Aquatic product multi-purpose complementary combined drying system and control method thereof

Abstract

This invention relates to the field of aquatic product drying technology, and more particularly to a multi-energy complementary combined drying system for aquatic products and its control method. The system includes a drying chamber, a hot water storage tank, a gas-fired boiler, an air-source heat pump system, a solar collector, a solar circulating water pump, and a control system. The hot water storage tank is connected to a heat exchanger inside the drying chamber via the drying circulating water pump, forming a drying heating loop. The gas-fired boiler and the hot water storage tank are connected in a closed loop to form a supplementary heating loop. The solar collector and the hot water storage tank constitute a solar thermal storage loop. The air-source heat pump uses a loop with a four-way reversing valve and a two-way electronic expansion valve. The circulating air passes through the evaporator and condenser sequentially before returning to the drying chamber, forming a dehumidification and heating loop. The control system monitors the evaporator coil temperature and controls the four-way reversing valve and the circulating water pump accordingly. This invention achieves multi-heat source complementary combined supply via solar energy, air-source heat pump, and gas-fired boiler, providing continuous and stable supplementary heating during defrosting and reducing overall operating energy consumption.

Description

Technical Field

[0001] This invention relates to the technical field of aquatic product drying, and in particular to a multi-energy complementary combined drying system for aquatic products and its control method. Background Technology

[0002] Aquatic products have a high water content after harvesting or fishing, and are rich in protein and fat. If they are not dehydrated in time, they are prone to spoilage, fat oxidation, and flavor deterioration. Drying is one of the commonly used preservation methods in aquatic product processing. Existing aquatic product drying technologies mainly include air source heat pump drying and solar drying. Air source heat pump drying technology has advantages such as energy saving, controllable temperature and humidity, and suitability for low-temperature drying, and has attracted attention in the aquatic product processing field. Solar drying technology is clean and pollution-free, has low operating costs, and can provide some of the heat required for drying when sunlight conditions are good. Combining solar energy with air source heat pumps helps to leverage the advantages of each and reduce system operating energy consumption.

[0003] However, when operating an air-source heat pump in winter or in low-temperature, high-humidity coastal environments, condensation and frost easily form on the evaporator surface because the heat exchange temperature is lower than the ambient air dew point temperature. Once the frost layer covers the evaporator surface, it increases the heat exchange resistance, reduces the evaporator's heat absorption efficiency, and leads to a decrease in the heat pump's coefficient of performance (COP) and a reduction in dehumidification capacity. When frost is severe, normal drying operation must be stopped for defrosting. During defrosting, the system's heating capacity is reduced or interrupted, causing temperature fluctuations within the drying chamber, affecting the continuity of the drying process and the quality of the dried materials. Although solar energy can serve as an auxiliary heat source, its heating supply is constrained by weather and diurnal variations, making it difficult to provide continuous and stable heat compensation during heat pump frost formation. Summary of the Invention

[0004] This invention provides a multi-energy complementary combined drying system for aquatic products and its control method, which can effectively solve the problems in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A multi-energy complementary combined drying system for aquatic products includes: This includes drying boxes, hot water storage tanks, gas boilers, air source heat pump systems, solar collectors, solar circulating water pumps, and control systems. The outlet of the hot water storage tank is connected to the inlet of the heat exchanger installed in the drying box via the drying circulating water pump, and the outlet of the heat exchanger is connected to the return water outlet of the hot water storage tank, forming a drying and heating circuit that supplies heat to the drying box. The outlet of the gas boiler is connected to the heat replenishment inlet of the hot water storage tank, and the heat replenishment outlet of the hot water storage tank is connected to the inlet of the gas boiler via the gas boiler circulating water pump, forming a heat replenishment circuit to replenish heat to the hot water storage tank. The outlet of the solar collector is connected to the solar inlet of the hot water storage tank via the first valve, and the solar outlet of the hot water storage tank is connected to the inlet of the solar collector via the second valve and the solar circulating water pump, forming a solar thermal storage circuit for storing heat in the hot water storage tank. The air source heat pump system includes a compressor, evaporator, condenser, four-way reversing valve, and two-way electronic expansion valve; the compressor, four-way reversing valve, condenser, two-way electronic expansion valve, and evaporator are connected by refrigerant pipelines to form a refrigerant circulation loop; the air outlet of the drying box is connected to the air inlet of the drying box through the evaporator and condenser in sequence to form a circulating air dehumidification and heating loop. The control system includes a sensor group and a controller. The sensor group includes a first temperature sensor for detecting the temperature of the evaporator coil. The input terminal of the controller is connected to the output terminal of the first temperature sensor, and the output terminal of the controller is connected to the control terminal of the four-way reversing valve, the control terminal of the drying circulating water pump, and the control terminal of the gas boiler circulating water pump.

[0006] Furthermore, a water vapor trap and a vacuum pump are connected in series on the drying chamber.

[0007] Furthermore, the heat exchanger is a tubular heat exchanger or a plate heat exchanger.

[0008] Furthermore, the heat exchanger is located inside the drying chamber and adjacent to the material placement space inside the drying chamber.

[0009] Furthermore, the sensor group also includes a first temperature and humidity sensor installed in the exhaust duct of the drying chamber and a second temperature and humidity sensor installed in the supply duct. The controller's input is also connected to the output of the first and second temperature and humidity sensors.

[0010] Furthermore, the air source heat pump system also includes an electric heater, which is located in the air supply duct and downstream of the condenser; The controller's output is also connected to the electric heater's control terminal.

[0011] Furthermore, the compressor's discharge port is connected to the first interface of the four-way reversing valve, and the compressor's suction port is connected to the second interface of the four-way reversing valve. The third port of the four-way reversing valve is connected to one end of the condenser, and the fourth port of the four-way reversing valve is connected to one end of the evaporator. The other end of the evaporator is connected to the other end of the condenser via a two-way electronic expansion valve.

[0012] Furthermore, the air outlet of the drying oven is connected to the air inlet side of the evaporator via an exhaust fan, and the air outlet side of the condenser is connected to the air inlet of the drying oven via a ventilation fan.

[0013] Furthermore, the gas-fired boiler is a condensing gas-fired hot water boiler, and the fuel for the gas-fired boiler is any one of natural gas, liquefied natural gas, or liquefied petroleum gas.

[0014] The present invention also provides a control method for a multi-energy complementary combined drying system for aquatic products, used in the aforementioned multi-energy complementary combined drying system for aquatic products, comprising: The controller uses a sensor array to detect the coil temperature of the evaporator and determines whether the evaporator has entered the frosting state based on the coil temperature. When the controller determines that the evaporator has entered the frosting condition, the controller controls the four-way reversing valve to switch the refrigerant flow direction, so that the air source heat pump system enters the reverse circulation defrosting state. During reverse-cycle defrosting, the controller prioritizes using the heat from the hot water storage tank to heat the drying chamber via the drying heating circuit; The controller uses a sensor array to detect the temperature of the hot water storage tank and the air supply temperature of the drying chamber, and controls the supplementary heating based on these temperatures. When the temperature of the hot water storage tank is lower than the preset hot water storage tank temperature threshold, the controller starts the gas boiler to supplement the hot water storage tank through the heat supplementation circuit, so as to maintain the heat supply to the drying box by the heat exchanger installed in the drying box. When the temperature of the hot water storage tank is lower than the preset hot water storage tank temperature threshold and the air supply temperature of the drying box is lower than the preset air supply temperature threshold, the controller starts the electric heater installed in the air supply pipeline to provide auxiliary heating for the air supply.

[0015] The technical solution of this invention can achieve the following technical effects: The system comprises a multi-stage heat source system using solar energy, air source heat pumps, and gas boilers. Through the independent parallel layout of solar energy storage circuits, supplementary heat circuits, and drying heating circuits, it achieves automatic switching and coordinated supply of heat sources under different operating conditions. This fully utilizes clean energy to reduce operating costs, while the rapid response characteristics of the gas boiler compensate for insufficient heating from solar energy and heat pumps at night and under low-temperature, high-humidity conditions. A first temperature sensor installed on the evaporator coil monitors the frosting status in real time. Upon determining frosting, the controller switches the four-way reversing valve to put the heat pump into reverse circulation defrosting mode. During defrosting, the system prioritizes using the stored heat from the hot water tank to maintain heating in the drying chamber. When heat storage is insufficient, the gas boiler supplementary heat circuit and electric heater are activated sequentially for multi-stage heat compensation, ensuring controllable temperature fluctuations within the drying chamber throughout the defrosting process. The water vapor trap and vacuum pump in the drying chamber enable the system to perform both vacuum low-temperature drying and circulating hot air drying, reducing the risks of protein denaturation, fat oxidation, and surface hardening during the drying process of aquatic products.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the multi-energy complementary combined drying system for aquatic products in an embodiment of the present invention; The following components are labeled in the attached diagram: 1. Drying oven; 2. Hot water storage tank; 3. Gas boiler; 4. Solar collector; 5. Solar circulating water pump; 6. Drying circulating water pump; 7. Heat exchanger; 8. Gas boiler circulating water pump; 9. First valve; 10. Second valve; 11. Compressor; 12. Evaporator; 13. Condenser; 14. Four-way reversing valve; 15. Two-way electronic expansion valve; 16. Controller; 17. First temperature sensor; 18. Water vapor trap; 19. Vacuum pump; 20. First temperature and humidity sensor; 21. Second temperature and humidity sensor; 22. Electric heater; 23. Exhaust fan; 24. Ventilation fan. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] like Figure 1As shown, the multi-energy complementary combined drying system for aquatic products of the present invention includes a drying chamber 1, a hot water storage tank 2, a gas boiler 3, an air source heat pump system, a solar collector 4, a solar circulating water pump 5, and a control system. The outlet of the hot water storage tank 2 is connected to the inlet of a heat exchanger 7 installed in the drying chamber 1 via the drying circulating water pump 6, and the outlet of the heat exchanger 7 is connected to the return outlet of the hot water storage tank 2, forming a drying and heating circuit for supplying heat to the drying chamber 1. The outlet of the gas boiler 3 is connected to the heat replenishment inlet of the hot water storage tank 2, and the heat replenishment outlet of the hot water storage tank 2 is connected to the inlet of the gas boiler 3 via the gas boiler circulating water pump 8, forming a heat replenishment circuit for replenishing heat to the hot water storage tank 2. The outlet of the solar collector 4 is connected to the solar inlet of the hot water storage tank 2 via a first valve 9, and the solar outlet of the hot water storage tank 2 is connected to the inlet of the solar collector 4 via a second valve 10 and the solar circulating water pump 5, forming a solar heat storage circuit for storing heat in the hot water storage tank 2. The air source heat pump system... The system includes a compressor 11, an evaporator 12, a condenser 13, a four-way reversing valve 14, and a two-way electronic expansion valve 15. The compressor 11, the four-way reversing valve 14, the condenser 13, the two-way electronic expansion valve 15, and the evaporator 12 are connected through refrigerant pipelines to form a refrigerant circulation loop. The air outlet of the drying chamber 1 is connected to the air inlet of the drying chamber 1 via the evaporator 12 and the condenser 13 in sequence, forming a circulating air dehumidification and heating loop. The control system includes a sensor group and a controller 16. The sensor group includes a first temperature sensor 17 for detecting the temperature of the coil of the evaporator 12. The input terminal of the controller 16 is connected to the output terminal of the first temperature sensor 17, and the output terminal of the controller 16 is connected to the control terminal of the four-way reversing valve 14, the control terminal of the drying circulating water pump 6, and the control terminal of the gas boiler circulating water pump 8, respectively. It can realize the complementary supply of multiple heat sources such as solar energy, air source heat pump, and gas boiler, and maintain the stable and continuous operation of the drying system while reducing energy consumption.

[0022] The implementation of heat exchanger 7 includes, but is not limited to, tubular heat exchangers and plate heat exchangers, as long as they can achieve indirect heat exchange between hot water and the air inside the drying chamber 1. In practical applications, tubular heat exchangers are preferred. They consist of multiple parallel heat exchange tubes, with the two ends of the heat exchange tubes connected to the inlet manifold and the outlet manifold, respectively. When hot water flows through the inside of the heat exchange tubes, it releases heat to the circulating air inside the drying chamber 1 through the tube wall. Heat exchanger 7 is located inside the drying chamber 1 and is adjacent to the material placement space inside the drying chamber 1. Specifically, heat exchanger 7 is installed on the inner wall of the drying chamber 1 near the air inlet, so that the air heated by heat exchanger 7 can flow evenly along the material placement space to improve heat transfer efficiency.

[0023] A water vapor trap 18 and a vacuum pump 19 are connected in series on the drying chamber 1. The vacuum pump 19 is used to perform vacuum treatment on the drying chamber 1. Specifically, the inlet of the water vapor trap 18 is connected to the top exhaust port of the drying chamber 1 through a pipeline, and the outlet of the water vapor trap 18 is connected to the suction port of the vacuum pump 19 through a pipeline. After the vacuum pump 19 is started, the water vapor inside the drying chamber 1 is drawn into the water vapor trap 18 under negative pressure. The water vapor trap 18 has a built-in coil-type condenser coil, and the inlet of the condenser coil is connected to the cooling water source. When the vapor flows over the surface of the condenser coil, it condenses into liquid water and is collected in the water collection tank at the bottom of the water vapor trap 18. It is then periodically discharged through the drain valve. The non-condensable gas after dehumidification is discharged into the atmosphere through the vacuum pump 19. The vacuum pump 19, together with the water vapor trap 18, maintains the set vacuum level inside the drying chamber 1 to reduce the evaporation temperature of the moisture inside the aquatic products and achieve low-temperature vacuum drying. By setting the structure of the water vapor trap 18 and the vacuum pump 19, the synergistic operation effect of low-temperature vacuum drying and hot air circulation drying can be achieved.

[0024] In the circulating air dehumidification and heating circuit, the air outlet of the drying chamber 1 is connected to the air inlet side of the evaporator 12 via the exhaust fan 23, and the air outlet side of the condenser 13 is connected to the air inlet of the drying chamber 1 via the ventilation fan 24. In the non-working state, both the exhaust fan 23 and the ventilation fan 24 are stopped, and the air inside the drying chamber 1 is in a naturally still state. In the working state, the exhaust fan 23 starts and sends the hot and humid air discharged from the drying chamber 1 into the evaporator 12. The hot and humid air is cooled to below the dew point temperature as it flows over the surface of the evaporator 12 coils, and the water vapor in it condenses into liquid water and flows along the surface of the evaporator 12 coils. The air flows down through the drain pipe and is discharged. The dehumidified, low-temperature dry air then enters the condenser 13 and exchanges heat with the high-temperature refrigerant flowing through the condenser 13. The air is heated to the set drying temperature. Driven by the ventilation fan 24, the heated dry air is sent back to the drying chamber 1 through the air supply pipe. It flows through the material placement space and blows on the surface of the aquatic products to remove the moisture that has migrated from the inside of the materials to the surface. The air carrying the moisture enters the evaporator 12 again through the exhaust fan 23, completing one dehumidification and heating cycle. This cycle is repeated to achieve continuous dehumidification and heating of the air inside the drying chamber 1.

[0025] In the refrigerant circulation loop of the air source heat pump system, the discharge port of compressor 11 is connected to the first port of four-way reversing valve 14, and the suction port of compressor 11 is connected to the second port of four-way reversing valve 14; the third port of four-way reversing valve 14 is connected to one end of condenser 13, and the fourth port of four-way reversing valve 14 is connected to one end of evaporator 12; the other end of evaporator 12 is connected to the other end of condenser 13 via bidirectional electronic expansion valve 15; under normal drying operation, four-way reversing valve 14 is in the first port of condenser 13. In the first operating position, the high-temperature, high-pressure gaseous refrigerant discharged from the compressor 11 flows from the first port of the four-way reversing valve 14 to the third port and then enters the condenser 13. Inside the condenser 13, the refrigerant releases heat to the circulating air flowing over its outer surface and condenses into high-pressure liquid refrigerant. The high-pressure liquid refrigerant flows through the refrigerant pipeline to the bidirectional electronic expansion valve 15. After being throttled and depressurized by the bidirectional electronic expansion valve 15, it becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant and enters the evaporator 12. Inside the evaporator 12, the low-temperature, low-pressure refrigerant absorbs the flowing air... The refrigerant evaporates into low-pressure gaseous refrigerant by the heat of the circulating air on the surface of the evaporator coil 12. This low-pressure gaseous refrigerant flows through the fourth port of the four-way reversing valve 14 to the second port and then returns to the suction port of the compressor 11, completing the normal drying cycle. In reverse defrosting mode, the four-way reversing valve 14 switches to the second operating position. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 11 flows through the first port of the four-way reversing valve 14 to the fourth port and preferentially enters the evaporator 12. The high-temperature refrigerant flows through the interior of the evaporator coil 12. Heat is released from the frost layer covering the surface of the evaporator coil 12, causing the frost layer to melt and fall off. The refrigerant itself condenses into a high-pressure liquid refrigerant and flows through the bidirectional electronic expansion valve 15 for throttling and pressure reduction before entering the condenser 13. After absorbing heat and evaporating in the condenser 13, it returns to the suction port of the compressor 11 through the third port of the four-way reversing valve 14. Through the reversing control of the four-way reversing valve 14, the air source heat pump system can switch between normal dry operation and reverse circulation defrosting operation without the need to set up an independent defrosting heat exchange circuit.

[0026] To determine the frosting condition and control defrosting of the evaporator 12, a first temperature sensor 17 is installed on the surface of the evaporator 12 coil or the outer wall of the refrigerant outlet pipe of the evaporator 12. This sensor is used to detect the coil temperature of the evaporator 12 in real time and transmit the temperature signal to the controller 16. The controller 16 has preset coil temperature thresholds and duration thresholds. When the evaporator 12 coil temperature read by the controller 16 is lower than the preset coil temperature threshold and this state continues for a preset duration threshold, the controller 16 determines that the evaporator 12 has entered the frosting condition. As an alternative determination method, the controller 16 can also use air source heat... The controller 16 comprehensively judges the cumulative running time of the pump and the changes in the heat exchange state of the evaporator 12. That is, when the cumulative running time of the air source heat pump reaches the preset time threshold and the temperature difference between the inlet and outlet air of the evaporator 12 shrinks to below the set value, the controller 16 determines that the heat exchange efficiency of the evaporator 12 has decreased and the surface is covered with frost, and also determines that the evaporator 12 has entered the frosting condition. After the controller 16 determines that the evaporator 12 has entered the frosting condition, the controller 16 sends a reversing signal to the control terminal of the four-way reversing valve 14 to control the four-way reversing valve 14 to switch the refrigerant flow direction, so that the air source heat pump system switches from the normal drying operation state to the reverse circulation defrosting state. During reverse circulation defrosting, to avoid significant temperature fluctuations inside the drying chamber 1 due to the temporary loss of dehumidification and heating capacity of the air source heat pump during defrosting, the controller 16 prioritizes using the heat from the hot water storage tank 2 to heat the drying chamber 1 through the drying heating circuit. Specifically, the controller 16 starts the drying circulating water pump 6. The high-temperature hot water at the top of the hot water storage tank 2 enters the drying circulating water pump 6 through the outlet. After being pressurized by the drying circulating water pump 6, it is delivered to the inlet of the heat exchanger 7 located inside the drying chamber 1. When the hot water flows through the inside of the heat exchanger 7, it releases heat to the air inside the drying chamber 1 through the wall of the heat exchanger 7. The low-temperature return water after heat exchange returns to the return port of the hot water storage tank 2 through the outlet pipe of the heat exchanger 7, thereby maintaining the heating inside the drying chamber 1 during defrosting. When the sensor group detects that the temperature of the hot water storage tank 2 is lower than the preset hot water storage tank temperature threshold, the controller 16 starts the gas boiler 3 to supplement the heat to the hot water storage tank 2 through the heat supplementation circuit. Specifically, the controller 16 starts the gas boiler circulating water pump 8 and turns on the gas boiler 3. The low temperature return water in the lower or middle part of the hot water storage tank 2 enters the gas boiler circulating water pump 8 through the heat supplementation outlet. After being pressurized by the gas boiler circulating water pump 8, it is delivered to the inlet of the gas boiler 3. The water is heated and raised in temperature inside the gas boiler 3 and then flows into the heat supplementation inlet of the hot water storage tank 2 through the outlet of the gas boiler 3 to maintain the heat reserve of the hot water storage tank 2 and the continuous heat supply of the heat exchanger 7 to the drying box 1. When the temperature of the hot water storage tank 2 is lower than the preset hot water storage tank temperature threshold and the air supply temperature of the drying chamber 1 is lower than the preset air supply temperature threshold, the controller 16 starts the electric heater 22 installed in the air supply pipeline to assist in heating the air supply. The electric heater 22 is installed in the air supply pipeline and is located downstream of the condenser 13 and upstream of the air inlet of the drying chamber 1. If the condenser 13 cannot effectively heat the circulating air during the reverse circulation defrosting period, the controller 16 turns on the electric heater 22 so that the circulating air flowing through the electric heater 22 is directly heated and then sent into the drying chamber 1. After defrosting is completed, the controller 16 controls the four-way reversing valve 14 to reset to the normal drying operation state, and at the same time selectively shuts down the electric heater 22, the gas boiler 3 or the drying circulating water pump 6 according to the temperature of the hot water storage tank 2 and the air supply temperature. By employing the multi-stage heating strategy described above—prioritizing the use of heat from the hot water storage tank 2 during reverse-cycle defrosting, then starting the gas boiler 3 for supplementary heating, and finally starting the electric heater 22 for auxiliary heating—a smooth transition in heating supply to the drying chamber 1 and the beneficial effect of continuous drying can be achieved during defrosting.

[0027] The sensor group also includes a first temperature and humidity sensor 20 installed in the exhaust duct of the drying chamber 1 and a second temperature and humidity sensor 21 installed in the supply duct; the input terminal of the controller 16 is also connected to the output terminals of the first temperature and humidity sensor 20 and the second temperature and humidity sensor 21; the first temperature and humidity sensor 20 is used to detect the temperature and relative humidity of the hot and humid air discharged from the drying chamber 1, and the second temperature and humidity sensor 21 is used to detect the temperature and relative humidity of the circulating air supplied to the drying chamber 1; by comparing the detection values ​​of the second temperature and humidity sensor 21 and the first temperature and humidity sensor 20, the controller 16 can calculate the dehumidification rate and dehumidification load of the material inside the drying chamber 1 in real time, and then adjust the operating frequency of the compressor 11, the speed of the ventilation fan 24 and the opening of the bidirectional electronic expansion valve 15 to maintain the temperature and humidity inside the drying chamber 1 within the set process range; through the above optimized design, the precise control of temperature and humidity in the drying process is achieved, and the consistency of drying quality is improved.

[0028] The second temperature and humidity sensor 21 can be installed on the inner wall of the pipe between the downstream of the electric heater 22 and the air outlet of the drying chamber 1, and the sensor probe extends into the central area of ​​the pipe to ensure that the detected value can represent the true temperature and humidity state of the airflow; the first temperature and humidity sensor 20 can be installed on the inner wall of the pipe between the air outlet of the drying chamber 1 and the exhaust fan 23, and the sensor probe extends into the central area of ​​the pipe to detect the actual temperature and humidity of the air discharged from the drying chamber 1.

[0029] The air source heat pump system also includes an electric heater 22, which is installed in the air supply duct and located downstream of the condenser 13. The output of the controller 16 is also connected to the control terminal of the electric heater 22. Under normal drying operation, when the temperature of the circulating air at the outlet of the condenser 13 does not reach the set drying air supply temperature, the controller 16 turns on the electric heater 22 to provide auxiliary heating to the circulating air until the outlet temperature of the condenser 13 recovers to above the set value and then stops the auxiliary heating. Under reverse circulation defrosting, the electric heater 22 serves as a tertiary heat compensation method. It is activated when the heat supply from the hot water storage tank 2 is insufficient and the heat compensation from the gas boiler 3 still cannot meet the air supply temperature requirements, providing immediate heat compensation to the circulating air to achieve multi-stage heat compensation and ensure the continuity and reliability of the drying process.

[0030] The electric heater 22 can be made of finned heating tubes, with multiple U-shaped heating tubes running through the finned assembly. The wiring terminals of the heating tubes are centrally located in the junction box and electrically connected to the controller 16. The entire heater is installed in the flange interface of the air supply duct for easy maintenance and replacement. As an alternative, the electric heater 22 can also be made of PTC ceramic heating element, which has the advantages of positive temperature coefficient characteristics, power self-limiting temperature, and high safety.

[0031] The gas-fired boiler 3 is a condensing gas-fired hot water boiler. The fuel for the gas-fired boiler 3 is any one of natural gas, liquefied natural gas, or liquefied petroleum gas. The condensing gas-fired hot water boiler is equipped with a main heat exchanger and a condensing heat exchanger. The high-temperature flue gas generated by the combustion of fuel in the combustion chamber flows through the main heat exchanger and the condensing heat exchanger in sequence. The main heat exchanger is used for primary heating of the circulating water, and the condensing heat exchanger is used to recover the latent heat of water vapor in the flue gas and perform secondary heating of the circulating water, thereby improving the thermal efficiency of the boiler. The outlet water temperature of the gas-fired boiler 3 is controlled by the controller 16 by adjusting the opening of the gas supply valve and the working load of the burner.

[0032] The hot water storage tank 2 is a vertical cylindrical sealed tank with an outer wall covered by an insulation layer made of rigid polyurethane foam or rock wool. Inside the hot water storage tank 2, near the upper outlet, is a baffle plate. The baffle plate is annular, with its inner ring bent upwards to form an overflow weir. This allows the hottest water at the top to overflow preferentially to the outlet area, ensuring that the dry heating circuit prioritizes the use of the high-temperature hot water from the storage tank 2. Inside the hot water storage tank 2, near the lower return outlet, is a water distributor consisting of multiple radially distributed outlet pipes with downward-facing distribution holes. This ensures that the low-temperature return water after heat exchange is evenly distributed at the bottom of the storage tank 2, reducing disturbance to the upper high-temperature water layer, maintaining temperature stratification within the storage tank 2, and improving heat storage efficiency.

[0033] This invention also provides a control method for a multi-energy complementary combined drying system for aquatic products, the method comprising the following steps: The first temperature sensor 17 continuously collects the temperature value of the surface of the evaporator coil 12 and converts it into an electrical signal, which is then transmitted to the controller 16. The controller 16 compares the received coil temperature value with the internally preset coil temperature threshold. If the coil temperature is lower than the preset threshold and the duration exceeds the set time, it is determined that the surface of the evaporator 12 is covered with frost and has entered the frosting condition. As an alternative determination method, the controller 16 can also read the cumulative running time of the air source heat pump. When the cumulative running time reaches the preset time threshold and the temperature difference between the inlet and outlet air of the evaporator 12 decreases by more than a set percentage compared to the initial running state, it is also determined that the evaporator 12 has entered the frosting condition.

[0034] When the controller 16 determines that the evaporator 12 has entered the frosting condition, the controller 16 controls the four-way reversing valve 14 to switch the refrigerant flow direction, so that the air source heat pump system enters the reverse circulation defrosting state; in the reverse circulation defrosting state, the high temperature and high pressure refrigerant discharged by the compressor 11 flows into the evaporator 12 first to heat and defrost the coil of the evaporator 12.

[0035] During the reverse circulation defrosting, the controller 16 controls the start of the drying circulation water pump 6, so that the high-temperature hot water in the hot water storage tank 2 is transported to the heat exchanger 7 installed in the drying box 1 through the drying circulation water pump 6, and heat is released to the air inside the drying box 1 through the heat exchanger 7.

[0036] The second temperature sensor is installed at the outlet of the hot water storage tank 2 to detect the outlet water temperature of the hot water storage tank 2, and the second temperature and humidity sensor 21 is installed in the air supply duct to detect the air supply temperature of the drying box 1. The controller 16 reads the above detection values ​​in real time and compares them with the internal preset threshold. When the temperature of the hot water storage tank 2 is lower than the preset hot water storage tank temperature threshold, the controller 16 starts the gas boiler circulating water pump 8 and turns on the gas boiler 3, so that the low temperature return water in the lower or middle part of the hot water storage tank 2 enters the gas boiler 3 for heating and then flows back to the upper part of the hot water storage tank 2, so as to maintain the heat supply of the drying box 1 to the drying box 1 by the heat exchanger 7 installed in the drying box 1.

[0037] When the temperature of the hot water storage tank 2 is lower than the preset hot water storage tank temperature threshold and the air supply temperature of the drying box 1 is lower than the preset air supply temperature threshold, the controller 16 sends a start signal to the control terminal of the electric heater 22. After the electric heater 22 is powered on, it heats up and instantly heats the circulating air flowing through the air supply duct.

[0038] After defrosting is completed, the controller 16 controls the four-way reversing valve 14 to reset to the normal drying operation state, and the air source heat pump system resumes the function of dehumidifying and reheating the circulating air; the controller 16 gradually shuts down the electric heater 22, the gas boiler 3 or the drying circulating water pump 6 according to the temperature of the hot water storage tank 2 and the air supply temperature, so that the system smoothly transitions to the normal operation mode.

[0039] In this control method, the controller 16 controls and selects any one of the following modes based on solar irradiance conditions, the temperature of the hot water storage tank 2, and the drying process settings: solar-heat pump drying combined operation mode, gas boiler-heat pump drying combined operation mode, solar-gas boiler-heat pump drying combined operation mode, or hot water storage tank-heat pump drying combined operation mode. When there is sufficient solar radiation during the day and the temperature difference between the outlet water temperature of the solar collector 4 and the bottom water temperature of the hot water storage tank 2 is greater than 8℃, the controller 16 opens the first valve 9 and the second valve 10, starts the solar circulating water pump 5, so that the circulating water in the lower part of the hot water storage tank 2 enters the solar collector 4 for heating and then flows back to the upper part of the hot water storage tank 2, and the system enters the solar-heat pump drying combined operation mode. When solar energy is insufficient, controller 16 starts gas boiler 3 and gas boiler circulating water pump 8, opens the third valve and the fourth valve, so that the return water in the lower or middle part of the hot water storage tank 2 enters the gas boiler 3 for heating and then flows back to the upper part of the hot water storage tank 2. The system enters the gas boiler-heat pump drying combined operation mode or the solar energy-gas boiler-heat pump drying combined operation mode. When the water temperature at the top of the hot water storage tank 2 meets the requirements of the drying process, the system directly adopts the hot water storage tank-heat pump drying combined operation mode, using the heat stored in the hot water storage tank 2 to heat the drying box 1 through the drying heating circuit. When the water temperature at the top of the hot water storage tank 2 reaches the vacuum drying requirement, the controller 16 starts the vacuum pump 19 to perform vacuum treatment on the drying chamber 1, and starts the drying circulating water pump 6 to allow hot water to enter the heat exchanger 7 set in the drying chamber 1 to indirectly heat the aquatic products. At the same time, the air source heat pump system is used to dehumidify and reheat the hot and humid air discharged from the drying chamber 1 before sending it back to the drying chamber 1, so as to realize the coordinated operation of vacuum drying and hot air circulation drying.

[0040] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A multi-energy complementary combined drying system for aquatic products, characterized in that, It includes a drying box (1), a hot water storage tank (2), a gas boiler (3), an air source heat pump system, a solar collector (4), a solar circulating water pump (5), and a control system; The outlet of the hot water storage tank (2) is connected to the inlet of the heat exchanger (7) installed in the drying box (1) via the drying circulating water pump (6), and the outlet of the heat exchanger (7) is connected to the return water outlet of the hot water storage tank (2), forming a drying and heating circuit that supplies heat to the drying box (1). The outlet of the gas boiler (3) is connected to the heat replenishment inlet of the hot water storage tank (2), and the heat replenishment outlet of the hot water storage tank (2) is connected to the inlet of the gas boiler (3) via the gas boiler circulating water pump (8), forming a heat replenishment circuit to replenish the hot water storage tank (2). The outlet of the solar collector (4) is connected to the solar inlet of the hot water storage tank (2) via the first valve (9), and the solar outlet of the hot water storage tank (2) is connected to the inlet of the solar collector (4) via the second valve (10) and the solar circulating water pump (5), thus forming a solar heat storage circuit for storing heat in the hot water storage tank (2). The air source heat pump system includes a compressor (11), an evaporator (12), a condenser (13), a four-way reversing valve (14), and a two-way electronic expansion valve (15); the compressor (11), the four-way reversing valve (14), the condenser (13), the two-way electronic expansion valve (15), and the evaporator (12) are connected by refrigerant pipelines to form a refrigerant circulation loop; the air outlet of the drying box (1) is connected to the air inlet of the drying box (1) in sequence through the evaporator (12) and the condenser (13) to form a circulating air dehumidification and heating loop; The control system includes a sensor group and a controller (16). The sensor group includes a first temperature sensor (17) for detecting the temperature of the coil of the evaporator (12). The input terminal of the controller (16) is connected to the output terminal of the first temperature sensor (17). The output terminal of the controller (16) is connected to the control terminal of the four-way reversing valve (14), the control terminal of the drying circulating water pump (6), and the control terminal of the gas boiler circulating water pump (8), respectively.

2. The multi-energy complementary combined drying system for aquatic products according to claim 1, characterized in that, A water vapor trap (18) and a vacuum pump (19) are connected in series on the drying box (1).

3. The multi-energy complementary combined drying system for aquatic products according to claim 1, characterized in that, The heat exchanger (7) is a tubular heat exchanger or a plate heat exchanger.

4. The multi-energy complementary combined drying system for aquatic products according to claim 1, characterized in that, The heat exchanger (7) is located inside the drying chamber (1) and is adjacent to the material placement space inside the drying chamber (1).

5. The multi-energy complementary combined drying system for aquatic products according to claim 1, characterized in that, The sensor group also includes a first temperature and humidity sensor (20) installed in the exhaust duct of the drying box (1) and a second temperature and humidity sensor (21) installed in the supply duct. The input terminal of the controller (16) is also connected to the output terminals of the first temperature and humidity sensor (20) and the second temperature and humidity sensor (21).

6. The multi-energy complementary combined drying system for aquatic products according to claim 5, characterized in that, The air source heat pump system also includes an electric heater (22), which is disposed in the air supply duct and located downstream of the condenser (13); The output of the controller (16) is also connected to the control terminal of the electric heater (22).

7. The multi-energy complementary combined drying system for aquatic products according to claim 1, characterized in that, The exhaust port of the compressor (11) is connected to the first interface of the four-way reversing valve (14), and the intake port of the compressor (11) is connected to the second interface of the four-way reversing valve (14). The third port of the four-way reversing valve (14) is connected to one end of the condenser (13), and the fourth port of the four-way reversing valve (14) is connected to one end of the evaporator (12). The other end of the evaporator (12) is connected to the other end of the condenser (13) via the bidirectional electronic expansion valve (15).

8. The multi-energy complementary combined drying system for aquatic products according to claim 1, characterized in that, The air outlet of the drying chamber (1) is connected to the air inlet side of the evaporator (12) via an exhaust fan (23), and the air outlet side of the condenser (13) is connected to the air inlet of the drying chamber (1) via a ventilation fan (24).

9. The multi-energy complementary combined drying system for aquatic products according to claim 1, characterized in that, The gas boiler (3) is a condensing gas-fired hot water boiler, and the fuel of the gas boiler (3) is any one of natural gas, liquefied natural gas or liquefied petroleum gas.

10. A control method for a multi-energy complementary combined drying system for aquatic products, characterized in that, The method for the multi-energy complementary combined drying system for aquatic products as described in any one of claims 1-9 comprises: The controller (16) determines whether the evaporator (12) has entered the frosting condition based on the coil temperature of the evaporator (12) by detecting the coil temperature of the evaporator (12). When the controller (16) determines that the evaporator (12) has entered the frosting condition, the controller (16) controls the four-way reversing valve (14) to switch the refrigerant flow direction, so that the air source heat pump system enters the reverse circulation defrosting state; During reverse-cycle defrosting, the controller (16) prioritizes using the heat from the hot water storage tank (2) to heat the drying box (1) via the drying heating circuit; The temperature of the hot water storage tank (2) and the air supply temperature of the drying box (1) are detected by the sensor group, and the controller (16) controls the supplementary heating according to the temperature of the hot water storage tank (2) and the air supply temperature of the drying box (1). When the temperature of the hot water storage tank (2) is lower than the preset hot water storage tank temperature threshold, the controller (16) starts the gas boiler (3) to supplement the heat to the hot water storage tank (2) through the heat supplementation circuit, so as to maintain the heat supply of the heat exchanger (7) installed in the drying box (1) to the drying box (1); When the temperature of the hot water storage tank (2) is lower than the preset hot water storage tank temperature threshold and the air supply temperature of the drying box (1) is lower than the preset air supply temperature threshold, the controller (16) starts the electric heater (22) installed in the air supply pipeline to provide auxiliary heating for the air supply.

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