NL2032848B1

NL2032848B1 - Ventilation system with cooling wall for grain pile

Info

Publication number: NL2032848B1
Application number: NL2032848A
Authority: NL
Inventors: Guo Zhenqi; Ding Chao; Huang Lisong; Chang Le; Zhao Siqi; Liu Qiang
Original assignee: Nanjing Univ Of Finance & Economics
Priority date: 2022-06-28
Filing date: 2022-08-24
Publication date: 2024-01-16

Abstract

Disclosed is a ventilation system with a cooling wall for a grain pile. The ventilation. systenl includes several air conditioners, where a lower ventilation ground cage with a sector—shaped cross section and an upper ventilation ground cage with a semicircular 5 cross section are provided; a cambered surface of the upper ventilation ground cage consists of a first cambered surface and a second, cambered, surface, and, the second, cambered, surface and a cambered surface of the lower ventilation ground cage are provided with openings and form a double—layer annular ventilation duct; 10 and the upper ventilation ground cage and the lower ventilation ground cage are connected to an air supply pipe and an air return pipe of the air conditioner respectively to form a cooling air internal circulation pipe network. The system. can effectively solve the problem of storage loss at a high temperature.

Description

VENTILATION SYSTEM WITH COOLING WALL FOR GRAIN PILE

TECHNICAL FIELD

The present invention belongs to the technical field of grain storage, and particularly relates to a ventilation method and sys- tem with a cooling wall for a granary.

BACKGROUND ART

Low-temperature grain storage, recognized as a green storage technology in modern storage technology, uses a natural cold source in a low temperature season or a grain cooler to cool a grain pile in a warehouse, so as to keep grains at a low tempera- ture (an overall average grain temperature is less than 15°C, a local maximum temperature is not more than 20°C), which is condu- cive to delaying grain aging and quality deterioration, and inhib- iting the occurrence and development of worms. There has been 265 green low-temperature grain depots built in Sichuan Province, with a storage capacity of 6.41 million tons, which basically achieves the full coverage of the reserves; Henan Province has promoted the construction of high-standard granary and green storage facili- ties, and has successively constructed low-temperature warehouse with a storage capacity of 3.69 million tons; and jiangsu Province has made full efforts to promote the construction of high-quality grain projects to achieve a low-temperature and quasi-low- temperature grain storage capacity of 20.99 million tons. It can be seen that the low-temperature grain storage technology has been gradually promoted and popularized in China, and achieves a desir- able grain storage effect.

However, in the actual implementation of low-temperature grain storage, it is found that when a high temperature environ- ment is above 30°C in summer, continuous heat transfer of an outer wall of the granary and poor local ventilation causes the tempera- ture rise of the grains close to the wall and the local grains, and further causes the problem of "colder center and hotter skin", and when the temperature of the grains close to the wall increased to a certain value and maintained high, it would spread to other grains around, causing insect pests, mildew, dewfall and other problems, which seriously threatened the safety of grain storage.

Therefore, how to effectively solve the problem of "colder center and hotter skin" is a technical bottleneck to be solved urgently in the field of low-temperature grain storage.

In order to solve the above problems, a traditional method generally prolongs a ventilation time or increases ventilation power for cooling, however, such method causes increased energy consumption and poor cooling effect on the grains close to the wall of the granary. For example, disclosed in a Chinese patent with Application No: 201110152852.9 are a method and system for stratified ventilation in a granary, in which some horizontal ven- tilation channels are provided on the ground of the granary and inside a grain pile, so as to improve a cooling effect of the grain pile and a drying effect in the granary; disclosed in a Chi- nese patent with Application No: 201510608233.4 are a ventilation system and method for a granary, in which parameters of tempera- ture and humidity inside the granary, and temperature and humidity of air inside and outside the granary are detected, and a control module is used to regulate an opening timing of a fan, so as to regulate a temperature of the granary; disclosed in a Chinese pa- tent with Application No: 201610259887.5 is a transverse circula- tion ventilation device, in which horizontal and vertical air channels and circulation air channels are arranged, and a princi- ple of transverse ventilation is used to adjust and reduce a tem- perature of a grain pile; and disclosed in a Chinese patent with

Application No: 202122018722.8 is a ventilation device for a low- temperature grain storage, in which global and local grain temper- ature is regulated by means of detection of a temperature and hu- midity sensor and opening and closing of an air valve controlled by an air channel. However, the above patents do not aim at tem- perature reduction of the wall of the granary, the grains close to the granary wall cannot be ventilated well, there is a certain ventilation dead angle, the grain close to the wall still rises quickly with the increase of the outdoor environment temperature, and simply increasing the ventilation time has a poor effect on solving the problem of "colder center and hotter skin".

SUMMARY

An objective of the present invention is to provide a venti- lation method and system with a cooling wall for a grain pile, so as to cooling grains close to a granary wall, and further to solve the problem that an existing ventilation system for a granary can- not effectively solve storage loss caused by a "colder center and hotter skin" phenomenon of storage grains under a high temperature environment.

In order to achieve the above objective, the present inven- tion uses the following technical solution:

Firstly, the present application provides a ventilation sys- tem with a cooling wall for a grain pile. The system includes sev- eral refrigeration air conditioners (preferably variable frequency air conditioners), an air supply (return) pipe out of the granary, a double-layer annular ventilation ground cage in the granary, etc.; the refrigeration air conditioner includes an air outlet pipe and an air return pipe; a circle of end-to-end lower ventila- tion ground cages is arranged along a bottom of a granary wall, a cross section of each lower ventilation ground cages is of a quad- rant-shaped sector (that is, a central angle of the sector is 90°), and two right-angled sides (that is, radius of a circumfer- ence where the sector is located) of the sector are arranged along a side wall of the granary and the ground respectively; a circle of end-to-end upper ventilation ground cages is arranged along the side wall of the granary, a cross section of each upper ventila- tion ground cage is of a semicircle (a central angle of the semi- circle is 180°), a diameter of the semicircle is arranged along the side wall of the granary, and the upper ventilation ground cage is located below a grain stacking line (an intersection line of a highest surface of the grains contained in the granary and the wall of the granary) and is 0.5 m-1 m away from the grain stacking line; a semicircular cambered surface of the cross section of the upper ventilation ground cage is integral and consists of a mount- ed upper first cambered surface and a mounted lower second cam-

bered surface; the second cambered surface is provided with uni- form openings, and the first cambered surface is provided with no opening; a cambered surface of the lower ventilation ground cage is provided with uniform openings; the upper ventilation ground cage and the lower ventilation ground cage form a double-layer an- nular ventilation pipeline in the granary; and the upper ventila- tion ground cage is connected to an air outlet pipe of the refrig- eration air conditioner by means of a hose, and the lower ventila- tion ground cage is connected to an air return pipe of the refrig- eration air conditioner by means of a hose, so as to form a cool- ing air internal circulation pipe network.

Preferably, in the ventilation system with a cooling wall for a grain pile, an opening rate of the second cambered surface of the upper ventilation ground cage and the cambered surface of the lower ventilation ground cage is 30%-35%; and the upper and lower ventilation ground cages are both preferably made of galva- nized steel plates (for example, steel plates with a model of

D¥X51D+Z), the steel plates have thickness not less than 2 mm, and the upper ventilation ground cage and the lower ventilation ground cage are fixed to the side wall of the granary by means of rivets or other conventional means.

Preferably, in the ventilation system with a cooling wall for a grain pile, perimeters of circumferences where the first cam- bered surface and the second cambered surface of the upper venti- lation ground cage are located are equal.

Preferably, in the ventilation system with a cooling wall for a grain pile, the grain pile in the granary is not lower than 6.5 m, one refrigeration air conditioner is mounted outside each of two long wall surfaces of the granary, the air conditioners are less than 2 m above the surface of grains, and air inlets and air outlets of the air conditioners are connected to the upper venti- lation ground cage and the lower ventilation ground cage respec- tively by means of hoses (preferably fully-closed heat insulation hoses).

The ventilation system with a cooling wall for a grain pile is applied in such a manner that a refrigeration function of an air conditioner is started, cooling air is pumped into a grain pile by means of an air outlet pipe and an upper ground cage, and a lower ground cage directionally sucks the cooling air into the air return pipe through a grain layer by means of negative pres- sure, so as to form a cooling-wall-type air wall isolation belt, 5 which blocks a temperature disturbance influence, caused by high- temperature heat transfer of the wall of the granary, on the grain pile. When a wall temperature is higher than 30°C in summer, the ventilation system may keep a grain storage temperature around 15°C within 0.25 m away from the wall, so as to ensure balance of an internal temperature and near-wall temperature of the grain pile, and an average grain temperature is below 15°C, so as to achieve high-efficiency, energy-saving and green low-temperature grain storage.

In comparison to existing granary ventilation systems and methods, the present invention has the advantages that: 1. The ventilation method and system provided in the present invention are more practical, and on the basis of an existing tem- perature control system for a granary, ventilation and cooling for a granary wall for the first time may effectively remove an ad- verse influence of the high temperature environment on the temper- ature disturbance of the grain pile in the granary in summer, and overcome a technical bottleneck problem, faced by the low- temperature storage technology, of the grain storage loss caused by the "colder center and hotter skin" phenomenon. 2. The present invention provides ventilation method and sys- tem that are more energy efficient. The system pumps cooling air into the grain pile by means of an upper ground cage, and a lower ground cage directionally sucks the cooling air into an air return pipe through a grain layer by means of negative pressure, so as to form a cooling-wall-type air wall isolation belt, which blocks an influence of outside high-temperature transfer on the grain tem- perature in the granary. During a storage period, annual low- temperature storage may be achieved without long-term ventilation and cooling in the grain pile, so as to effectively save energy. 3. The ventilation method and system provided in the present invention may ensure that the temperature of the grain pile is kept below 15°C all over the year, and may improve a safe moisture content of grain by 1-2%, which not only reduces a drying cost be- fore warehouse entry, but also eliminates a wetting process after warehouse exit, so as to effectively reduce storage and processing costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating mounting of a ven- tilation system with a cooling wall for a grain pile in the pre- sent invention;

FIG. 2 is a structural schematic diagram of a lower ventila- tion ground cage of a ventilation system with a cooling wall for a grain pile in the present invention;

FIG. 3 is a schematic cross-sectional view of a lower venti- lation ground cage after mounting;

FIG. 4 is a structural schematic diagram of an upper ventila- tion ground cage of a ventilation system with a cooling wall for a grain pile in the present invention;

FIG. 5 is a schematic cross-sectional view of an upper venti- lation ground cage after mounting cavity;

FIG. 6 is a graph showing changes of average grain tempera- tures at surfaces close to the granary walls (0.25 m) of a venti- lation system in the present invention and a traditional above- ground cage ventilation system over ventilation time in an envi- ronment with a high temperature of 31°C; and l-granary wall; 2-lower ventilation ground cage; 3-hose; 4 - air conditioner; 5-upper ventilation ground cage; 5-1-first cam- bered surface; 5-2-second cambered surface; 6-opening; and 7- ground.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical solutions of the present invention will be de- scribed below in detail in conjunction with the accompanying draw- ings, and the embodiments described are merely some of the embodi- ments of the present invention. Based on the embodiments of the present invention, all other embodiments acquired by those of or- dinary skill in the art without making creative efforts fall with- in the scope of protection of the present invention.

This embodiment provides a ventilation system with a cooling wall for a grain pile. FIG. 1 is a structural schematic diagram of a granary ventilation system provided in an embodiment of the pre- sent invention. As shown in FIG. 1, the granary ventilation system provided in the embodiment includes a variable frequency refriger- ation air conditioner, an air supply pipe out of the granary, an air return pipe out of the granary, and a double-layer annular ventilation ground cage in the granary. An annular lower ventila- tion ground cage 2 is arranged along a granary internal wall at a bottom of the granary (as shown in FIG.2}), a cross section of the lower ventilation ground cage 2 is of a quadrant-shaped sector, and two right-angled sides (that is radius of a circumference where the sector is located) of the sector are arranged along a side wall of the granary and the ground respectively (as shown in

FIG. 3). A circle of end-to-end upper ventilation ground cages 5 is arranged along a side wall of the granary (as shown in FIG. 4), a cross section of each upper ventilation ground cage is of a sem- icircle, a diameter of the semicircle is arranged along the side wall of the granary (as shown in FIG. 5), and the upper ventila- tion ground cage is located below a grain stacking line (an inter- section line of a highest grain loading surface in the granary and the granary wall) and is 1 m away from the grain stacking line. A semicircular cambered surface of the cross section of the upper ventilation ground cage 5 is integral and consists of a mounted upper first cambered surface 5-1 and a mounted lower second cam- bered surface 5-2, the second cambered surface 5-2 is provided with uniform openings, and the first cambered surface 5-1 is pro- vided with no opening. In this embodiment, perimeters of circum- ferences where the first cambered surface 5-1 and the second cam- bered surface 5-2 are located are equal.

The lower ventilation ground cage 2 is connected to an air return port of the refrigeration air conditioner 4 by means of an extra-wall heat insulation airflow hose 3 to form an air return pipe out of the granary; and the upper ventilation ground cage 5 is connected to an air outlet of the refrigeration air conditioner 4 by means of an extra-wall heat insulation airflow hose 3 to form an air supply pipe out of the granary, and the two pipes form a cooling air internal circulation pipe network together.

In this embodiment, the lower ventilation ground cage 2 and the upper ventilation ground cage 5 are both made of galvanized steel plates with a model of DX51D+Z, the thickness is 2 mm, an opening rate of the second cambered surface 5-2 and a cambered surface of the lower ventilation ground cage 2 is 30%, and an ap- erture of each opening is 2.5 mm.

In this embodiment, a large warehouse (24 m * 30 m) of a grain storage depot in Nanjing is selected, the granary is 10 m high, and a grain pile in the granary is 7m high. One refrigera- tion air conditioner 4 is mounted on each of two long side walls 1 of the granary, the type of the refrigeration air conditioners is

MDB224WP, power of a single air conditioner is configured to be 22.4 kW, an air volume is 4000 m’/h, an output air temperature is set to be 14°C, and the refrigeration air conditioner is 8.5 m from the bottom of the granary.

In this embodiment, the extra-wall heat insulation airflow hoses 3 connecting the ventilation ground cages and the air inlet and outlet of the air conditioner are steel-wire-skeleton rubber telescopic hoses, manufactured by Hebei Biaohui Rubber and Plastic

Products Co., Ltd., with a model of DN40-DN1600 and a thickness of 3 mm, and outer layers of the hoses are completely wrapped in heat insulation asbestos (air conditioning pipe).

The ventilation system runs as follows: cooling air is pumped into a grain pile by means of an air outlet pipe of an air condi- tioner and an upper ground cage 5, and a lower ground cage 2 di- rectionally sucks the cooling air into the air return pipe through a grain layer by means of negative pressure, so as to form a cool- ing-wall-type air wall isolation belt, which blocks a temperature disturbance influence, caused by high-temperature heat transfer of the wall of the granary, on the grain pile, such that the ventila- tion system keeps a grain storage temperature around 15°C within 0.25 m away from the wall all year round, and an overall grain temperature is below 15°C, so as to achieve high-efficiency, ener- gy-saving and green low-temperature grain storage.

A comparison of running parameters of the ventilation system in this embodiment with those of a conventional ventilation system is as shown in Table 1 below:

Table 1 Spatial distribution of temperature of grain pile in granary after using embodiment ventilation system and traditional ventilation system under high temperature environment entilation type raditional ventilation system [Embodiment ventilation system

First layer Us OP 23.6 14,9

Average grain temperature/°C 25.6 59 7 14.3 9.5

Note: a measurement time of temperature data in the table is

July 23, 2021, and a measurement location is a large warehouse (24 m * 30 m) of a grain storage depot in Nanjing, with an air- conditioning outlet temperature at 14°C; where the grain layer is divided according to: a first layer (0.5 m below a grain surface), a second layer (2 m below the grain surface), a third layer (3.5 m below the grain surface), a fourth layer (5 m below the grain sur- face) and a fifth layer (6.5 m below the grain surface); the grain temperature is measured by means of a temperature measuring cable embedded in the grain pile, a distance between every two adjacent temperature sensors on the temperature measuring cable is 1.5 m, and a measuring accuracy error of grain temperature is 0.5°C; a layout of the temperature measurement cables is: six sets of tem- perature measuring cables are arranged in sequence with a longitu- dinal span (24 m length direction) and numbered 1, 2, 3, 4, 5 and 6 in sequence, and adjacent temperature measuring points are sepa- rated by 4.8 m in transverse direction (30 m span direction) and by 4.6 m in longitudinal direction (24 m span direction); and in a ventilation process, the temperature of grain condition is detect- ed every 3 hours, and temperature data in the table contain high- est, lowest and average temperature of each grain layer in one day.

Table 1 shows statistical results of the spatial distribution of the temperatures of the grain pile in the granary after using the ventilation system of this embodiment (only the embodiment ventilation system is started without other additional ventilation and cooling system) and a traditional above-ground cage ventila- tion system under the environment at a high temperature (higher than 31°C). It can be seen from Table 1 that the ventilation sys- tem of the present invention may ensure that the grain temperature in the granary is lower than 15°C under a high temperature envi- ronment in summer, a maximum temperature is not higher than 15°C, a temperature difference between layers of grains and a tempera- ture difference in each layer are low, and the grain temperature in the granary as a whole is balanced. However, for the tradition- al ventilation system under a high temperature environment in sum- mer, it is difficult to ensure a low temperature grain storage re- dquirement that the grain temperature is lower than 15°C, the tem- perature difference in the layer is high, a maximum temperature is above 23°C, and it is difficult to ensure the safety of grain storage.

As shown in FIG. 6, a graph showing changes of average grain temperatures at surfaces close to granary walls (0.25 m) of a ven- tilation system in the present invention and a traditional above- ground cage ventilation system (that is, a system disclosed in literature “Liu Qiang. Simulation and Optimization of Mechanical

Ventilation Process for Grain Storage in Large Warehouse [D]. Nan-

Jing: nanjing University of Finance and Economics, 2016.) over ventilation time in an environment at a high temperature of 30°C.

It can be seen from the figure that in the ventilation system in the present invention, the average grain temperature at the sur- face close to the granary wall (0.25 m) may be reduced from 28.5°C to less than 15°C within 100 hours of continuous ventilation, while the grain temperature at the surface close to the granary wall in the traditional ventilation system is still at a high lev- el, and it needs more than a multiple of ventilation time to re- duce the grain temperature to less than 15°C. It can be seen that the ventilation system in the present invention may effectively reduce the grain temperature at a surface close to the granary wall in a high-temperature environment and shorten the ventilation time. In addition, when the air conditioner of the ventilation system in the present invention is configured to be 44.8 kW, the average grain temperature at the surface closed to the granary wall (0.25 m) may be less than 15°C within 100 h, which is equiva- lent to 4480 kW.h of energy consumption, while the traditional above-ground cage ventilation system is configured to be 60.0 kW, the average grain temperature at the surface closed to the granary wall (0.25 m) may be less than 15°C within 200 h and more, which is equivalent to 12000 kW.h of energy consumption. Therefore, the ventilation system in the present invention may reduce 62.7% of energy consumption, which has a significant energy saving ad- vantage.

Although the implementation mode and a working effect of the present invention are described above in detail, the present in- vention is not limited to the above implementation mode, and for those ordinary skilled in the art, after learning the contents contained in the present invention, various modifications, equiva- lents, and improvements made within the spirit and principles of the present invention and without departing from the principles of the present invention should be included within the scope of pro- tection of the present invention.

Claims

CONCLUSIONS

A grain stack cooling wall ventilation system comprising a plurality of air conditioners, the ventilation system comprising a circle of continuous lower ventilation cages along a bottom of a granary wall, a cross-section of each lower ventilation cage being of a quadrant-shaped sector; a circle of continuous upper ventilation cages is provided along a side wall of the granary, a cross-section of each upper ventilation cage is a semicircle, and the upper ventilation cages are located below a grain loading line; a domed surface of the upper ventilation cage is integral and consists of an upper first domed surface and a lower second domed surface, and the second domed surface has an opening; wherein a curved surface of the lower ventilation cage is provided with an opening; and wherein the upper ventilation cage is connected to an air exhaust pipe of the air conditioner, and wherein the lower ventilation cage is connected to an air return pipe of the air conditioner to form an internal circulation pipe network for cooling air.

A grain stack cooling wall ventilation system according to claim 1, wherein the upper ventilation cage supplies air in positive pressure and the lower ventilation cage draws air in negative pressure to form an insulating belt-shaped air wall with a cooling wall-like shape.

3. Ventilation system with a cooling wall for a grain stack according to claim 1, wherein the second arched surface and the arched surface of the lower ventilation cage have an opening degree of 30% to 35%.

4. Ventilation system with a cooling wall for a grain stack according to claim 1, wherein contours of peripheral edges where the first curved surface and the second curved surface are located are equal.

A grain stack cooling wall ventilation system according to claim 1, wherein the grain stack in the granary is not lower than 6.5 m, and the air conditioner is located less than 2 m above a surface of grains.

A grain stack cooling wall ventilation system according to claim 1, wherein the upper ventilation cage is 0.5 m to 1 m away from a grain stack line.