Heat pump drying system and method for controlling moisture removal of heat pump drying system

Abstract

The present application relates to the technical field of heat pump drying, and particularly provides a heat pump drying system and a dehumidification control method thereof, aiming to solve the problem of large heat loss and influence on drying quality when the system dehumidifies. To this end, the heat pump drying system comprises a first electromagnetic valve, a second electromagnetic valve, a heat recovery heat exchanger, and a compressor, a condenser, an expansion device and an evaporator connected in sequence to constitute a main loop of refrigerant circulation, the first electromagnetic valve is arranged between the outlet of the expansion device and the first interface of the evaporator, the second electromagnetic valve is arranged between the outlet of the expansion device and the inlet of the heat recovery heat exchanger, and the outlet of the heat recovery heat exchanger is connected with the second interface of the evaporator, and the control method comprises detecting the operation mode of the heat pump drying system, when the heat pump drying system enters a forced dehumidification mode, the first electromagnetic valve is controlled to be closed, and the second electromagnetic valve is controlled to be opened, so that the heat in the humid hot air is recovered while dehumidifying, the heat loss is reduced, and the baking quality is improved.

Description

Technical Field

[0001] This invention relates to the field of heat pump drying technology, specifically providing a dehumidification control method for a heat pump drying system and a heat pump drying system. Background Technology

[0002] Flue-cured tobacco is the primary material for cigarette production, and its preparation involves controlling the moisture content of the tobacco leaves to ensure timely dehydration and drying. This process requires specialized curing barns equipped with heat sources and ventilation / dehumidification systems. Currently, the most common heat source used in curing barns is an air-source heat pump dryer. Ventilation / dehumidification equipment includes air inlet doors, exhaust doors, and circulating fans to drive airflow. The curing process in this type of barn is as follows: hot air generated in the hot air chamber, equipped with a dryer heat exchanger, enters the tobacco loading chamber under the action of the circulating fan. The hot air penetrates the tobacco layer evenly at set airflow and pressure conditions, exchanging moisture and heat with the tobacco leaves, gradually curing them. After the moisture and heat exchange, the temperature of the hot air decreases, its relative humidity increases, and it contains more pollutants such as carbon dioxide. Under the action of the circulating fan, it flows back to the hot air chamber, is reheated, and enters the next cycle. During the drying period, when the humidity in the tobacco loading chamber exceeds the set humidity, some of the humid and hot air needs to be discharged in a timely manner, and correspondingly, fresh air needs to be added.

[0003] However, when the hot, humid air is expelled, it carries away a significant portion of the heat from the curing barn. The duration of dehumidification determines the amount of heat loss; the longer the dehumidification time, the greater the heat loss and the greater the temperature drop, leading to temperature fluctuations within the curing barn. Furthermore, the dehumidification process during tobacco drying is generally carried out based on the personal experience of the tobacco curing master, which easily results in a large waste of heat, affecting the drying effect and quality.

[0004] Therefore, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problems of large heat loss during dehumidification in existing heat pump drying systems, which affects the drying effect and drying quality.

[0006] In a first aspect, the present invention provides a dehumidification control method for a heat pump drying system, the heat pump drying system comprising: a heating chamber connected to a drying oven, the heating chamber having an openable and closable dehumidification port, and a dehumidification fan installed at the dehumidification port; a compressor, a condenser, an expansion device, and an evaporator sequentially connected to form a refrigerant circulation main loop; a first solenoid valve disposed between the outlet of the expansion device and a first interface of the evaporator; a second solenoid valve and a heat recovery heat exchanger, the second solenoid valve being disposed between the outlet of the expansion device and the inlet of the heat recovery heat exchanger, the outlet of the heat recovery heat exchanger being connected to a second interface of the evaporator; the control method comprising: detecting the operating mode of the heat pump drying system; and when the heat pump drying system enters a forced dehumidification mode, controlling the first solenoid valve to close and the second solenoid valve to open.

[0007] In a specific embodiment of the dehumidification control method for the above-mentioned heat pump drying system, the control method further includes: when the heat pump drying system is in automatic dehumidification mode, acquiring the actual humidity inside the drying room; when the actual humidity is higher than the preset humidity, controlling the dehumidification port to open, and controlling the heat pump drying system to enter forced dehumidification mode.

[0008] In a specific embodiment of the dehumidification control method for the above-mentioned heat pump drying system, the control method further includes: in forced dehumidification mode, controlling the dehumidification fan to start and run at a first speed; calculating the actual humidity decrease rate in the drying room based on the actual humidity in the drying room; and controlling the subsequent operation of the dehumidification fan based on the actual humidity decrease rate.

[0009] In a specific embodiment of the dehumidification control method for the above-mentioned heat pump drying system, the control method further includes: when the heat pump drying system is in manual dehumidification mode, acquiring the opening and closing state of the dehumidification port; when the dehumidification port is in the open state, controlling the heat pump drying system to enter the forced dehumidification mode.

[0010] In a specific embodiment of the dehumidification control method of the above-mentioned heat pump drying system, the control method further includes: in the forced dehumidification mode, controlling the dehumidification fan to start and run at a third speed; calculating the actual humidity decrease rate in the drying room based on the actual humidity in the drying room; and controlling the dehumidification fan to stop running when the actual humidity decrease rate is higher than the second preset humidity decrease rate.

[0011] In a specific embodiment of the dehumidification control method for the above-mentioned heat pump drying system, the control method further includes: after the dehumidification fan stops running, obtaining the actual humidity inside the drying room; when the actual humidity is higher than the preset humidity, controlling the dehumidification fan to run at a first speed.

[0012] In a specific embodiment of the dehumidification control method for the above-mentioned heat pump drying system, the control method further includes: after the dehumidification fan runs at a first speed, calculating the actual humidity decrease rate in the drying room based on the actual humidity in the drying room; and controlling the subsequent operation of the dehumidification fan based on the actual humidity decrease rate.

[0013] In a specific implementation of the dehumidification control method for the aforementioned heat pump drying system, the step of "controlling the subsequent operation of the dehumidification fan based on the actual humidity decrease rate" further includes: when the actual humidity decrease rate is lower than the first preset humidity decrease rate, controlling the dehumidification fan to operate at a second speed.

[0014] In a specific implementation of the dehumidification control method for the aforementioned heat pump drying system, the step of "controlling the subsequent operation of the dehumidification fan based on the actual humidity decrease rate" further includes: when the actual humidity decrease rate is higher than the preset humidity decrease rate, controlling the dehumidification fan to operate at a third speed; wherein, the third speed < the first speed < the second speed.

[0015] In a second aspect, the present invention also provides a heat pump drying system, including a controller configured to perform the dehumidification control method described above.

[0016] By employing the above technical solution, a heat recovery heat exchanger is installed in the heating chamber, and a solenoid valve is used to switch the refrigerant flow path. This allows for the recovery of heat from the humid air while simultaneously dehumidifying, reducing heat loss. Furthermore, the refrigerant with partially recovered heat re-enters the evaporator, reducing system energy consumption during drying mode and improving the machine's heating capacity at low temperatures, ensuring stable heat input and thus improving baking quality. A dehumidification duct is also installed in the heating chamber, allowing the humid air in the drying oven to converge within the duct, further enhancing heat recovery efficiency.

[0017] Furthermore, the dehumidification control method of the heat pump drying system of the present invention also provides dehumidification control methods for the system in automatic dehumidification mode and manual dehumidification mode. Compared with the existing dehumidification method that relies on the personal experience of the tobacco curing master, it can ensure the curing effect and curing quality, as well as reduce heat loss. Attached Figure Description

[0018] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0019] Figure 1 This is a schematic diagram of the structure of the heat pump drying system of the present invention;

[0020] Figure 2 This is a schematic diagram of the refrigerant circulation principle of the heat pump drying system of the present invention;

[0021] Figure 3 This is a flowchart of the main steps of the dehumidification control method of the heat pump drying system of the present invention;

[0022] Figure 4 This is a possible complete flowchart of the dehumidification control method of the heat pump drying system of the present invention;

[0023] List of reference numerals in the attached diagram:

[0024] 1. Heating chamber; 101. Exhaust vent; 102. Fresh air inlet; 103. Return air inlet; 104. Air inlet; 2. Exhaust duct; 3. Exhaust fan; 4. Heat recovery heat exchanger; 5. Compressor; 6. Condenser; 7. Expansion device; 8. First solenoid valve; 9. Second solenoid valve; 10. Evaporator; 11. Drying room. Detailed Implementation

[0025] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0026] It should be noted that in the description of this invention, terms such as "inner" and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. This is merely for ease of description and does not indicate or imply that the relevant devices or elements must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention. Furthermore, ordinal numbers such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] Furthermore, it should be noted that although the various steps of the control method of the present invention are described in a specific order in the description of the present invention, these orders are not restrictive. Without departing from the basic principles of the present invention, those skilled in the art can perform the steps in different orders.

[0029] First refer to Figure 1 and Figure 2,in, Figure 1 This is a schematic diagram of the heat pump drying system of the present invention. Figure 2 This is a schematic diagram of the refrigerant circulation principle of the heat pump drying system of the present invention.

[0030] like Figure 1 As shown, the heat pump drying system includes a heating chamber 1, a condenser 6, and an outdoor unit ( Figure 1 (Not shown) and a heat recovery heat exchanger 4. The heating chamber 1 is equipped with an openable and closable exhaust port 101. An exhaust duct 2 is installed inside the heating chamber 1, connected to the exhaust port 101. The heat recovery heat exchanger 4 is located inside the exhaust duct 2. A condenser 6 is located inside the heating chamber 1. The outdoor unit, including a compressor 5, an expansion device 7, and an evaporator 10, is located outside the heating chamber 1. An exhaust fan 3 is installed at the exhaust port 101 to accelerate airflow and improve exhaust efficiency and the heat exchange efficiency of the heat recovery heat exchanger 4. The heating chamber 1 is also equipped with an air inlet 104, a return air inlet 103, and a fresh air inlet 102. The air inlet 104 and return air inlet 103 allow the heating chamber 1 to communicate with the drying oven 11, while the fresh air inlet 102 allows the heating chamber 1 to communicate with the external environment.

[0031] like Figure 2 As shown, compressor 5, condenser 6, expansion device 7, and evaporator 10 are sequentially connected to form the main refrigerant circulation loop. The heat pump drying system also includes a first solenoid valve 8 and a second solenoid valve 9. The first solenoid valve 8 is located between the outlet of expansion device 7 and the first interface of evaporator 10, and the second solenoid valve 9 is located between the outlet of expansion device 7 and the inlet of heat recovery heat exchanger 4. The outlet of heat recovery heat exchanger 4 is connected to the second interface of evaporator 10. Specifically, the refrigerant flow path of the heat pump drying system changes according to the different operating modes of the heat pump drying system. When the heat pump drying system enters the forced dehumidification mode, the first solenoid valve 8 is closed and the second solenoid valve 9 is opened. After the refrigerant passes through the expansion device 7 for throttling, it first enters the heat recovery heat exchanger 4 to recover some of the heat from the humid air before entering the evaporator 10. When the heat pump drying system enters the drying mode, the first solenoid valve 8 is opened and the second solenoid valve 9 is closed. After the refrigerant passes through the expansion device 7 for throttling, it directly enters the evaporator 10.

[0032] For example, the first solenoid valve 8 is configured as a normally closed solenoid valve, and the second solenoid valve 9 is configured as a normally open solenoid valve, with the first solenoid valve 8 and the second solenoid valve 9 interlocked for control.

[0033] For example, the expansion device 7 is configured as an electronic expansion valve.

[0034] For example, a damper (not shown in the figure) is provided at the exhaust port 101 to control the opening and closing of the exhaust port 101.

[0035] See below. Figure 3The figure shows a flowchart of the main steps of the dehumidification control method of the heat pump drying system of the present invention. Figure 3 As shown, the control method of the present invention includes the following steps:

[0036] S1, detects the operating mode of the heat pump drying system;

[0037] S2, when the heat pump drying system enters the forced dehumidification mode, the first solenoid valve 8 is closed and the second solenoid valve 9 is opened.

[0038] In step S1, the heat pump drying system operates in two modes: automatic dehumidification and manual dehumidification. Generally, the factory default operating mode is automatic dehumidification, but users can switch to manual dehumidification as needed. Alternatively, the user can select either automatic or manual dehumidification mode after powering on the system.

[0039] In this embodiment, the different operating speeds of the dehumidifying fan 3 of the present invention correspond to different gears. Specifically, when the dehumidifying fan 3 operates at the third speed, it is at its lowest speed, which is the low gear; when the dehumidifying fan 3 operates at the first speed, it is in the middle speed, which is the medium gear; and when the dehumidifying fan 3 operates at the second speed, it is at its highest speed, which is the high gear.

[0040] When the heat pump drying system is in automatic dehumidification mode, the dehumidification control method specifically includes the following steps:

[0041] S11, obtain the actual humidity inside the drying room 11;

[0042] S12, when the actual humidity is higher than the preset humidity, control the vent 101 to open and control the heat pump drying system to enter the forced dehumidification mode.

[0043] When the heat pump drying system is in automatic dehumidification mode and then enters forced dehumidification mode, the dehumidification control method also includes the following steps:

[0044] S31 controls the dehumidification fan 3 to start and run at the first speed (equivalent to medium speed);

[0045] S32, Calculate the rate of decrease of actual humidity in drying room 11 based on the actual humidity inside the drying room 11;

[0046] S33 controls the subsequent operation of the dehumidification fan 3 based on the actual rate of humidity decrease.

[0047] When the heat pump drying system is in manual dehumidification mode, the specific steps of the dehumidification control method include:

[0048] S110, Obtain the open / closed state of the exhaust port 101;

[0049] S120, when the exhaust port 101 is open, the heat pump drying system is controlled to enter the forced dehumidification mode.

[0050] When the heat pump drying system is in manual dehumidification mode and then enters forced dehumidification mode, the dehumidification control method also includes the following steps:

[0051] S310 controls the dehumidification fan 3 to start and run at the third speed (equivalent to low gear);

[0052] S320, calculate the rate of decrease of actual humidity in drying room 11 based on the actual humidity inside the drying room 11;

[0053] S330, when the actual humidity decrease rate is higher than the second preset humidity decrease rate, control the dehumidification fan 3 to stop running;

[0054] S340: After the dehumidification fan 3 stops running, the actual humidity inside the drying room 11 is obtained;

[0055] S350, when the actual humidity is higher than the preset humidity, control the dehumidification fan 3 to run at the first speed (equivalent to medium speed);

[0056] S360, after the dehumidification fan 3 runs at the first speed (equivalent to medium speed), calculate the actual humidity decrease rate in the drying room 11 based on the actual humidity in the drying room 11;

[0057] S370 controls the subsequent operation of the dehumidification fan 3 based on the actual rate of humidity decrease.

[0058] In the above steps, those skilled in the art will know that there is a certain functional relationship between temperature difference and humidity. Based on the temperature difference between the dry-bulb temperature and the wet-bulb temperature inside the drying chamber 11, the actual humidity inside the drying chamber 11 can be obtained. The lower the humidity, the lower the wet-bulb temperature. The rate of humidity decrease can be calculated by obtaining the rate of decrease of the wet-bulb temperature. Therefore, in automatic dehumidification mode, the wet-bulb temperature decrease rate is set to 0.5℃ / 5s as the judgment threshold to obtain the first preset humidity decrease rate. In manual dehumidification mode, the wet-bulb temperature decrease rate is set to 0.1℃ / min to obtain the second preset humidity decrease rate.

[0059] Specifically, in automatic dehumidification mode, the dehumidification vent 101 will only open when the actual humidity inside the drying chamber 11 meets the preset humidity. That is, dehumidification only occurs after the humidity inside the drying chamber 11 has accumulated to a certain level. In manual dehumidification mode, the dehumidification vent 101 may remain open continuously, resulting in the extreme situation of continuous dehumidification in the drying chamber 11. In the initial stage of system operation, the humidity inside the drying chamber 11 is low; therefore, the first preset humidity reduction rate is set higher than the second preset humidity reduction rate. Of course, the wet-bulb temperature reduction rates listed above are merely illustrative and not restrictive. Those skilled in the art can flexibly adjust and set the wet-bulb temperature reduction rate according to actual needs, and this invention does not impose any limitations in this regard.

[0060] In steps S33 and S370, the step of "controlling the subsequent operation of the exhaust fan 3" specifically includes:

[0061] S381, when the actual humidity decrease rate is lower than the first preset humidity decrease rate, control the dehumidification fan 3 to run at the second speed (equivalent to high speed);

[0062] S382, when the actual humidity decreases faster than the preset humidity decrease rate, control the dehumidification fan 3 to run at the third speed (equivalent to low speed).

[0063] In step S381, if the actual humidity in the curing barn 11 decreases slowly, there is a risk that the tobacco leaves will spoil due to slow dehumidification in the curing barn 11. Therefore, the speed of the dehumidification fan 3 is increased to a high speed to speed up the dehumidification of the curing barn 11.

[0064] In step S381, if the actual humidity inside the curing barn 11 drops too quickly, the cold air entering the curing barn 11 too quickly will easily cause drastic fluctuations in the internal temperature of the curing barn 11, thereby affecting the curing quality of the tobacco leaves. Therefore, the speed of the dehumidification fan 3 is reduced to a low setting to slow down the dehumidification of the curing barn 11.

[0065] See below. Figure 4 Taking the heat pump drying system in automatic dehumidification mode as an example, a possible control process of the present invention will be introduced.

[0066] like Figure 4 As shown, a possible complete process of the dehumidification control method of the present invention is as follows:

[0067] S101, Obtain the actual humidity inside the drying room 11;

[0068] S102, compare whether the actual humidity is higher than the preset humidity;

[0069] If the actual humidity is higher than the preset humidity, then step S103 is executed;

[0070] If the actual humidity is lower than the preset humidity, then proceed to step S109;

[0071] S103, control the first solenoid valve 8 to close and the second solenoid valve 9 to open, so that the heat pump drying system enters the forced dehumidification mode.

[0072] S104 controls the exhaust fan 3 to start and run at medium speed;

[0073] S105, Calculate the actual humidity decrease rate inside the drying room 11 based on the actual humidity inside the drying room 11;

[0074] S106, compare whether the actual humidity decrease rate is lower than the preset humidity decrease rate;

[0075] When the actual humidity decrease rate is lower than the first preset humidity decrease rate, step S107 is executed;

[0076] If the actual humidity decreases at a rate higher than the preset humidity decrease rate, then step S108 is executed.

[0077] S107 controls the exhaust fan 3 to operate at high speed;

[0078] S108 controls the exhaust fan 3 to run at a low speed;

[0079] S109 controls the first solenoid valve 8 to open and the second solenoid valve 9 to close.

[0080] This invention provides a dehumidification control method for a heat pump drying system. By installing a heat recovery heat exchanger 4 in the heating chamber 1 and switching the refrigerant flow path using a solenoid valve, heat can be recovered from the humid air while dehumidifying, thus reducing heat loss. Simultaneously, the refrigerant with partially recovered heat re-enters the evaporator 10. During drying mode, this reduces system energy consumption and improves the machine's heating capacity at low temperatures, ensuring stable heat input and improving baking quality. A dehumidification duct 2 is also installed in the heating chamber 1, allowing the humid air in the drying chamber 11 to converge within the duct, further improving heat recovery efficiency.

[0081] Furthermore, the dehumidification control method of the heat pump drying system of the present invention also provides dehumidification control methods for the system in automatic dehumidification mode and manual dehumidification mode. Compared with the existing dehumidification method that relies on the personal experience of the tobacco curing master, it can ensure the curing effect and curing quality, as well as reduce heat loss.

[0082] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method of dehumidification control for a heat pump drying system, characterized by, The heat pump drying system comprises: a heating chamber connected with the curing barn, the heating chamber being provided with an openable and closable moisture outlet, and a moisture exhaust fan being arranged at the moisture outlet; a compressor, a condenser, an expansion device and an evaporator connected in sequence to form a main refrigerant circulation loop; a first electromagnetic valve arranged between an outlet of the expansion device and a first interface of the evaporator; a second electromagnetic valve arranged between the outlet of the expansion device and an inlet of a heat recovery heat exchanger, and an outlet of the heat recovery heat exchanger being connected with a second interface of the evaporator; the control method comprises: detecting an operation mode of the heat pump drying system; when the heat pump drying system enters a forced moisture exhaust mode, controlling the first electromagnetic valve to be closed and the second electromagnetic valve to be opened; when the heat pump drying system is in an automatic moisture exhaust mode, acquiring an actual humidity in the curing barn; when the actual humidity is higher than a preset humidity, controlling the moisture outlet to be opened and the heat pump drying system to enter the forced moisture exhaust mode; when the heat pump drying system is in a manual moisture exhaust mode, acquiring an opening and closing state of the moisture outlet; when the moisture outlet is in an open state, controlling the heat pump drying system to enter the forced moisture exhaust mode; when the heat pump drying system is in the manual moisture exhaust mode and enters the forced moisture exhaust mode, the control method further comprises: controlling the moisture exhaust fan to start and run at a third rotating speed; calculating an actual humidity drop speed in the curing barn according to the actual humidity in the curing barn; when the actual humidity drop speed is higher than a second preset humidity drop speed, controlling the moisture exhaust fan to stop running.

2. The dehumidification control method of a heat pump drying system according to claim 1, characterized by, when the heat pump drying system is in the automatic moisture exhaust mode and enters the forced moisture exhaust mode, the control method further comprises: controlling the moisture exhaust fan to start and run at a first rotating speed; calculating an actual humidity drop speed in the curing barn according to the actual humidity in the curing barn; controlling subsequent running of the moisture exhaust fan based on the actual humidity drop speed.

3. The dehumidification control method of a heat pump drying system according to claim 1, characterized by, the control method further comprises: after the moisture exhaust fan stops running, acquiring the actual humidity in the curing barn; when the actual humidity is higher than the preset humidity, controlling the moisture exhaust fan to run at the first rotating speed.

4. The dehumidification control method of a heat pump drying system according to claim 3, characterized by, the control method further comprises: after the moisture exhaust fan runs at the first rotating speed, calculating an actual humidity drop speed in the curing barn according to the actual humidity in the curing barn; controlling subsequent running of the moisture exhaust fan based on the actual humidity drop speed.

5. The dehumidification control method of a heat pump drying system according to claim 2 or 4, characterized in that, the step of "controlling subsequent running of the moisture exhaust fan based on the actual humidity drop speed" further comprises: when the actual humidity drop speed is lower than a first preset humidity drop speed, controlling the moisture exhaust fan to run at a second rotating speed.

6. The dehumidification control method of a heat pump drying system according to claim 5, wherein, the step of "controlling subsequent running of the moisture exhaust fan based on the actual humidity drop speed" further comprises: when the actual humidity drop speed is higher than a preset humidity drop speed, controlling the moisture exhaust fan to run at a third rotating speed; wherein the third rotating speed < the first rotating speed < the second rotating speed.

7. A heat pump drying system comprising a controller configured to perform the dehumidification control method of any one of claims 1 to 6.

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