A heat pump dryer unit and a heat pump drying control method

Abstract

This invention discloses a heat pump drying unit and a heat pump drying control method. The heat pump drying unit is distributed in a first drying chamber, a second drying chamber, and a third drying chamber. Items to be dried pass through the first, second, and third drying chambers sequentially to complete the drying process. The heat pump drying unit includes three independent refrigerant systems: a first refrigerant system, a second refrigerant system, and a third refrigerant system. The refrigerant used in the first and second refrigerant systems is different from that used in the third refrigerant system. By controlling the three refrigerant systems, the first drying chamber is stabilized within a first preset temperature range, the second drying chamber within a second preset temperature range, and the third drying chamber within a third preset temperature range; the first preset temperature range < the second preset temperature range < the third preset temperature range. This invention achieves parallel processing in three stages across three drying chambers, realizing assembly line operation and improving drying efficiency. The use of multiple refrigerants and multiple systems maximizes the heat exchange capacity of the refrigerants, improving the unit's energy efficiency.

Description

Technical Field

[0001] This invention relates to the field of heat pump drying technology, and more specifically, to a heat pump drying unit and a heat pump drying control method. Background Technology

[0002] Currently, heat pump drying units can be used to dry seafood, agricultural products, and tobacco. Based on the dehumidification method, heat pump drying technology is mainly divided into open-loop drying and closed-loop drying. Closed-loop drying means that the air inside the drying chamber does not come into contact with the outside environment, while open-loop drying means that the hot and humid air inside the drying chamber is directly exhausted to the outside through dehumidification, and then replenished with fresh natural air. In principle, both utilize a reverse Carnot cycle to absorb low-temperature heat energy from the air and integrate it into high-temperature heat energy to provide heating for the drying chamber.

[0003] Taking tobacco as an example, the three-stage drying process for flue-cured tobacco includes: the yellowing stage, the color-fixing stage, and the drying stage, corresponding to the low-temperature stage, the medium-temperature stage, and the high-temperature stage, respectively. Heat pump drying units generally use a high-temperature refrigerant as the heat exchange medium. However, in the low-temperature stage of the three-stage drying process, the high-temperature refrigerant performs poorly, resulting in low energy efficiency and poor unit performance. Furthermore, within a single drying chamber, only one unit controls the temperature rise and fall of the chamber for the three-stage drying process, meaning that one box of tobacco cannot be dried before another box can be dried, leading to low drying efficiency.

[0004] There is currently no effective solution to the problem of low energy efficiency and low drying efficiency caused by the use of a single refrigerant in existing heat pump dryers. Summary of the Invention

[0005] This invention provides a heat pump dryer unit and a heat pump drying control method to at least solve the problems of low energy efficiency and low drying efficiency caused by the use of a single refrigerant in existing heat pump dryers.

[0006] To solve the above-mentioned technical problems, the present invention provides a heat pump drying unit, wherein the heat pump drying unit is distributed in a first drying room, a second drying room and a third drying room, and the items to be dried are dried by passing through the first drying room, the second drying room and the third drying room in sequence.

[0007] The heat pump dryer unit includes: a first refrigerant system, a second refrigerant system, and a third refrigerant system that are independent of each other; the refrigerant injected into the first refrigerant system and the second refrigerant system is different from the refrigerant injected into the third refrigerant system;

[0008] By controlling the first refrigerant system, the second refrigerant system, and the third refrigerant system, the temperature of the first drying chamber is stabilized within a first preset temperature range, the temperature of the second drying chamber is stabilized within a second preset temperature range, and the temperature of the third drying chamber is stabilized within a third preset temperature range.

[0009] Among them, the first preset temperature range < the second preset temperature range < the third preset temperature range.

[0010] Optionally, the first refrigerant system includes a first compressor, a first condenser, a first throttling element, and a first evaporator connected in sequence; the first refrigerant system further includes a first subcooler and a first reversing valve;

[0011] The first reversing valve is installed on the pipeline between the first condenser and the first throttling element;

[0012] The inlet of the first subcooler is connected to the first reversing valve, and the outlet of the first subcooler is connected to the inlet of the first throttling element; when the first reversing valve is open, the outlet of the first condenser is connected to the inlet of the first subcooler, and when the first reversing valve is closed, the outlet of the first condenser is connected to the inlet of the first throttling element.

[0013] The first evaporator is located outdoors, the first condenser is located inside the first drying chamber, and the first subcooler is located inside the second drying chamber.

[0014] Optionally, the second refrigerant system includes a second compressor, a second condenser, a second throttling element, and a second evaporator connected in sequence; the second refrigerant system also includes a second subcooler and a second reversing valve;

[0015] The second reversing valve is installed on the pipeline between the second condenser and the second throttling element;

[0016] The inlet of the second subcooler is connected to the second reversing valve, and the outlet of the second subcooler is connected to the inlet of the second throttling element; when the second reversing valve is open, the outlet of the second condenser is connected to the inlet of the second subcooler, and when the second reversing valve is closed, the outlet of the second condenser is connected to the inlet of the second throttling element.

[0017] The second evaporator and the second condenser are both located in the second drying chamber, and the second subcooler is located in the first drying chamber.

[0018] Optionally, the third refrigerant system includes a third compressor, a third condenser, a third throttling element, and a third evaporator connected in sequence;

[0019] The third evaporator is located inside the second drying chamber, and the third condenser is located inside the third drying chamber.

[0020] Optionally, an electric heating device may be installed at the air outlet of the third condenser.

[0021] Optionally, under the same operating mode, the working pressure of the refrigerant injected into the first refrigerant system and the second refrigerant system is higher than the working pressure of the refrigerant injected into the third refrigerant system.

[0022] This invention also provides a heat pump drying control method, applied to the heat pump drying unit described in this invention, the method comprising:

[0023] Monitor the temperatures of the first drying chamber, the second drying chamber, and the third drying chamber;

[0024] Based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled to stabilize the temperature of the first drying chamber within a first preset temperature range, the temperature of the second drying chamber within a second preset temperature range, and the temperature of the third drying chamber within a third preset temperature range.

[0025] Optionally, based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including:

[0026] In response to the power-on command, the first refrigerant system and the first reversing valve are opened;

[0027] After a preset time, the third refrigerant system is turned on;

[0028] When the temperature of the first drying chamber reaches the first preset temperature range, the temperature of the second drying chamber reaches the second preset temperature range, the temperature of the third drying chamber reaches the third preset temperature range, and the first batch of items to be dried has completed the first stage of baking in the first drying chamber, the first batch of items to be dried is transferred to the second drying chamber, the second refrigerant system is turned on, and the first reversing valve is turned off.

[0029] Optionally, based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including:

[0030] After the last batch of items to be dried is transferred to the second drying chamber, when the temperature of the second drying chamber is stable within the second preset temperature range and there is no need to open the first reversing valve for temperature replenishment, the first refrigerant system is shut down.

[0031] After the last batch of items to be dried is transferred to the third drying chamber, the second refrigerant system is turned off when the temperature of the third drying chamber stabilizes within the third preset temperature range.

[0032] After the last batch of items to be dried completes the third stage of drying in the third drying room, the third refrigerant system is turned off.

[0033] Optionally, after transferring the last batch of items to be dried to the second drying room, the process further includes:

[0034] Obtain the current temperature and temperature drop rate of the second drying chamber;

[0035] If the temperature drop rate is greater than a preset threshold, or if the current temperature is lower than the second preset temperature range, then it is determined that the first reversing valve needs to be opened for temperature compensation.

[0036] Optionally, after transferring the last batch of items to be dried to the third drying room, the process further includes:

[0037] If the compressor frequency of the third refrigerant system rises to the maximum allowable frequency and the temperature of the second drying chamber drops to the preset temperature, the electric heating device is turned on, wherein the electric heating device is located at the air outlet of the third condenser;

[0038] When the last batch of items to be dried has completed the third stage of drying in the third drying room, the third refrigerant system and the electric heating device are turned off.

[0039] Optionally, based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including:

[0040] During the drying process, when the temperature of the second drying chamber is detected to be rising continuously, the second reversing valve is opened and the output of the first refrigerant system is reduced.

[0041] When the temperature of the second drying chamber is monitored to be stable within the second preset temperature range, the second reversing valve is closed.

[0042] Optionally, based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including:

[0043] During the drying process, when the temperature of the second drying chamber is detected to be lower than the second preset temperature range or the temperature drop rate is greater than the preset threshold, the second reversing valve is closed, the first reversing valve is opened, and the output of the first refrigerant system is increased.

[0044] When the temperature of the third drying chamber is monitored to be stable within the third preset temperature range, the first reversing valve is closed, reducing the output of the first refrigerant system and the third refrigerant system, while the output of the second refrigerant system remains unchanged.

[0045] This invention also provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method described in this invention.

[0046] This invention also provides a non-volatile computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method described in this invention.

[0047] By applying the technical solution of this invention, based on a three-stage drying system that separates drying chambers into different temperature zones, the items to be dried are transferred sequentially from the first drying chamber to the second and then to the third drying chamber during the drying operation to complete the drying at each stage. The three drying chambers process the three stages in parallel, realizing assembly line operation and allowing three batches of items to be dried to be dried simultaneously, greatly improving drying efficiency. By adopting multiple refrigerants and multiple systems, the maximum heat exchange capacity of the refrigerants can be utilized, improving the unit's energy efficiency, reducing the temperature transition time of the materials to be dried, and reducing the possibility of deterioration or deformation of the materials to be dried due to insufficient heating rate or untimely dehumidification. This solves the problem of low energy efficiency caused by using a single refrigerant. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the dual-refrigerant, three-system, integrated heat pump dryer unit provided in Embodiment 1 of the present invention;

[0049] Figure 2 This is a flowchart of the heat pump drying control method provided in Embodiment 2 of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] It should be noted that the terms "first," "second," etc., used in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0052] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0053] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0054] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0055] The optional embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0056] Example 1

[0057] This embodiment provides a heat pump drying unit, which is distributed in a first drying chamber, a second drying chamber, and a third drying chamber. Items to be dried are sequentially dried through these three drying chambers. The items to be dried can be tobacco, seafood, agricultural products, etc.

[0058] A heat pump dryer unit comprises three independent refrigerant systems: a first refrigerant system, a second refrigerant system, and a third refrigerant system. The refrigerant used in the first and second refrigerant systems differs from that used in the third refrigerant system. "Independent" means that the refrigerants in each system do not circulate between them.

[0059] By controlling the first refrigerant system, the second refrigerant system, and the third refrigerant system, the temperature of the first drying chamber is stabilized within a first preset temperature range, the temperature of the second drying chamber is stabilized within a second preset temperature range, and the temperature of the third drying chamber is stabilized within a third preset temperature range. Wherein, the first preset temperature range < the second preset temperature range < the third preset temperature range.

[0060] The first drying chamber corresponds to the low-temperature stage, the second drying chamber to the medium-temperature stage, and the third drying chamber to the high-temperature stage. Therefore, the first drying chamber can also be called the low-temperature drying chamber, the second drying chamber can also be called the medium-temperature drying chamber, and the third drying chamber can also be called the high-temperature drying chamber. The first, second, and third preset temperature ranges are the target temperature ranges corresponding to the low-temperature, medium-temperature, and high-temperature stages, respectively. The first, second, and third preset temperature ranges can be set according to actual drying needs. For example, the first preset temperature range can be 40–42℃, corresponding to a dehydration rate of 0.3–0.5% / h; the second preset temperature range can be 53–55℃, corresponding to a dehydration rate of 0.9–1.2% / h; and the third preset temperature range can be 74–75℃, corresponding to a dehydration rate of 0.3–0.7% / h.

[0061] This embodiment is based on a three-stage drying system with separate drying chambers at different temperature ranges. During the drying operation, the items to be dried are transferred sequentially from the first drying chamber to the second and then to the third drying chamber to complete the drying at each stage. The three drying chambers process the three stages in parallel, realizing assembly line operation. Three batches of items to be dried can be dried at the same time, which greatly improves the drying efficiency. By using multiple refrigerants and multiple systems, the maximum heat exchange capacity of the refrigerant can be utilized, improving the unit's energy efficiency, reducing the temperature transition time of the dried materials, and reducing the possibility of deterioration or deformation of the dried materials due to insufficient heating rate or untimely dehumidification. This solves the problem of low energy efficiency caused by using a single refrigerant.

[0062] Under the same operating mode, the refrigerant pressure in the first and second refrigerant systems is higher than that in the third refrigerant system. That is, the first and second refrigerant systems use the same refrigerant, but it is a refrigerant that performs well in low-temperature environments (i.e., a low-temperature refrigerant), such as R410a. The third refrigerant system uses a refrigerant that performs well in high-temperature environments (i.e., a high-temperature refrigerant), such as R134a. Different refrigerants and different systems each operate at suitable ambient temperatures, ensuring that the overall system capacity and efficiency reach their optimal state.

[0063] like Figure 1 As shown, the heat pump dryer units are distributed in the first drying chamber 1, the second drying chamber 2, and the third drying chamber 3. The heat pump dryer units include: a first refrigerant system 10, a second refrigerant system 20, and a third refrigerant system 30, which are independent of each other.

[0064] The first refrigerant system 10 includes a first compressor 11, a first condenser 12, a first throttling element 13, and a first evaporator 14 connected in sequence. The first refrigerant system 10 also includes a first subcooler 15 and a first reversing valve 16. The first reversing valve 16 is disposed on the pipeline between the first condenser 12 and the first throttling element 13. The inlet of the first subcooler 15 is connected to the first reversing valve 16, and the outlet of the first subcooler 15 is connected to the inlet of the first throttling element 13.

[0065] The first reversing valve 16 is used to switch the flow path. When the first reversing valve 16 is open, it connects the outlet of the first condenser 12 with the inlet of the first subcooler 15 (connecting the first subcooler 15 to the refrigerant circulation loop of the first refrigerant system 10). When the first reversing valve 16 is closed, it connects the outlet of the first condenser 12 with the inlet of the first throttling element 13.

[0066] The first evaporator 14 is located outdoors, the first condenser 12 is located inside the first drying chamber 1, and the first subcooler 15 is located inside the second drying chamber 2.

[0067] If the first reversing valve 16 is opened, the refrigerant in the first refrigerant system 10 absorbs heat from the first evaporator 14, flows through the first compressor 11 to the first condenser 12 to release heat, then flows to the first subcooler 15 to release heat, and after throttling, flows back to the first evaporator 14 to absorb heat, thus cycling.

[0068] The first refrigerant system 10 enables the temperature of the first drying chamber 1 to reach the target temperature range (i.e., the first preset temperature range), and the first evaporator 14 can absorb heat from the outside, while the first subcooler 15 can provide heat to the second drying chamber 2.

[0069] refer to Figure 1 The second refrigerant system 20 includes a second compressor 21, a second condenser 22, a second throttling element 23, and a second evaporator 24 connected in sequence. The second refrigerant system 20 also includes a second subcooler 25 and a second reversing valve 26. The second reversing valve 26 is disposed on the pipeline between the second condenser 22 and the second throttling element 23. The inlet of the second subcooler 25 is connected to the second reversing valve 26, and the outlet of the second subcooler 25 is connected to the inlet of the second throttling element 23.

[0070] The second reversing valve 26 is used to switch the flow path. When the second reversing valve 26 is open, it connects the outlet of the second condenser 22 with the inlet of the second subcooler 25 (connecting the second subcooler 25 to the refrigerant circulation loop of the second refrigerant system 20). When the second reversing valve 26 is closed, it connects the outlet of the second condenser 22 with the inlet of the second throttling element 23.

[0071] The second evaporator 24 and the second condenser 22 are both located in the second drying chamber 2, and the second subcooler 25 is located in the first drying chamber 1.

[0072] If the second reversing valve 26 is opened, the refrigerant in the second refrigerant system 20 absorbs heat from the second evaporator 24, flows through the second compressor 21 to the second condenser 22 to release heat, then flows to the second subcooler 25 to release heat, and after throttling, flows back to the second evaporator 24 to absorb heat, thus cycling.

[0073] The second refrigerant system 20 can bring the temperature of the second drying chamber 2 to the target temperature range (i.e., the second preset temperature range), and the second subcooler 25 can release heat to the first drying chamber 1, thereby removing excess heat from the second drying chamber 2.

[0074] The first subcooler 15 and the second subcooler 25 can be small condensers, mainly used for heat balance between the first drying chamber 1 and the second drying chamber 2.

[0075] refer to Figure 1 The third refrigerant system 30 includes a third compressor 31, a third condenser 32, a third throttling element 33, and a third evaporator 34 connected in sequence. The third evaporator 34 is located inside the second drying chamber 2, and the third condenser 32 is located inside the third drying chamber 3.

[0076] The third refrigerant system 30 enables the temperature of the third drying chamber 3 to reach the target temperature range (i.e., the third preset temperature range), and the third evaporator 34 can absorb heat from the second drying chamber 2.

[0077] An electric heating device can be installed at the air outlet of the third condenser 32 to supplement the temperature of the third drying chamber 3 when needed.

[0078] In this embodiment, the first drying chamber 1 exchanges heat with the external environment, while the second drying chamber 2 and the third drying chamber 3 do not exchange heat with the outside. In this type of open-close integrated heat pump dryer unit, all the heat in the drying chamber comes from the external heat absorbed by the first evaporator 14, and drying is mainly achieved through heat exchange between the drying chambers.

[0079] Example 2

[0080] This embodiment provides a heat pump drying control method, applied to the heat pump drying unit described in the above embodiment. Figure 2 This is a flowchart of the heat pump drying control method provided in Embodiment 2 of the present invention, as follows: Figure 2 As shown, the method includes the following steps:

[0081] S201 monitors the temperatures of the first drying chamber, the second drying chamber, and the third drying chamber.

[0082] S202, based on the monitored temperature, controls the first refrigerant system, the second refrigerant system and the third refrigerant system to stabilize the temperature of the first drying chamber within a first preset temperature range, the temperature of the second drying chamber within a second preset temperature range, and the temperature of the third drying chamber within a third preset temperature range.

[0083] This embodiment is based on a three-stage drying system with separate drying chambers at different temperature ranges. During the drying operation, the items to be dried are transferred sequentially from the first drying chamber to the second and then to the third drying chamber to complete the drying at each stage. The three drying chambers process the three stages in parallel, realizing assembly line operation. Three batches of items to be dried can be dried at the same time, which greatly improves the drying efficiency. By using multiple refrigerants and multiple systems, the maximum heat exchange capacity of the refrigerant can be utilized, improving the unit's energy efficiency, reducing the temperature transition time of the dried materials, and reducing the possibility of deterioration or deformation of the dried materials due to insufficient heating rate or untimely dehumidification. This solves the problem of low energy efficiency caused by using a single refrigerant.

[0084] In one embodiment, controlling the first refrigerant system, the second refrigerant system, and the third refrigerant system based on the monitored temperature includes:

[0085] In response to the power-on command, the first refrigerant system and the first reversing valve are activated;

[0086] After the first preset time, the third refrigerant system will be activated;

[0087] Once the temperature of the first drying chamber reaches the first preset temperature range, the temperature of the second drying chamber reaches the second preset temperature range, and the temperature of the third drying chamber reaches the third preset temperature range, and the first batch of items to be dried has completed the first stage of drying in the first drying chamber, the first batch of items to be dried is transferred to the second drying chamber, the second refrigerant system is turned on, and the first reversing valve is closed. Afterwards, all three refrigerant systems remain operational.

[0088] In this embodiment, turning on the refrigerant system refers to turning on the compressor and throttling element in the refrigerant system. The preset time can be set according to the actual situation. The third drying chamber absorbs heat from the second drying chamber, so the preset time needs to be set to ensure that the second drying chamber heats up to a certain level and that there is enough heat in the second drying chamber before the third refrigerant system is turned on to provide heat for the third drying chamber. For example, the preset time can be set to 2 hours.

[0089] Once the items to be dried have been baked in any drying room for the corresponding time, the baking of that stage can be considered complete. The specific time can be adjusted according to the actual items to be dried. For example, for flue-cured tobacco, the time corresponding to the medium temperature stage is 40 hours, and the time corresponding to the high temperature stage is 30 hours.

[0090] In this implementation, during the initial startup of the unit, before any items are placed in the second drying chamber, the first reversing valve is opened, and both the first and second drying chambers heat up simultaneously. Once a certain temperature is reached, the third refrigerant system is activated to provide heat to the third drying chamber. This process does not require activating the second refrigerant system, saving energy. The second refrigerant system is only activated when all three drying chambers have reached their respective target temperature ranges and items are placed in the second drying chamber. This ensures that items entering different drying chambers reach the desired baking temperature in the shortest possible time and minimizes drastic temperature fluctuations caused by low item temperatures.

[0091] In one embodiment, controlling the first refrigerant system, the second refrigerant system, and the third refrigerant system based on the monitored temperature includes: after transferring the last batch of items to be dried to the second drying chamber, when the temperature of the second drying chamber stabilizes within a second preset temperature range and there is no need to open the first reversing valve for supplemental heating, shutting off the first refrigerant system; after transferring the last batch of items to be dried to the third drying chamber, when the temperature of the third drying chamber stabilizes within a third preset temperature range, shutting off the second refrigerant system; and after the last batch of items to be dried completes the third stage of baking in the third drying chamber, shutting off the third refrigerant system.

[0092] In this implementation method, when the drying operation is about to be completed and the unit needs to be shut down, the three refrigerant systems are shut down one by one according to the actual situation of each drying room, so as to ensure the drying effect and achieve energy saving.

[0093] Specifically, after transferring the last batch of items to be dried to the second drying chamber, the process also includes: obtaining the current temperature and temperature drop rate of the second drying chamber; if the temperature drop rate is greater than a preset threshold, or if the current temperature is lower than a second preset temperature range, then it is determined that the first reversing valve needs to be opened for supplemental heating.

[0094] In this embodiment, if the temperature of the second drying chamber is too low or the temperature drops too quickly, it means that the second drying chamber needs additional heat to ensure that its temperature is within the second preset temperature range. At this time, the first reversing valve needs to be opened to supplement the temperature of the second drying chamber (i.e., to provide heat to the second drying chamber) in order to ensure the normal drying of the corresponding medium temperature stage of the second drying chamber. At this time, the first refrigerant system cannot be shut down.

[0095] Considering special circumstances such as malfunction of the second refrigerant system or extremely harsh external environments, after transferring the last batch of items to the third drying chamber, the following steps are also included: if the compressor frequency of the third refrigerant system increases to the maximum permissible frequency and the temperature of the second drying chamber drops to the preset temperature, then the electric heating device is activated. This electric heating device is located at the air outlet of the third condenser. When the last batch of items has completed the third stage of drying in the third drying chamber, the third refrigerant system and the electric heating device are shut off. The preset temperature can be a relatively low value, such as 20°C.

[0096] In this embodiment, when the drying operation is about to be completed, only the third drying chamber contains items to be dried, meaning only the third drying chamber needs to perform the drying work. The second drying chamber continuously provides heat to the third drying chamber, and the temperature of the second drying chamber will gradually decrease. When the third refrigerant system can no longer regulate and the temperature of the second drying chamber drops to a certain level, the electric heating device is turned on to supplement the temperature, so as to ensure that the third drying chamber can perform the drying operation normally.

[0097] Considering that the return air carries away a large amount of heat during baking and dehumidification, which may lead to heat supersaturation, and that the third drying chamber is within the normal temperature range, the heat removed by the third evaporator remains constant, causing the second drying chamber to accumulate residual heat from dehumidification and its temperature to continue to rise. To address this issue, this embodiment provides a specific control method. Specifically, based on the monitored temperature, the first, second, and third refrigerant systems are controlled, including:

[0098] During the drying process, all three refrigerant systems are in operation. When the temperature of the second drying chamber continues to rise, it indicates that there is too much heat in the second drying chamber. The second reversing valve is opened to transfer the excess heat in the second drying chamber to the first drying chamber, and the output of the first refrigerant system is reduced to receive the excess heat in the second drying chamber.

[0099] When the temperature of the second drying chamber is monitored to be stable within the second preset temperature range, the second reversing valve is closed.

[0100] During the above control process, the first reversing valve is closed, and the outputs of the second and third refrigerant systems remain unchanged.

[0101] This embodiment addresses the issue of excessive heat in the second drying chamber, thereby maintaining a stable temperature within the chamber.

[0102] Considering that excessive heat loss and temperature drop in the third drying chamber may occur due to human intervention or decreased ambient temperature, a decrease in the temperature of the second drying chamber may result when the third refrigerant system increases its capacity by drawing more heat from the second drying chamber. This embodiment provides a specific control method to address this problem. Specifically, based on the monitored temperature, the first, second, and third refrigerant systems are controlled, including:

[0103] During the drying process, all three refrigerant systems are in operation. When the temperature of the second drying chamber is detected to be lower than the second preset temperature range or the temperature drop rate is greater than the preset threshold, it indicates that the heat in the second drying chamber is too low. The second reversing valve is closed, the first reversing valve is opened, and the output of the first refrigerant system is increased to supplement the heat of the second drying chamber and ensure the heat balance of the second drying chamber.

[0104] When the temperature of the third drying chamber is monitored to be stable within the third preset temperature range, the first reversing valve is closed, reducing the output of the first and third refrigerant systems, while the output of the second refrigerant system remains unchanged.

[0105] This embodiment addresses the issue of insufficient heat in the second drying chamber, ensuring a stable temperature within the chamber.

[0106] The above-described heat pump drying control method will be described below with reference to a specific embodiment. However, it is worth noting that this specific embodiment is only for better illustration of this application and does not constitute an improper limitation of this application. The same or corresponding terminology as in the above embodiment will not be repeated in this embodiment.

[0107] Taking tobacco drying (flue-cured tobacco) as an example, combined with Figure 1 To explain. All the heat in the three drying chambers comes from the external heat absorbed by the first evaporator 14.

[0108] Upon initial startup of the heat pump dryer unit, the first refrigerant system 10 is activated first, and the first reversing valve 16 is opened, simultaneously raising the temperature of the first drying chamber 1 and the second drying chamber 2. Two hours after the first refrigerant system 10 is activated, the third refrigerant system 30 is activated to ensure that all three drying chambers reach their respective preset temperature ranges. When the temperature of the first drying chamber 1 reaches the first preset temperature range and the first box of tobacco has been dried in the first drying chamber 1 for the specified time, the low-temperature drying stage of the first box of tobacco is considered complete. The first box of tobacco is then transferred from the first drying chamber 1 to the second drying chamber 2, the second refrigerant system 20 is allowed to be activated, the first reversing valve 16 is closed, and the first refrigerant system 10, the second refrigerant system 20, and the third refrigerant system 30 all continue to operate, preparing for the subsequent continuous drying of tobacco.

[0109] During the drying process, the heat surplus / deficit is controlled as follows:

[0110] (1) Excessive heat in the second drying chamber 2

[0111] Because the dehumidification return air from the tobacco baking process carries out a large amount of heat, heat supersaturation will occur. Since the third drying chamber 3 is within the third preset temperature range, the heat carried away by the third evaporator 34 remains unchanged. The second drying chamber 2 will accumulate residual heat from dehumidification, and the temperature will continue to rise. At this time, the second reversing valve 26 is opened, and the refrigerant in the second refrigerant system 20 runs along the subcooling route, transferring the excess heat to the first drying chamber 1. The first refrigerant system 10 reduces its system capacity (for example, by reducing the frequency of the first compressor 11) to receive the excess heat from the second drying chamber 2. The third refrigerant system 30 remains unchanged.

[0112] (2) The heat in the second drying chamber 2 is too low.

[0113] If excessive heat is lost from the third drying chamber 3 due to human factors or a decrease in ambient temperature, causing a temperature drop, the third refrigerant system 30 increases its capacity to draw more heat from the second drying chamber 2, resulting in a temperature drop in the second drying chamber 2. At this point, the second reversing valve 26 is closed, and the first reversing valve 16 is opened. The refrigerant in the first refrigerant system 10 travels through the cold path, and the output of the first refrigerant system 10 is increased (e.g., by increasing the frequency of the first compressor 11) to supplement heat to the second drying chamber 2, ensuring heat balance and maintaining the temperature of the second drying chamber 2 until the temperature of the third drying chamber 3 reaches and stabilizes within the third preset temperature range. Then, the first reversing valve 16 is closed, reducing the capacity of the first refrigerant system 10 and the third refrigerant system 30 (the capacity of the first refrigerant system 10 and the third refrigerant system 30 was increased previously; when the temperatures of the second drying chamber 2 and the third drying chamber 3 return to their respective preset temperature ranges, such high system capacity is no longer needed to maintain them, hence the capacity reduction). The second refrigerant system 20 remains unchanged, ensuring that the temperatures of the three drying chambers remain stable.

[0114] After the low-temperature curing stage of the last batch of tobacco is completed, the last batch is moved to the second drying chamber 2. Once the temperature of the second drying chamber 2 stabilizes and there is no need to open the first reversing valve 16 for supplemental heating, the first refrigerant system 10 is shut down first, while the second reversing valve 26 remains operational. During this period, the temperatures of the second drying chamber 2 and the third drying chamber 3 are adjusted according to the aforementioned heat surplus / deficit control method until the medium-temperature curing stage of the last batch of tobacco is completed. Then, the last batch of tobacco is moved entirely to the third drying chamber 3, and once the temperature of the third drying chamber 3 stabilizes, the second refrigerant system 20 is shut down. After the high-temperature curing stage of the last batch of tobacco is completed, the third refrigerant system 30 is shut down, thus completing the unit shutdown. As a special case, when the compressor frequency of the third refrigerant system 30 reaches the maximum allowable frequency and the temperature of the second drying chamber 2 drops to 20°C, the electric heating device in the third refrigerant system 30 is activated for supplemental heating until the high-temperature curing stage is completed, at which point the third refrigerant system 30 and the electric heating device are shut down.

[0115] The medium-temperature stage of tobacco curing is the stage with the greatest heat exchange. Under good insulation conditions and without any abnormalities in the overall system, the heat released by the second condenser 22 is often greater than the heat required to maintain the temperature of the second drying chamber 2 without opening the second reversing valve 26. Therefore, under normal circumstances, it is not necessary to maintain the first refrigerant system 10 and open the first reversing valve 16 to supplement the heat of the second drying chamber 2. Opening the first refrigerant system 10 to supplement the heat of the second drying chamber 2 is generally done in the initial stage when the tobacco is transferred from the first drying chamber 1 to the second drying chamber 2. The tobacco needs to absorb a large amount of heat to evaporate its own moisture, which leads to an increase in the heat load of the second drying chamber 2. At this time, the first refrigerant system 10 and the second refrigerant system 20 need to work together to maintain the temperature stability of the second drying chamber 2.

[0116] Example 3

[0117] This embodiment provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the method described in the above embodiment.

[0118] Example 4

[0119] This embodiment provides a non-volatile computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, it implements the steps of the method described in the above embodiment.

[0120] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0121] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat pump drying unit, characterized in that, The heat pump drying unit is distributed in the first drying room, the second drying room and the third drying room. The items to be dried are dried by passing through the first drying room, the second drying room and the third drying room in sequence. The heat pump dryer unit includes: a first refrigerant system, a second refrigerant system, and a third refrigerant system that are independent of each other; the refrigerant injected into the first refrigerant system and the second refrigerant system is different from the refrigerant injected into the third refrigerant system; By controlling the first refrigerant system, the second refrigerant system, and the third refrigerant system, the temperature of the first drying chamber is stabilized within a first preset temperature range, the temperature of the second drying chamber is stabilized within a second preset temperature range, and the temperature of the third drying chamber is stabilized within a third preset temperature range. Wherein, the first preset temperature range < the second preset temperature range < the third preset temperature range; The first refrigerant system includes a first compressor, a first condenser, a first throttling element, and a first evaporator connected in sequence; the first refrigerant system also includes a first subcooler and a first reversing valve; the first reversing valve is disposed on the pipeline between the first condenser and the first throttling element; the inlet of the first subcooler is connected to the first reversing valve, and the outlet of the first subcooler is connected to the inlet of the first throttling element; when the first reversing valve is open, it connects the outlet of the first condenser with the inlet of the first subcooler, and when the first reversing valve is closed, it connects the outlet of the first condenser with the inlet of the first throttling element; the first evaporator is located outdoors, the first condenser is located inside the first drying chamber, and the first subcooler is located inside the second drying chamber; The second refrigerant system includes a second compressor, a second condenser, a second throttling element, and a second evaporator connected in sequence; the second refrigerant system also includes a second subcooler and a second reversing valve; the second reversing valve is disposed on the pipeline between the second condenser and the second throttling element; the inlet of the second subcooler is connected to the second reversing valve, and the outlet of the second subcooler is connected to the inlet of the second throttling element; when the second reversing valve is open, it connects the outlet of the second condenser with the inlet of the second subcooler; when the second reversing valve is closed, it connects the outlet of the second condenser with the inlet of the second throttling element; the second evaporator and the second condenser are both located in the second drying chamber, and the second subcooler is located in the first drying chamber; The third refrigerant system includes a third compressor, a third condenser, a third throttling element, and a third evaporator connected in sequence; the third evaporator is located in the second drying chamber, and the third condenser is located in the third drying chamber.

2. The heat pump dryer unit according to claim 1, characterized in that, An electric heating device is installed at the air outlet of the third condenser.

3. The heat pump dryer unit according to any one of claims 1 to 2, characterized in that, Under the same operating mode, the working pressure of the refrigerant injected into the first refrigerant system and the second refrigerant system is higher than that of the refrigerant injected into the third refrigerant system.

4. A heat pump drying control method, characterized in that, The method, applied to the heat pump dryer unit according to any one of claims 1 to 3, comprises: Monitor the temperatures of the first drying chamber, the second drying chamber, and the third drying chamber; Based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled to stabilize the temperature of the first drying chamber within a first preset temperature range, the temperature of the second drying chamber within a second preset temperature range, and the temperature of the third drying chamber within a third preset temperature range.

5. The method according to claim 4, characterized in that, Based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including: In response to the power-on command, the first refrigerant system and the first reversing valve are opened; After a preset time, the third refrigerant system is turned on; When the temperature of the first drying chamber reaches the first preset temperature range, the temperature of the second drying chamber reaches the second preset temperature range, the temperature of the third drying chamber reaches the third preset temperature range, and the first batch of items to be dried has completed the first stage of baking in the first drying chamber, the first batch of items to be dried is transferred to the second drying chamber, the second refrigerant system is turned on, and the first reversing valve is turned off.

6. The method according to claim 4, characterized in that, Based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including: After the last batch of items to be dried is transferred to the second drying chamber, when the temperature of the second drying chamber is stable within the second preset temperature range and there is no need to open the first reversing valve for temperature replenishment, the first refrigerant system is shut down. After the last batch of items to be dried is transferred to the third drying chamber, the second refrigerant system is turned off when the temperature of the third drying chamber stabilizes within the third preset temperature range. After the last batch of items to be dried completes the third stage of drying in the third drying room, the third refrigerant system is turned off.

7. The method according to claim 6, characterized in that, After transferring the last batch of items to be dried to the second drying room, the process also includes: Obtain the current temperature and temperature drop rate of the second drying chamber; If the temperature drop rate is greater than a preset threshold, or if the current temperature is lower than the second preset temperature range, then it is determined that the first reversing valve needs to be opened for temperature compensation.

8. The method according to claim 6, characterized in that, After transferring the last batch of items to be dried to the third drying room, the process also includes: If the compressor frequency of the third refrigerant system rises to the maximum allowable frequency and the temperature of the second drying chamber drops to the preset temperature, the electric heating device is turned on, wherein the electric heating device is located at the air outlet of the third condenser; When the last batch of items to be dried has completed the third stage of drying in the third drying room, the third refrigerant system and the electric heating device are turned off.

9. The method according to claim 4, characterized in that, Based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including: During the drying process, when the temperature of the second drying chamber is detected to be rising continuously, the second reversing valve is opened and the output of the first refrigerant system is reduced. When the temperature of the second drying chamber is monitored to be stable within the second preset temperature range, the second reversing valve is closed.

10. The method according to claim 4, characterized in that, Based on the monitored temperature, the first refrigerant system, the second refrigerant system, and the third refrigerant system are controlled, including: During the drying process, when the temperature of the second drying chamber is detected to be lower than the second preset temperature range or the temperature drop rate is greater than the preset threshold, the second reversing valve is closed, the first reversing valve is opened, and the output of the first refrigerant system is increased. When the temperature of the third drying chamber is monitored to be stable within the third preset temperature range, the first reversing valve is closed, reducing the output of the first refrigerant system and the third refrigerant system, while the output of the second refrigerant system remains unchanged.

11. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor, when executing the computer program, implements the steps of the method according to any one of claims 4 to 10.

12. A non-volatile computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 4 to 10.

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