Temperature and humidity controlled multifunctional grain air conditioning system and control method thereof

Abstract

The application provides a temperature and humidity controlled multifunctional grain air conditioning system and a control method thereof. The system comprises a refrigeration cycle unit, a supply air unit, a double-path air inlet switching unit, a temperature and humidity detection unit, a humidification unit, a variable frequency control unit and a control unit. The system is provided with three operation modes of grain pile cooling, grain surface cooling and natural ventilation. The control unit adjusts the air volume and pressure working condition of the centrifugal fan, the opening degree of the return air butterfly valve and the fresh air butterfly valve and the start and stop of the refrigeration cycle according to the mode switching instruction, so that the air inlet source is all outdoor fresh air, all indoor return air or a mixture of the two. The application integrates the functions of the grain cooler, the grain air conditioner and the ventilator in one device, and can simultaneously adjust the temperature and humidity in the grain depot, thereby better storing the grain.

Description

Technical Field

[0001] This invention relates to the field of low-temperature grain storage technology, and in particular to a multifunctional grain air conditioning system with temperature and humidity control and its control method. Background Technology

[0002] If grain is stored in granaries for extended periods without proper air conditioning, the sealed environment can create a hotter and more humid environment than the outside, fostering the growth of pests and diseases and potentially causing the grain to rot. When the temperature drops below 15℃-20℃, the development of eggs from common grain storage pests slows down significantly or even stops, reducing the hatching rate.

[0003] Low-temperature grain storage is a grain storage technology that maintains the temperature inside the grain warehouse at 15℃ or below for a long period of time. Because it can reduce the use of chemical fumigation (spraying of pesticides), low-temperature grain storage is currently recognized as a safe, reliable and environmentally friendly grain storage technology. It can effectively inhibit the growth of pests and diseases, reduce the metabolism of grain, delay the aging of grain, and keep it as fresh as possible.

[0004] Existing low-temperature grain storage equipment mainly includes grain coolers, grain air conditioners, and ventilators. Grain coolers are primarily used for localized or whole-warehouse heat treatment of newly arrived grain, locally heated grain, and grain with overall high temperatures. Grain air conditioners mainly regulate the air in the upper space above the grain in the grain silo. Ventilators are mainly used to directly introduce outside air into the grain silo for ventilation and cooling when the ambient temperature is low in winter. Currently, the operating mode of the low-temperature grain storage system is as follows: When new grain is delivered in spring and summer, grain coolers are used to lower the overall temperature inside the silo to the storage conditions, and then grain air conditioners are turned on to control the temperature of the upper space above the grain to maintain the storage temperature as much as possible. If the external heat load is too high and the temperature cannot be maintained, the grain coolers need to be turned on for overall cooling. When the ambient temperature is low in autumn and winter, only the ventilators are turned on to introduce air into the silo to achieve the effect of low-temperature grain storage. In particular, since most grain depots are only equipped with one grain cooler, it needs to be moved to different grain silos for use when needed. This operation requires a lot of manpower and resources for equipment deployment, operation, and maintenance.

[0005] Furthermore, most existing grain air conditioners use fixed-frequency compressors and fans that cannot adjust their operation according to environmental changes, resulting in high energy consumption. They only lower the temperature to a low-temperature storage range but cannot regulate humidity, and some even lack the ability to detect humidity levels within the grain silo. However, the humidity of the storage environment has a significant impact on grain. Too low humidity causes internal moisture loss during grain metabolism, leading to aging and weight loss during storage; while too high humidity may promote microbial growth, causing mold growth. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a multifunctional grain air conditioning system and its control method that controls temperature and humidity. This system can switch modes and integrate the functions of a grain cooler, a grain air conditioner, and a ventilator into a single device, saving initial investment and reducing the operating cost of low-temperature grain storage systems. Furthermore, it can simultaneously regulate the temperature and humidity within the grain silo for better grain storage.

[0007] A multi-functional grain air conditioning system with temperature and humidity control, the system comprising a refrigeration cycle unit, the refrigeration cycle unit comprising at least a compressor, an evaporator, a condenser, and an electronic expansion valve; the system further comprising: The air supply unit includes a centrifugal fan disposed on the evaporator side and a PID regulating fan frequency converter connected thereto. The PID regulating fan frequency converter is used to control the operating conditions of the centrifugal fan, and the operating conditions include at least one of the centrifugal fan's air volume, air pressure, and air speed. The dual-inlet air switching unit includes a return air inlet connected to the inside of the grain silo, a fresh air inlet connected to the outside environment, and a return air butterfly valve and a fresh air butterfly valve respectively installed at the return air inlet and the fresh air inlet. The temperature and humidity detection unit includes at least an ambient temperature sensor for detecting the outside temperature, a return air temperature and humidity sensor for detecting the return air temperature and humidity inside the grain silo, and a supply air temperature and humidity sensor for detecting the treated supply air temperature and humidity. A humidification unit, including a humidifier and a water supply device for supplying water to the humidifier; A variable frequency control unit, including a compressor inverter connected to the compressor; The control unit is configured to switch between grain pile cooling mode, grain surface cooling mode, and natural ventilation mode based on mode switching commands. In the grain pile cooling mode, the centrifugal fan is controlled to operate under high air volume and high air pressure conditions, the return air butterfly valve is closed and the fresh air butterfly valve is fully opened, so that the incoming air is all outdoor fresh air. In the grain surface cooling mode, the centrifugal fan is controlled to operate in a low air volume and low air pressure condition, the return air butterfly valve is fully opened and the fresh air butterfly valve is closed, so that the incoming air is the return air of the whole room; In the natural ventilation mode, the refrigeration cycle is turned off, the centrifugal fan is controlled to operate under high air volume and high air pressure conditions, the return air butterfly valve is closed, and the fresh air butterfly valve is fully opened to make the incoming air all outdoor fresh air. Furthermore, the control unit is also configured to adjust the speed of the compressor, the speed of the centrifugal fan, and the start / stop of the humidifier based on the data fed back by the temperature and humidity detection unit.

[0008] Preferably, the water supply device of the humidification unit includes a water receiving tray, which is located below the evaporator and is used to collect condensate; the humidifier is installed in the water receiving tray.

[0009] Preferably, the water receiving tray is provided with a drain outlet and an external water supply interface, so that water can be supplied to the water receiving tray through the external water supply interface when the condensate is insufficient.

[0010] Preferably, the condenser side is provided with an EC fan, which is a variable frequency fan.

[0011] Preferably, a low-pressure intake side inspection valve, an intake temperature sensor, and an intake pressure sensor are provided on the low-pressure intake pipe side of the system; an exhaust pressure sensor and an exhaust temperature sensor are provided on the high-pressure exhaust pipe side; a high-pressure liquid pipe side inspection valve, a condensation pressure sensor, and a condensation temperature sensor are provided on the high-pressure liquid pipe side, and a drying filter is provided before the electronic expansion valve.

[0012] Preferably, the control unit is equipped with a remote communication interface for receiving mode switching commands from the upper-level intelligent grain depot integrated system.

[0013] Preferably, the control unit is connected to a human-machine interface, which is used to display the system operating status and internal environmental parameters of the grain silo, and provides a user input interface for setting the operating mode and working parameters.

[0014] A control method for a temperature and humidity controlled multifunctional grain air conditioning system, applied to the temperature and humidity controlled multifunctional grain air conditioning system as described in any of the preceding claims, the method comprising: Receive mode switching command, operate in grain pile cooling mode, grain surface cooling mode or natural ventilation mode based on the mode switching command, and adjust the opening of return air butterfly valve and / or fresh air butterfly valve to select the ratio of indoor return air and outdoor fresh air in the air intake source.

[0015] Preferably, the method further includes: Acquire the supply air temperature and humidity detected by the supply air temperature and humidity sensor; Using the supply air temperature as the control benchmark: Based on the difference between the set temperature and the detected temperature, the compressor speed or start / stop is controlled by a PID algorithm; Based on the supply air humidity: when the dehumidification demand reaches the preset threshold and the supply air temperature meets the preset dehumidification temperature condition, the compressor is turned on for dehumidification; when the humidification demand reaches the preset threshold, the humidifier is turned on and the water in the water tray is used for atomized humidification.

[0016] The aforementioned solution, by pre-setting three operating modes—grain pile cooling, grain surface cooling, and natural ventilation—within a single air conditioning system, and utilizing a dual-intake switching unit and a centrifugal fan with adjustable airflow and pressure, allows a single device to completely replace the separate grain cooler, grain air conditioner, and ventilator required in traditional technologies, thus achieving "one machine for multiple uses." Furthermore, the system is equipped with a compressor inverter and a PID-controlled fan inverter, which dynamically adjusts the compressor speed, fan speed, and humidifier start / stop based on the supply air temperature and humidity feedback from the temperature and humidity detection unit, achieving closed-loop precise control of temperature and humidity within the grain silo. Attached Figure Description

[0017] Figure 1 This is a system block diagram of this application; Figure 2 This is a flowchart of the method in this application.

[0018] Figure label: 1. Evaporator; 2. Centrifugal fan; 3. PID regulating fan inverter; 4. Low-pressure suction side inspection valve; 5. Suction temperature sensor; 6. Suction pressure sensor; 7. Compressor; 8. Compressor inverter; 9. Discharge pressure sensor; 10. Discharge temperature sensor; 11. Ambient temperature sensor; 12. Condenser; 13. EC fan; 14. Condensation pressure sensor; 15. Condensation temperature sensor; 16. High-pressure liquid line side inspection valve; 17. Dryer filter; 18. Electronic expansion valve; 19. Return air temperature and humidity sensor; 20. Humidifier; 21. Drain tray; 22. Supply air temperature and humidity sensor; 23. Return air butterfly valve; 24. Fresh air butterfly valve. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below. Example

[0020] This embodiment discloses a multifunctional grain air conditioning system with temperature and humidity control, such as... Figure 1 As shown, the system includes a refrigeration cycle unit, an air supply unit, a dual-intake switching unit, a temperature and humidity detection unit, a humidification unit, a frequency converter control unit, and a control unit. Its specific component composition is as follows: Figure 1 The following is a detailed description of each part.

[0021] The refrigeration cycle unit includes at least a compressor 7, an evaporator 1, a condenser 12, and an electronic expansion valve 18. The compressor 7 has an exhaust pressure sensor 9 and an exhaust temperature sensor 10 on its exhaust pipe side to detect the pressure and temperature of the refrigerant in the exhaust pipe. When the exhaust pressure exceeds the set high-pressure alarm value and persists for a certain period, the system issues an alarm and shuts down for protection. The compressor 7 has a low-pressure suction side maintenance valve 4, a suction temperature sensor 5, and a suction pressure sensor 6 on its suction pipe side. The maintenance valve 4 is used for vacuuming the refrigeration system and replenishing refrigerant; the suction temperature sensor 5 and suction pressure sensor 6 are used to calculate the suction superheat and control the opening of the electronic expansion valve 18 accordingly. When the suction pressure is lower than the set low-pressure alarm value and persists for a certain period, the system also issues an alarm and shuts down. The condenser 12 side has an EC fan 13, which is a variable frequency controlled fan that automatically adjusts its speed according to the pressure value detected by the condensing pressure sensor 14: the fan starts when the condensing pressure is greater than or equal to the set opening pressure, and the higher the pressure, the higher the fan frequency, thus ensuring stable operation of the refrigeration cycle. The high-pressure liquid line is equipped with a high-pressure liquid line inspection valve 16, a condensing pressure sensor 14, and a condensing temperature sensor 15. A dryer filter 17 is also provided before the electronic expansion valve 18 to filter impurities in the pipeline and absorb moisture.

[0022] In this embodiment, the compressor 7 is connected to the compressor inverter 8, which can change the compressor's operating frequency and start / stop according to the control unit's instructions, thereby adjusting the cooling capacity output and regulating the temperature and humidity of the supplied air.

[0023] The air supply unit includes a centrifugal fan 2 located on the evaporator 1 side and a PID-regulated fan inverter 3 connected to it. The centrifugal fan 2 has a wide range of airflow and pressure performance. Its speed can be adjusted via the PID-regulated fan inverter 3 to switch between high airflow and high pressure conditions (suitable for grain pile cooling and natural ventilation modes) and low airflow and low pressure conditions (suitable for grain surface cooling modes). The PID-regulated fan inverter 3 is controlled by the control unit to precisely control the fan speed according to the control unit's instructions.

[0024] The dual-intake switching unit includes a return air inlet connected to the inside of the grain silo, a fresh air inlet connected to the outside environment, and return air butterfly valves 23 and fresh air butterfly valves 24 respectively located at the return air inlet and fresh air inlet. The ratio of indoor return air to outdoor fresh air in the intake air can be flexibly controlled by changing the opening degree of the two butterfly valves. For example, in the grain pile cooling mode with the default of all outdoor fresh air, return air butterfly valve 23 is fully closed (0% opening), and fresh air butterfly valve 24 is fully open (100% opening); in the grain surface cooling mode with the default of all indoor return air, return air butterfly valve 23 is fully open, and fresh air butterfly valve 24 is fully closed; when mixed intake air is required, any ratio can be set according to the ambient temperature and the required temperature and humidity inside the silo.

[0025] The temperature and humidity detection unit includes at least: an ambient temperature sensor 11, installed on the outdoor unit housing, for detecting the ambient temperature; a return air temperature and humidity sensor 19, located at the junction of outdoor fresh air and indoor return air, for detecting the temperature and humidity of the return air; and a supply air temperature and humidity sensor 22, installed on the outlet duct of the centrifugal fan 2, for detecting the temperature and humidity of the supply air after it has been processed by the refrigeration system. The detection data from all the above sensors are transmitted to the control unit in real time.

[0026] The humidification unit includes a humidifier 20 and a water supply device for supplying water to the humidifier. In this embodiment, the water supply device is specifically a water tray 21 located below the evaporator 1. The surface temperature of the evaporator 1 is usually lower than the air dew point temperature, and a large amount of condensate is generated during operation. The condensate flows into the water tray 21 along the evaporator fins. The humidifier 20 is installed in the water tray 21 and can atomize the water in the water tray into tiny water droplets and mix them into the airflow. The water tray 21 is provided with a drain outlet and an external water supply interface: when the condensate level exceeds the height of the drain outlet, the excess water is automatically discharged; when the condensate is insufficient and the system determines that humidification is needed, water can be added to the water tray 21 through the external water supply interface to ensure that the humidification function is normal and usable. The external water supply interface can be connected to tap water or manually added water, and the water supply can be controlled by the control unit to make or break the water supply in conjunction with a solenoid valve.

[0027] The variable frequency control unit includes the compressor inverter 8 described above, which can change the operating frequency of the compressor according to the instructions of the control unit.

[0028] The control unit connects to all the aforementioned sensors, actuators (butterfly valves, PID regulating fan inverters, compressor inverters, EC fans, humidifiers), and the human-machine interface. The control unit has preset grain pile cooling mode, grain surface cooling mode, and natural ventilation mode, and is equipped with a remote communication interface to receive mode switching commands and setting parameters from the upper-level intelligent grain depot integrated system. It also uploads system operating status, temperature and humidity data, alarm information, etc., to the upper-level system. The human-machine interface protection display screen can display a series of system operating status parameters and environmental parameters within the grain silo, including system operating status, compressor operating status and speed, centrifugal fan operating status and speed, axial fan operating status, humidifier operating status, cooling demand, dehumidification demand, humidification demand, superheat, electronic expansion valve opening, return air temperature and humidity, supply air temperature and humidity, return air butterfly valve opening, fresh air butterfly valve opening, intake temperature, exhaust temperature, high pressure, and low pressure. Users can set parameters such as operating mode, target temperature, target humidity, cooling hysteresis, dehumidification threshold, and humidification threshold through this interface.

[0029] The control unit is configured to switch between grain pile cooling mode, grain surface cooling mode, and natural ventilation mode according to received mode switching commands, and control the centrifugal fan operation, butterfly valve opening, and refrigeration cycle start / stop according to the preset logic of each mode. Simultaneously, the control unit also adjusts the compressor speed, centrifugal fan speed, and humidifier start / stop in real time based on data feedback from the temperature and humidity detection unit, thereby achieving closed-loop intelligent control of temperature and humidity within the grain silo. See Example 2 for specific control methods.

[0030] This embodiment integrates the above-mentioned units into a single device and pre-sets three dedicated operating modes, thereby realizing the functions of three independent devices: a traditional grain cooler, a grain air conditioner, and a ventilator. Example

[0031] This embodiment provides a control method for a multi-functional grain air conditioning system with temperature and humidity control based on the system described in Embodiment 1.

[0032] like Figure 2 The control unit receives mode switching instructions from the human-machine interface or remote communication interface, and operates the system according to the corresponding grain pile cooling mode, grain surface cooling mode or natural ventilation mode according to the mode switching instructions.

[0033] When the system enters the grain pile cooling mode, the control unit first activates the refrigeration cycle. The compressor inverter and EC fan operate at their initial frequencies. Simultaneously, the return air butterfly valve is fully closed and the fresh air butterfly valve is fully open, ensuring that all incoming air is fresh outdoor air. The centrifugal fan is adjusted to high air volume and high air pressure conditions via PID control of the fan inverter, ensuring that the cold air can overcome the resistance of the grain pile and enter evenly from the bottom cage of the grain silo, penetrating the entire grain pile for overall cooling of newly arrived grain or grain in a silo that is at high temperature. The supply air temperature and humidity sensor monitors the supply air parameters in real time, and the control unit adjusts the compressor speed and fan speed accordingly to gradually reduce the supply air temperature to the set value.

[0034] When the system enters the grain surface cooling mode, the control unit starts the refrigeration cycle, adjusts the return air butterfly valve to full open and the fresh air butterfly valve to full close, so that all the incoming air is indoor return air; the centrifugal fan switches to low air volume and low air pressure mode, and the air supply direction is the upper space of the grain surface to maintain the grain surface temperature.

[0035] When the system enters natural ventilation mode, the control unit shuts off the refrigeration cycle, and the compressor, EC fan and electronic expansion valve stop working, with only the air supply unit operating; the butterfly valve status is the same as the grain pile cooling mode (return air butterfly valve fully closed, fresh air butterfly valve fully open), and the centrifugal fan operates in a high air volume and high air pressure condition, directly sending low-temperature outside air into the bottom of the grain pile for ventilation and cooling.

[0036] In any of the above modes, the control unit allows the user or the host system to adjust the opening ratio of the return air butterfly valve and the fresh air butterfly valve through commands, so as to achieve mixed intake of fresh air and return air.

[0037] In grain pile cooling mode or grain surface cooling mode, since the system operates in a refrigeration cycle, the air conditioning unit needs to be controlled based on the supply air temperature and / or supply air humidity.

[0038] Temperature control is based on the supply air temperature and employs a PID algorithm. The control unit reads the supply air temperature detected by the supply air temperature and humidity sensor, as well as the user-set target temperature and cooling hysteresis temperature, and calculates the temperature deviation. When the cooling demand is ≥100%, the inverter compressor 7 starts; when the controlled temperature is ≤set temperature - set cooling hysteresis temperature, and the cooling demand is ≤0%, the compressor stops. The centrifugal fan 2 controls its speed output according to the cooling demand. The speed of the centrifugal fan is controlled proportionally to the cooling demand; the greater the cooling demand, the higher the fan speed to enhance heat exchange, and the lower the cooling demand, the lower the fan speed to achieve energy saving.

[0039] Humidity control is divided into dehumidification control and humidification control. The air conditioning unit is controlled based on the supply air humidity. The variable frequency compressor 7 calculates the required speed using a PID temperature algorithm based on the difference between the set humidity and the humidity detected by the temperature and humidity sensors 22. When the dehumidification demand is ≥100%, and the dehumidification low temperature limit + dehumidification low temperature hysteresis ≤ supply air temperature ≤ supply air temperature setting + dehumidification upper limit, the compressor is activated for dehumidification. The compressor speed = calculated cooling demand + dehumidification frequency boost. The dehumidification speed of the variable frequency fan 2 is output according to the ratio of cooling demand × dehumidification airflow rate. The speed control priority of the variable frequency fan 2 is dehumidification > cooling > standby. The air conditioning unit is also controlled based on the supply air humidity. The humidifier 20 calculates the humidification demand using a PID temperature algorithm based on the difference between the set humidity and the humidity detected by the temperature and humidity sensors 22. When the centrifugal fan 2 has been running normally for 30 seconds and the temperature meets the humidification requirement, and the humidification demand reaches 100%, the humidifier 20 is activated. The humidifier 20 is installed in the water collection tray 21 below the evaporator 1. The atomized water used by the humidifier 20 comes from the condensate collected from the evaporator 1 or from external water supply. The water collection tray 21 is provided with a drain outlet, which allows water to be drained when the water level in the water collection tray is higher than the drain outlet.

[0040] The control unit monitors the exhaust and intake pressures in real time: when the exhaust pressure exceeds the high-pressure alarm value for several seconds, the system immediately shuts down and alarms to prevent damage to the compressor; when the intake pressure falls below the low-pressure alarm value for several seconds, the system shuts down and alarms to prevent system leaks or evaporator icing. The pressure value detected by the condensing pressure sensor is used to adjust the speed of the EC fan: the fan starts when the condensing pressure reaches the fan's opening pressure; the fan frequency increases linearly when the pressure is within the range of the opening pressure plus the hysteresis; the fan runs at full speed when the pressure exceeds the opening pressure plus the hysteresis; and the fan stops when the pressure is below the opening pressure minus the hysteresis. Furthermore, the compressor inverter and the PID-controlled fan inverter internally implement overcurrent and phase loss protection, cutting off the output and reporting a fault code in case of abnormalities. If any temperature and humidity sensor reading exceeds a reasonable range or communication is interrupted, the control unit uses the backup default value or suspends phase-closed-loop control and issues an alarm for maintenance.

[0041] The above method intelligently switches between three modes: grain pile cooling, grain surface cooling, and natural ventilation. A single device can perform the functions of three independent devices: a traditional grain cooler, a grain air conditioner, and a ventilator. Furthermore, it can automatically switch operating modes and precisely adjust the compressor, fan, humidifier, and other components based on changes in the external environment and the actual temperature and humidity inside the grain silo, achieving minimal energy consumption while meeting the requirements of low-temperature grain storage.

[0042] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A multifunctional grain air conditioning system with temperature and humidity control, the system comprising a refrigeration cycle unit, the refrigeration cycle unit comprising at least a compressor, an evaporator, a condenser, and an electronic expansion valve; characterized in that, The system also includes: The air supply unit includes a centrifugal fan disposed on the evaporator side and a PID regulating fan frequency converter connected thereto. The PID regulating fan frequency converter is used to control the operating conditions of the centrifugal fan, and the operating conditions include at least one of the centrifugal fan's air volume, air pressure, and air speed. The dual-inlet air switching unit includes a return air inlet connected to the inside of the grain silo, a fresh air inlet connected to the outside environment, and a return air butterfly valve and a fresh air butterfly valve respectively installed at the return air inlet and the fresh air inlet. The temperature and humidity detection unit includes at least an ambient temperature sensor for detecting the outside temperature, a return air temperature and humidity sensor for detecting the return air temperature and humidity inside the grain silo, and a supply air temperature and humidity sensor for detecting the treated supply air temperature and humidity. A humidification unit, including a humidifier and a water supply device for supplying water to the humidifier; A variable frequency control unit, including a compressor variable frequency drive connected to the compressor; The control unit is configured to switch between grain pile cooling mode, grain surface cooling mode, and natural ventilation mode based on mode switching commands. In the grain pile cooling mode, the centrifugal fan is controlled to operate under high air volume and high air pressure conditions, the return air butterfly valve is closed and the fresh air butterfly valve is fully opened, so that the incoming air is all outdoor fresh air; In the grain surface cooling mode, the centrifugal fan is controlled to operate under low air volume and low air pressure conditions, the return air butterfly valve is fully opened and the fresh air butterfly valve is closed, so that the incoming air is the return air of the whole room; In the natural ventilation mode, the refrigeration cycle is turned off, the centrifugal fan is controlled to operate under high air volume and high air pressure conditions, the return air butterfly valve is closed, and the fresh air butterfly valve is fully opened to make the incoming air all outdoor fresh air. Furthermore, the control unit is also configured to adjust the speed of the compressor, the speed of the centrifugal fan, and the start / stop of the humidifier based on the data fed back by the temperature and humidity detection unit.

2. The multi-functional grain air conditioning system with temperature and humidity control according to claim 1, characterized in that, The water supply device of the humidification unit includes a water receiving tray, which is located below the evaporator and is used to collect condensate; the humidifier is installed in the water receiving tray.

3. A multi-functional grain air conditioning system with temperature and humidity control according to claim 2, characterized in that, The water receiving tray is equipped with a drain outlet and an external water supply interface. When the condensate is insufficient, water is supplied to the water receiving tray through the external water supply interface.

4. A multi-functional grain air conditioning system with temperature and humidity control according to claim 1, characterized in that, An EC fan is provided on the condenser side, and the EC fan is a variable frequency fan.

5. A multi-functional grain air conditioning system with temperature and humidity control according to claim 1, characterized in that, The system is equipped with a low-pressure intake side inspection valve, an intake temperature sensor, and an intake pressure sensor on the low-pressure intake pipe side; an exhaust pressure sensor and an exhaust temperature sensor on the high-pressure exhaust pipe side; and a high-pressure liquid pipe side inspection valve, a condensation pressure sensor, and a condensation temperature sensor on the high-pressure liquid pipe side, and a drying filter is provided before the electronic expansion valve.

6. A multi-functional grain air conditioning system with temperature and humidity control according to claim 1, characterized in that, The control unit is equipped with a remote communication interface for receiving mode switching commands from the upper-level intelligent grain depot integrated system.

7. A multi-functional grain air conditioning system with temperature and humidity control according to claim 1, characterized in that, The control unit is connected to a human-machine interface, which is used to display the system operating status and internal environmental parameters of the grain warehouse, and provides a user input interface for setting the operating mode and working parameters.

8. A control method for a multifunctional grain air conditioning system with temperature and humidity control, characterized in that, The method, applied to a multi-functional grain air conditioning system for temperature and humidity control as described in any one of claims 1-7, comprises: Receive mode switching command, operate in grain pile cooling mode, grain surface cooling mode or natural ventilation mode based on the mode switching command, and adjust the opening of return air butterfly valve and / or fresh air butterfly valve to select the ratio of indoor return air and outdoor fresh air in the air intake source.

9. The control method for a multifunctional grain air conditioning system with temperature and humidity control according to claim 8, characterized in that, Also includes: Acquire the supply air temperature and humidity detected by the supply air temperature and humidity sensor; Using the supply air temperature as the control benchmark: Based on the difference between the set temperature and the detected temperature, the compressor speed or start / stop is controlled by a PID algorithm; Based on the supply air humidity: when the dehumidification demand reaches the preset threshold and the supply air temperature meets the preset dehumidification temperature condition, the compressor is turned on for dehumidification; when the humidification demand reaches the preset threshold, the humidifier is turned on and the water in the water tray is used for atomized humidification.

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