CN115325783A - Heat pump drying system for preserved fruits and control system thereof - Google Patents

Heat pump drying system for preserved fruits and control system thereof Download PDF

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Publication number
CN115325783A
CN115325783A CN202210857223.4A CN202210857223A CN115325783A CN 115325783 A CN115325783 A CN 115325783A CN 202210857223 A CN202210857223 A CN 202210857223A CN 115325783 A CN115325783 A CN 115325783A
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Prior art keywords
heat pump
frequency
stop valve
heat exchanger
expansion stop
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CN202210857223.4A
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CN115325783B (en
Inventor
郭小璇
孙乐平
韩帅
陈卫东
肖静
卢健斌
龚文兰
郭敏
吴晓锐
吴宁
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Electric Power Research Institute of Guangxi Power Grid Co Ltd
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Electric Power Research Institute of Guangxi Power Grid Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B9/00—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards
    • F26B9/06—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards in stationary drums or chambers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • F25B41/24—Arrangement of shut-off valves for disconnecting a part of the refrigerant cycle, e.g. an outdoor part
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/31—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/06—Controlling, e.g. regulating, parameters of gas supply
    • F26B21/08—Humidity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/06—Controlling, e.g. regulating, parameters of gas supply
    • F26B21/10—Temperature; Pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/06—Chambers, containers, or receptacles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
    • Y02P60/80—Food processing, e.g. use of renewable energies or variable speed drives in handling, conveying or stacking
    • Y02P60/85—Food storage or conservation, e.g. cooling or drying

Abstract

The invention relates to the technical field of heat pump drying, in particular to a heat pump drying system for preserved fruits and a control system thereof. The heat pump drying system can adjust the working frequency of the compressor and the working frequency of the fan by adopting the frequency converter so as to adjust the flow rate of the refrigerant and the drying air volume and realize the adjustment according to requirements. The control system of the invention adopts the fuzzification principle to adjust the frequency of the compressor, adjust the opening degree of the second expansion stop valve and the first expansion stop valve, adopts PID proportion control to adjust the opening degree of the moisture discharging port, and designs the fuzzy rule table based on the negative feedback principle and the expert experience. The invention adopts an intelligent control strategy and an Internet of things technology to solve the problems of low control precision, poor disturbance rejection, low informatization and the like in the existing heat pump drying system, improves the automation and intelligence level, and realizes the main indexes of system energy conservation, product quality improvement, high efficiency and reliability.

Description

Heat pump drying system for preserved fruits and control system thereof
Technical Field
The invention relates to the technical field of heat pump drying, in particular to a heat pump drying system for preserved fruits and a control system thereof.
Background
The working principle of heat pump drying is that heat energy is provided by a heat pump to heat a drying working medium (air), and the moisture of the drying material is gradually separated from the surface under the action of the drying working medium and the drying material, so that the drying purpose is realized. The heat pump drying system is composed of a heat pump system and a drying chamber, wherein the heat pump system mainly comprises a compressor, an expansion valve, an evaporator, a condenser and the like. The heat pump can work in a heating mode and a refrigerating mode, so that the drying temperature in the material drying process can be freely set, and different drying process temperature requirements can be met. The heat pump can obtain high-grade heat energy only by consuming a small amount of electric energy, and compared with the traditional mode of obtaining heat energy by burning fossil energy, the heat pump has the remarkable advantages of no pollution, high efficiency and the like, and is concerned about and widely researched and applied as a new energy technology.
The heat pump drying is a complex process control system, the working process involves process variables such as evaporator temperature, refrigerant flow and pressure, drying room temperature and humidity, drying air speed and the like, and actuators in the system comprise a compressor, an expansion valve, a fan, an electric heater, a switching value actuator and the like. The heat pump drying is applied to the food field of preserved fruits (dried fruits) and the like, and higher requirements are put forward on the quality of dried food and the energy efficiency of a drying system.
Disclosure of Invention
In order to solve the problems and meet the requirements of high precision and high disturbance resistance of controlled quantity and equipment intellectualization in the drying process, the invention provides a heat pump drying system for preserved fruits and a control system thereof, and the specific technical scheme is as follows:
a heat pump drying system for preserved fruits comprises a heat pump subsystem, a drying chamber and a frequency converter, wherein the heat pump subsystem comprises a first heat exchanger, a first expansion stop valve, a second expansion stop valve, a four-way reversing valve, a second heat exchanger and a compressor;
the second heat exchanger is arranged at the top of the drying chamber, and the first heat exchanger, the first expansion stop valve, the second expansion stop valve and the second heat exchanger are sequentially connected; the four-way reversing valve is respectively connected with the second heat exchanger, the compressor and the first heat exchanger;
the top of the drying chamber is also provided with a fan and an electric heater, the upper part of the drying chamber is provided with a moisture exhaust port, the lower part of the drying chamber is provided with a drying material rack, a weight sensor is arranged below the drying material rack, and the drying chamber is also provided with a humidity sensor and a temperature sensor;
the compressor and the fan are respectively connected with a frequency converter, and the frequency converter is used for adjusting the working frequency of the compressor and the working frequency of the fan so as to adjust the flow rate of the refrigerant and the drying air volume;
the working modes of the heat pump subsystem comprise a heating mode and a refrigerating mode, when the heat pump subsystem works in the heating mode, the second heat exchanger is a condenser, and the first heat exchanger is an evaporator; when the air conditioner works in a refrigeration mode, the second heat exchanger is an evaporator, and the first heat exchanger is a condenser.
A control system of a heat pump drying system for preserved fruits is applied to the heat pump drying system and comprises a PLC (programmable logic controller), a data acquisition module, a human-computer interface (HMI) and a cloud platform;
the data acquisition module is connected with a humidity sensor, a temperature sensor, a weight sensor and the heat pump subsystem of the heat pump drying system, and is used for acquiring the operating condition data of the heat pump subsystem, the temperature and the humidity in the drying chamber and the weight of the drying material rack and transmitting the acquired data to the PLC; the PLC is respectively connected with the frequency converter, the first expansion stop valve, the second expansion stop valve and the moisture exhaust port actuator, the moisture exhaust port actuator is connected with the moisture exhaust port, and the PLC is used for controlling the opening degree of the moisture exhaust port according to an expert database, fuzzy rules and PID control rules, controlling the opening degrees of the first expansion stop valve and the second expansion stop valve so as to adjust the flow of refrigerant and control the frequency of the frequency converter;
the human-computer interface HMI is connected with the PLC and used for human-computer interaction;
the cloud platform is connected with the human-computer interface HMI and used for monitoring the operation condition of the heat pump drying system and storing monitoring data.
Preferably, the cloud platform comprises an MQTT message proxy server and a database server, the human-computer interface HMI is connected with the MQTT message proxy server, and the running state and the fault information of the equipment are issued to the client through an MQTT protocol; the database server is used for storing data and providing data service.
Preferably, the PLC controls the operation condition of the heat pump drying system according to an expert database, and the expert database stores the temperature and humidity of dried preserved fruit, the water content of materials, the drying time, the system energy efficiency and the superheat degree of a compressor, a fan, a first heat exchanger or a second heat exchanger.
Preferably, the PLC controller adjusts the frequency of the frequency converter and the opening degrees of the first expansion stop valve and the second expansion stop valve according to a fuzzy rule, and when adjusting the frequency of the frequency converter, the input variable is a temperature error value between the temperature in the drying chamber and a set temperature, and the output value is the frequency of the frequency converter;
when the opening degrees of the first and second expansion stop valves are adjusted, the input amount is an error between the superheat degree of the first or second heat exchanger and the set superheat degree, and the output amount is the opening degrees of the first and second expansion stop valves.
Preferably, the PLC controller controls the actuator of the moisture exhaust port according to a PID control rule, and further adjusts the opening of the moisture exhaust port, and specifically, inputs an error value between the set humidity of the drying chamber and the actual humidity measured by the humidity sensor into the PLC controller, and outputs the opening of the moisture exhaust port to adjust the humidity of the drying chamber.
Preferably, in the fuzzy rule for adjusting the frequency of the frequency converter by the PLC controller, the input variable is an error value of the set temperature, and the input variable is expressed as: negative large, negative middle, negative small, zero, positive small, positive middle, positive large, denoted as NL, NM, NS, Z, PS, PM, PL, respectively, input ranges are: [ -6, -4], [ -6, -2], [ -4,0], [ -2,2], [0,4], [2,6], [4,6], the membership function selecting a trapezoidal distribution shape and a triangle shape;
the linguistic variables for the output compressor frequency change are: NL, NM, NS, Z, PS, PM, PL, indicating the increase in compressor frequency from a negative large value for rapid increase in frequency to a positive large value for rapid decrease in frequency, with a normalized range of discourse [ -1,1]Scale factor K u Set to 0.01.
Preferably, the fuzzy rule adopts an if-then fuzzy inference method, and the fuzzy rule table is shown in table 1:
TABLE 1 fuzzy rule Table
Fuzzy rule If temperature error value Frequency variation of Then compressor Output weights OW [ i]
1 NL NL -1
2 NM NM -0.7
3 NS NS -0.3
4 Z Z 0
5 PS PS 0.3
6 PM PM 0.7
7 PL PL 1
Weights OW [ i ] output in Table 1]Taking the intermediate value of each fuzzy set, defuzzifying and adopting a weighted average method, wherein the calculation formula is as follows:
Figure BDA0003756086150000041
FS i the membership of the fuzzy set is output.
The invention has the beneficial effects that: the invention provides a heat pump drying system for preserved fruits and a control system thereof.
Because the heat pump drying chamber is a nonlinear time-varying system and is difficult to establish a model by using a differential equation of a traditional physical system, the control system of the invention adjusts the frequency of the compressor based on the fuzzification principle, adjusts the opening degrees of the second expansion stop valve and the first expansion stop valve, and adjusts the opening degree of the moisture exhaust port by adopting PID proportion control, and the design of the fuzzy rule table is designed based on a negative feedback principle and expert experience. The invention adopts an intelligent control strategy and the Internet of things technology to solve the problems of low control precision, poor disturbance rejection, low informatization and the like in the existing heat pump drying system, improves the automation and intelligence level, and realizes the main indexes of system energy conservation, product quality improvement, high efficiency and reliability.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
FIG. 1 is a schematic diagram of a heat pump drying system of the present invention;
FIG. 2 is a schematic diagram of the control system of the present invention;
FIG. 3 is a diagram of the cloud platform MQTT architecture of the present invention.
FIG. 4 is a fuzzy control schematic of the present invention;
FIG. 5 is a trapezoidal membership function of the error values for temperature;
FIG. 6 is a triangular membership function of the error value of temperature;
FIG. 7 is a triangular membership function for the output compressor frequency.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
As shown in fig. 1, the embodiment of the present invention provides a heat pump drying system for preserved fruit, comprising a heat pump subsystem, a drying chamber 1 and a frequency converter, wherein the heat pump subsystem comprises a first heat exchanger 13, a first expansion stop valve 11, a second expansion stop valve 14, a four-way reversing valve 10, a second heat exchanger 2 and a compressor 9;
the second heat exchanger 2 is arranged at the top of the drying chamber 1, and the first heat exchanger 13, the first expansion stop valve 11, the second expansion stop valve 14 and the second heat exchanger 2 are connected in sequence; the four-way reversing valve 10 is respectively connected with the second heat exchanger 2, the compressor 9 and the first heat exchanger 13;
the top of the drying chamber 1 is also provided with a fan 3 and an electric heater 4, the upper part of the drying chamber 1 is provided with a moisture exhaust port 8, the lower part of the drying chamber 1 is provided with a drying material rack 6, a weight sensor 7 is arranged below the drying material rack 6, and the drying chamber 1 is also provided with a humidity sensor 5 and a temperature sensor 12;
the compressor 9 and the fan 3 are respectively connected with a frequency converter, and the frequency converter is used for adjusting the working frequency of the compressor and the working frequency of the fan so as to adjust the flow rate of the refrigerant and the drying air volume;
the working modes of the heat pump subsystem comprise a heating mode and a refrigerating mode, when the heat pump subsystem works in the heating mode, the second heat exchanger 2 is a condenser, and the first heat exchanger 13 is an evaporator; when operating in the cooling mode, the second heat exchanger 2 is an evaporator and the first heat exchanger 13 is a condenser. A closed circulation system is formed in the drying chamber 1, the temperature of the drying chamber 1 is raised in a heating mode, the second heat exchanger 2 is a condenser, the first heat exchanger 13 is an evaporator, an expansion valve of a second expansion stop valve 14 at the outlet of the condenser stops working, a stop valve connected in parallel with the second expansion stop valve is communicated and flows through a refrigeration working medium, an expansion valve of a first expansion stop valve 11 at the inlet of the evaporator works, and a stop valve connected in parallel with the first expansion stop valve is communicated. And otherwise, the temperature of the drying chamber 1 is reduced in the refrigeration mode, the second heat exchanger 2 is an evaporator, the first heat exchanger 13 is a condenser, the expansion valve of the first expansion stop valve 11 at the outlet of the condenser stops working, the stop valve connected in parallel with the expansion valve is communicated and flows through the refrigeration working medium, the expansion valve of the second expansion stop valve 14 at the inlet of the evaporator works, and the stop valve connected in parallel with the expansion valve is communicated.
As shown in fig. 2, the specific embodiment of the present invention further provides a control system for a heat pump drying system for preserved fruit, which is applied to the heat pump drying system, and comprises a PLC controller, a data acquisition module, a human-computer interface HMI, and a cloud platform;
the data acquisition module is connected with a humidity sensor 5, a temperature sensor 12, a weight sensor 7 and the heat pump subsystem of the heat pump drying system, and is used for acquiring the operating condition data of the heat pump subsystem, the temperature and humidity in the drying chamber and the weight of the drying material rack 6 and transmitting the acquired data to the PLC; the PLC is respectively connected with a frequency converter, a first expansion stop valve 11, a second expansion stop valve 14 and a moisture exhaust port actuator, the moisture exhaust port actuator is connected with a moisture exhaust port 8, and the PLC is used for controlling the opening degree of the moisture exhaust port 8 according to an expert database, fuzzy rules and PID control rules, controlling the opening degrees of the first expansion stop valve 11 and the second expansion stop valve 14 to adjust the flow rate of refrigerant and control the frequency of the frequency converter;
the human-computer interface HMI is connected with the PLC and used for human-computer interaction;
the cloud platform is respectively connected with the PLC and the human-computer interface HMI and used for monitoring the operation condition of the heat pump drying system and storing monitoring data.
As shown in fig. 3, the cloud platform includes an MQTT message proxy server and a database server, and the human-machine interface HMI is connected with the MQTT message proxy server and issues the device operating state and the fault information to the client through an MQTT protocol; the database server is used for storing data and providing data service.
The MQTT message agent server adopts an Aliskian MQTT server, after the human-computer interface HMI and the Aliskian MQTT server are connected, the information of equipment operation, state, fault and the like is published to the cloud platform through an MQTT protocol, the client side such as a mobile phone APP and Web subscribes the relevant operation data information, and when the operation data changes, the client side can receive the data sent by the MQTT server. Compared with a client-server response communication mode used in the traditional mode, the MQTT communication mode reduces the burden of a server, saves communication flow and has excellent performance when a cloud platform carries out group control on a plurality of drier equipment.
The PLC controls the operation condition of the heat pump drying system according to an expert database, wherein the expert database stores the temperature and humidity of dried preserved fruit, the water content of materials, the drying time, the system energy efficiency and the superheat degree of the compressor 9, the fan 3, the first heat exchanger 13 or the second heat exchanger 2.
The PLC adjusts the frequency of the frequency converter and the opening degrees of the first expansion stop valve 11 and the second expansion stop valve 14 according to the fuzzy rule, when the frequency of the frequency converter is adjusted, the input variable is a temperature error value between the temperature in the drying chamber 1 and the set temperature, and the output value is the frequency of the frequency converter;
when the opening degrees of the first and second expansion cut-off valves 11 and 14 are adjusted, the input amount is an error between the superheat degree of the first or second heat exchanger 13 or 2 and the set superheat degree, and the output amount is the opening degrees of the first and second expansion cut-off valves 11 and 14.
As shown in fig. 4, in the fuzzy rule for the PLC controller to adjust the frequency of the inverter, the input variable is an error value of a set temperature, and the output variable is a frequency variation of the compressor. The magnitude of the error value according to the set temperature is expressed by a language variable as: negative big, negative middle, negative small, zero, positive small, positive middle, positive big, expressed as NL, NM, NS, Z, PS, PM, PL, respectively; in the range of discourse area [ -6 ], the input ranges are respectively: [ -6, -4], [ -6, -2], [ -4,0], [ -2,2], [0,4], [2,6], [4,6], the membership function selects trapezoidal distribution shapes and triangles, as shown in fig. 5 and fig. 6 respectively, and the membership of input values to each fuzzy variable is calculated through the membership function.
The input temperature is x, the membership degree of the fuzzy set can be calculated by the following C language function, wherein a, b, C and d are respectively domain ranges of the fuzzy set, and b and C are equal when the membership function is a triangle:
Figure BDA0003756086150000081
Figure BDA0003756086150000091
the linguistic variables for the output compressor frequency change are: NL, NM, NS, Z, PS, PM, PL, indicating the increase in compressor frequency from a negative large value for rapid increase in frequency to a positive large value for rapid decrease in frequency, with a normalized range of discourse [ -1,1]Scale factor K u Set to 0.01, and its membership function is shown in fig. 7.
The fuzzy rule is designed by expert experience knowledge, an if-then fuzzy reasoning method is adopted, the control quantity should be increased due to large error, the principle that the error is in direct proportion to the control quantity is adopted, a fuzzy rule table is shown in table 1, and the design of the fuzzy rule table is generally designed based on a negative feedback principle and expert experience.
TABLE 1 fuzzy rule Table
Fuzzy rule If temperature error value Frequency variation of Then compressor Output weights OW [ i]
1 NL NL -1
2 NM NM -0.7
3 NS NS -0.3
4 Z Z 0
5 PS PS 0.3
6 PM PM 0.7
7 PL PL 1
The weight OW [ i ] output in the table 1 is the intermediate value of each fuzzy set, and the output fuzzy variable value obtained based on fuzzy reasoning is clarified by adopting a weighted average method, wherein the calculation formula is as follows:
Figure BDA0003756086150000092
FS i to output the membership of the fuzzy set.
The fuzzy rule table is expressed by the structure variable in the C language as follows, and is initialized according to the fuzzy rule table:
struct fuzzy_rule
{ float input1; // degree of input membership
float output1; // fuzzy output value
float f; // fuzzy rule weights
}struct fuzzy_rule R[7]。
After defuzzification, the calculation formula of the output compressor frequency f is as follows:
f＝f_old+output/K u f _ old is initialized to 50Hz, K u The quantization scale value is output for blurring.
The expansion valve flow control system adopts fuzzy logic control, controls the refrigerant flow of the evaporator through the opening of the electronic expansion valve, enables the superheat degree of the evaporator to be optimal, fully provides the refrigerant for the evaporator, and ensures the stable operation of the system. The input of the fuzzy control is the superheat error, and the output is the opening degree of the expansion valve. The design of the fuzzy rule table is generally designed based on the negative feedback principle and the expert experience, and the design method is the same as that described above.
The PLC controller adopts a PID control rule to control the moisture discharging port actuator, so as to adjust the opening degree of the moisture discharging port 8, specifically, an error value between the set humidity of the drying chamber 1 and the actual humidity measured by the humidity sensor 5 is input into the PLC controller, and the opening degree of the moisture discharging port 8 is output to adjust the humidity of the drying chamber 1.
Those of ordinary skill in the art will appreciate that the elements of the examples described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the components of the examples have been described above generally in terms of their functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the technical solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the embodiments provided in the present application, it should be understood that the division of the unit is only one division of logical functions, and other division manners may be used in actual implementation, for example, multiple units may be combined into one unit, one unit may be split into multiple units, or some features may be omitted.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims (8)

1. A heat pump drying system for preserved fruits is characterized by comprising a heat pump subsystem, a drying chamber (1) and a frequency converter, wherein the heat pump subsystem comprises a first heat exchanger (13), a first expansion stop valve (11), a second expansion stop valve (14), a four-way reversing valve (10), a second heat exchanger (2) and a compressor (9);
the second heat exchanger (2) is arranged at the top of the drying chamber (1), and the first heat exchanger (13), the first expansion stop valve (11), the second expansion stop valve (14) and the second heat exchanger (2) are sequentially connected; the four-way reversing valve (10) is respectively connected with the second heat exchanger (2), the compressor (9) and the first heat exchanger (13);
the top of the drying chamber (1) is also provided with a fan (3) and an electric heater (4), the upper part of the drying chamber (1) is provided with a moisture exhaust port (8), the lower part of the drying chamber is provided with a drying material rack (6), a weight sensor (7) is arranged below the drying material rack (6), and the drying chamber (1) is also provided with a humidity sensor (5) and a temperature sensor (12);
the compressor (9) and the fan (3) are respectively connected with a frequency converter, and the frequency converter is used for adjusting the working frequency of the compressor and the working frequency of the fan so as to adjust the flow rate of the refrigerant and the dry air volume;
the working modes of the heat pump subsystem comprise a heating mode and a refrigerating mode, when the heat pump subsystem works in the heating mode, the second heat exchanger (2) is a condenser, and the first heat exchanger (13) is an evaporator; when the air conditioner works in a refrigeration mode, the second heat exchanger (2) is an evaporator, and the first heat exchanger (13) is a condenser.
2. A control system of a heat pump drying system for preserved fruits is characterized by being applied to the heat pump drying system of claim 1 and comprising a PLC (programmable logic controller), a data acquisition module, a human-computer interface (HMI) and a cloud platform; the data acquisition module is connected with a humidity sensor (5), a temperature sensor (12) and a weight sensor (7) of the heat pump drying system and the heat pump subsystem, and is used for acquiring the operation condition data of the heat pump subsystem, the temperature and the humidity in the drying chamber and the weight of a drying material rack (6) and transmitting the acquired data to the PLC; the PLC is respectively connected with a frequency converter, a first expansion stop valve (11), a second expansion stop valve (14) and a moisture exhaust port actuator, the moisture exhaust port actuator is connected with a moisture exhaust port (8), and the PLC is used for controlling the opening degree of the moisture exhaust port (8) according to an expert database, fuzzy rules and PID control rules, controlling the opening degrees of the first expansion stop valve (11) and the second expansion stop valve (14) to adjust the flow rate of refrigerant and control the frequency of the frequency converter;
the human-computer interface HMI is connected with the PLC and used for human-computer interaction;
the cloud platform is connected with the human-computer interface HMI and used for monitoring the operation condition of the heat pump drying system and storing monitoring data.
3. The control system of the heat pump drying system for preserved fruit according to claim 2, wherein the cloud platform comprises an MQTT message proxy server and a database server, the human-machine interface HMI is connected with the MQTT message proxy server and issues the running state and fault information of the equipment to the client through an MQTT protocol; the database server is used for storing data and providing data service.
4. The control system of the heat pump drying system for preserved fruits according to claim 2, wherein the PLC controls the operation condition of the heat pump drying system according to an expert database, and the expert database stores the temperature and humidity of dried preserved fruits, the water content of materials, the drying time, the system energy efficiency and the superheat degree of a compressor (9), a fan (3), a first heat exchanger (13) or a second heat exchanger (2).
5. The control system of the heat pump drying system for preserved fruit according to claim 2, wherein the PLC controller adjusts the frequency of the frequency converter and the opening degrees of the first expansion stop valve (11) and the second expansion stop valve (14) according to a fuzzy rule, when adjusting the frequency of the frequency converter, the input variable is a temperature error value between the temperature in the drying chamber (1) and a set temperature, and the output value is the frequency of the frequency converter;
when the opening degrees of the first expansion stop valve (11) and the second expansion stop valve (14) are adjusted, the input amount is the error between the superheat degree of the first heat exchanger (13) or the second heat exchanger (2) and the set superheat degree, and the output amount is the opening degrees of the first expansion stop valve (11) and the second expansion stop valve (14).
6. The control system of the heat pump drying system for preserved fruit according to claim 2, wherein the PLC controller controls the actuator of the moisture exhaust port according to a PID control rule, and further adjusts the opening degree of the moisture exhaust port (8), and specifically, an error value between the set humidity of the drying chamber (1) and the actual humidity measured by the humidity sensor (5) is input into the PLC controller, and the opening degree of the moisture exhaust port (8) is output to adjust the humidity of the drying chamber (1).
7. The control system of a heat pump drying system for preserved fruit as claimed in claim 5, wherein in the fuzzy rule of the PLC controller adjusting the frequency of the frequency converter, the input variable is an error value of the set temperature, and the input variable is expressed by language variables according to the magnitude of the error value as: negative large, negative middle, negative small, zero, positive small, positive middle, positive large, denoted as NL, NM, NS, Z, PS, PM, PL, respectively, input ranges are: [ -6, -4], [ -6, -2], [ -4,0], [ -2,2], [0,4], [2,6], [4,6], membership functions selecting trapezoidal distribution shapes and triangles;
the linguistic variables that output the change in compressor frequency are: NL, NM, NS, Z, PS, PM, PL, indicating the increase of compressor frequency from negative to positive values, positive values for rapid increase of frequency and negative values for rapid decrease of frequency, and normalized discourse range [ -1,1]Scale factor K u Set to 0.01.
8. The control system of claim 7, wherein the fuzzy rule is based on if-then fuzzy inference, and the table of fuzzy rules is shown in table 1:
TABLE 1 fuzzy rule Table
Fuzzy rule If temperature error value Frequency variation of Then compressor Output weights OW [ i] 1 NL NL -1 2 NM NM -0.7 3 NS NS -0.3 4 Z Z 0 5 PS PS 0.3 6 PM PM 0.7 7 PL PL 1
Weights OW [ i ] output in Table 1]Taking the intermediate value of each fuzzy set, defuzzifying and adopting a weighted average method, wherein the calculation formula is as follows:
Figure FDA0003756086140000031
FS i the membership of the fuzzy set is output.
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1737456A (en) * 2004-08-17 2006-02-22 Lg电子株式会社 Electricity generating and air conditioning system with dehumidifier
CN103175382A (en) * 2011-12-26 2013-06-26 中国科学院理化技术研究所 Heat pump drying system
US20150153078A1 (en) * 2013-12-02 2015-06-04 Hyundai Motor Company Heat pump system for vehicle
CN104904894A (en) * 2015-06-30 2015-09-16 四川中测量仪科技有限公司 Tea leaf aroma improving machine and tea leaf intelligent control aroma improving pattern
CN109632304A (en) * 2018-12-25 2019-04-16 哈尔滨工业大学 Four-point contact ball running in machine and control method
CN111365977A (en) * 2020-03-23 2020-07-03 顺德职业技术学院 Control method of closed type variable frequency heat pump drying equipment

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1737456A (en) * 2004-08-17 2006-02-22 Lg电子株式会社 Electricity generating and air conditioning system with dehumidifier
CN103175382A (en) * 2011-12-26 2013-06-26 中国科学院理化技术研究所 Heat pump drying system
US20150153078A1 (en) * 2013-12-02 2015-06-04 Hyundai Motor Company Heat pump system for vehicle
CN104904894A (en) * 2015-06-30 2015-09-16 四川中测量仪科技有限公司 Tea leaf aroma improving machine and tea leaf intelligent control aroma improving pattern
CN109632304A (en) * 2018-12-25 2019-04-16 哈尔滨工业大学 Four-point contact ball running in machine and control method
CN111365977A (en) * 2020-03-23 2020-07-03 顺德职业技术学院 Control method of closed type variable frequency heat pump drying equipment

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