Alternating heating and dehumidifying agricultural product heat pump drying system and method

Abstract

This invention discloses an alternating heating and dehumidification heat pump drying system and method for agricultural products, which solves the problem of excessive sensible heat transfer during the drying process of agricultural products in the prior art. It has the beneficial effects of alternating heating and dehumidification and reducing energy consumption. The specific solution is as follows: An alternating heating and dehumidification heat pump drying system for agricultural products includes at least two drying chambers, each of which is connected to a corresponding hot air circulation component. The heating component includes a condenser, a first heat exchange fan, and an auxiliary heater connected in sequence. The condenser and the auxiliary heater are respectively connected to two adjacent drying chambers. The dehumidification component includes an evaporator and a second heat exchange fan connected in sequence. The evaporator and the second heat exchange fan are respectively connected to two adjacent drying chambers. The evaporator is connected to the condenser. An expansion valve is installed on the connecting pipe on one side of the evaporator and the condenser, and a compressor is installed on the connecting pipe on the other side of the evaporator and the condenser, so as to realize alternating heating and dehumidification between the two adjacent drying chambers.

Description

Technical Field

[0001] This invention relates to the field of drying technology, and in particular to a heat pump drying system and method for agricultural products using alternating heating and dehumidification. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Heat pump drying technology is a drying technology with significant energy-saving advantages and is widely used in agricultural product processing. A heat pump drying system utilizes an evaporator to absorb heat from the drying medium for dehumidification and energy recovery, transferring the heat to the evaporator. Simultaneously, the condenser transfers heat to the drying medium for reheating. Dehumidifying the drying medium requires lowering its temperature to the dew point, and this heat transfer relies on the compressor, which consumes a significant amount of energy.

[0004] Chinese patent CN114935260A discloses an air-source heat pump dryer unit. By adding a total heat exchanger, it recovers heat from the return air to preheat the dehumidified, low-temperature dry air, thereby improving the system's energy efficiency and dehumidification effect. However, because the drying medium returns to the drying chamber after being dehumidified and reheated sequentially through the evaporator and condenser, the temperature of the drying medium in the loop remains consistently higher than the dew point temperature. The dehumidification process requires continuously lowering the temperature of the high-temperature medium to the dew point, resulting in a high coefficient of performance (COP) for the heat pump drying system but low energy utilization efficiency.

[0005] As a convective drying method, heat pump drying of agricultural products exhibits nonlinear dehydration characteristics. During the drying process, there is a significant change in the moisture gradient between the material surface and its interior. In the later stages of drying, the evaporation of surface moisture is controlled by the diffusion rate of moisture within the agricultural product, and the drying rate decreases continuously over time. To reduce drying energy consumption while ensuring drying quality, agricultural product drying typically requires the regulation of temperature and humidity parameters. Chinese patent CN114442703B discloses a control method and control system for a closed-loop drying system. This system regulates the temperature inside the drying chamber through a heat pump subsystem and controls the humidity through an airflow conveying device installed in the drying chamber. Using a high-temperature, high-humidity drying medium leads to a significant increase in drying time and may prevent the material's moisture content from being reduced to the target level. Conversely, using a high-temperature, low-humidity drying medium results in continuous high energy consumption of the heat pump system, reduced dehumidification efficiency of the evaporator, and a significant increase in the system's unit dehumidification energy consumption, which is detrimental to overall energy conservation in the drying process.

[0006] In summary, the inventors have found that existing heat pump drying equipment dries agricultural products in a drying chamber, generating a lot of moisture in the later stages of heating. To remove this moisture, the existing technology couples heating and dehumidification, resulting in a large amount of sensible heat transfer and high energy consumption per unit of dehydration. Moreover, in the later stages of drying, agricultural products are in a high-temperature and high-humidity state, which reduces drying efficiency and makes it difficult to achieve the goal of high-efficiency and energy-saving drying, greatly hindering the development and application of heat pump drying technology for agricultural products. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide an alternating heating and dehumidification heat pump drying system and method for agricultural products, which improves the energy utilization efficiency of the drying process and is of great significance for achieving efficient and energy-saving drying of agricultural products.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] An alternating heating and dehumidification heat pump drying system for agricultural products includes at least two drying chambers, a hot air circulation component, a heating component, and a dehumidification component. Each drying chamber is connected to a corresponding hot air circulation component. The heating component includes a condenser, a first heat exchange fan, and an auxiliary heater connected in sequence. The condenser and the auxiliary heater are connected to two adjacent drying chambers respectively. The dehumidification component includes an evaporator and a second heat exchange fan connected in sequence. The evaporator and the second heat exchange fan are connected to two adjacent drying chambers respectively. The evaporator is connected to the condenser. An expansion valve is installed on the connecting pipe on one side of the evaporator and the condenser, and a compressor is installed on the connecting pipe on the other side of the evaporator and the condenser. When the compressor is working, the condenser circulates and heats the drying medium in one of the two adjacent drying chambers, and the evaporator cools and dehumidifies the drying medium in the other drying chamber, thereby realizing alternating heating and dehumidification between the two adjacent drying chambers.

[0010] As described above, an alternating heating and dehumidification heat pump drying system for agricultural products includes two drying chambers, namely a first drying chamber and a second drying chamber, with the heating component and the dehumidification component located between the first drying chamber and the second drying chamber.

[0011] As described above, in an alternating heating and dehumidification heat pump drying system for agricultural products, the hot air circulation component includes a circulating fan connected to the drying chamber, and a temperature sensor and a relative humidity sensor are installed in the pipeline connecting the circulating fan and the drying chamber.

[0012] In the agricultural product heat pump drying system with alternating heating and dehumidification as described above, the expansion valve, the compressor, the hot air circulation assembly, the heating assembly, and the dehumidification assembly are respectively connected to the central controller.

[0013] As described above, in an alternating heating and dehumidification heat pump drying system for agricultural products, the central controller controls the opening of the expansion valve and the compressor based on the temperature change of the drying medium in one of the drying chambers, and controls the heating component to connect with that drying chamber, and controls the dehumidification component to connect with the adjacent drying chamber.

[0014] As described above, in an alternating heating and dehumidification heat pump drying system for agricultural products, the central controller controls the dehumidification component to connect with the drying chamber and the heating component to connect with the adjacent drying chamber based on the relative humidity change of the drying medium in one of the drying chambers.

[0015] As described above, in an alternating heating and dehumidification heat pump drying system for agricultural products, the heating component is connected to two adjacent drying chambers via heating dampers, and the dehumidification component is connected to two adjacent drying chambers via dehumidification dampers. Each heating damper and each dehumidification damper are connected to the central controller.

[0016] As described above, in an alternating heating and dehumidification heat pump drying system for agricultural products, a rack assembly is installed in the drying chamber for placing agricultural products. The central controller calculates the increase rate of relative humidity of the drying medium per unit time. When the increase rate of relative humidity of the drying medium per unit time is lower than the target humidity growth rate, the target relative humidity value of the drying medium is subtracted from the target humidity gradient value and used as the new target relative humidity value.

[0017] Secondly, the present invention also provides a heat pump drying method for agricultural products using alternating heating and dehumidification, employing the aforementioned heat pump drying system for agricultural products using alternating heating and dehumidification, comprising the following:

[0018] When agricultural products are placed in the drying chamber, the heating circulation component is turned on, the auxiliary heater in the heating component is turned on, and the connection between the heating component and each drying chamber is opened, causing the temperature of the drying medium in the drying chamber to rise continuously.

[0019] When the temperature of the drying medium in one of the two adjacent drying chambers exceeds the target temperature, the auxiliary heater is turned off, the connection between the heating component and the other drying chamber is disconnected, the compressor and expansion valve are turned on, and the connection between the dehumidification component and the other drying chamber is opened. The surface temperature of the condenser rises and the surface temperature of the evaporator falls, so that the drying medium in one drying chamber is circulated and heated, while the drying medium in the other drying chamber is cooled and dehumidified.

[0020] The above-mentioned alternating heating and dehumidification heat pump drying method for agricultural products includes the following:

[0021] When the relative humidity of the drying medium in one of the two adjacent drying chambers is greater than the target relative humidity value, disconnect the connection between the drying chamber and the heating component, open the connection between the drying chamber and the dehumidification component, and dehumidify the drying medium in the drying chamber. Then, open the connection between the heating component and the other drying chamber, disconnect the connection between the dehumidification component and the other drying chamber, and heat the drying medium in the other drying chamber.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1) This invention adopts an independent multi-drying chamber structure, with the heating component and dehumidification component connected to each drying chamber respectively. The evaporator and condenser are used to alternately heat and dehumidify the drying medium in the drying chamber, replacing the current heat pump drying equipment's coupled heating and dehumidification mode. This avoids repeated heating of the drying medium during the dehumidification process and solves the problem of high energy consumption per unit of dehydration caused by a large amount of sensible heat transfer during the dehumidification process.

[0024] 2) This invention replaces the existing linear temperature and humidity control method of drying medium with an alternating heating and dehumidification method. It improves energy utilization efficiency under high relative humidity conditions and ensures high dehydration efficiency of agricultural products under variable temperature and humidity conditions. It reduces the energy input of agricultural products after entering the slow-down drying section, effectively solving the problems of low drying efficiency and high energy consumption of agricultural products.

[0025] 3) The hot air circulation component in this invention includes a temperature sensor and a humidity sensor. The central controller adjusts the connection or disconnection of the heating component and the dehumidification component with the corresponding drying chamber based on the data detected by the temperature sensor and the humidity sensor. It can also set the target temperature requirement and the target relative humidity requirement, and determine the increase rate of relative humidity per unit time, so as to better match the drying characteristics of agricultural products and improve the drying efficiency. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] Figure 1 This is a schematic diagram of the structure of an alternating heating and dehumidification heat pump drying system for agricultural products according to one or more embodiments of the present invention.

[0028] Figure 2 This is a flowchart of an alternating heating and dehumidification heat pump drying method for agricultural products according to one or more embodiments of the present invention.

[0029] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0030] The components are as follows: 1. First circulating fan; 2. First relative humidity sensor; 3. First temperature sensor; 4. First drying chamber; 5. First heating damper; 6. Second heating damper; 7. Auxiliary heater; 8. First heat exchange fan; 9. Third heating damper; 10. Condenser; 11. Fourth heating damper; 12. Second drying chamber; 13. Second circulating fan; 14. Second temperature sensor; 15. Second relative humidity sensor; 16. Expansion valve; 17. First dehumidification damper; 18. Evaporator; 19. Second dehumidification damper; 20. Second heat exchange fan; 21. Third dehumidification damper; 22. Fourth dehumidification damper; 23. Compressor. Detailed Implementation

[0031] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] As described in the background section, existing agricultural product heat pump heating systems suffer from the problem of coupled heating and dehumidification. To address this technical issue, this invention proposes an agricultural product heat pump drying system and method with alternating heating and dehumidification.

[0034] Example 1

[0035] In a typical embodiment of the present invention, reference is made to Figure 1 As shown, an alternating heating and dehumidification heat pump drying system for agricultural products includes a first drying chamber 4, a second drying chamber 12, an expansion valve 16, a compressor 23, and a hot air circulation component, a heating component, and a dehumidification component connected to the first drying chamber 4 and the second drying chamber 12 via air ducts. The heating circulation component circulates hot air within the first drying chamber 4 and the second drying chamber 12. The heating component heats the drying medium within the first drying chamber 4 and the second drying chamber 12. The dehumidification component dehumidifies the drying medium within the two drying chambers.

[0036] In this system, the first drying chamber 4 and the second drying chamber 12 are equipped with racks of the same specifications and number. The racks support trays, and the agricultural products are placed in the trays. Each drying chamber is equipped with a door that can be opened or closed. After drying, the agricultural products are removed. In some examples, a conveyor assembly is installed inside the drying chamber to transport the agricultural products. The conveyor assembly can be an existing open belt conveyor mechanism. The conveyor mechanism is connected to a central controller. After drying, the central controller controls the conveyor mechanism to start working and send the agricultural products out of the first drying chamber 4 or the second drying chamber 12. Each drying chamber is equipped with a gate on the inlet side and the outlet side of the conveyor assembly. The gate can be closed or opened. When the inlet gate is open, the agricultural products are sent into the conveyor assembly. When the outlet gate is open, the agricultural products are sent out of the conveyor assembly.

[0037] The hot air circulation assembly includes a first circulating fan 1, a second circulating fan 13, a first temperature sensor 3, a second temperature sensor 14, a first relative humidity sensor 2, and a second relative humidity sensor 15. The air inlet and outlet of the first circulating fan 1 are connected to the first drying chamber 4 through an air duct to form an airflow loop structure. The air duct is equipped with the first temperature sensor 3 and the first relative humidity sensor 2 to monitor the parameters of the internal drying medium. The air inlet and outlet of the second circulating fan 13 are connected to the second drying chamber 12 through an air duct to form a loop structure. The air duct is equipped with the second temperature sensor 14 and the second relative humidity sensor 15 to monitor the parameters of the internal drying medium. In this embodiment, the first temperature sensor 3 and the second temperature sensor 14 are both high-precision PT100 type temperature sensors (thermal resistance temperature sensors based on platinum material), and the first relative humidity sensor 2 and the second relative humidity sensor 15 are both high-temperature resistant capacitive humidity sensors. The probes of each sensor are placed inside the air duct.

[0038] The heating assembly includes an auxiliary heater 7, a first heat exchange fan 8, a condenser 10, a first heating damper 5, a second heating damper 6, a third heating damper 9, and a fourth heating damper 11. The outlet of the auxiliary heater 7 is connected to the first drying chamber 4 through the second heating damper 6 and to the second drying chamber 12 through the third heating damper 9. The inlet of the auxiliary heater 7 is connected to the outlet of the first heat exchange fan 8. The inlet of the first heat exchange fan 8 is connected to the outlet of the condenser 10. The inlet of the condenser 10 is connected to the first drying chamber 4 through the first heating damper 5 and to the second drying chamber 12 through the fourth heating damper 11. The drying medium flowing out of the first drying chamber 4 or the second drying chamber 12 first passes through the condenser 10 and then enters the first heat exchange fan 8 and the auxiliary heater 7, where the drying medium is heated by the auxiliary heater 7 or the condenser 10.

[0039] Specifically, the auxiliary heater 7 is an electric heater, and the first heating damper 5, the second heating damper 6, the third heating damper 9, and the fourth heating damper 11 are selected as electric or pneumatic valves.

[0040] The dehumidification assembly includes an evaporator 18, a second heat exchange fan 20, a first dehumidification damper 17, a second dehumidification damper 19, a third dehumidification damper 21, and a fourth dehumidification damper 22. The outlet of the second heat exchange fan 20 is connected to the second drying chamber 12 through the second dehumidification damper 19 and to the first drying chamber 4 through the third dehumidification damper 21. The inlet of the second heat exchange fan 20 is connected to the outlet of the evaporator 18. The inlet of the evaporator 18 is connected to the second drying chamber 12 through the first dehumidification damper 17 and to the first drying chamber 4 through the fourth dehumidification damper 22. The drying medium flowing out of the first drying chamber 4 or the second drying chamber 12 first passes through the evaporator 18 and then enters the second heat exchange fan 20. During the repeated flow of the drying medium, the drying medium is cooled and dehumidified when passing through the evaporator 18.

[0041] Specifically, the first dehumidification damper 17, the second dehumidification damper 19, the third dehumidification damper 21, and the fourth dehumidification damper 22 are equipped with electric or pneumatic valves, and the evaporator 18 is equipped with a condensate collection device.

[0042] The opening and closing states of the first heating damper 5 and the second heating damper 6 are the same. After opening, the drying medium in the first drying chamber 4 is heated by the condenser 10, the first heat exchange fan 8, and the auxiliary heater 7 and then returned to the first drying chamber 4. The opening and closing states of the third heating damper 9 and the fourth heating damper 11 are the same. After opening, the drying medium in the second drying chamber 12 is heated by the condenser 10, the first heat exchange fan 8, and the auxiliary heater 7 and then returned to the second drying chamber 12.

[0043] The first dehumidifying damper 17 and the second dehumidifying damper 19 are in the same opening and closing state. After opening, the drying medium in the second drying chamber 12 is dehumidified through the evaporator 18 and the second heat exchange fan 20 and then returns to the second drying chamber 12. The third dehumidifying damper 21 and the fourth dehumidifying damper 22 are in the same opening and closing state. After opening, the drying medium in the first drying chamber 4 is dehumidified through the evaporator 18 and the second heat exchange fan 20 and then returns to the first drying chamber 4.

[0044] It should be noted that both the heating damper and the dehumidifying damper are existing solenoid valves.

[0045] In addition, the evaporator 18 is connected to the condenser 10. An expansion valve 16 is installed on the connecting pipe between the evaporator 18 and the condenser 10 on one side, and a compressor 23 is installed on the connecting pipe between the evaporator 18 and the condenser 10 on the other side. When the compressor 23 is working, the internal refrigerant flows as follows: the high-temperature and high-pressure refrigerant generated by the compressor 23 enters the condenser 10 for condensation and heat release, and then becomes a low-temperature and low-pressure refrigerant through the expansion valve 16. The low-temperature and low-pressure gas absorbs heat and vaporizes through the evaporator 18, and returns to the compressor 23. This increases the surface temperature of the condenser and decreases the surface temperature of the evaporator 18, which is beneficial for heating the drying medium in one drying chamber and for cooling and dehumidifying the drying medium in another drying chamber. The alternating heating and dehumidification of the drying medium in the drying chamber by the heating component and the dehumidification component replaces the current mode of coupled heating and dehumidification in heat pump drying equipment, avoiding repeated heating of the drying medium during the dehumidification process.

[0046] It should be noted that a central controller is set up, which can be a PLC controller or other type of controller. The central controller is electrically connected to the first circulating fan 1, the first relative humidity sensor 2, the first temperature sensor 3, the first heating damper 5, the second heating damper 6, the auxiliary heater 7, the first heat exchange fan 8, the third heating damper 9, the fourth heating damper 11, the second circulating fan 13, the second temperature sensor 14, the second relative humidity sensor 15, the expansion valve 16, the first dehumidification damper 17, the second dehumidification damper 19, the second heat exchange fan 20, the third dehumidification damper 21, the fourth dehumidification damper 22, and the compressor 23. This enables real-time monitoring of temperature and relative humidity parameters during the operation of the drying system, as well as separate control of the compressor 23, each damper, each fan, and the auxiliary heater 7. Moreover, in this embodiment, an alternating heating and dehumidification drying method is used instead of the linear temperature and humidity control method of the drying medium. This improves energy utilization efficiency under high relative humidity conditions and ensures high dehydration efficiency of agricultural products under changing temperature and humidity conditions, reducing the energy input of agricultural products after entering the slow-down drying section.

[0047] In addition, the central controller is equipped with a display screen, which can display the data collected by each sensor. The central controller is connected to an input keyboard, through which relevant parameters can be input.

[0048] Example 2

[0049] This embodiment describes a heat pump drying method for agricultural products using alternating heating and dehumidification. It employs the heat pump drying system for agricultural products using alternating heating and dehumidification as described in Embodiment 1. (Refer to...) Figure 2 As shown, this can be achieved through the following steps:

[0050] Step 1: Place the agricultural raw materials on trays in the first drying chamber 4 and the second drying chamber 12, set the target temperature, target relative humidity, target humidity increase rate, target humidity gradient and other parameters, and monitor the temperature and humidity levels of the drying medium in real time using the first temperature sensor, the second temperature sensor, the first relative humidity sensor and the second relative humidity sensor. Start the first circulating fan 1 and the second circulating fan 13 to begin the heating stage of drying.

[0051] The target temperature is 45℃~50℃, and the target relative humidity is 55%~60%.

[0052] In addition, the target humidity increase rate is 0.5% / min to 1.5% / min; the target humidity gradient is 4% to 6%.

[0053] Step 2: The central controller sequentially starts the first heating damper 5, the second heating damper 6, the third heating damper 9, the fourth heating damper 11, the first heat exchange fan 8, and the auxiliary heater 7. The first heat exchange fan 8 simultaneously blows the drying medium from the first drying chamber 4 and the second drying chamber 12 into the auxiliary heater 7 for circulating heating. At this time, the temperature of the drying medium continuously rises. The first temperature sensor 3 measures the temperature value of the drying medium in the first drying chamber 4. When the temperature of the drying medium inside the first drying chamber 4 exceeds the target temperature value, the auxiliary heater 7, the third heating damper 9, and the fourth heating damper 11 are closed, and the first dehumidification damper 17, the second dehumidification damper 19, the second heat exchange fan 20, and the compressor 23 are opened. The surface temperature of the condenser rises and the surface temperature of the evaporator falls. The first heat exchange fan 8 blows the drying medium from the first drying chamber 4 into the condenser 10 for circulating heating, and the second heat exchange fan 20 blows the drying medium from the second drying chamber 12 into the evaporator 18 for circulating cooling and dehumidification. The drying process enters the alternating heating and dehumidification stage.

[0054] Step 3: The first relative humidity sensor 2 measures the relative humidity value of the drying medium in the first drying chamber 4. When the relative humidity of the drying medium inside the first drying chamber 4 exceeds the target relative humidity value, the third heating damper 9, the fourth heating damper 11, the third dehumidifying damper 21, and the fourth dehumidifying damper 22 are opened, and the first heating damper 5, the second heating damper 6, the first dehumidifying damper 17, and the second dehumidifying damper 19 are closed. The first heat exchange fan 8 blows the drying medium in the second drying chamber 12 into the condenser 10 for circulating heating, and the second heat exchange fan 20 blows the drying medium in the first drying chamber 4 into the evaporator 18 for cooling and dehumidification. The second relative humidity sensor 15 measures the relative humidity value of the drying medium in the second drying chamber 12. When the relative humidity of the drying medium inside the second drying chamber 12 exceeds the target relative humidity value, the first heating damper 5, the second heating damper 6, and the first dehumidifying damper are opened. 17. The second dehumidification damper 19 closes the third heating damper 9, the fourth heating damper 11, the third dehumidification damper 21, and the fourth dehumidification damper 22. The first heat exchange fan 8 blows the drying medium in the first drying chamber 4 into the condenser 10 for circulating heating, and the second heat exchange fan 20 blows the drying medium in the second drying chamber 12 into the evaporator 18 for cooling and dehumidification. As drying proceeds, the moisture content of the material decreases, and the rate of moisture evaporation decreases accordingly. When the increase in relative humidity of the drying medium per unit time detected by the first relative humidity sensor 2 or the second relative humidity sensor 15 is lower than the rate of increase in target humidity, the target relative humidity value is reduced by the target humidity gradient value to obtain the new target relative humidity value, so as to promote the evaporation of moisture from the material. When the relative humidity of the drying medium no longer increases, the evaporation and drying of the material moisture basically stops, the moisture content of the material decreases to the target moisture content, and the drying ends.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat pump drying system for agricultural products with alternating heating and dehumidification, characterized in that, It includes at least two drying chambers, a hot air circulation assembly, a heating assembly, and a dehumidification assembly. Each drying chamber is connected to the corresponding hot air circulation assembly. The heating assembly includes a condenser, a first heat exchange fan, and an auxiliary heater connected in sequence. The condenser and the auxiliary heater are respectively connected to two adjacent drying chambers. The dehumidification assembly includes an evaporator and a second heat exchange fan connected in sequence. The evaporator and the second heat exchange fan are respectively connected to two adjacent drying chambers. The evaporator is connected to the condenser. An expansion valve is installed on the connecting pipe on one side of the evaporator and the condenser. A compressor is installed on the connecting pipe on the other side of the evaporator and the condenser. When the compressor is working, the condenser circulates and heats the drying medium in one of the two adjacent drying chambers, and the evaporator cools and dehumidifies the drying medium in the other drying chamber, so as to realize alternating heating and dehumidification between the two adjacent drying chambers. The hot air circulation assembly includes a circulating fan connected to the drying chamber, and a temperature sensor and a relative humidity sensor are installed in the pipeline connecting the circulating fan and the drying chamber. The expansion valve, the compressor, the hot air circulation assembly, the heating assembly, and the dehumidification assembly are all connected to a central controller. The central controller controls the opening of the expansion valve and the compressor based on the temperature change of the drying medium in one of the drying chambers, and controls the connection between the heating assembly and the drying chamber, and the connection between the dehumidification assembly and the adjacent drying chamber, based on the relative humidity change of the drying medium in one of the drying chambers. The central controller calculates the rate of increase of the relative humidity of the drying medium in the drying room per unit time. When the rate of increase of the relative humidity of the drying medium per unit time is lower than the rate of increase of the target humidity, the target relative humidity value of the drying medium is subtracted from the target humidity gradient value and used as the new target relative humidity value.

2. The agricultural product heat pump drying system with alternating heating and dehumidification according to claim 1, characterized in that, The drying chamber includes two parts, namely a first drying chamber and a second drying chamber, and the heating component and the dehumidification component are located between the first drying chamber and the second drying chamber.

3. The agricultural product heat pump drying system with alternating heating and dehumidification according to claim 1, characterized in that, The heating component is connected to the two adjacent drying chambers through heating dampers, and the dehumidification component is connected to the two adjacent drying chambers through dehumidification dampers. Each heating damper and each dehumidification damper is connected to the central controller.

4. The agricultural product heat pump drying system with alternating heating and dehumidification according to claim 1, characterized in that, The drying chamber is equipped with a rack assembly for placing agricultural products.

5. A heat pump drying method for agricultural products using alternating heating and dehumidification, characterized in that, An agricultural product heat pump drying system using alternating heating and dehumidification as described in any one of claims 1-4 includes the following components: When agricultural products are placed in the drying chamber, the heating circulation component is turned on, the auxiliary heater in the heating component is turned on, and the connection between the heating component and each drying chamber is opened, causing the temperature of the drying medium in the drying chamber to rise continuously. When the temperature of the drying medium in one of the two adjacent drying chambers exceeds the target temperature, the auxiliary heater is turned off, the connection between the heating component and the other drying chamber is disconnected, the compressor and expansion valve are turned on, and the connection between the dehumidification component and the other drying chamber is opened. The surface temperature of the condenser rises and the surface temperature of the evaporator falls, so that the drying medium in one drying chamber is circulated and heated, while the drying medium in the other drying chamber is cooled and dehumidified.

6. The method for drying agricultural products by alternating heating and dehumidification using a heat pump according to claim 5, characterized in that, Includes the following: When the relative humidity of the drying medium in one of the two adjacent drying chambers is greater than the target relative humidity value, disconnect the connection between the drying chamber and the heating component, open the connection between the drying chamber and the dehumidification component, and dehumidify the drying medium in the drying chamber. Then, open the connection between the heating component and the other drying chamber, disconnect the connection between the dehumidification component and the other drying chamber, and heat the drying medium in the other drying chamber.

Images