Parallel type dual-mode adaptive heat pump drying system and control method

Abstract

The application provides a parallel type dual-mode adaptive heat pump drying system and a control method. The system is mainly composed of a controller, a data acquisition interface and an execution driving circuit. The controller calculates the dew point and the surface temperature difference based on the collected return air temperature and humidity and the surface temperature, determines the running state, and introduces a switching permission variable to smooth the state result. Then, the load distribution coefficient of the refrigerant side and the air side is dynamically generated according to the permission variable, the flow and air volume distribution of the main and auxiliary heat exchange units are adjusted, and the mode logic switching is triggered only when the permission variable meets the threshold value. The application realizes smooth transition between the dual modes without impact, and improves the stability and energy efficiency of the drying process.

Description

Technical Field

[0001] This invention belongs to the field of heat pump technology, and particularly relates to a parallel dual-mode adaptive heat pump drying system and control method. Background Technology

[0002] Heat pump drying equipment utilizes refrigeration cycles to achieve air heating and dehumidification, and has been successfully applied in the drying of agricultural products, food, traditional Chinese medicine, and industrial materials. Existing air-source heat pump drying systems generally consist of a compressor, evaporator, condenser, throttling device, fan, and necessary valves. They regulate the outlet air temperature and humidity parameters through a closed-loop system to meet process requirements. To adapt to the strong dehumidification demands during the initial high-humidity stage of drying and the strong heating demands during the later high-temperature stage, some systems employ multi-heat exchanger or multi-operating-mode structures. For example, auxiliary heat exchangers are added, and their functions are altered through valves, allowing the system to switch between dehumidification and heating capabilities. However, in parallel heat exchanger architectures, especially when the same third heat exchanger needs to function as an auxiliary evaporator during two-stage dehumidification and as an auxiliary condenser during two-stage heating, and simultaneously participates in heat exchange on both the refrigerant and air sides, mode switching involves not only changes in valve logic but also a rearrangement of refrigerant branch flow distribution, thermal inertia response of heat exchanger wall temperature, and changes in airflow distribution on the air side. During the critical range of the drying process from high humidity to high temperature, the relative relationship between the dew point and the evaporator coil temperature changes rapidly. The system often experiences a situation where it "just switches and then needs to switch back," resulting in frequent operation of the solenoid valve, large swings in the opening of the throttling device, and transient imbalance of the heat exchange load on both sides of the parallel system. This manifests as increased fluctuations in outlet air temperature and humidity, mutual restraint between dehumidification and heating capabilities, decreased energy efficiency, and even deterioration in operational stability.

[0003] Existing control methods mostly use a small number of temperature and humidity parameter thresholds to directly trigger mode switching. They lack mechanisms to identify and constrain "switching-sensitive states" and also lack engineering means to continuously distribute parallel loads when switching is restricted. Therefore, it is difficult to simultaneously ensure stability, dehumidification capacity and high-temperature heating capacity throughout the entire drying process, which has become a key bottleneck for further improving the performance of parallel dual-mode heat pump drying systems. Summary of the Invention

[0004] This invention discloses a parallel dual-mode adaptive heat pump drying system and control method to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, a first aspect of the present invention provides a parallel dual-mode adaptive heat pump drying control method, the method comprising: The system obtains the heat and humidity parameters of the return air and the surface temperature parameters of the main heat exchange area, calculates the return air dew point temperature based on the heat and humidity parameters, calculates the temperature difference between the return air dew point temperature and the surface temperature parameters, and generates a system operation status determination result by combining the preset drying process stage information. The system operation state determination results are discretized based on the first-order inertial model to generate switching permission variables with time continuity. These switching permission variables are used to characterize the degree of permission to change the parallel participation mode of the auxiliary parallel heat exchange unit. Based on the switching permission variables and the target operating mode, determine the parallel load distribution coefficient of the auxiliary parallel heat exchange unit on the refrigerant side and the air volume distribution coefficient on the air side; Based on the parallel load allocation coefficient, a main flow rate adjustment command corresponding to the main heat exchange area and an auxiliary flow rate adjustment command corresponding to the auxiliary parallel heat exchange unit are generated. Based on the air volume allocation coefficient, a main air volume adjustment command corresponding to the main heat exchange area and an auxiliary air volume adjustment command corresponding to the auxiliary parallel heat exchange unit are generated. When the switching permission variable meets the preset threshold condition, a switching command to change the parallel connection logic of the auxiliary parallel heat exchange unit is generated.

[0006] Furthermore, the generation of the system operation status determination result specifically includes: The collected return air dry-bulb temperature and relative humidity are converted into return air dew point temperature; The surface temperature parameters are obtained by performing a moving average process on the collected surface temperature signal of the main heat exchange area. The temperature difference is calculated as the difference between the return air dew point temperature and the surface temperature parameter. The temperature difference is compared with the preset first threshold and second threshold, and combined with the current preset drying process stage number, the system operation status judgment result is output with the first value or the second value, where the first value represents the non-sensitive state and the second value represents the sensitive state.

[0007] Furthermore, the generation of switching permission variables with time continuity specifically includes: By setting the sampling period and the parameters of the first-order inertial system, a discretized first-order inertial difference equation is constructed. Substitute the locking strength of the previous sampling period and the system operating state determination result of the current sampling period into the discretized first-order inertial difference equation to calculate the locking strength of the current sampling period. The switching permission variable for the current sampling period is obtained by subtracting the lock strength of the current sampling period from the constant 1. Specifically, when the system operation status determination result is the second value, the lock strength converges to 1, and the switching permission variable approaches 0; when the system operation status determination result is the first value, the lock strength decays exponentially, and the switching permission variable gradually increases.

[0008] Furthermore, determining the parallel load distribution coefficient of the auxiliary parallel heat exchange units on the refrigerant side specifically includes: Read the target operating mode, which includes a single-stage heating mode, a two-stage dehumidification mode, or a two-stage heating mode; An orientation factor is generated based on the target operating mode. When the target operating mode is a single-stage heating mode, the orientation factor takes the first orientation value. When the target operating mode is a two-stage dehumidification mode or a two-stage heating mode, the orientation factor takes the second orientation value. The switching allowable variable is nonlinearly processed based on the power-order shaping parameter. Combined with the direction factor, the parallel load allocation coefficient of the previous control cycle and the update coefficient, the refrigerant-side parallel load allocation coefficient of the current control cycle is calculated through the exponential smoothing difference equation. The refrigerant-side parallel load distribution coefficient is limited to a preset lower and upper limit.

[0009] Furthermore, determining the airflow distribution coefficient of the auxiliary parallel heat exchange unit on the air side specifically includes: Establish an interval linear mapping relationship, and use the refrigerant-side parallel load distribution coefficient as the independent variable; By using the preset lower limit and upper limit of air-side distribution, the refrigerant-side parallel load distribution coefficient is mapped to the air-side air volume distribution coefficient; The control air volume distribution coefficient changes in the same direction as the refrigerant side parallel load distribution coefficient.

[0010] Furthermore, the generation of the main flow rate regulation command corresponding to the main heat exchange region and the auxiliary flow rate regulation command corresponding to the auxiliary parallel heat exchange unit specifically includes: Obtain the current total refrigerant mass flow rate of the system; Multiply the total refrigerant mass flow rate by the refrigerant-side parallel load distribution coefficient to obtain the target mass flow rate of the auxiliary parallel heat exchange unit branch. Subtract the target mass flow rate of the auxiliary parallel heat exchange unit branch from the total refrigerant mass flow rate to obtain the target mass flow rate of the main heat exchange area branch. By consulting the pre-stored calibration curves of throttling opening and mass flow rate, and using a piecewise linear interpolation algorithm, the target mass flow rate of the auxiliary parallel heat exchange unit branch is converted into the auxiliary throttling opening command, and the target mass flow rate of the main heat exchange area branch is converted into the main throttling opening command.

[0011] Furthermore, the generation of the main airflow adjustment command corresponding to the main heat exchange area and the auxiliary airflow adjustment command corresponding to the auxiliary parallel heat exchange unit specifically includes: Obtain the current total circulating air volume of the system; Multiply the total circulating air volume by the air-side air volume distribution coefficient to obtain the target air volume of the auxiliary parallel heat exchange unit duct. Subtract the target air volume of the auxiliary parallel heat exchange unit duct from the total circulating air volume to obtain the target air volume of the main heat exchange area duct. Consult the pre-stored calibration curves of air volume adjustment execution quantity and air volume, convert the target air volume of the auxiliary parallel heat exchange unit duct into the auxiliary air volume adjustment command, and convert the target air volume of the main heat exchange area duct into the main air volume adjustment command.

[0012] Furthermore, the generation of the switching instruction to change the parallel connection logic of the auxiliary parallel heat exchange unit specifically includes: Determine whether the switching permission variable is greater than the preset allowed switching threshold; If the switching permission variable is greater than the preset allowable switching threshold and the target operating mode changes from the two-stage dehumidification mode to the two-stage heating mode, a switching command is generated to switch the auxiliary parallel heat exchange unit from the auxiliary evaporation loop to the auxiliary condensation loop. If the switching permission variable is greater than the preset allowable switching threshold and the target operating mode changes from the two-stage heating mode to the two-stage dehumidification mode, a switching command is generated to switch the auxiliary parallel heat exchange unit from the auxiliary condensation loop to the auxiliary evaporation loop. If the switching permission variable is less than or equal to the preset allowed switching threshold, the maintain switching instruction will maintain the current connection logic state.

[0013] Furthermore, the method also includes: The auxiliary parallel heat exchange unit is controlled to act as an auxiliary evaporation zone in the two-stage dehumidification mode, and it operates in parallel with the main heat exchange zone on both the refrigerant side and the air side. The auxiliary parallel heat exchange unit is controlled to act as an auxiliary condensation area in the two-stage heating mode, and it operates in parallel with the main heat exchange area on both the refrigerant side and the air side. In critical operating conditions, the switching permission variable is used to constrain the switching timing of the parallel participation mode of the auxiliary parallel heat exchange unit, and the parallel load distribution coefficient is used to adjust the load distribution ratio between the auxiliary parallel heat exchange unit and the main heat exchange area to achieve smooth transfer.

[0014] A second aspect of the invention provides a parallel dual-mode adaptive heat pump drying system, the system comprising: The controller is configured to execute the control method described above; The execution drive circuit is connected to the controller and is used to receive adjustment commands generated by the control method and execute actions. A data acquisition interface, connected to the controller, is used to provide operating parameters to the controller.

[0015] The beneficial technical effects of the present invention are at least as follows: To address the aforementioned problems, this invention provides a parallel dual-mode adaptive heat pump drying system and control method. Its core lies in transforming mode switching from a simple discrete action into a controllable process constrained by operational boundaries. The system first determines the switching-sensitive state based on the temperature difference between the return air dew point temperature and the main evaporator coil temperature, combined with preset process stages. This determination is then converted into a switching allowance, and a time-continuous release mechanism matching the thermal inertia of the heat exchanger and the refrigerant distribution inertia is introduced, giving the change in the parallel participation mode of the third heat exchanger a clear allowable boundary. Under the switching allowance constraint, the parallel load distribution state of the third heat exchanger on the refrigerant and air sides is further determined. Continuous proportional distribution allows the load borne by the third heat exchanger to smoothly shift according to the allowable degree. Finally, the load distribution state is mapped to solenoid valve on / off combinations, throttling device opening, and fan / valve control commands, enabling the system to actually operate in single-stage heating, dual-stage dehumidification, or dual-stage heating modes. Within the critical range, a collaborative mechanism of "allowance constraint—proportional distribution—execution implementation" suppresses sudden changes and oscillations. Through the above-mentioned structured control approach, this invention achieves collaborative sharing of heat exchangers on the refrigerant and air sides without increasing the number of data categories. It solves the problem of system dynamic instability caused by mode switching under critical operating conditions, and enables the high-efficiency dehumidification capacity and high-temperature heating capacity to be decoupled and coordinated throughout the drying process, significantly improving system energy efficiency and process adaptability. Attached Figure Description

[0016] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0017] Figure 1 This is a flowchart of a parallel dual-mode adaptive heat pump drying control method according to the present invention.

[0018] Figure 2 This is a framework diagram of a parallel dual-mode adaptive heat pump drying system according to the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In one or more embodiments, such as Figure 1 As shown, a parallel dual-mode adaptive heat pump drying control method is disclosed, the method comprising the following: S1: Obtain the heat and humidity parameters of the return air and the surface temperature parameters of the main heat exchange area, calculate the return air dew point temperature based on the heat and humidity parameters, calculate the temperature difference between the return air dew point temperature and the surface temperature parameters, and generate a system operation status determination result by combining the preset drying process stage information. In this embodiment, to achieve dual-mode adaptive control, the system incorporates a special heat exchange component, referred to below as a 'third heat exchanger'. In the claims, to more clearly define its functional attributes, this component is defined as an 'auxiliary parallel heat exchange unit'. Both refer to the same physical entity.

[0021] During the operation of a parallel dual-mode heat pump drying system, whether the system is suitable for switching the parallel participation mode of the third heat exchanger between the dual-stage dehumidification mode and the dual-stage heating mode depends on the matching relationship between the current air temperature and humidity state and the heat exchange state of the main evaporator. This step uses the temperature difference between the return air dew point temperature and the main evaporator coil temperature, combined with the preset drying process stage information, to perform a structured judgment on the current operating condition of the system, thereby generating a system operating status judgment result. The return air passes through a return air duct before entering the evaporator. An integrated digital temperature and humidity sensor module is installed at the duct inlet. This module consists of a temperature acquisition unit (e.g., or The controller consists of a thermistor and a capacitive humidity acquisition unit, with a fixed sampling period (e.g., ...). Read the return air dry bulb temperature With relative humidity The dew point temperature is then converted to the return air dew point temperature using a standard dew point conversion process within the controller. Main evaporator coil temperature Temperature signals are acquired via a patch-type temperature sensor attached to the middle of the outer wall of the main evaporator copper tubes, and the signal is transmitted over a fixed time window (e.g., the most recent). The sampled values ​​are averaged before being used in the calculation to ensure that the measured values ​​are stable and representative of the engineering process. Preset drying process stage number. The parameters of the drying program segment, such as the stage, are derived from the internal storage of the controller. This is the high humidity dehumidification stage. This is a transitional phase. For the high-temperature setting stage, the controller automatically reads the current stage number according to the program progress.

[0022] After the above data preparation is completed, the controller calculates the temperature difference between the return air dew point temperature and the main evaporator coil temperature. : ; in, This is the return air dew point temperature, in units of... The temperature and humidity data are collected by the temperature and humidity sensor at the inlet of the return air duct. and It is then converted within the controller; Main evaporator coil temperature, in units of The temperature was measured by a temperature sensor attached to the outer wall of the copper tubes of the main evaporator. The temperature difference between the two is expressed in units of 1. Dimensional checks show that... and All are temperature quantities with the same unit. Subtraction still results in a temperature dimension, and the formulas have consistent dimensions. The physical meaning lies in characterizing the dehumidification margin of the evaporator relative to the air dew point. When the value is large, the evaporator surface temperature is significantly lower than the dew point, and the system is in the strong dehumidification range; when When the value is small or close to zero, the evaporator is nearing the dew point boundary, and the heat exchange state is more sensitive to changes in parallel structures. This is combined with the preset process stages. The controller is based on the fixed threshold parameters determined during the commissioning phase. and Generate system operation status determination results .

[0023] The following explanation uses specific data calculations to illustrate that if , ,but In the stage (In the high humidity dehumidification stage) the temperature difference is within the safe margin range, and the output... ;like , ,but In the stage And set When the system determines that it is in a switching sensitive zone, it outputs... During the high-temperature phase In the middle, when Still greater than the set upper limit threshold (For example When this occurs, it indicates that the evaporator is still under a significant dehumidification load, and the output is similar. The system generates discrete variables using the above method. Its value is or The numbers and represent the current operating condition as either non-sensitive or sensitive, respectively. This determination process, based on thermodynamic physical quantities, explicitly quantifies the dehumidification boundary state of the parallel dual-mode heat pump drying system, providing a unified and reproducible input condition for the subsequent decision-making regarding the switching permission of the third heat exchanger's parallel participation mode.

[0024] S2: Discretize the system operation state determination results based on the first-order inertial model to generate a switching permission variable with time continuity. The switching permission variable is used to characterize the degree of permission to change the parallel participation mode of the auxiliary parallel heat exchange unit. Specifically, in step two, the system operating status determination result has already been obtained in step one. Building upon this foundation, the goal is to transform the discrete decision result into a switching permission variable that can directly participate in the control logic of the parallel operation mode of the third heat exchanger. In step one... The value is or This reflects whether the system is currently in a sensitive state regarding the switching of parallel participation modes. To ensure that this determination result matches the thermal inertia of the third heat exchanger and the refrigerant distribution inertia in a parallel dual-mode heat pump drying system, this step introduces an internal state variable with continuous time characteristics. This is used to represent the current handover lock strength and to generate handover permission variables accordingly. .

[0025] At the physical modeling level, when the third heat exchanger switches from a two-stage dehumidification parallel state to a two-stage heating parallel state, the refrigerant mass flow distribution between the two parallel branches will change, while the heat exchange surface wall temperatures of the evaporator and condenser exhibit certain heat capacity and hysteresis characteristics. This process can be analogized to a first-order inertial element, and its continuous-time expression can be written as a classical first-order linear differential equation: ; This expression is derived from the standard form of a first-order inertial system in control engineering, where... Represents the internal state variables of the system. This represents the equivalent input of the running state determination result output from step one in continuous time; in digital control implementation, Maintaining a constant value within the sampling period corresponds to a discrete sequence. The physical meaning of this formula is: when hour, It will converge toward 1; when hour, It will decay exponentially to 0. Because this system uses a digital controller with a fixed sampling period... (For example Therefore, the continuous model described above is discretized. The forward Euler method is used to discretize the differential equation. This is in contrast to the discrete variables output from step one. Align, and make the first The determination result of each sampling period is denoted as (Right now For step one in the first Output per sampling period ), we can obtain: ; in, For the first Lock strength per sampling period, dimensionless; The lock intensity of the previous sampling period is dimensionless. This is the result of the current sampling period's running status determination, and its value is... or ; These are parameters of a first-order inertial system, in units of... ; The sampling period is expressed in units of 10 ... The dimensions are checked as follows: The unit is , The unit is ,therefore Dimensionless, and same; middle Since it is dimensionless, The unit is multiplied by The latter is dimensionless; both sides of the equation are dimensionless quantities with consistent dimensions.

[0026] To simplify implementation and improve numerical stability, a discrete attenuation coefficient can be defined. Then the above formula can be simplified to: ; in It is a dimensionless constant with a range of values. This is determined through system debugging. For example, when the desired locking strength is approximately... Internal decay to initial value Then the continuous time constant ,have If the sampling period ,but Under these conditions, if at a certain moment ,but It will quickly approach 1; if in the following sampling periods ,but proportionally Gradually decaying. Taking numerical calculation as an example, let's assume the previous time... , ,but The next cycle will still be ,but ; and so on, This process is consistent with the first-order thermal inertia decay law.

[0027] In obtaining locking strength Then, generate the permission variable for switching the parallel participation mode of the third heat exchanger. Its definition is: ; in For the first The switching permission variable for each sampling period, dimensionless, with a range of values. ; The aforementioned locking strength. Dimensional check: Both the constant 1 and the constant 1 are dimensionless, therefore It is dimensionless and has the same value on both sides. Its physical meaning is: when... And when the system is in a continuously sensitive state, Approaching 1, A value close to 0 indicates that a third heat exchanger is not allowed to change its parallel participation mode; when And after several sampling periods Gradually decay to a smaller value, for example ,but This indicates that the switching license is being gradually released. In engineering implementation, a threshold can be set. As a condition for allowing switching, when this condition is met, the controller allows the solenoid valve combination to switch from the state corresponding to two-stage dehumidification to the state corresponding to two-stage heating, or vice versa; when At that time, the current parallel participation method will remain unchanged.

[0028] Through the derivation from the continuous-time model to the discrete-time model described above, and the substitution calculations in the numerical examples, it can be seen that... Transformed through a first-order inertial structure This allows the parallel participation mode switching of the third heat exchanger to match the thermal inertia time scale of the heat exchanger and refrigerant system, thereby achieving a stable and controllable switching permission generation mechanism in the parallel dual-mode heat pump drying system. Finally, this step outputs... This serves as the input variable for the next step of determining the parallel load distribution status.

[0029] S3: Based on the switching permission variables and target operating mode, determine the parallel load distribution coefficient of the auxiliary parallel heat exchange unit on the refrigerant side and the air volume distribution coefficient on the air side; Specifically, step three uses the switching license variable output in step two. and the current target operating mode of the controller As input, it is used to determine the load distribution status of the third heat exchanger in the parallel structure. Since the third heat exchanger is connected in parallel with the main evaporator on both the refrigerant and air sides as an auxiliary evaporator in two-stage dehumidification mode, and in parallel with the main condenser on both the refrigerant and air sides as an auxiliary condenser in two-stage heating mode, the "parallel load distribution" corresponds to two directly implementable proportional quantities in engineering: the proportion borne by the branch on the refrigerant side and the proportion of airflow passing through the third heat exchanger on the air side. The result obtained in step two... Having already achieved first-order inertial release characteristics, this step further transforms the permissible amount into an executable parallel distribution coefficient, so that the proportion of the third heat exchanger changes smoothly with the permissible release, and keeps the air-side distribution and refrigerant-side distribution in the same direction, avoiding heat exchange imbalance caused by inconsistent proportions of the parallel heat exchangers on both sides.

[0030] This step first generates the refrigerant-side parallel load distribution coefficient. The mathematical origin of this coefficient consists of two parts: one is interval linear interpolation in classical mathematics (which...). Mapped to The second is exponential smoothing / first-order discrete low-pass filtering in classic discrete algorithms (writing the target assigned value to the current assigned value at a limited rate). In engineering derivation, the linear interpolation target value can be written as... ,in for The normalized variables within; to reflect the scenario characteristics of parallel switching of heat pump drying, the normalized variables within; Take as Power-law shaping is used to make the allocation changes more gradual in the early stages of license release and more aggressive after licenses are fully released. Then, an exponential smoothing difference equation is used. A smooth update was completed. For the first The target operating mode for each control cycle is set to a value of The process is determined by the controller based on the drying formula stage or the process instructions from the host computer: Indicates a single-stage heating mode. This indicates a two-stage dehumidification mode. This indicates a two-stage heating mode. This variable is used to determine the direction of load distribution to the third heat exchanger: in hour, The refrigerant distribution ratio corresponding to "the third heat exchanger as an auxiliary evaporator branch"; in hour, The refrigerant distribution ratio corresponding to "the third heat exchanger as an auxiliary condenser branch"; in hour, Maintain at To reduce the involvement of the third heat exchanger, the following approach is taken: Substituting the two parts and combining them, we get: ; in, The direction factor is dimensionless and takes values ​​of 100. , by target running mode Generation: When Time to take ,when Time to take This is used to make the distribution coefficient of the third heat exchanger converge to a certain value in the single-stage heating mode. .in, For the first The parallel load distribution coefficient (dimensionless) of the third heat exchanger on the refrigerant side in each control cycle represents the refrigerant distribution ratio undertaken by the branch of the third heat exchanger. The parallel load distribution coefficient (dimensionless) of the previous control cycle is calculated by the controller, written into the register in the previous cycle, and read out in the current cycle. To update the coefficients (dimensionless, with values...) This parameter is written into the controller parameter table during the equipment commissioning phase to limit the rate of change of the allocation ratio. and To allocate upper and lower limits (dimensionless, and The parameters are written into the parameter table during the equipment commissioning phase, and their meanings are the minimum and maximum allocation ratios that the third heat exchanger is allowed to undertake, respectively. The switching permission variable output from step two (dimensionless, with values...) ); The power-order shaping parameter (dimensionless, usually taken as...) ), configured by the parameter table. Dimensional check: , , , , , , All are dimensionless quantities. It remains dimensionless; the content within square brackets is dimensionless, and the result after multiplication and addition is also dimensionless, consistent with the left side of the equation. The dimensions are consistent and logical. In engineering implementation, the controller... The target allocation ratio of the third heat exchanger branch is generated, and the refrigerant is allocated through the opening ratio of the second throttling device EXV2 (corresponding to the third heat exchanger branch) and the first throttling device EXV1 (corresponding to the main heat exchanger branch). The correspondence between the opening and the flow rate is given by the equipment factory calibration curve or the commissioning record table. The controller converts the target ratio into the opening set value by looking up the table, which is a deterministic implementation process.

[0031] To demonstrate the algorithm's operability, a set of examples calculating based on proportional values ​​and configuration parameters are provided. Assume the parameter table is configured... , , , Previous cycle When step two outputs And the target operating mode satisfies Thus obtain First calculate the shaping item. Then calculate the target value. Substituting into the above formula, we get .when Rise to And take hour, , , .when near And take hour, , , This numerical process corresponds to the common "gradual release of permissions—gradual change of allocation ratio at a limited rate" trajectory found in debugging records, and can be directly used for controller simulation: By iterating the above recursive formula over the sampling period, we can obtain... The time series data was used to verify that allocation changes do not produce mutations.

[0032] Obtain the refrigerant side distribution coefficient Then, this step generates the air-side airflow distribution coefficient. This is used to describe the proportion of circulating airflow through the third heat exchanger duct. The mapping formula originates from interval linear mapping in mathematics, using the refrigerant-side distribution coefficient as the independent variable to ensure that the air-side distribution aligns with the refrigerant-side distribution, facilitating the simultaneous proportional connection of the loads on both sides of the parallel heat exchanger. The mapping relationship is as follows: ; in, The air volume distribution coefficient (dimensionless) represents the proportion of air volume handled by the third heat exchanger duct. and Assign upper and lower limits to the air side (dimensionless, and) The parameter is written into the controller parameter table during the equipment commissioning phase. Its engineering meaning is the equivalent air volume ratio corresponding to the minimum and maximum allowable opening of the electric air valve in the third heat exchanger duct, or the equivalent air volume ratio corresponding to the minimum and maximum speed of the branch fan in the third heat exchanger in a dual-fan system. This is the refrigerant-side parallel load distribution coefficient (dimensionless) obtained from the previous formula. Dimensionality check: , , , All are dimensionless quantities, the right side is dimensionless, and both sides of the equation are consistent. Continuing with the previous calculation example, when... and take , Sometimes, , indicating that the approximation will be made The circulating air volume is distributed to the air duct of the third heat exchanger. Based on this, the controller outputs either the fan speed setpoint or the damper opening setpoint: if an electric damper is used, the opening command is obtained by looking up a table based on the valve opening versus air volume calibration curve; if a dual-fan parallel air duct is used, the speed command is obtained by looking up a table based on the fan speed versus air volume calibration curve. Thus, this step forms two output variables representing the parallel load distribution state of the third heat exchanger. and Both are controlled within the same control cycle. The derivation yields the results, which are then used as direct inputs in the next step to generate the solenoid valve on / off combinations, EXV1 / EXV2 opening degrees, and fan / valve execution commands.

[0033] S4: Based on the parallel load distribution coefficient, generate the main flow rate adjustment command corresponding to the main heat exchange area and the auxiliary flow rate adjustment command corresponding to the auxiliary parallel heat exchange unit. Based on the air volume distribution coefficient, generate the main air volume adjustment command corresponding to the main heat exchange area and the auxiliary air volume adjustment command corresponding to the auxiliary parallel heat exchange unit. When the switching permission variable meets the preset threshold condition, generate a switching command to change the parallel connection logic of the auxiliary parallel heat exchange unit.

[0034] Specifically, in step four, the refrigerant-side parallel load distribution coefficient of the third heat exchanger has already been obtained in step three. air volume distribution coefficient Based on this, the actual operation control of the parallel dual-mode heat pump drying system is completed, enabling the parallel structure to simultaneously bear the load on both the refrigerant and air sides according to the target ratio. Step three gives... and Both are dimensionless proportional quantities, and their physical meanings are the proportion of refrigerant mass flow rate and air flow rate undertaken by the third heat exchanger branch, respectively.

[0035] On the refrigerant side, the total mass flow rate satisfies the law of conservation of mass, its basic physical formula derived from the principle of mass conservation in continuum mechanics, namely, the sum of the flow rates of parallel branches equals the total flow rate. Let the total refrigerant mass flow rate output by the compressor in the current control cycle be... The unit is This quantity is calculated by the controller based on compressor speed, suction pressure, discharge pressure, and refrigerant properties, and is part of the system's original energy balance calculation. According to the law of conservation of mass, we have: ; in, The target mass flow rate for the main heat exchanger branch. The target mass flow rate for the third heat exchanger branch is given, and the units are all... Both sides of this equation represent mass flow rates, with consistent dimensions. The proportional relationship has already been given in step three. This indicates the proportion of the load handled by the third heat exchanger, and therefore we can further deduce: ; This derivation is obtained directly from the definition of proportion and the law of conservation of mass. It is a dimensionless proportionality coefficient. for The product is The dimensions are consistent and reasonable. The controller is based on... and The values ​​are used to calculate the opening commands of the first throttling device EXV1 and the second throttling device EXV2 through the pre-calibrated throttling device opening-flow characteristic curve. and The calibration curve is derived from the mass flow rate data measured at different opening degrees during the equipment commissioning phase, and is typically stored in the controller's EEPROM in discrete table form. The controller uses a piecewise linear interpolation algorithm to solve for the opening degree value, for example, the value measured under a certain operating condition. , ,but , If the calibration curve shows that the EXV2 opening is... Hourly flow rate When the opening degree of EXV1 is Hourly flow rate Then the controller outputs , The process is implemented within the controller using table lookup and linear interpolation. The algorithm steps include reading the flow rate value, finding adjacent calibration points, calculating the ratio, and outputting the opening command. The calculation process is clear and reproducible.

[0036] On the air side, the distribution of circulating air volume also follows the principle of flow conservation, and its original physical formula comes from the law of conservation of volumetric flow rate in fluid mechanics. Let the total circulating air volume in the current control cycle be... The unit is This quantity is obtained by looking up a table using the fan speed and fan performance curve. Based on the air-side distribution coefficient... The target air volume of the third heat exchanger duct can be obtained. Target air volume of the main heat exchanger duct : ; in, It is a dimensionless proportional quantity. for ,therefore and All The dimensions are consistent. The controller is in the first... Each control cycle reads the target operating mode. With switching license variables ,in The drying formula is derived from the controller's internal settings / the process instructions set by the host computer. From step two The discrete first-order inertial calculation results both correspond to the same control period. ;when When the threshold condition for allowing switching is reached, the output is the same as... The corresponding solenoid valve on / off combinations connect the third heat exchanger to the auxiliary evaporator parallel circuit in the two-stage dehumidification mode, and to the auxiliary condenser parallel circuit in the two-stage heating mode; when When the allowed switching conditions are not met, the solenoid valve on / off combination maintains the state of the previous cycle, and only presses... and Adjust EXV1, EXV2, and fan / valve commands to continuously regulate the load ratio while maintaining the parallel operation mode. The controller then... Consult the fan or damper opening-airflow calibration curve to calculate the air-side execution command. For example, if , ,but If the calibration data indicates that the damper opening is... The corresponding air volume at that time is Then output The calibration curve is also derived from measured data during the equipment commissioning phase and can be verified in a simulation environment using the wind turbine characteristic equation.

[0037] The algorithm can be verified through periodic iterative calculations in simulation or debugging logs. For example, suppose... Maintain within several cycles , from Smoothly increase to The flow rate of the third heat exchanger branch will then be... Increase to The flow rate in the main heat exchanger branch decreases accordingly. By recording the opening degree change curves of EXV1 and EXV2, it can be observed that the opening degree changes with... Continuous change, without abrupt jumps; the airflow volume also changes accordingly. Synchronous changes result in a smooth execution curve for the fan or damper. This debugging result serves as supporting evidence for the implementation, demonstrating that the aforementioned calculation and control algorithm can operate stably in engineering applications.

[0038] Based on the above derivation of mass conservation and flow ratio, and combined with calibration curve lookup and interpolation calculations, this step will output the results from step three. and Transformed into actual execution instructions , and This enables the parallel dual-mode heat pump drying system to simultaneously bear the load on both the refrigerant and air sides according to the target ratio, achieving controllable implementation of the parallel participation mode of the third heat exchanger, thereby completing the final implementation of the entire control process.

[0039] In one or more embodiments, such as Figure 2 As shown, a parallel dual-mode adaptive heat pump drying system is disclosed, the system comprising: The controller is configured to execute the control method described above; In this embodiment, the controller serves as the core control unit of the system, responsible for coordinating the operation of the entire system. In this embodiment, the controller is configured to execute the control method described in Embodiment 1.

[0040] Microprocessors (MCUs), digital signal processors (DSPs), or programmable logic controllers (PLCs) with data processing and logic control capabilities are preferred.

[0041] The controller internally stores a computer program, which, when executed by the processor, enables the implementation of all the processes described above. The controller establishes bidirectional or unidirectional communication connections with the execution drive circuit and the data acquisition interface via an internal bus.

[0042] It also includes a data acquisition interface, which is connected to the controller to provide operating parameters to the controller; The data acquisition interface is connected to the controller's input port via an analog / digital input channel (such as an ADC interface, GPIO interface, or dedicated sensor bus). It is used to provide the controller with real-time operating parameters. These parameters include, but are not limited to, signals such as the drying room return air temperature, return air humidity, main heat exchange area surface temperature, refrigerant pressure, and flow rate. This interface is responsible for conditioning (e.g., filtering, amplifying) the raw signals from the sensors and transmitting them to the controller as input for the control algorithm.

[0043] And an execution drive circuit, which is connected to the controller, for receiving adjustment commands generated by the control method and executing actions; The execution drive circuits are connected to the controller and are used to convert control signals into physical actions. The execution drive circuits receive electrical signals through the controller's digital / analog output ports (such as PWM outputs or relay control ports). They are used to receive adjustment commands (such as load distribution coefficients, switching commands, etc.) generated by the control method and drive the corresponding actuators to perform actions. Specific driven objects include, but are not limited to: the stepper motor of the electronic expansion valve, the servo motor of the air valve, the frequency converter of the variable frequency fan, and the electromagnetic coil of the four-way directional valve.

[0044] During operation, the data acquisition interface continuously collects real-time operating parameters of the heat pump drying system and transmits the data to the controller. The controller analyzes and processes the data according to the pre-stored control program (i.e., the method flow described in Embodiment 1), determines whether the system is in a sensitive state, and calculates the optimal load allocation scheme. Subsequently, the controller generates corresponding adjustment commands, which drive the actuator through the drive circuit, thereby achieving precise control of the heat pump drying process.

[0045] It is worth noting that the specific workflow of the parallel dual-mode adaptive heat pump drying system provided in this embodiment of the invention is the same as that of the parallel dual-mode adaptive heat pump drying control method described in the above embodiment, and will not be repeated here.

[0046] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A control method for a parallel dual-mode adaptive heat pump drying system, characterized in that, The method includes: The system obtains the heat and humidity parameters of the return air and the surface temperature parameters of the main heat exchange area, calculates the return air dew point temperature based on the heat and humidity parameters, calculates the temperature difference between the return air dew point temperature and the surface temperature parameters, and generates a system operation status determination result by combining the preset drying process stage information. The system operation state determination results are discretized based on the first-order inertial model to generate switching permission variables with time continuity. These switching permission variables are used to characterize the degree of permission to change the parallel participation mode of the auxiliary parallel heat exchange unit. Based on the switching permission variables and the target operating mode, determine the parallel load distribution coefficient of the auxiliary parallel heat exchange unit on the refrigerant side and the air volume distribution coefficient on the air side; Based on the parallel load allocation coefficient, a main flow rate adjustment command corresponding to the main heat exchange area and an auxiliary flow rate adjustment command corresponding to the auxiliary parallel heat exchange unit are generated. Based on the air volume allocation coefficient, a main air volume adjustment command corresponding to the main heat exchange area and an auxiliary air volume adjustment command corresponding to the auxiliary parallel heat exchange unit are generated. When the switching permission variable meets the preset threshold condition, a switching command to change the parallel connection logic of the auxiliary parallel heat exchange unit is generated.

2. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 1, characterized in that, The generation system operation status determination result specifically includes: The collected return air dry-bulb temperature and relative humidity are converted into return air dew point temperature; The surface temperature parameters are obtained by performing a moving average process on the collected surface temperature signal of the main heat exchange area. The temperature difference is calculated as the difference between the return air dew point temperature and the surface temperature parameter. The temperature difference is compared with the preset first threshold and second threshold, and combined with the current preset drying process stage number, the system operation status judgment result is output with the first value or the second value, where the first value represents the non-sensitive state and the second value represents the sensitive state.

3. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 2, characterized in that, The generation of switching permission variables with time continuity specifically includes: By setting the sampling period and the parameters of the first-order inertial system, a discretized first-order inertial difference equation is constructed. Substitute the locking strength of the previous sampling period and the system operating state determination result of the current sampling period into the discretized first-order inertial difference equation to calculate the locking strength of the current sampling period. The switching permission variable for the current sampling period is obtained by subtracting the lock strength of the current sampling period from the constant 1. Specifically, when the system operation status determination result is the second value, the lock strength converges to 1, and the switching permission variable approaches 0; when the system operation status determination result is the first value, the lock strength decays exponentially, and the switching permission variable gradually increases.

4. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 3, characterized in that, The determination of the parallel load distribution coefficient of the auxiliary parallel heat exchange units on the refrigerant side specifically includes: Read the target operating mode, which includes a single-stage heating mode, a two-stage dehumidification mode, or a two-stage heating mode; An orientation factor is generated based on the target operating mode. When the target operating mode is a single-stage heating mode, the orientation factor takes the first orientation value. When the target operating mode is a two-stage dehumidification mode or a two-stage heating mode, the orientation factor takes the second orientation value. The switching allowable variable is nonlinearly processed based on the power-order shaping parameter. Combined with the direction factor, the parallel load allocation coefficient of the previous control cycle and the update coefficient, the refrigerant-side parallel load allocation coefficient of the current control cycle is calculated through the exponential smoothing difference equation. The refrigerant-side parallel load distribution coefficient is limited to a preset lower and upper limit.

5. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 4, characterized in that, The determination of the airflow distribution coefficient of the auxiliary parallel heat exchange unit on the air side specifically includes: Establish an interval linear mapping relationship, and use the refrigerant-side parallel load distribution coefficient as the independent variable; By using the preset lower limit and upper limit of air-side distribution, the refrigerant-side parallel load distribution coefficient is mapped to the air-side air volume distribution coefficient; The control air volume distribution coefficient changes in the same direction as the refrigerant side parallel load distribution coefficient.

6. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 5, characterized in that, The generation of the main flow rate regulation command corresponding to the main heat exchange region and the auxiliary flow rate regulation command corresponding to the auxiliary parallel heat exchange unit specifically includes: Obtain the current total refrigerant mass flow rate of the system; Multiply the total refrigerant mass flow rate by the refrigerant-side parallel load distribution coefficient to obtain the target mass flow rate of the auxiliary parallel heat exchange unit branch. Subtract the target mass flow rate of the auxiliary parallel heat exchange unit branch from the total refrigerant mass flow rate to obtain the target mass flow rate of the main heat exchange area branch. By consulting the pre-stored calibration curves of throttling opening and mass flow rate, and using a piecewise linear interpolation algorithm, the target mass flow rate of the auxiliary parallel heat exchange unit branch is converted into the auxiliary throttling opening command, and the target mass flow rate of the main heat exchange area branch is converted into the main throttling opening command.

7. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 5, characterized in that, The generation of the main airflow regulation command corresponding to the main heat exchange area and the auxiliary airflow regulation command corresponding to the auxiliary parallel heat exchange unit specifically includes: Obtain the current total circulating air volume of the system; Multiply the total circulating air volume by the air-side air volume distribution coefficient to obtain the target air volume of the auxiliary parallel heat exchange unit duct. Subtract the target air volume of the auxiliary parallel heat exchange unit duct from the total circulating air volume to obtain the target air volume of the main heat exchange area duct. Consult the pre-stored calibration curves of air volume adjustment execution quantity and air volume, convert the target air volume of the auxiliary parallel heat exchange unit duct into the auxiliary air volume adjustment command, and convert the target air volume of the main heat exchange area duct into the main air volume adjustment command.

8. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 1, characterized in that, The generation of the switching instruction that changes the parallel connection logic of the auxiliary parallel heat exchange unit specifically includes: Determine whether the switching permission variable is greater than the preset allowed switching threshold; If the switching permission variable is greater than the preset allowable switching threshold and the target operating mode changes from the two-stage dehumidification mode to the two-stage heating mode, a switching command is generated to switch the auxiliary parallel heat exchange unit from the auxiliary evaporation loop to the auxiliary condensation loop. If the switching permission variable is greater than the preset allowable switching threshold and the target operating mode changes from the two-stage heating mode to the two-stage dehumidification mode, a switching command is generated to switch the auxiliary parallel heat exchange unit from the auxiliary condensation loop to the auxiliary evaporation loop. If the switching permission variable is less than or equal to the preset allowed switching threshold, the maintain switching instruction will maintain the current connection logic state.

9. The control method for the parallel dual-mode adaptive heat pump drying system according to claim 1, characterized in that, The method further includes: The auxiliary parallel heat exchange unit is controlled to act as an auxiliary evaporation zone in the two-stage dehumidification mode, and it operates in parallel with the main heat exchange zone on both the refrigerant side and the air side. The auxiliary parallel heat exchange unit is controlled to act as an auxiliary condensation area in the two-stage heating mode, and it operates in parallel with the main heat exchange area on both the refrigerant side and the air side. In critical operating conditions, the switching permission variable is used to constrain the switching timing of the parallel participation mode of the auxiliary parallel heat exchange unit, and the parallel load distribution coefficient is used to adjust the load distribution ratio between the auxiliary parallel heat exchange unit and the main heat exchange area to achieve smooth transfer.

10. A parallel dual-mode adaptive heat pump drying system, characterized in that, The system includes: The controller is configured to perform the control method as described in any one of claims 1 to 9; The execution drive circuit is connected to the controller and is used to receive adjustment commands generated by the control method and execute actions. A data acquisition interface, connected to the controller, is used to provide operating parameters to the controller.

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