Heat pump system for drying equipment and control method of heat pump system

Abstract

The invention relates to the technical field of agricultural product drying, and discloses a heat pump system for drying equipment and a control method thereof.The heat pump system comprises a case, an air mixing cavity, an air return channel and a heat pump, a fresh air fan and an exhaust fan are arranged on the case, and an air return fan is arranged in the air return channel; high-temperature and high-humidity airflow exhausted by the humidity exhaust channel is mixed with environment fresh air and then cooled and dehumidified through the evaporator, the dehumidified first mixed airflow is divided into two strands, one strand of airflow is exhausted out of the machine box through the exhaust outlet, the other strand of airflow passes through the air return channel to form return air, and the return air is heated by the condenser and then returns into the drying cavity through the air inlet channel. And cyclic heating of the materials in the drying cavity is achieved. Besides, a function relation expression among the control air volume of the air return fan, the environment new house flow and the environment fresh air temperature can be constructed by utilizing test data, so that the air volume of the air return fan is accurately adjusted in real time, and the air inlet temperature in the air inlet channel of the drying cavity is ensured to meet the design temperature requirement.

Description

Technical Field

[0001] The invention relates to the technical field of drying agricultural products, and in particular to a heat pump system for drying equipment and a control method thereof. Background Art

[0002] In traditional heat pump drying equipment, although the ambient fresh air can be mixed with the high-temperature and high-humidity return air in the drying chamber for heat exchange after entering the chassis, and then dehumidified and cooled by the evaporator, and then heated by the condenser and sent to the drying room to achieve heating and drying of the materials, the existing drying equipment lacks a precise adjustment mechanism for the return air volume according to the fresh air temperature and flow rate, resulting in large fluctuations in the temperature in the drying chamber. Summary of the invention

[0003] In view of this, the present invention provides a heat pump system for drying equipment and a control method thereof, which can realize real-time and precise adjustment of the air volume of the return air fan to ensure that the inlet air temperature in the air inlet channel of the drying chamber meets the design temperature requirements.

[0004] In order to achieve the above technical effects, the present invention provides a heat pump system for drying equipment, comprising:

[0005] A chassis, wherein the chassis is provided with a fresh air inlet, an exhaust port, an air inlet channel and a dehumidification channel, wherein a temperature sensor and a fresh air fan are provided in the fresh air inlet, wherein the temperature sensor is used to obtain the temperature of the ambient fresh air, wherein the exhaust port is provided with an exhaust fan, wherein the air inlet channel is used to provide a drying airflow to the drying chamber, and wherein the dehumidification channel is used to discharge the high-temperature and high-humidity gas in the drying chamber to the outside of the drying chamber;

[0006] An air mixing chamber, wherein the air mixing chamber is arranged in the chassis, the fresh air inlet and the dehumidification channel are both connected to the air inlet end of the air mixing chamber, and the air outlet is arranged at a chassis position corresponding to the air mixing chamber;

[0007] A return air channel, one end of which is connected to the air outlet of the air mixing chamber, and the other end of which is connected to the air inlet channel, wherein a return air fan is arranged in the return air channel;

[0008] A heat pump, the heat pump includes a compressor, a condenser, an expansion throttle valve and an evaporator forming a circulation loop; the evaporator is arranged between the air inlet end and the air outlet end of the air mixing chamber, the condenser is arranged in the return air channel, and the condenser is used to heat the airflow entering the return air channel.

[0009] Furthermore, the air outlet and the return air channel are arranged at intervals along the length direction of the chassis.

[0010] Furthermore, there are at least two groups of heat pumps, the evaporator of each group of heat pumps is arranged in series in the air mixing chamber, and the condenser of each group of heat pumps is arranged in series in the return air channel.

[0011] Furthermore, an electric auxiliary heating mechanism is provided at an upstream position close to the air inlet channel, and a control switch for controlling the opening and closing of the electric auxiliary heating mechanism is provided on the electric auxiliary heating mechanism.

[0012] In order to achieve the above technical effects, the present invention further provides a control method for a heat pump system for a drying device. The control method is based on the heat pump system for the drying device, and includes:

[0013] Set the fresh air fan and exhaust air fan to the same specifications;

[0014] Start the heat pump, fresh air fan, exhaust fan and return air fan, and test the return air fan air volume value when the high-temperature air flow temperature in the air inlet channel is stable and reaches the design required temperature value under different fresh air fan test air volume and ambient fresh air temperature combination parameter conditions; during the test, keep the air volume of the exhaust fan equal to the test air volume of the fresh air fan;

[0015] According to the design required temperature value of high-temperature airflow in the air inlet duct, the test air volume of the fresh air fan, the ambient fresh air temperature and the corresponding test air volume of the exhaust fan, a return air fan air volume control curve based on the test air volume of the fresh air fan, the ambient fresh air temperature and meeting the design required temperature value of high-temperature airflow in the air inlet duct is constructed;

[0016] According to the initial moisture content of the material to be dried, the controlled moisture content of the finished product of the material to be dried, the processing capacity of the material to be dried per unit time of the drying equipment, and the performance parameters of the ambient fresh air, the fresh air volume when the material to be dried is dried in the drying equipment is analyzed and obtained;

[0017] According to the return air fan air volume control curve and the fresh air volume, the real-time flow control value of the return air fan is analyzed and obtained to adjust the air volume of the return air fan in real time.

[0018] Furthermore, one or more combinations of polynomial fitting, neural network model, and deep learning model are used to construct a return air fan volume control curve based on the fresh air fan test air volume, ambient fresh air temperature, and meeting the design requirement temperature value of high-temperature airflow in the air inlet duct.

[0019] Further, when selecting the fresh air fan and the dehumidification fan, the first air volume value W of the fresh air fan and the dehumidification fan when they are running stably is s according to The analysis results show that ω1 is the initial moisture content of the material to be dried, ω2 is the controlled moisture content of the finished material to be dried, H is the processing capacity of the material to be dried per unit time of the drying equipment, and ρo For high temperature and high humidity airflow at temperature T out Absolute humidity of steam under s It is the absolute humidity of the fresh air.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention starts the fresh air fan, exhaust fan, return air fan and heat pump, and the ambient fresh air enters the chassis from the fresh air inlet. The high-temperature and high-humidity airflow discharged from the dehumidification channel is mixed with the ambient fresh air entering the fresh air inlet to form a first mixed airflow that enters the evaporator for cooling and dehumidification. The first mixed airflow after dehumidification is divided into two streams, one of which is discharged from the exhaust port outside the chassis, and the other is formed into return air after passing through the return air channel. The return air is heated by the condenser to form high-temperature and low-humidity return air that returns to the drying chamber from the air inlet channel, thereby realizing cyclic heating of the materials in the drying chamber.

[0022] 2. Use the test data to construct a functional relationship between the control air volume of the return air fan and the ambient fresh air flow and ambient fresh air temperature, so as to achieve real-time and precise adjustment of the air volume of the return air fan to ensure that the inlet air temperature in the air inlet channel of the drying chamber meets the design temperature requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a schematic diagram of the structure of a heat pump system for a drying device in an embodiment;

[0025] Figure 2 This is a flow chart of a control method for a heat pump system of a drying device in an embodiment;

[0026] Among them, 1. Chassis; 2. Fresh air inlet; 3. Exhaust port; 4. Air inlet channel; 5. Dehumidification channel; 6. Mixing air chamber; 7. Return air channel; 8. Condenser; 9. Evaporator; 10. Electric auxiliary heating mechanism. DETAILED DESCRIPTION

[0027] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0028] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0029] Example

[0030] See also Figure 1 , a heat pump system for drying equipment, comprising:

[0031] A chassis 1 is provided with a fresh air inlet 2, an exhaust port 3, an air inlet channel 4 and a dehumidification channel 5. A temperature sensor and a fresh air fan are provided in the fresh air inlet 2. The temperature sensor is used to obtain the temperature of the ambient fresh air. The exhaust port 3 is provided with an exhaust fan. The air inlet channel 4 is used to provide a drying airflow to the drying chamber. The dehumidification channel 5 is used to discharge the high-temperature and high-humidity gas in the drying chamber to the outside of the drying chamber.

[0032] An air mixing chamber 6, wherein the air mixing chamber 6 is disposed in the chassis 1, the fresh air inlet 2 and the moisture removal channel 5 are both connected to the air inlet end of the air mixing chamber 6, and the air outlet 3 is disposed at a position of the chassis 1 corresponding to the air mixing chamber 6;

[0033] A return air channel 7, one end of which is connected to the air outlet of the air mixing chamber 6, and the other end of which is connected to the air inlet channel 4. A return air fan is provided in the return air channel 7;

[0034] A heat pump includes a compressor, a condenser 8, an expansion throttle valve and an evaporator 9 forming a circulation loop; the evaporator 9 is arranged between the air inlet end of the air mixing chamber 6 and the air outlet end of the air mixing chamber 6, and the condenser 8 is arranged in the return air channel 7, and the condenser 8 is used to heat the airflow entering the return air channel 7.

[0035] In this embodiment, the air inlet end of the drying chamber is connected to the air inlet channel, and the exhaust end of the drying chamber is connected to the dehumidification channel 5. During the material drying process, by turning on the fresh air fan, the exhaust fan, the return air fan and the heat pump, the ambient fresh air enters the chassis 1 from the fresh air inlet 2, and the airflow in the drying chamber is discharged through the dehumidification channel 5. The high-temperature and high-humidity airflow discharged from the dehumidification channel 5 is mixed with the ambient fresh air entering the fresh air inlet 2 to form a first mixed airflow that enters the evaporator 9 for cooling and dehumidification. The first mixed airflow after dehumidification is divided into two streams, one of which is discharged from the exhaust port 3 outside the chassis 1, and the other is formed after passing through the return air channel 7 to form return air. The return air is heated by the condenser 8 to form a high-temperature and low-humidity return air that returns to the drying chamber from the air inlet channel 4, thereby realizing the circulation heating of the material in the drying chamber.

[0036] In this embodiment, the exhaust port 3 and the return air channel 7 are spaced apart along the length direction of the chassis 1, so that the air flows flowing out from the outlet of the evaporator 9 enter the corresponding channels respectively without interfering with each other, and the return air flow of the entire drying equipment can be kept stable without causing the problem of excessive or low local return air flow.

[0037] In this embodiment, there are at least two groups of heat pumps, and the evaporator 9 of each group of heat pumps is arranged in series in the mixing air chamber 6, and the condenser 8 of each group of heat pumps is arranged in series in the return air channel 7. The first mixed airflow in the mixing air chamber 6 can be pre-heated with one of the evaporators 9, and then heat-exchanged with the other evaporator 9 in series. By matching the relevant parameters of the two groups of evaporators 9 in the same mixing air chamber 6 and designing them, such as setting different circulating media in the two groups of evaporators 9 connected in series, the heat exchange efficiency of the evaporator 9 is matched with the corresponding inlet airflow temperature, so that the heat exchange efficiency is improved and the dehumidification effect is ensured.

[0038] In this embodiment, an electric auxiliary heating mechanism 10 is further provided at an upstream position near the air inlet channel 4, and a control switch for controlling the opening and closing of the electric auxiliary heating mechanism 10 is also provided on the electric auxiliary heating mechanism 10. When the ambient fresh air temperature is low and the condenser 8 cannot meet the temperature in the air inlet channel 4, the electric auxiliary heating mechanism 10 can be turned on to heat the airflow in the air inlet channel, thereby further ensuring that the air inlet temperature in the air inlet channel 4 of the drying chamber meets the design temperature requirement.

[0039] Based on the same inventive concept, this embodiment also provides a control method for a heat pump system of a drying device, see Figure 2 , the specific steps are as follows:

[0040] Step 1: Set the fresh air fan and exhaust fan to the same specifications;

[0041] Step 2: Start the heat pump, fresh air fan, exhaust fan and return air fan, and test the return air fan air volume value when the high-temperature air flow temperature in the air inlet channel 4 is stable and reaches the design required temperature value under different fresh air fan test air volume and ambient fresh air temperature combination parameter conditions; during the test, keep the air volume of the exhaust fan equal to the test air volume of the fresh air fan;

[0042] Step 3: According to the required temperature value of the high-temperature airflow design in the air inlet duct 4, the fresh air fan test air volume, the ambient fresh air temperature and the corresponding exhaust fan test air volume, a return air fan air volume control curve based on the fresh air fan test air volume, the ambient fresh air temperature and meeting the required temperature value of the high-temperature airflow design in the air inlet duct 4 is constructed;

[0043] Step 4: Analyze and obtain the fresh air volume when the material to be dried is dried in the drying equipment according to the initial moisture content of the material to be dried, the controlled moisture content of the finished material to be dried, the processing capacity of the material to be dried per unit time of the drying equipment, and the performance parameters of the ambient fresh air. Analyze and obtain the real-time flow control value of the return air fan according to the return air fan volume control curve and the fresh air volume, so as to adjust the air volume of the return air fan in real time.

[0044] This embodiment uses test data to construct a functional relationship between the control air volume of the return air fan and the ambient fresh air flow and ambient fresh air temperature, so as to achieve real-time and precise adjustment of the air volume of the return air fan to ensure that the inlet air temperature in the air inlet channel 4 of the drying chamber meets the design temperature requirements.

[0045] In this embodiment, one or more combinations of polynomial fitting, neural network model, and deep learning model can be used to construct a return air fan air volume control curve based on the test air volume of the fresh air fan, the ambient fresh air temperature, and the temperature value that meets the design requirement of the high-temperature airflow in the air inlet channel 4. It should be noted that other methods that can realize the construction of a functional relationship between the control air volume of the return air fan and the ambient fresh air flow and the ambient fresh air temperature are also applicable to the present invention.

[0046] In this embodiment, when selecting the fresh air fan and the dehumidification fan, the first air volume value W of the fresh air fan and the dehumidification fan when they are running stably is s according to The analysis results show that ω1 is the initial moisture content of the material to be dried, ω2 is the controlled moisture content of the finished material to be dried, H is the processing capacity of the material to be dried per unit time of the drying equipment, and ρ o For high temperature and high humidity airflow at temperature T out Absolute humidity of steam under s It is the absolute humidity of the fresh air in the environment. While ensuring that the temperature of the drying chamber meets the requirements, it can also ensure the drying effect of different materials to be dried and meet the moisture control requirements during the drying process.

[0047] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A heat pump system for drying equipment, characterized in that: include: A chassis, wherein the chassis is provided with a fresh air inlet, an exhaust port, an air inlet channel and a dehumidification channel, wherein a temperature sensor and a fresh air fan are provided in the fresh air inlet, wherein the temperature sensor is used to obtain the temperature of the ambient fresh air, wherein the exhaust port is provided with an exhaust fan, wherein the air inlet channel is used to provide a drying airflow to the drying chamber, and wherein the dehumidification channel is used to discharge the high-temperature and high-humidity gas in the drying chamber to the outside of the drying chamber; An air mixing chamber, wherein the air mixing chamber is arranged in the chassis, the fresh air inlet and the dehumidification channel are both connected to the air inlet end of the air mixing chamber, and the air outlet is arranged at a chassis position corresponding to the air mixing chamber; A return air channel, one end of which is connected to the air outlet of the air mixing chamber, and the other end of which is connected to the air inlet channel, wherein a return air fan is arranged in the return air channel; A heat pump, the heat pump includes a compressor, a condenser, an expansion throttle valve and an evaporator forming a circulation loop; the evaporator is arranged between the air inlet end and the air outlet end of the air mixing chamber, the condenser is arranged in the return air channel, and the condenser is used to heat the airflow entering the return air channel.

2. The heat pump system for drying equipment according to claim 1, characterized in that: The air outlet and the return air channel are spaced apart along the length direction of the chassis.

3. The heat pump system for drying equipment according to claim 1, characterized in that: There are at least two groups of heat pumps, the evaporator of each group of heat pumps is arranged in series in the air mixing chamber, and the condenser of each group of heat pumps is arranged in series in the return air channel.

4. The heat pump system for drying equipment according to claim 1, characterized in that: An electric auxiliary heating mechanism is also provided at an upstream position close to the air inlet channel, and a control switch for controlling the opening and closing of the electric auxiliary heating mechanism is also provided on the electric auxiliary heating mechanism.

5. A control method for a heat pump system for drying equipment, the control method is based on the heat pump system for drying equipment according to claim 1, characterized in that: include: Set the fresh air fan and exhaust air fan to the same specifications; Start the heat pump, fresh air fan, exhaust fan and return air fan, and test the return air fan air volume value when the high-temperature air flow temperature in the air inlet channel is stable and reaches the design required temperature value under different fresh air fan test air volume and ambient fresh air temperature combination parameter conditions; during the test, keep the air volume of the exhaust fan equal to the test air volume of the fresh air fan; According to the design required temperature value of high-temperature airflow in the air inlet duct, the test air volume of the fresh air fan, the ambient fresh air temperature and the corresponding test air volume of the exhaust fan, a return air fan air volume control curve based on the test air volume of the fresh air fan, the ambient fresh air temperature and meeting the design required temperature value of high-temperature airflow in the air inlet duct is constructed; According to the initial moisture content of the material to be dried, the controlled moisture content of the finished product of the material to be dried, the processing capacity of the material to be dried per unit time of the drying equipment, and the performance parameters of the ambient fresh air, the fresh air volume when the material to be dried is dried in the drying equipment is analyzed and obtained; According to the return air fan air volume control curve and the fresh air volume, the real-time flow control value of the return air fan is analyzed and obtained to adjust the air volume of the return air fan in real time.

6. The control method for a heat pump system for drying equipment according to claim 5, characterized in that: One or more combinations of polynomial fitting, neural network model, and deep learning model are used to construct a return air fan volume control curve based on the fresh air fan test air volume, ambient fresh air temperature, and meeting the design requirement temperature value of high-temperature airflow in the air inlet duct.

7. The control method for a heat pump system for drying equipment according to claim 5, characterized in that: When selecting the fresh air fan and the dehumidification fan, the first air volume value W of the fresh air fan and the dehumidification fan when they are running stably s according to The analysis results show that ω1 is the initial moisture content of the material to be dried, ω2 is the controlled moisture content of the finished material to be dried, H is the processing capacity of the material to be dried per unit time of the drying equipment, and ρ o For high temperature and high humidity airflow at temperature T out Absolute humidity of steam under s It is the absolute humidity of the fresh air.

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