ventilation system, wherein air duct A or air duct C is used alternately as the air intake duct, and the ventilation method includes:

[0018] Step 1: Load the grain into the warehouse, and select a fan type that provides uniform temperature and ventilation after loading.

[0019] Step 2: Turn on the first and third fans. At this time, both air ducts A and C serve as air intake channels. Low-temperature cold air enters the interior of the warehouse through air ducts A and C respectively, enters the center of the grain pile from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot air flow to turn to air ducts B and D to be discharged outside the warehouse, and ventilates for time t1.

[0020] Step 3: Turn off the third fan and turn on the first fan. At this time, air duct A serves as the air intake channel and air duct C serves as the exhaust channel and leads to the atmosphere. Low-temperature cold air enters the interior of the warehouse through air duct A, enters the interior of the grain pile laterally from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot air flow to be discharged from the warehouse through air ducts B, air duct C, and air duct D, and ventilation is carried out for time t2.

[0021] Step 4: Turn on the third fan and turn off the first fan. At this time, air duct A serves as the exhaust channel and leads to the atmosphere, while air duct C serves as the air intake channel. Low-temperature cold air enters the interior of the warehouse through air duct C, enters the interior of the grain pile laterally from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot airflow to be discharged from the warehouse through air ducts A, B, and D, and ventilation is carried out for time t3.

[0022] Step 5: Repeat steps 2 through 4.

[0023] Thirdly, a method for cooling and ventilating a vertical grain pile in a warehouse, employing the aforementioned vertical grain pile cooling and ventilation system, wherein air duct A or air duct C is used alternately as the air intake duct, and the ventilation method includes:

[0024] Step 1: Load the grain into the warehouse, and select a fan type that provides uniform temperature and ventilation after loading.

[0025] Step 2: Turn on the first fan and turn off the third fan. At this time, air duct A serves as the air intake channel and air duct C serves as the exhaust channel and leads to the atmosphere. Low-temperature cold air enters the interior of the warehouse through air duct A, enters the interior of the grain pile laterally from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot airflow to be discharged from the warehouse through air ducts B, air duct C, and air duct D, and ventilation is carried out for time t1.

[0026] Step 3: Turn off the first fan and turn on the third fan. At this time, air duct A serves as the exhaust channel and opens to the atmosphere, while air duct C serves as the air intake channel. Low-temperature cold air enters the interior of the warehouse through air duct C, enters the interior of the grain pile laterally from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot airflow to be discharged from the warehouse through air ducts A, B, and D, and ventilation is carried out for time t2.

[0027] Step four, repeat steps two and three.

[0028] Fourthly, regarding the adoption of the aforementioned vertical grain storage cooling and ventilation system, the fan selection method includes:

[0029] Step 1: Determine the ventilation volume of the cooling and ventilation unit based on local autumn and winter cold weather conditions and working requirements: Determine the relevant parameters of the warehouse and grain pile;

[0030] Step 2: Determine the effective ventilation bed length and static pressure;

[0031] Step 3: Estimate fan power: Calculate the total power requirement based on the weight of the grain pile and the power requirement per unit area;

[0032] Step 4: Select the fan model: Based on the ventilation volume and static pressure requirements, consult the fan manufacturer catalog and select the appropriate fan model.

[0033] Compared with the prior art, this application has at least the following beneficial effects:

[0034] Based on further analysis and research of existing technical problems, this application solves the ventilation problem of reinforced concrete silos with diameters of 6-12 meters and grain pile heights of 26-50 meters, which helps to promote the construction of such silos in my country and save land in urban suburbs. The ventilation system of this application includes a vertical reinforced concrete silo and four small-power fans. The silo is a reinforced concrete circular silo. Four longitudinally distributed semi-circular air ducts with radii of 0.3-0.5m are evenly arranged along the height direction on the inner wall of the cylindrical silo, symmetrically arranged in pairs, with an opening ratio of 25%-30%. This application adopts a crossflow ventilation method, which has low horizontal airflow resistance and horizontal airflow... The shorter path allows for the use of smaller, more powerful ventilation fans, reducing noise and lowering equipment and operating costs. Lower-power fans result in lower heat rise during compression. Higher total ventilation volume leads to shorter cooling and ventilation times for grain piles, resulting in lower energy consumption. Horizontal airflow can provide higher airflow through the central core grain pile of circular or non-circular silos, rapidly cooling grain piles with high content of deposits or impurities, resulting in excellent ventilation. Simultaneously, it provides an alternating airflow ventilation method, effectively solving the problem of dead zones in the center of the grain pile and further improving ventilation efficiency. Furthermore, it also provides a method for selecting ventilation fans. Attached Figure Description

[0035] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0036] Figure 1 A schematic diagram of the air duct distribution of a vertical warehouse grain pile cooling and ventilation system provided in one embodiment of this application;

[0037] Figure 2 A schematic cross-sectional view of the air duct distribution of a vertical warehouse grain pile cooling and ventilation system provided in one embodiment of this application;

[0038] Figure 3A schematic diagram of the static pressure of a ventilated wheat grain pile at different unit ventilation volumes, provided in one embodiment of this application. Figure 1 ;

[0039] Figure 4 A schematic diagram of the static pressure of a ventilated corn pile at different unit ventilation volumes, provided in one embodiment of this application. Figure 2 ;

[0040] Figure 5 for Figure 1 Schematic diagram of airflow isobars on the cross section of the middle two air duct silo Figure 1 (A is the air intake duct, and C is the exhaust duct);

[0041] Figure 6 for Figure 1 The shaded area in the cross-section of the silo in the middle two ventilation ducts indicates the minimum area for cooling and drying the grain pile. Figure 2 (A is the air intake duct, and C is the exhaust duct);

[0042] Figure 7 for Figure 1 Schematic diagram of airflow distribution in the four-channel silo Figure 1 (Schematic diagram of isobars of airflow on a cross-section);

[0043] Figure 8 for Figure 1 Schematic diagram of airflow distribution in the four-channel silo Figure 2 (A schematic diagram showing the minimum cooling and drying area of ​​the grain pile as indicated by the shaded area in the cross section);

[0044] Figure 9 A schematic diagram of a four-channel crossflow ventilation system provided in one embodiment of this application. Figure 1 (Air intake duct A);

[0045] Figure 10 A schematic diagram of a four-channel crossflow ventilation system provided in one embodiment of this application. Figure 2 (Air intake duct C)

[0046] Explanation of reference numerals in the attached figures:

[0047] 1. Silo wall; 2. Air duct A; 3. Air duct B; 4. Air duct C; 5. Air duct D; 6. Grain pile; 7. Silo bottom; 8. Silo top space; 9. First fan; 10. Third fan. Detailed Implementation

[0048] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," "third," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "comprising," "including," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0050] The terms used in this application, such as "upper," "lower," "left," "right," and "middle," are generally used to indicate the general relative positional relationship for the purpose of intuitive understanding by referring to the accompanying drawings, and are not absolute limitations on the positional relationship in the actual product.

[0051] An embodiment of this application provides a cooling and ventilation system for vertical grain piles in a warehouse, such as... Figures 1-10 As shown, the structure includes a vertical silo, a first fan 9, a second fan, a third fan 10, and a fourth fan. The silo is a reinforced concrete silo. The bottom of the silo is designated as the silo bottom 7, the top as the silo headspace 8, and the cylindrical inner wall of the silo is designated as the silo wall 1. The silo diameter is 6–12 m, and the grain loading height is 26–50 m. Four longitudinally distributed air ducts are evenly arranged along the height of the silo wall 1, and are designated as air duct A2, air duct B3, air duct C4, and air duct D5 respectively in a clockwise direction around the circumference. A2 and C4 are two opposing air intake ducts, facing each other directly. B3 and D5 are two opposing exhaust ducts, with the exhaust ducts at a 90° angle to the air intake ducts on the circumference. The first fan 9 and the second fan (not shown) are located at the bottom of the outer part of the warehouse, and the third fan 10 and the fourth fan (not shown) are located at the top of the warehouse. The first fan 9, the second fan, the third fan 10, and the fourth fan are respectively connected to air ducts A2, B3, C4, and D5 through ventilation openings.

[0052] The air intake and exhaust ducts are perforated plates, and the diameter of the perforations is smaller than the minimum grain size, meaning the size of the perforations is limited to prevent grain leakage.

[0053] Preferably, the straight-line distance between the centers of the two air intake ducts is 1.0 times the diameter of the warehouse; the distance from the air intake duct to the two exhaust ducts is 0.7 times the diameter of the warehouse.

[0054] Preferably, the intake duct and the exhaust duct have the same dimensions;

[0055] The cross-sectional shape of the air intake and exhaust ducts is a semi-circular duct with a radius of 0.3 to 0.5 m. The material is 1.5 to 2 mm thick cold-rolled perforated plate, and the hole type is a bridge-type double hole with an opening rate of 25% to 30%.

[0056] Preferably, air vents and covers are provided on the side of air ducts A2 and C4 respectively, near the first fan 9 and the third fan 10.

[0057] Preferably, the first fan 9, the second fan, the third fan 10 and the fourth fan are centrifugal fans.

[0058] Preferably, the first fan 9, the second fan, the third fan 10 and the fourth fan are axial flow fans.

[0059] Preferably, air ducts A2, B3, C and D5 are all composed of multiple air duct units, adjacent air duct units are fixedly connected, and the length of each air duct unit is 1m.

[0060] Preferably, the ventilation system is an exhaust airflow system, with negative pressure installed on duct A2 or duct C4, and the other three ducts serving as air intake supply ducts.

[0061] The working principle of the above embodiment is as follows: based on the fact that the long axis of the grains is horizontally distributed when the grains are put into the warehouse, the airflow resistance in the horizontal direction is 0.6 times that in the vertical direction. By changing the traditional arrangement of the ventilation ducts in the silo from the bottom of the silo to a longitudinal distribution along the height of the inner wall of the silo, the longest path of airflow is changed to 0.6 times the diameter of the silo, i.e., 6 to 12m. Therefore, natural ventilation, axial flow fans and low-speed centrifugal fans can be used to ventilate the silo with a grain pile 6 height of 26 to 50 meters. Based on the relationship between the static pressure of different grain piles 6, the effective ventilation length of the grain pile 6 and the unit ventilation volume, the air volume, power, type and number of fans used for ventilation can be selected.

[0062] Based on the above-mentioned vertical grain storage cooling and ventilation system, the crossflow ventilation method provided in this application includes the following three types:

[0063] The first method is a cooling and ventilation method for vertical grain piles in warehouses, as detailed below:

[0064] Step 1: Load the grain into the warehouse, and after loading, select the type of fan that provides uniform temperature and ventilation. The selection of the fan type is made by checking the ventilation volume and calculating the static pressure in the fan manufacturer's catalog.

[0065] Step 2: Turn on the first fan 9 and the third fan 10. Low-temperature cold air enters the interior of the warehouse through air duct A2 and air duct C4, enters the center of the grain pile 6 laterally from the side of the grain pile 6, and after contacting the hot air inside the grain pile 6, pushes the hot air to turn to air duct B3 and air duct D5 and is discharged outside the warehouse.

[0066] Airflow distribution: such as Figure 7 , Figure 8As shown, the fastest airflow will travel along a straight line between each inlet and each outlet duct, very close to the wall on each side of the inlet duct; the slowest airflow should travel directly along a straight line between the two inlets, splitting at the center of the silo near the intersection of the two 0.16-inch water column pressure lines and turning towards the two outlets. Since this airflow path is approximately twice the length of the shortest airflow path between the inlets and outlets, the slowest airflow speed is about half that of the shortest airflow path. There is an area around the center of the silo where the two straight pressure lines intersect, where little or no airflow may occur, especially when the center of the silo contains a high proportion of grain dust, broken grains, and impurities.

[0067] Figure 7 The pressure drop in the display chamber is approximately 0.15 inches of water column. For a typical unit airflow pattern, these pressure differences can be compared using the shortest and longest airflow paths. The shortest path is 0.7 times the chamber diameter; the longest path approaches the center of the chamber first, and due to the characteristics of this type of four-channel chamber, the airflow path turns 90° at the center to reach the outlet duct. Logically, significant cooling or drying occurs near the center of this four-channel chamber or silo. Figure 8 As shown.

[0068] During ventilation, each of these four-channel silos should have a diamond-shaped central dead zone or core, which cannot be adequately cooled and cools very slowly. Due to the temperature difference between the center of grain pile 6 and the already cooled grain pile 6 located 1-2 meters away, the central core of grain pile 6 may cool slowly through heat conduction, and may not be ventilated to a level that prevents grain deterioration. To address the problem of these stagnant air zones, this application also proposes a second method using alternating airflow. In the four-channel silo system, during part of the ventilation time, one of the two intake channels is used as an exhaust channel (one intake channel and three exhaust channels), and the central dead zone can be ventilated through the silo via direct airflow; the specific ventilation method is as follows:

[0069] The second method is a cooling and ventilation system for vertical grain piles in a warehouse. This system is designed for forced ventilation, with four air ducts constantly in use. Simultaneously, air duct A2 or air duct C4 is used alternately as an intake duct, with one duct serving as the intake pipe and the other, opposite, serving as the central exhaust duct of the grain pile. Figure 9 , Figure 10 As shown. The specific ventilation method is as follows:

[0070] Step 1: Load the grain into the warehouse, and after loading, select a type of fan that provides uniform temperature and ventilation. The type of fan can be selected by checking the unit ventilation volume and calculating the static pressure in the fan manufacturer's catalog.

[0071] Step 2: Turn on the first fan 9 and turn off the third fan 10. At this time, air duct A2 serves as the air intake channel and air duct C4 serves as the exhaust channel and leads to the atmosphere. The first fan 9 pushes the low-temperature cold air into the interior of the warehouse through air duct A2 and enters the interior of the grain pile 6 laterally from the side of the grain pile 6. After contacting the hot air inside the grain pile 6, it pushes the hot air out of the warehouse through air ducts B3, C4, and D5, and ventilates for time t1.

[0072] Step 3: Turn off the first fan 9 and turn on the third fan 10. At this time, the airflow direction is reversed. Air duct A2 serves as the exhaust channel and leads to the atmosphere, while air duct C4 serves as the air intake channel. The third fan 10 pushes the low-temperature air into the interior of the warehouse through air duct C4 and enters the interior of the grain pile 6 laterally from the side of the grain pile 6. After contacting the hot air inside the grain pile 6, it pushes the hot air out of the warehouse through air ducts A2, B3, and D5, and ventilates for time t2.

[0073] Step four, repeat steps two and three.

[0074] Preferably, the ventilation time in step one and step two can be equal.

[0075] The reverse airflow in the second ventilation method eliminates the dead zones in the cooling ventilation mode, as the airflow will flow through all four areas between the intake duct and the adjacent exhaust duct. The direct distance between the intake duct and the adjacent exhaust duct is a ratio of 0.7D to 1.0D (D is the duct diameter). Based on the length of the airflow path, duct C4 is the same as ducts B3 and D5, with each duct receiving approximately 70% of the exhaust volume.

[0076] The direct distance from the center of air duct A2 to the center of air duct C4 is 1.0 times the diameter of the warehouse, while the distance from air duct A2 to air ducts B3 and D5 is only 0.7 times the diameter of the warehouse. Grain ventilated through air ducts B3 and D5 initially receives more airflow compared to the airflow flowing through the center of grain pile 6 to air duct C4. If the airflow reverses from air duct A2 to air duct C4, the airflow along paths C-D and C-B is greater than when the airflow originated from air duct A2; the longer airflow distance along paths A-C and C-A is compensated for by continuous alternating airflow throughout the ventilation process.

[0077] The intake duct periodically switches from duct A2 to duct C4 to cool the grain along the walls of ducts C4 and B, and between ducts C4 and D5. The four-duct crossflow ventilation system is physically designed so that all four ducts are the same size; the only mechanical adjustment is to reverse the intake or delivery air ducts A2 and C4 through the silo. Valves are installed on these ducts, and when two fans switch, the first intake duct acts as the opposite exhaust duct, opening to the atmosphere, while the second intake duct is pressurized.

[0078] In summary, regarding the first method, which uses two opposing air intakes and two opposing exhausts in the four-channel model, there is a ventilation dead zone between the central and side exhaust channels of grain pile 6. The second method, with its one air intake channel and three exhaust channels, offers the advantage of reverse airflow, allowing airflow to move in all directions and through the center of grain pile 6. The key factor is that air must be forced to flow in all directions of the silo. Using alternating airflow into the channels with three exhaust channels achieves satisfactory cooling, and the airflow directly passes through the center of the silo to the opposite exhaust channel, effectively solving the problem of the central dead zone in grain pile 6.

[0079] This application also provides a third method, combining the first and second methods. First, the first fan 9 and the third fan 10 are turned on, selecting a two-in, two-out mode for lateral ventilation for a certain period. Then, the first fan 9 and the third fan 10 are switched, using alternating airflow for another period of lateral ventilation to ensure effective ventilation and heat dissipation at the center of the grain pile 6. The specific details of this ventilation method are as follows:

[0080] Step 1: Load the grain into the warehouse, and after loading, select the type of fan that provides uniform temperature and ventilation. The selection of the fan type is made by checking the ventilation volume and calculating the static pressure in the fan manufacturer's catalog.

[0081] Step 2: Turn on the first fan 9 and the third fan 10. At this time, both air duct A2 and air duct C4 serve as air intake channels. Low-temperature air enters the interior of the warehouse through air duct A2 and air duct C4 respectively, enters the center of the grain pile 6 from the side of the grain pile 6, and after contacting the hot air inside the grain pile 6, pushes the hot air to turn to air duct B3 and air duct D5 to be discharged outside the warehouse, and ventilation is carried out for time t1.

[0082] Step 3: Turn off the third fan 10, and turn on the first fan 9. At this time, air duct A2 serves as the air intake channel, and air duct C4 serves as the exhaust channel and leads to the atmosphere. The first fan 9 brings low-temperature air into the warehouse through air duct A2, and it enters the warehouse laterally from the side of the grain pile 6. After contacting the hot air inside the grain pile 6, it pushes the hot air out of the warehouse through air ducts B3, C4, and D5, and ventilates for time t2.

[0083] Step 4: Turn on the third fan 10 and turn off the first fan 9. At this time, air duct A2 serves as the exhaust channel and opens to the atmosphere, while air duct C4 serves as the air intake channel. The third step is to introduce low-temperature air into the warehouse through air duct C4, and then laterally into the warehouse from the side of the grain pile 6. After contacting the hot air inside the grain pile 6, the hot air is pushed out of the warehouse through air ducts A2, B3, and D5, and ventilation is carried out for time t3.

[0084] Step 5: Repeat steps 2 through 4.

[0085] In addition, this ventilation system can also be designed as an exhaust airflow system, with negative pressure set on air duct A2 or air duct C4, and the other three air ducts can be used as air intake supply air ducts; the negative pressure generated by the fan on air duct A2 or air duct C4 draws the low-temperature cold air in the other three air ducts from the side of the grain pile 6, and then, after contacting the hot air in the grain pile 6, pushes the hot air to be discharged outside the warehouse through air duct A2 or air duct C4.

[0086] Compared with traditional vertical ventilation, the crossflow ventilation provided in this application has the following advantages: ① The horizontal airflow resistance is approximately 50% to 60% of the vertical airflow resistance of the grain pile; ② The horizontal airflow path is generally approximately 20% to 30% of the vertical airflow path; ③ A smaller power ventilation fan can be used, reducing equipment and operating costs; ④ The use of a lower power fan results in a lower fan compression heat rise; ⑤ The total ventilation volume is higher, the cooling and ventilation time of the grain pile is shorter, and energy consumption is lower; ⑥ The horizontal airflow can provide a higher airflow through the central core grain pile of the silo or round silo (depending on the duct pattern), rapidly cooling the pile or grain pile with high impurity content; ⑦ In tropical and subtropical regions, the crossflow exhaust ventilation technology eliminates the compression heat that results in maximum cooling.

[0087] In addition, this application also provides a method for selecting ventilation fans for vertical grain stacks, including the following steps:

[0088] Step 1: Determine the unit ventilation volume requirement; determine the relevant parameters of the warehouse and grain pile. The relevant parameters of the warehouse include the diameter and height of the warehouse, and the relevant parameters of the grain pile include the volume, weight, bulk density, ventilation volume, etc.

[0089] Step 2: Determine the effective ventilation bed length and static pressure; the effective ventilation bed length is calculated based on the geometry of the grain pile and the airflow coefficient, and the static pressure is determined by referring to the chart based on the bulk density of the grain pile, the ventilation length, and the airflow rate.

[0090] Step 3: Estimate the fan power; calculate the total power requirement based on the weight of the grain pile and the power requirement per unit area.

[0091] Step 4: Select the fan model; based on the ventilation volume and static pressure requirements, consult the fan manufacturer directory and select the appropriate fan model.

[0092] Example 1:

[0093] (1) For vertical reinforced concrete circular silos with a diameter (d) of 6–12 m and a grain pile height (h) of 26–50 m, four semi-circular air ducts with a radius of 0.3–0.5 m are evenly arranged along the height direction on the inner wall of the silo (e.g., Figure 1The ventilation ducts (A, B, C, and D) are made of 1.5–2 mm thick cold-rolled high-quality perforated plate. The size of the perforations is limited to prevent grain leakage, and the perforation type is a bridge-type double-hole type with an opening rate of 25%–30%. Each section of the ventilation duct is 1 m long, of uniform specifications, and fixed together. They are installed in place according to requirements before loading grain into the circular silo. Ventilation ducts A, B, C, and D can be connected to small-power axial flow fans or centrifugal fans A, B, C, and D respectively through ventilation openings.

[0094] (2) Select a fan type that ensures uniform temperature and ventilation after loading the grain. When the circular silo is designed with d = 8m and h = 30m, and is filled with grade II wheat (bulk density 770kg / m³),... 3 The weight is 1161 tons. A 6(m) millimeter diameter is used. 3 / h) / t of unit ventilation volume, the effective ventilation length of the grain stack bed is 8m×0.6 (horizontal airflow coefficient)=4.8m. Figure 3 This refers to the static pressure and fan power requirements of a ventilated wheat grain pile at different airflow rates (grain pile density 830 kg / m³). 3 (The fan's static efficiency is 50%). Figure 3 The static pressure is 0.36 kPa, and the estimated power is approximately 0.13 kW / 100 t. For the entire grain pile, this translates to 0.13 kW / 100 t × 1161 t = 1.5 kW. At 6 (m 3 When the ventilation volume is / h) / t, the total ventilation volume for 1161t of wheat is 6966m³. 3 / h. The selection of a fan should be made by consulting the fan manufacturer's catalog for airflow rates and calculating the static pressure. When the fan efficiency is approximately 50%, a ventilation volume of 6966m³ / h is suitable. 3 At 0.36 kPa, the fan power should be close to 1.5 kW. Referring to Table 1, a fan with a power of 2.24 kW, a diameter of 45.7 cm, a speed of 3500 rpm, and an air volume of 7815 m³ / h can be selected. 3 One axial flow fan with a capacity of 1.24kW / h, or a power of 2.24kW, a speed of 1750rpm, and an air volume of 7340m³ / h. 3 One low-speed centrifugal fan with a speed of / h. This fan is connected to the air intake duct A, while the other ducts B, C, and D serve as exhaust ducts and do not require connection to ventilation fans.

[0095] If local low-temperature weather conditions are rare, then 12 (m) should be used. 3 / h) / t unit ventilation volume, 8m × 0.6 (horizontal airflow coefficient) = 4.8m is the effective ventilated grain stack length. (Check...) Figure 3 The static pressure is approximately 0.48 kPa, the estimated power is approximately 0.3 kW / 100 t, and the total power required for the entire grain pile is 3.5 kW. At 0.48 kPa, the required total gas flow rate is 12 × 1161 t = 13932 m³ / t. 3 / h. Referring to Table 1, you can select a power of 3.73kW, a diameter of 61cm, a rotation speed of 3500rpm, and an air volume of 15291m³ / h. 3 One axial flow fan with a capacity of / h. This fan is connected to the intake duct A, while the other ducts B, C, and D serve as exhaust ducts and do not require connection to ventilation fans.

[0096] When a circular silo is designed with d = 12m and h = 50m, and filled with secondary corn (bulk density 690kg / m³) 3 The amount is 3900 tons. For 6 (m 3 / h) / t of unit ventilation volume, the effective ventilation length of the grain stack bed is 12m×0.6 (horizontal airflow coefficient)=7.2m. Figure 4 Static pressure and fan power requirements for ventilated corn piles at different airflow rates (bulk density 764 kg / m³) 3 (The fan's static efficiency is 50%). Figure 4 In the middle, the static pressure is 0.18 kPa, and the estimated power is about 0.06 kW / 100t, which translates to 0.06 kW / 100t × 3900t = 2.34 kW for the entire grain pile. At 6 (m 3 When the ventilation volume is / h) / t, the total ventilation volume for 3900t corn is 23400m³. 3 / h. When the fan efficiency is approximately 50%, then for a total ventilation volume of 23400m³ / h. 3 At 0.18 kPa, the fan power should be close to 2.34 kW. Referring to Table 1, a fan with a power of 3.73 kW, a diameter of 61 cm, a speed of 3500 rpm, and an air volume of 17840 m³ / h can be selected. 3 Two axial flow fans with a capacity of / h are connected to the intake ducts A and C respectively, while the exhaust ducts B and D do not require fan connection. Figure 5 ).

[0097] Based on the limited local low-temperature weather conditions, 12 (m) was adopted. 3 / h) / t unit ventilation volume, 12m × 0.6 (horizontal airflow coefficient) = 7.2m is the effective ventilated grain stack length. (Check...) Figure 4 The static pressure is approximately 0.25 kPa, the estimated power is approximately 0.17 kW / 100 t, and the total power required for the entire grain pile is 6.63 kW. At 0.25 kPa, the required total ventilation volume is 12 × 3900 t = 46800 m³. 3 / h. Referring to Table 1, you can select a power of 7.46kW, a diameter of 66cm, a speed of 3500rpm, and an air volume of 26335m³ / h. 3 Two axial flow fans with a capacity of / h are connected to the intake ducts A and C respectively, while the exhaust ducts B and D do not require fan connection. Figure 5 ).

[0098] Table 1. Performance data of ventilation fans (static pressure)

[0099]

[0100] (3) Ventilation scheme optimization

[0101] When a single fan is used for forced ventilation, the diagram of isobars on the cross-section of the silo is as follows: Figure 5 Where A is the intake duct and C is the exhaust duct, static pressure is expressed in inches of water column, 1 inch of water column equals 0.322 Pa. The static pressure gradually decreases from the air inlet to the outlet. The ventilation dead zone is the fan-shaped area along the air outlet end, such as... Figure 6 The shaded area. The solution is to use A as the exhaust duct and C as the intake duct during the latter half of the cooling and ventilation process.

[0102] When two fans are used for forced ventilation, the isobaric diagram of the airflow on the cross section of the silo is as follows: Figure 7 Where A and C are the intake air ducts, and B and D are the exhaust air ducts. From the air inlet to the outlet, the static pressure gradually decreases, and the ventilation dead zone is the area along the diameter BD, as shown below. Figure 8 The shaded area. The solution is to use A as the air intake duct and B, C, and D as the exhaust ducts during the first half of the cooling and ventilation period. During the second half of the cooling and ventilation period, C will be the air intake duct and A, B, and D will be the exhaust ducts.

[0103] Example 2:

[0104] A reinforced concrete circular silo with a diameter of 7.6m and a height of 30m was used to determine the static pressure and fan power requirements for a crossflow ventilation fan system for a 1000t grain pile. Four equally spaced vertical air ducts were used for crossflow ventilation, with alternating air supply ducts. One requirement was a 6m and 12m diameter silo for the wheat grain pile. 3 The design of the fan is / h / t. Secondly, for these two types of crossflow ventilation, the static pressure and power of the push-pull type and the full-deep-bed type crossflow ventilation for wheat grain piles are compared.

[0105] Method: Using Figure 9 , Figure 10 The system employs a four-duct crossflow ventilation system, with one duct serving as the air inlet and the other three as the exhaust outlets. For airflow from two adjacent ducts, the airflow distance varies from 0.75D to 0.9D (where D is the bin diameter), while the longest path to the opposite duct is 1.0D to 1.3D. For approximate calculations, it is assumed that the ventilation ducts are flush with the bin walls, and that the average airflow distance for all three exhaust ducts is 1.0D, or 7.6m.

[0106] For small-grain grains like wheat, the drag on the horizontal component of airflow is... Figure 7 (Note: Bulk density 0.83t / m³) 3(Fan static efficiency 50%), check the 7.6m distance of the wheat grain pile deep bed and multiply by the static pressure or airflow resistance coefficient of 0.6. From Table 1, select 6 and 12 (m) for wheat. 3 / h) / t Fan type and size.

[0107] (1) Crossflow ventilation: for 6 (m 3 / h) / t of ventilation volume, the effective depth of the grain pile bed is 7.6m×0.6 (horizontal airflow coefficient)=4.6m. Figure 7 In the middle, the static pressure is 0.33 kPa, and the estimated power is about 0.13 kW / 100t, which translates to 0.13 kW / 100t × 1000t = 1.3 kW for the entire grain pile. At 6m... 3 When the unit ventilation volume is / h / t, the total ventilation volume for 1000t wheat is 6000m³. 3 / h. The selection of a fan should be made by consulting the fan manufacturer's catalog for ventilation capacity and calculating the static pressure. If the fan efficiency is approximately 50%, then for a 6000m³ / h fan... 3 At 0.33 kPa, the fan power should be close to 1.3 kW.

[0108] With 12m 3 With a unit ventilation volume of / h / t, 7.6m × 0.6 (horizontal airflow coefficient) = 4.6m is the effective grain pile depth. Figure 7 The static pressure is approximately 0.45 kPa, the estimated power is approximately 0.3 kW / 100 t, and the total power required for the entire grain pile is 3.0 kW. At 0.45 kPa, the required total gas flow rate is 12 × 1000 t = 12000 m³. 3 / h.

[0109] (2) Compared with push-pull ventilation fans perpendicular to the grain pile

[0110] At a unit ventilation volume of 6 (m) 3 When the grain pile depth is 30 / 2 = 15m and the grain mass is 1000t, a push-pull cooling and ventilation system is designed. Figure 7 The total ventilation volume of the wheat grain pile is 6000m³. 3 The required static pressure is 1.55 kPa at a grain pile depth of 15 m. The estimated power is approximately 0.50 kW / 100 t, with a total power of 5 kW, achieved by two 2.5 kW blowers.

[0111] At a unit ventilation volume of 12 (m³) 3 When / h) / t, from Figure 7 The total ventilation volume of the wheat grain pile is 12000m³. 3 / h, requiring 3.13kPa at a grain pile depth of 15 meters. Estimated power is approximately 2.0kW / 100t, with a total power of 20kW, consisting of two 10kW blowers.

[0112] (3) Comparison with vertical grain pile full-depth ventilation fans

[0113] At a unit ventilation volume of 6 (m) 3 When / h) / t, from Figure 7 The total ventilation volume of the wheat grain pile is 6000m³. 3 At a depth of 30m in a grain pile, the airflow requires 5.86kPa per hour. The estimated power is approximately 2.0kW / 100t, with a total power of 20kW. This exceeds the rated fan pressure rating in the ventilation monograph table, but there are fans on the market with pressures higher than those described in the ventilation monograph table.

[0114] At a unit ventilation volume of 12 (m³) 3 In the case of / h) / t, with 12(m 3 A ventilation depth of 30m for wheat is impractical. The fan and static pressure requirements exceed practical limitations.

[0115] The comparison of the three scenarios above shows that in a silo with a diameter of 7.6m and a height of 30m, crossflow ventilation has great potential to improve the cooling rate of tall grain piles in silos or high-plated steel silos while maintaining low operating costs. For slender grains, such as wheat, horizontal airflow ventilation effectively reduces static pressure by about 40% compared to vertical ventilation for the same grain type and pile depth. Slender grains tend to align horizontally along their long axis, which reduces horizontal airflow resistance. However, for generally spherical grains like soybeans, sorghum, and millet, there is no significant difference in static pressure between horizontal and vertical airflow. The packing factor is the main difference between horizontal and vertical airflow for round grains.

[0116] Table 2 Comparison of fan power and static pressure for three ventilation methods in a 30mm high wheat grain pile inside a silo

[0117]

[0118] Table 2 summarizes the results of the above examples. (With 6 (m) 3 For cross-flow ventilation of wheat at a unit ventilation volume of / h) / t, at the same airflow rate as vertical push-pull ventilation, only about 1 / 5 of the fan power and static pressure are required. (The last part, "12(m"), appears to be an unrelated fragment and is omitted from the translation.) 3 For wheat grain piles with airflow of / h) / t, the required fan power and static pressure for in-line or push-pull vertical ventilation are about 7 times that of the same wheat grain pile using crossflow ventilation.

[0119] When using 6m 3 When using full-depth forced-in or forced-out ventilation with a / h / t airflow, the selected fan power and the unit ventilation volume of 12 (m³) 3The 12(m²) / t push-pull ventilation is almost identical, but the static pressure is increased by 87%. From a practical point of view, using 12(m²) / t... 3 The power and static pressure required for the airflow are too high to push air through a 30m wheat pile, although this is physically possible. Therefore, using only fans at significantly higher pressures than 6m is insufficient, whether at the bottom or top of the grain silo. 3 It seems impractical to perform full-depth vertical ventilation with a unit ventilation volume of / h) / t.

[0120] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A method for cooling and ventilating grain piles in a vertical warehouse, characterized in that, The system includes a vertical storage silo, a first fan, a second fan, a third fan, and a fourth fan. The storage silo is a reinforced concrete silo with a diameter of 6-12 meters and a grain pile height of 26-50 meters. Four longitudinally distributed air ducts are evenly arranged along the height of the cylindrical inner wall of the storage silo, and are respectively labeled as air duct A, air duct B, air duct C, and air duct D in a clockwise direction around the circumference. Air ducts A and C are two opposing air intake ducts, and air ducts B and D are two opposing air exhaust ducts. The first and second fans are located at the bottom of the storage silo, and the third and fourth fans are located at the top of the storage silo. The first, second, third, and fourth fans are respectively connected to air ducts A, B, C, and D. The air intake duct and the air exhaust duct are perforated plates, and the diameter of the perforations is smaller than the minimum particle size of the grain. The air duct A or air duct C is used alternately as the air intake duct, and the ventilation method includes: Step 1: Load the grain into the warehouse, and select a fan type that provides uniform temperature and ventilation after loading. Step 2: Turn on the first fan and turn off the third fan. At this time, air duct A serves as the air intake channel and air duct C serves as the exhaust channel and leads to the atmosphere. Low-temperature cold air enters the interior of the warehouse through air duct A, enters the interior of the grain pile laterally from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot airflow to be discharged from the warehouse through air ducts B, air duct C, and air duct D, and ventilation is carried out for time t1. Step 3: Turn off the first fan and turn on the third fan. At this time, air duct A serves as the exhaust channel and opens to the atmosphere, while air duct C serves as the air intake channel. Low-temperature cold air enters the interior of the warehouse through air duct C, enters the interior of the grain pile laterally from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot airflow to be discharged from the warehouse through air ducts A, B, and D, and ventilation is carried out for time t2. Step four, repeat steps two and three.

2. The method for cooling and ventilating grain piles in a vertical warehouse according to claim 1, characterized in that, The straight-line distance between the centers of the two air intake ducts is 1.0 times the diameter of the warehouse; the distance from the air intake duct to the two exhaust ducts is 0.7 times the diameter of the warehouse.

3. The method for cooling and ventilating grain piles in a vertical warehouse according to claim 1, characterized in that, The intake and exhaust ducts have the same dimensions; The cross-sectional shape of the air intake duct and the air exhaust duct is a semi-circular duct with a radius of 0.3 to 0.5 m. The material is a 1.5 to 2 mm thick cold-rolled perforated plate, and the hole type is a bridge-type double hole with an opening rate of 25% to 30%.

4. The method for cooling and ventilating grain piles in a vertical warehouse according to claim 1, characterized in that, The first, second, third, and fourth fans are centrifugal fans.

5. The method for cooling and ventilating grain piles in a vertical warehouse according to claim 1, characterized in that, The first, second, third, and fourth fans are axial flow fans.

6. The method for cooling and ventilating grain piles in a vertical warehouse according to claim 1, characterized in that, On air duct A and air duct C, a vent and a cover are respectively provided on the side near the first fan and the third fan; The air ducts A, B, C and D are all composed of multiple air duct units, which are fixedly connected to each other, and each air duct unit is 1m long.

7. The method for cooling and ventilating grain piles in a vertical warehouse according to claim 1, characterized in that, Negative air pressure is set on air duct A or air duct C, while the other three air ducts serve as air intake supply ducts.

8. The method for cooling and ventilating grain piles in a vertical warehouse according to claim 1, characterized in that, Between step one and step three, the following steps are also included: Turn on the first and third fans. At this time, air ducts A and C are used as air intake channels. Low-temperature cold air enters the interior of the warehouse through air ducts A and C respectively, enters the center of the grain pile from the side of the grain pile, comes into contact with the hot air inside the grain pile, and pushes the hot air flow to turn to air ducts B and D to be discharged outside the warehouse, and ventilation is carried out for time t1.

9. A method for selecting ventilation fans for vertical grain stacks in warehouses, characterized in that, The cooling and ventilation method for vertical grain piles in a warehouse as described in claim 1, wherein the fan selection method includes: Step 1: Determine the ventilation volume of the cooling and ventilation unit based on local autumn and winter cold weather conditions and working requirements: Determine the relevant parameters of the warehouse and grain pile; Step 2: Determine the effective ventilation bed length and static pressure; Step 3: Estimate fan power: Calculate the total power requirement based on the weight of the grain pile and the power requirement per unit area; Step 4: Select the fan model: Based on the ventilation volume and static pressure requirements, consult the fan manufacturer catalog and select the appropriate fan model.

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