Environment-friendly and energy-saving type marine product cold and hot air drying system and method

Abstract

The invention discloses an environment-friendly and energy-saving type marine product cold and hot air drying system and method, and belongs to the technical field of food processing intelligent control. The system comprises a drying chamber, an air energy unit, a main circulating fan, a dehumidification module, a heat recovery pipeline, a heat recovery induced draft fan, an auxiliary heater, a mode switching valve group, a control system and a plurality of sensors. The system returns dehumidified dry air to the air energy unit through the heat recovery pipeline to form closed loop circulation, and only moisture is discharged, but heat is not discharged. The system monitors the weight of marine products in real time and calculates the drying rate through an electronic scale, and dynamically adjusts the temperature and the wind speed of a drying chamber through a PID algorithm, so that the drying rate is kept within a target interval. The drying method comprises the three steps of intelligent mode decision making based on environmental parameters, dynamic optimization drying process control and drying end point judgment and shutdown. According to the system, efficient heat recycling, accurate drying parameter control and multi-sensor cooperative monitoring are achieved, energy consumption is remarkably reduced, and the product quality is improved.

Description

Technical Field

[0001] This invention belongs to the field of intelligent control technology for food processing, specifically relating to an environmentally friendly and energy-saving hot and cold air drying system and method for seafood. Background Technology

[0002] Seafood is rich in high-quality protein and various nutrients, but its high water content and loose structure make it highly susceptible to spoilage at room temperature. Drying is a crucial method for processing and preserving seafood. By reducing water content, it inhibits microbial growth and enzymatic reactions, extending shelf life and facilitating storage and transportation. Traditional natural sun-drying methods are severely constrained by weather conditions, making it difficult to guarantee hygiene, resulting in long drying cycles and inconsistent product quality. Modern seafood drying technology primarily employs hot air drying, using heating equipment to generate hot air for forced drying of seafood, which shortens the drying cycle and improves hygiene.

[0003] Existing hot air drying systems for seafood typically use coal-fired boilers, gas-fired boilers, or electric heaters as heat sources, resulting in high energy consumption, significant pollution emissions, and high operating costs. In recent years, air source heat pump technology has been increasingly applied to seafood drying. Air source heat pumps utilize the principle of a refrigeration cycle to absorb heat from the ambient air and release it into the drying chamber, offering a higher energy efficiency ratio compared to direct electric heating. However, existing air source drying systems still face numerous technical challenges. Current seafood drying systems generally operate in an open-loop manner, with the hot, humid air exhausted from the drying chamber directly released to the external environment. The air source unit needs to continuously draw in fresh air from the external environment and heat it to the target temperature. This open-loop approach leads to significant heat loss from the drying chamber with the exhaust, requiring the air source unit to overcome large temperature differences for heating, resulting in high operating power and overall high energy consumption. Especially in low-temperature winter conditions, the large temperature difference between the external air and the target temperature in the drying chamber reduces the heating efficiency of the air source unit, exacerbating the energy consumption problem. Furthermore, existing technologies lack effective heat recovery and utilization methods, failing to fully utilize the sensible heat carried by the exhaust airflow from the drying chamber, leading to serious energy waste. Existing drying control methods typically employ fixed parameter control, setting a fixed drying chamber temperature and air velocity based on the type of seafood before drying begins and maintaining these parameters constant throughout the drying process. This fixed parameter control ignores the dynamic characteristics of the seafood drying process. While seafood can withstand rapid drying when its moisture content is high in the early stages of drying, maintaining the same high temperature and air velocity conditions in the later stages, when the moisture content decreases, can easily cause excessive dehydration, hardening, and even cracking of the seafood's surface, affecting its appearance and taste. Existing technologies lack real-time monitoring and feedback control of the seafood's dehydration status, making it impossible to dynamically adjust process parameters according to the drying progress, resulting in unstable drying quality and a low pass rate. Furthermore, existing drying systems generally lack adaptability to environmental conditions, typically employing only a single hot air drying mode, using the same heating method regardless of the external ambient temperature. This fixed-mode operation results in significant energy consumption variations across different seasons and regions, failing to optimize the operation mode according to actual environmental conditions and missing energy-saving opportunities. Especially in the high temperatures of summer, when the outside air temperature is already high, using heating methods for drying is not only energy-intensive but also makes it difficult to precisely control the drying chamber temperature. Using cooling methods for low-temperature drying may be more energy-efficient and better preserve the color and flavor of seafood, but current technologies lack an intelligent switching mechanism between hot and cold air modes. Even in existing systems equipped with heat recovery devices, heat compensation typically relies on auxiliary heaters running at full power continuously or simple on / off control, failing to accurately calculate the required compensation power based on actual heat loss. This crude compensation method either leads to overheating, causing energy waste and temperature fluctuations, or underheating, affecting drying results and making it difficult to achieve the goal of supplementing heat as needed.Existing technologies lack precise heat compensation algorithms based on temperature difference and airflow parameters, which limits the full realization of the energy-saving potential of heat recovery systems.

[0004] Therefore, it is of great significance to design and develop an environmentally friendly and energy-saving seafood drying system and method that can solve the above problems, achieve efficient heat recovery and utilization, precise control of the drying process, and multi-parameter collaborative monitoring. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides an environmentally friendly and energy-saving hot and cold air drying system for seafood, comprising: The drying chamber is equipped with trays for placing seafood, and it also has air inlets and dehumidification outlets. An air source heat pump unit includes an evaporator and a condenser. The evaporator has an air inlet and an air outlet. The air outlet of the evaporator is connected to the air inlet of the drying chamber through an air inlet duct. The air source heat pump unit heats or cools the airflow entering the evaporator. The main circulating fan, located on the air inlet duct, sends the airflow output from the air source unit into the drying chamber; The dehumidification module includes an air inlet, an evaporator coil, a condenser coil, and a drain outlet. The air inlet of the dehumidification module is connected to the exhaust outlet of the drying chamber. Moisture in the evaporator coil is condensed in the airflow, and condensate is discharged through the drain outlet. The condenser coil is located downstream of the evaporator coil and preheats the dehumidified airflow. The dehumidification module is equipped with an air outlet. The heat recovery pipe connects to the air outlet of the dehumidification module at one end and to the air inlet of the evaporator of the air source heat pump unit at the other end, forming an airflow recovery path. A heat recovery exhaust fan, installed on the heat recovery duct, drives airflow from the dehumidification module to the evaporator of the air source heat pump unit; An auxiliary heater is installed on the heat recovery pipeline and located upstream or downstream of the heat recovery induced draft fan to compensate for the heating of the recovered airflow. The mode switching valve assembly includes an outdoor air inlet valve and a heat recovery valve. The outdoor air inlet valve connects the external environment to the air inlet of the air source unit evaporator, and the heat recovery valve connects the heat recovery pipeline to the air inlet of the air source unit evaporator. The mode switching valve assembly switches the air inlet source of the air source unit evaporator. The control system includes a processor and memory; The first temperature sensor is installed on the heat recovery pipe to collect the temperature of the recovered airflow. The first temperature sensor is connected to the control system through a signal line. The second temperature sensor is located in the drying chamber and collects the temperature inside the drying chamber. The second temperature sensor is connected to the control system via a signal line. The third temperature sensor is located at the air outlet of the air source unit's evaporator or on the air inlet duct to collect the temperature of the air output airflow from the air source unit. The third temperature sensor is connected to the control system via a signal line. A humidity sensor is installed in the drying chamber to collect the humidity inside the drying chamber. The humidity sensor is connected to the control system via a signal line. An electronic scale, located at the bottom of the drying chamber, supports the material trays and measures the weight of the seafood. The electronic scale is connected to the control system via a signal line. The control system is electrically connected to the air source heat pump unit, main circulating fan, dehumidification module, heat recovery induced draft fan, auxiliary heater and mode switching valve group through control lines to control the operating status of each component.

[0006] In a preferred embodiment, the airflow inside the dehumidification module flows sequentially through the evaporator coil and the condenser coil before being discharged from the outlet. The evaporator coil is connected to the refrigeration compressor inside the dehumidification module, and the condenser coil is also connected to the refrigeration compressor. The temperature of the evaporator coil is lower than the inlet dew point temperature, causing the moisture to condense. The temperature of the condenser coil is higher than the temperature of the evaporator coil, preheating and recovering the dehumidified airflow.

[0007] In a preferred embodiment, in hot air mode, the heat recovery valve is open and the outdoor air inlet valve is closed, and the airflow forms a closed loop along the following path: Drying chamber, drying chamber exhaust port, dehumidification module air inlet, dehumidification module evaporator coil, dehumidification module condenser coil, dehumidification module air outlet, heat recovery pipe, auxiliary heater, heat recovery induced draft fan, heat recovery valve, air source unit evaporator air inlet, air source unit evaporator, air inlet pipe, main circulation fan, drying chamber air inlet, drying chamber; In cold air mode, the outdoor air inlet valve is open and the heat recovery valve is closed, and the external airflow enters the air inlet of the air source unit evaporator through the outdoor air inlet valve.

[0008] In a preferred embodiment, the control system calculates the temperature difference using signals from the first and third temperature sensors, and sends a power control signal to the auxiliary heater based on the temperature difference; the control system calculates the drying rate using signals from the electronic scale, and sends a power adjustment signal to the air source heat pump unit and a speed adjustment signal to the main circulating fan based on the drying rate; the control system sends an opening / closing control signal to the mode switching valve group and a mode switching signal to the air source heat pump unit based on the energy cost calculation results.

[0009] This invention also provides an environmentally friendly and energy-saving method for drying seafood using hot and cold air, comprising the following steps: S1. Intelligent mode decision-making based on environmental parameters: collecting outdoor ambient temperature and humidity The target temperature for the corresponding hot air mode is read from the memory based on the type of seafood. Target temperature in cool air mode ; Calculate the energy consumption cost of hot air mode and cold air mode, compare the energy consumption cost of the two modes, and select the mode with lower energy consumption cost as the drying mode; According to the selected mode, control the mode switching valve group to switch the air intake source and control the air source unit to start the corresponding heating or cooling function. S2. Dynamic optimization of drying process control: S201. Real-time monitoring of seafood weight and calculation of drying rate. The target drying rate range is read from the memory based on the type of seafood and the current drying stage. S202. In hot air mode, the heat recovery valve is opened and the outdoor air inlet valve is closed. The humid and hot air discharged from the drying chamber is condensed and dehumidified by the evaporator coil of the dehumidification module and the condensate is discharged. The dehumidified and dried air is preheated by the condenser coil and then returned to the evaporator of the air source heat pump unit through the heat recovery pipeline to form a closed loop. The temperature of the recovered airflow in the heat recovery pipeline and the temperature of the output airflow of the air source heat pump unit are monitored, and the temperature difference between the two is calculated. Determine whether to activate the auxiliary heater based on the temperature difference and calculate the heating power. The auxiliary heater outputs power via pulse width modulation. S203. In cold air mode, the outdoor air inlet valve is opened and the heat recovery valve is closed, the air source unit cools and dehumidifies the outside air, and the treated cold air is sent into the drying room through the main circulation fan. The temperature and humidity in the drying room are monitored, and the cooling power of the air source unit is adjusted according to the monitoring values. S3. Drying endpoint determination and shutdown: Determine whether the seafood weight has reached the target value or whether the drying rate for multiple consecutive cycles has fallen below the endpoint threshold. When one of the conditions is met, the auxiliary heater, air source heat pump unit, main circulation fan, dehumidification module and heat recovery induced draft fan are shut down in sequence, and a drying completion signal is issued.

[0010] Furthermore, step S1 includes: S11. The control system collects the outdoor ambient temperature through a temperature sensor. Outdoor humidity is collected by a humidity sensor. ; S12. The control system reads the preset hot air mode target temperature from the memory according to the type of seafood. Target temperature in cool air mode And read the corresponding heating energy consumption coefficient. Refrigeration energy consumption coefficient Expected hot air drying time and expected cold air drying time ; S13. The control system calculates the energy consumption cost of the hot air mode based on the energy consumption model. Energy consumption cost of cooling mode ; in The heating energy consumption coefficient is expressed in units of 1000 kJ / m². ; The coefficient of performance (COP) for cooling is given in units of 1000 ppm. ; The target temperature for hot air mode, in °C; The target temperature for the air conditioning mode is in °C. This refers to the outdoor ambient temperature, in °C. The estimated hot air drying time is in hours (h). The estimated cold air drying time is in hours. Energy consumption cost in hot air mode, unit: ; Energy consumption cost in cooling mode, unit: ; S14. Control System Comparison and The value, if If the desired temperature is not specified, select the hot air mode; otherwise, select the cold air mode and store the selected mode and the corresponding target temperature. S15. The control system sends control commands according to the selected mode: if the hot air mode is selected, it sends a command to the mode switching valve group to open the heat recovery valve and close the outdoor air inlet valve, and sends a heating start command to the air source heat pump unit; if the cold air mode is selected, it sends a command to the mode switching valve group to open the outdoor air inlet valve and close the heat recovery valve, and sends a cooling start command to the air source heat pump unit; at the same time, it starts the main circulation fan, dehumidification module and heat recovery induced draft fan to complete system initialization.

[0011] Further, step S201 includes: S21. The control system starts a timer, which runs at intervals of... Measure the current weight of the seafood using an electronic scale. And store the measured values; S22. The control system reads the weight from the memory from the previous moment. Calculate the drying rate ; in The drying rate is expressed in units of... ; This represents the weight at the previous moment, in kg. The weight at the current moment, in kg; The time interval is expressed in minutes. S23. The control system reads the corresponding target drying rate range from the memory based on the type of seafood and the current drying stage. and read the PID control parameters. , , ; S24. Control System Comparison With the target interval: If Then set the adjustment direction to decrease; if If so, then set the adjustment direction to rise; if If so, then the current parameters remain unchanged; S25. When adjustment is required, the control system calculates the target drying rate. The midpoint of the interval is used to calculate the error. The temperature regulation amount is calculated using a PID algorithm. ; in This refers to the temperature regulation amount, expressed in °C. This is a proportionality constant, without units. The integral coefficient is expressed in units of 1000 ppm. ; These are the differential coefficients, in units of min; To represent the error, the unit is... ; The target drying rate is expressed in units of... ; S26. The control system according to Update the target temperature of the drying chamber Send power regulation commands to the air source heat pump unit to adjust the output temperature to... At the same time, it sends speed adjustment commands to the main circulating fan according to the adjustment direction, so as to achieve coordinated adjustment of temperature and wind speed.

[0012] Further, step S202 includes: S27. The control system collects the temperature of the recovery gas flow in the heat recovery pipeline in real time through the first temperature sensor. The output airflow temperature at the output end of the air source unit is collected in real time by a third temperature sensor. ; S28. The control system reads the current target temperature of the drying chamber from the memory. Calculate the temperature difference ; in This is the temperature difference, expressed in °C. The target temperature is expressed in °C. The output airflow temperature is expressed in °C. S29. The control system reads the preset temperature difference threshold from the memory. ,judge Is it greater than ;like If so, the auxiliary heater will not be activated; Then proceed to step S30; S30. The control system reads the specific heat capacity of air from the memory. air density Volumetric flow rate of heat recovery induced draft fan According to the formula Calculate the required heating power; in Heating power, in watts (W). Specific heat capacity of air, unit: ; Air density, unit: ; Volumetric flow rate, unit: ; S31. The control system sends a start command to the auxiliary heater and adjusts the duty cycle of the auxiliary heater using pulse width modulation (PWM) to make its output power reach the calculated value. This allows for precise heat compensation.

[0013] Furthermore, step S203 includes: S32. The control system collects the temperature of the drying chamber in real time via a second temperature sensor. The humidity in the drying room is collected in real time by a humidity sensor. ; S33. The control system reads the target temperature for the cooling mode from the memory. Upper temperature limit Lower limit of temperature Target humidity and humidity limit ; S34. Control system judgment: If or Then, a command to increase the cooling capacity is sent to the air source heat pump unit; if Then, a command to reduce the cooling power is sent to the air source heat pump unit; if and If so, the current cooling capacity will be maintained; S35. In cold air mode, the auxiliary heater is not activated, the dehumidification module continues to run and dehumidify, and the exhaust air is directly discharged to the external environment without entering the heat recovery pipe, thus achieving low-temperature dehumidification and drying.

[0014] Furthermore, step S3 includes: S36. The control system reads the preset target weight of the finished product from the memory. and allowable deviation The current weight measured by the electronic scale and Compare and calculate the absolute value of the difference. ; S37. The control system reads the preset endpoint rate threshold from the memory. and the number of judgment cycles Statistics recently Drying rate per cycle Determine if it is continuous Each cycle satisfies ; S38. Control system judgment: If , or continuous One cycle If the drying process is successful, proceed to step S39; otherwise, return to step S2 to continue drying. S39. The control system sends shutdown commands in the following order: first, shut down the auxiliary heater; after a delay of 5-10 seconds, shut down the air source heat pump unit; after a delay of 5-10 seconds, shut down the dehumidification module and the heat recovery induced draft fan; finally, shut down the main circulation fan; and send a drying completion signal through the display interface or buzzer to complete the entire drying process.

[0015] The beneficial effects achieved by this invention are as follows: First, this invention constructs a closed-loop heat recovery system to achieve energy-efficient operation of the drying process. In hot air mode, the system returns the humid air discharged from the drying chamber to the air source heat pump unit via a heat recovery pipeline after being processed by a dehumidification module, forming a closed-loop cycle. The heat in the drying chamber is not directly lost with the exhaust but is continuously recycled; only the condensed moisture needs to be discharged. After condensation and dehumidification by the evaporator coil inside the dehumidification module, the condenser coil preheats and recovers the dehumidified airflow, reducing temperature loss caused by dehumidification. The auxiliary heater precisely compensates for heat loss in the closed-loop heat recovery using pulse width modulation based on the temperature difference between the heat recovery pipeline and the output end of the air source heat pump unit, avoiding the energy waste caused by traditional full heating methods. This heat recovery technology allows the air source heat pump unit to only slightly heat the recovered airflow, which is already close to the target temperature, significantly reducing the heating power requirement. Compared with traditional open-loop drying methods, this reduces energy consumption and significantly improves the system's energy efficiency ratio.

[0016] Secondly, this invention designs a mode decision-making system based on environmental parameters to optimize energy consumption throughout the year. The control system calculates the energy costs of hot air and cold air modes based on outdoor ambient temperature, humidity, and the characteristics of the seafood, intelligently selecting the drying mode with lower energy costs as the current operating mode. An energy cost function considering the temperature difference between heating and cooling by the air source heat pump unit and the estimated drying time is established, enabling scientific decision-making through quantitative comparison of the economics of the two modes. The mode switching valve group switches the air intake source according to the decision result. In hot air mode, the heat recovery valve is opened to establish a closed-loop circulation; in cold air mode, the outdoor air intake valve is opened to utilize external air for cooling and dehumidification. This intelligent mode decision-making method breaks away from the traditional mode selection method that relies on experience or fixed seasonal divisions. The system can adapt to different seasonal environmental conditions. In summer, the cold air mode is used to reduce cooling energy consumption by utilizing ambient temperature; in winter, the hot air mode is used to efficiently heat by utilizing the heat pump, improving the system's adaptability and economy to complex and variable environments.

[0017] Third, this invention designs a dynamic adjustment and control method based on drying rate, achieving both guaranteed drying quality and improved drying efficiency. The control system periodically measures the weight of seafood using an electronic scale and calculates the drying rate. The actual drying rate is compared with a target drying rate range set according to the type of seafood and the drying stage. When the drying rate exceeds the upper limit of the target range, the system uses a PID algorithm to calculate the temperature adjustment and lowers the target temperature of the drying chamber while simultaneously reducing the speed of the main circulating fan to prevent the seafood from losing too much water, which could cause hardening and cracking of the skin. When the drying rate falls below the lower limit of the target range, the system reverses course, increasing the temperature and airflow to accelerate the drying process. This closed-loop control mechanism based on drying rate feedback allows drying parameters to be automatically adjusted according to the real-time dehydration status of the seafood, ensuring uniform drying inside and out and excellent color and quality. The coordinated adjustment of temperature and airflow is more effective than adjusting a single parameter, because the drying rate is affected by both temperature and airflow. Coordinated adjustment can more quickly and stably control the drying rate within the optimal range, shortening the drying cycle, improving production efficiency, and avoiding quality fluctuations caused by fixed parameter control methods.

[0018] Fourth, this invention achieves precise adjustment and improved process stability in the drying process through multi-sensor collaborative monitoring and multi-parameter collaborative control. The system is equipped with multiple temperature sensors to monitor the airflow temperature in the heat recovery pipeline, the temperature inside the drying chamber, and the output temperature of the air source heat pump unit. A humidity sensor monitors the humidity inside the drying chamber, and an electronic scale measures the weight of the seafood in real time. This sensor data provides comprehensive status information for the control system. The control system calculates the temperature difference based on the signals from the first and third temperature sensors and controls the power of the auxiliary heater. It calculates the drying rate based on the electronic scale signal and adjusts the power of the air source heat pump unit and the speed of the main circulating fan. It also adjusts the cooling power of the air source heat pump unit based on the temperature and humidity signals in the drying chamber. A coordinated control relationship is formed among the various actuators. This multi-sensor, multi-parameter collaborative control mechanism enables the system to dynamically adjust the operating parameters of each component according to the real-time status of the drying process, optimizing multiple variables such as temperature, humidity, weight, and power. This ensures a small temperature fluctuation range in the drying chamber and good process stability, avoiding the large temperature fluctuations caused by improper parameter settings or response lag in traditional control methods.

[0019] Fifth, this invention achieves reliable quality assurance and safe equipment operation through a dual endpoint judgment mechanism and orderly shutdown control. The control system employs a dual endpoint judgment mechanism combining weight target assessment and drying rate threshold assessment. This considers both whether the seafood weight reaches the target value and whether the drying rate for multiple consecutive cycles falls below the endpoint threshold, avoiding over-drying or under-drying problems that may occur when relying on a single judgment indicator. This improves the reliability of the drying endpoint judgment and the consistency of product moisture content. Upon meeting the termination conditions, the control system sequentially shuts down the auxiliary heater, air source heat pump unit, dehumidification module, heat recovery induced draft fan, and main circulation fan. Delays are set between each component to allow airflow to continue carrying away internal residual heat, preventing localized overheating or impact damage caused by sudden equipment shutdown and extending equipment lifespan. The entire system achieves fully automatic operation from mode selection and process control to endpoint judgment, reducing reliance on manual experience, simplifying operation, and making it suitable for industrial-scale application. Attached Figure Description

[0020] Figure 1 This is a dual Y-axis comparison graph of Examples 1, 2, and 3 with Comparative Examples 1 and 2 regarding total energy consumption and drying time.

[0021] Figure 2 This is a dual Y-axis comparison graph of Examples 1, 2, and 3 with Comparative Examples 1 and 2 regarding energy saving rate and temperature stability.

[0022] Figure 3 This is a comparison graph of the drying rate curves of Example 1 and Comparative Example 1. Figure 3Subplot (a) compares the drying rate during the early drying stage of Example 1 with the target range; subplot (b) compares the drying rate during the mid-drying stage of Example 1 with the target range; subplot (c) compares the drying rate during the entire drying stage of Comparative Example 1 with the fixed target rate.

[0023] Figure 4 This is a comparison graph of the cumulative energy consumption over time during the drying process between Example 1 and Comparative Examples 1 and 2.

[0024] Figure 5 This is a time-series graph showing the temperature, humidity, weight, and auxiliary heater power during the drying process in Example 1. Figure 5 Subplot (a) shows the temperature of the drying chamber over time; subplot (b) shows the humidity of the drying chamber over time; subplot (c) shows the weight of the seafood over time; and subplot (d) shows the output power of the auxiliary heater over time.

[0025] Figure 6 This is a flowchart of the environmentally friendly and energy-saving hot and cold air drying method for seafood according to the present invention.

[0026] Figure 7 This is a structural diagram of the environmentally friendly and energy-saving hot and cold air drying system for seafood of the present invention. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Reference Figures 6-7 This invention provides an environmentally friendly and energy-saving hot and cold air drying system for seafood. The system includes a drying chamber, an air source heat pump unit, a main circulating fan, a dehumidification module, a heat recovery pipeline, a heat recovery induced draft fan, an auxiliary heater, a mode switching valve group, a control system, and multiple sensors and measuring devices.

[0029] The drying chamber is the core working space of the system. It contains trays for placing seafood and features air inlets and exhaust vents. The air inlets are positioned to ensure even airflow distribution, while the exhaust vents allow for the smooth removal of humid air. The drying chamber shell is constructed with insulating materials to minimize heat loss, and the inner walls are made of stainless steel or food-grade coated materials to ensure hygiene requirements.

[0030] An air source heat pump unit consists of two main heat exchange components: an evaporator and a condenser. The evaporator has an inlet and an outlet. The inlet receives the airflow to be processed, while the outlet connects to the air inlet of the drying chamber via an inlet duct. Internally, the air source heat pump unit contains a refrigeration cycle component, including a compressor and an expansion valve. When operating in heating mode, the evaporator absorbs heat from the incoming airflow. The refrigerant evaporates within the evaporator and is then compressed by the compressor before entering the condenser. The condenser releases heat, heating the airflow passing through the evaporator, and hot air is output from the outlet. When operating in cooling mode, the refrigeration cycle reverses; the evaporator cools the incoming airflow, and cold air is output from the outlet. This dual-mode operation allows the system to adapt to different seasonal environmental conditions.

[0031] The main circulating fan is located on the air inlet duct, between the air source heat pump unit's outlet and the drying chamber's inlet. It delivers the treated airflow from the air source heat pump unit into the drying chamber at a certain speed, creating a circulating flow. The main circulating fan is driven by a variable frequency motor, and its speed can be adjusted by the control system, thereby changing the air velocity delivered into the drying chamber. The air velocity directly affects the convective heat transfer coefficient and moisture evaporation rate of the seafood surface; therefore, adjusting the main circulating fan speed is one of the important means to achieve drying rate control.

[0032] The dehumidification module is a key component for moisture removal and heat pre-recovery. It includes an air inlet, evaporator coil, condenser coil, drain outlet, and a refrigeration compressor that drives the coil. The air inlet of the dehumidification module is connected to the exhaust outlet of the drying chamber via a pipe. The humid, hot air exhausted from the drying chamber enters the dehumidification module and first flows through the evaporator coil. The surface temperature of the evaporator coil is controlled below the dew point temperature, causing water vapor in the humid air to condense into liquid water on the coil surface and be discharged through the drain outlet. The dehumidified dry air continues to flow through the condenser coil. The condenser coil is the condenser side of the dehumidification module's refrigeration cycle, and its temperature is higher than that of the evaporator coil. When the dry air flows through the condenser coil, it is reheated, achieving partial heat recovery. This design ensures that the temperature of the dehumidified air is not too low, reducing the energy consumption of subsequent heating. The dehumidification module has an air outlet from which the dehumidified and preheated airflow is discharged.

[0033] The heat recovery pipe connects the dehumidification module's air outlet to the air source heat pump unit's evaporator inlet, forming an airflow recovery path. The heat recovery pipe is constructed with insulated materials to minimize heat loss along its path. The airflow direction within the heat recovery pipe is driven by a heat recovery induced draft fan.

[0034] The heat recovery induced draft fan is installed on the heat recovery pipeline, overcoming the flow resistance of the pipeline and driving the dehumidified dry air from the dehumidification module to the air inlet of the air source heat pump unit evaporator. The installation of the heat recovery induced draft fan ensures the formation of a stable closed-loop airflow circulation in hot air mode, so that the hot and humid air discharged from the drying chamber is continuously returned to the system inlet after dehumidification treatment, avoiding direct heat loss with the exhaust.

[0035] An auxiliary heater is located on the heat recovery pipeline and typically uses electric heating elements to compensate for the heating of the recovered airflow. Due to heat loss along the dehumidification module and pipeline, the temperature of the recovered airflow may be lower than the temperature discharged from the drying chamber; the auxiliary heater compensates for this heat loss. The auxiliary heater is precisely controlled by the control system based on temperature sensor signals, using pulse width modulation (PWM) technology to adjust the output power and achieve on-demand heating.

[0036] The mode switching valve assembly includes an outdoor air intake valve and a heat recovery valve. The outdoor air intake valve connects the external environment to the air inlet of the air source heat pump unit's evaporator, while the heat recovery valve connects the heat recovery pipeline to the air inlet of the air source heat pump unit's evaporator. Both valves are driven by electric actuators and controlled by the control system. In hot air mode, the heat recovery valve is open, the outdoor air intake valve is closed, and the air source heat pump unit's evaporator draws air from the heat recovery pipeline. In cold air mode, the outdoor air intake valve is open, the heat recovery valve is closed, and the air source heat pump unit's evaporator draws air from the external environment.

[0037] The control system includes a processor and memory. The processor, which can be a programmable logic controller (PLC) or an embedded microprocessor, is responsible for executing control algorithms and sending control commands. The memory stores the control program, process parameters, sensor data, and various thresholds. The control system connects to various sensors via signal lines to collect real-time data and connects to various actuators via control lines to send control commands.

[0038] The first temperature sensor is installed on the heat recovery pipe to collect the temperature of the recovered airflow. Its installation location is typically chosen upstream of the auxiliary heater to accurately measure the airflow temperature before it enters the air source heat pump unit. The first temperature sensor is connected to the control system via a signal line, transmitting the temperature signal to the control system in real time.

[0039] The second temperature sensor is located inside the drying chamber to collect the temperature inside. The installation location of the second temperature sensor should avoid direct sunlight and direct airflow from the air inlet to obtain accurate data representing the average temperature of the drying chamber. The second temperature sensor is connected to the control system via a signal line.

[0040] The third temperature sensor is located at the outlet of the evaporator or on the inlet duct of the air source heat pump unit to collect the temperature of the output airflow. The measurement value of the third temperature sensor reflects the actual heating effect of the air source heat pump unit on the airflow. The third temperature sensor is connected to the control system via a signal line.

[0041] A humidity sensor is installed inside the drying chamber to collect the relative humidity. The humidity sensor can be capacitive or impedance-type, and its response speed and measurement accuracy meet the monitoring requirements of the drying process. The humidity sensor is connected to the control system via a signal line.

[0042] An electronic scale is located at the bottom of the drying chamber, supporting trays containing seafood and measuring its weight. The scale uses a high-precision load cell, with its range and resolution selected based on the batch size and drying loss. The scale is connected to the control system via a signal cable; the weight measurement data is fundamental for calculating the drying rate.

[0043] The control system is electrically connected to the air source heat pump unit, main circulating fan, dehumidification module, heat recovery induced draft fan, auxiliary heater and mode switching valve group through control lines to control the operating status of each component, including start-up and shutdown, power regulation, speed regulation, valve opening and closing, etc.

[0044] The airflow path inside the dehumidification module is that it flows sequentially through the evaporator coil and the condenser coil before exiting through the outlet. The evaporator coil is connected to the low-pressure side of the refrigeration compressor within the dehumidification module, while the condenser coil is connected to the high-pressure side of the refrigeration compressor. When the refrigeration compressor is operating, the refrigerant in the evaporator coil evaporates and absorbs heat, lowering the coil surface temperature below the dew point temperature. Water vapor in the humid air condenses into water droplets on the coil surface and collects, flowing towards the drain outlet. The refrigerant in the condenser coil condenses and releases heat, raising the coil surface temperature. The dehumidified dry air is heated as it flows through the condenser coil, achieving heat recovery and improving the system's energy efficiency ratio.

[0045] In hot air mode, the heat recovery valve is open and the outdoor air inlet valve is closed, forming a closed-loop airflow path as follows: Moist, hot air from the drying chamber is discharged from the drying chamber exhaust port, enters the dehumidification module inlet, flows sequentially through the dehumidification module evaporator and condenser coils, exits from the dehumidification module outlet, enters the heat recovery pipe, flows through the auxiliary heater and heat recovery induced draft fan, passes through the heat recovery valve, and enters the air source heat pump unit evaporator inlet. There, it is heated and exits from the air source heat pump unit evaporator outlet, enters the air inlet pipe, and after being pressurized by the main circulation fan, enters the drying chamber through the drying chamber inlet. The entire airflow path forms a closed loop, continuously circulating the air within the drying chamber, expelling only moisture and not heat, significantly improving thermal energy utilization.

[0046] In cooling mode, the outdoor air inlet valve is open and the heat recovery valve is closed, allowing ambient air to enter the air source heat pump unit's evaporator intake through the outdoor air inlet valve. The air source heat pump unit operates in cooling mode, cooling and dehumidifying the ambient air. The treated cool air is then discharged from the air source heat pump unit's evaporator outlet and sent to the drying chamber by the main circulation fan for low-temperature drying. Cooling mode is suitable for hot and humid environments in summer, utilizing the temperature difference with the ambient environment to reduce cooling energy consumption.

[0047] The control system calculates the temperature difference using signals from the first and third temperature sensors, reflecting the degree of heat loss in the heat recovery closed loop. Based on this temperature difference, the control system sends a power control signal to the auxiliary heater for precise heat compensation. The control system also calculates the drying rate using signals from the electronic scale, which is the rate at which seafood loses weight per unit time, reflecting the speed of dehydration. Based on a comparison of the drying rate with the target drying rate range, the control system sends a power adjustment signal to the air source heat pump unit to adjust the output temperature and a speed adjustment signal to the main circulating fan to adjust the airflow, achieving coordinated optimization of temperature and airflow to keep the drying rate within a reasonable range. Finally, based on energy cost calculations, the control system sends opening / closing control signals to the mode switching valve group and a mode switching signal to the air source heat pump unit, enabling intelligent selection between cold and hot air modes.

[0048] The environmentally friendly and energy-saving hot and cold air drying method for seafood using the above system includes an intelligent mode decision-making step S1 based on environmental parameters, a dynamic optimization drying process control step S2, and a drying endpoint judgment and shutdown step S3.

[0049] Step S1 is an intelligent mode decision based on environmental parameters. This step intelligently selects a drying mode with lower energy consumption cost based on the current external environmental conditions and the characteristics of seafood, so as to achieve energy-saving optimization for year-round operation.

[0050] In step S11, the control system collects the outdoor ambient temperature through a temperature sensor installed outdoors. Outdoor humidity is collected by a humidity sensor installed outdoors. Outdoor temperature and humidity sensors should be installed in locations that avoid direct sunlight and rain to obtain accurate environmental parameters.

[0051] In step S12, the control system reads preset parameters corresponding to the type of seafood from the memory based on the seafood type information input by the operator or preset in advance. These parameters include the target temperature for the hot air mode. Target temperature in cold air mode Heating energy consumption coefficient Refrigeration energy consumption coefficient Expected hot air drying time And the estimated cold air drying time The target temperature for hot air mode is typically determined based on the heat resistance and quality requirements of the seafood, while the target temperature for cold air mode is determined based on the low-temperature drying process. The coefficient of performance (COP) for heating and cooling reflects the energy consumption characteristics of the air source heat pump unit per unit temperature difference under different modes, and can be obtained through experimental measurement or performance parameters provided by the manufacturer. The estimated drying time is estimated based on the initial moisture content of the seafood, the target moisture content, and empirical values ​​of the drying rate under different modes.

[0052] In step S13, the control system calculates the energy consumption cost of the hot air mode based on the energy consumption model. Energy consumption cost of cooling mode The energy cost calculation is based on the following formula. The formula for calculating the energy cost in hot air mode is: ;in, The heating energy consumption coefficient is expressed in kW·h / (℃·h). The target temperature for hot air mode, in °C; This refers to the outdoor ambient temperature, in °C. The estimated hot air drying time is in hours (h). The energy cost for hot air mode is expressed in kW·h. The formula for calculating the energy cost for cold air mode is: ;in, The coefficient of performance (COP) is the energy efficiency ratio for cooling, expressed in kW·h / (°C·h). The target temperature for the air conditioning mode is in °C. This refers to the outdoor ambient temperature, in °C. The estimated cold air drying time is in hours. The energy consumption cost in cold air mode is expressed in kW·h.

[0053] The greater the temperature difference that an air source heat pump unit needs to overcome, the higher its energy consumption; conversely, the longer the drying time, the greater the cumulative energy consumption. By calculating and comparing the energy costs of two modes, the system can quantitatively assess the economics of different modes. For example, in summer, with an outdoor temperature of 35°C, using hot air mode results in a target temperature of 55°C, a temperature difference of 20°C, while using cold air mode results in a target temperature of 20°C, a temperature difference of only 15°C. Cold air mode typically has lower energy costs. Conversely, in winter, with an outdoor temperature of 5°C, using cold air mode results in a temperature difference of 15°C, while using hot air mode results in a temperature difference of 50°C. Although the temperature difference is greater in hot air mode, the higher heating efficiency of the heat pump and potentially shorter drying time may make the overall energy cost of hot air mode more favorable.

[0054] In step S14, the control system compares and The magnitude of the value. If Less than If the desired drying mode is selected, then hot air mode is chosen; otherwise, cold air mode is chosen. The control system stores the selected mode information and the corresponding target temperature in the memory for use in subsequent steps. This intelligent decision-making method based on energy consumption cost function breaks away from the traditional mode selection method that relies on experience or fixed seasonal divisions, and realizes dynamic optimization based on real-time environmental conditions, improving system adaptability and economy.

[0055] In step S15, the control system sends corresponding control commands according to the mode selected in step S14 to complete system initialization. If the hot air mode is selected, the control system sends a control command to the mode switching valve group, causing the electric actuator of the heat recovery valve to open the valve and simultaneously close the outdoor air inlet valve, cutting off the external air intake path and establishing a closed-loop airflow path for heat recovery. The control system sends a heating start command to the air source heat pump unit, causing the air source heat pump unit compressor to start and adjust the refrigerant flow direction, so that the evaporator operates in heating mode. If the cold air mode is selected, the control system sends a control command to the mode switching valve group, causing the outdoor air inlet valve to open and the heat recovery valve to close, establishing a path for drawing in air from the external environment. The control system sends a cooling start command to the air source heat pump unit, and the air source heat pump unit operates in cooling mode. Regardless of the selected mode, the control system simultaneously starts the main circulation fan, the dehumidification module refrigeration compressor, and the heat recovery induced draft fan, so that all components of the system work together to complete the initialization preparation before drying.

[0056] Step S2 involves dynamic optimization of the drying process control, which is the core of the entire drying method. Depending on the selected mode, step S2 executes corresponding control sub-steps. Step S2 includes steps S201, S202, and S203. Step S201 is a general real-time monitoring and adjustment process based on the drying rate, applicable to both hot and cold air modes; step S202 is a specific control process under hot air mode; and step S203 is a specific control process under cold air mode.

[0057] Step S201 involves real-time monitoring of the seafood weight and adjusting drying parameters according to the drying rate.

[0058] In step S21, the control system starts the built-in timer and sets the time interval. This time interval is typically selected based on the seafood batch size and drying rate, generally ranging from 3 to 10 minutes. The control system operates at intervals... Measure the current weight of the seafood using an electronic scale. The system stores the measured values ​​and timestamps in memory. Regular weight measurements are fundamental to monitoring the drying process, and the high precision of the electronic scale ensures the reliability of the measurement data.

[0059] In step S22, the control system reads the weight from the memory at the previous moment. The drying rate was calculated based on the two measurements taken. The formula for calculating the drying rate is: ;in, The drying rate is expressed in kg / min. This represents the weight at the previous moment, in kg. The weight at the current moment, in kg; The time interval is expressed in minutes. The numerator in the formula... Indicates time interval The mass of water lost by inland seafood, divided by the time interval. The rate of weight loss per unit time is the drying rate. The drying rate is a direct indicator of how quickly seafood is dehydrated and is also an important basis for judging whether the drying process is reasonable.

[0060] In step S23, the control system reads the corresponding target drying rate range from the memory based on the type of seafood and the current drying stage. and PID control parameters , , The drying process of seafood is generally divided into three stages: early, middle, and late. The moisture content of the material varies at each stage, and the appropriate drying rate also differs. In the early stage, the moisture content is high, allowing for a faster drying rate. In the middle stage, the drying rate needs to be appropriately reduced to prevent surface hardening. In the late stage, the moisture content is low, naturally slowing down the drying rate. Therefore, the target drying rate range is dynamically set based on the drying stage. PID control parameters include the proportional gain. Integral coefficient and differential coefficients These three parameters determine the response characteristics of the PID controller to deviations, and the best control effect can be obtained through experimental tuning.

[0061] In step S24, the control system compares the actual drying rate. and target interval The relationship. If Greater than This indicates that the seafood is losing water too quickly, posing a risk of skin hardening and cracking. The control system is set to adjust towards reducing temperature and wind speed. Less than This indicates that the seafood is losing water too slowly, resulting in low drying efficiency and potentially prolonging the drying cycle. The control system should be set to increase both temperature and airflow. exist and If the current drying rate is within a reasonable range, the control system maintains the current temperature and airflow parameters unchanged. This method of judgment based on the drying rate range avoids frequent adjustments and ensures process stability.

[0062] In step S25, when step S24 determines that adjustment is needed, the control system first calculates the target drying rate. The value is usually taken as the midpoint of the target interval, that is: Then calculate the error. ,error The drying rate is expressed in kg / min. The control system uses a PID algorithm to calculate the temperature adjustment. The formula for calculating the temperature regulation is: ;in, This refers to the temperature regulation amount, expressed in °C. This is a proportionality constant, without units. The integral coefficient is expressed in min. -1 ; These are the differential coefficients, in units of min; The error is expressed in kg / min. The integral term representing the error, in kg; The differential term represents the error, with units of kg / min².

[0063] The PID algorithm described above is a classic feedback control algorithm, where each of its three control actions has a different physical meaning and regulating effect. The proportional term... Instantaneous adjustments are made based on the current deviation; the larger the deviation, the larger the adjustment, resulting in a rapid response. (Integral term) Accumulate historical deviations to eliminate steady-state errors and avoid long-term deviations from the target. Differential term. By proactively adjusting based on the trend of deviation changes, the system's dynamic response speed and stability are improved. Through the integration of three control actions, the PID controller can accurately track the drying rate, ensuring that the seafood drying process is always in an optimal state, guaranteeing both drying efficiency and product quality.

[0064] In step S26, the control system adjusts the temperature accordingly. Update the target temperature of the drying chamber The calculation formula is: ;in, The target temperature before adjustment is reached. The control system sends a power adjustment command to the air source heat pump unit, adjusting the compressor speed or expansion valve opening to bring the air source heat pump unit's output temperature closer to the new target temperature. Simultaneously, the control system sends speed adjustment commands to the main circulating fan based on the adjustment direction. If the adjustment direction is downward, the control system appropriately reduces the speed of the main circulating fan, decreasing the airflow and slowing down the evaporation rate of moisture from the seafood surface; if the adjustment direction is upward, the control system appropriately increases the speed of the main circulating fan, increasing the airflow and accelerating convective heat transfer and moisture evaporation from the seafood surface. Coordinated regulation of temperature and airflow is more effective than adjusting either temperature or airflow alone, because the drying rate is affected by both factors simultaneously. Coordinated regulation allows for faster and more stable control of the drying rate to the target range.

[0065] Step S202 is a specific control process in hot air mode, which mainly involves the operation of heat recovery closed loop and precise heat compensation control.

[0066] In step S27, the control system collects the temperature of the recovery gas flow in the heat recovery pipeline in real time through the first temperature sensor. The output airflow temperature at the output end of the air source unit is collected in real time by a third temperature sensor. Recycled gas flow temperature This reflects the temperature of the airflow processed by the dehumidification module and returned through the heat recovery pipeline; the output airflow temperature. This reflects the temperature of the airflow heated by the air source heat pump and then delivered to the drying chamber. The two temperature sensors collect data at a high frequency, typically 1 to 10 times per second, to achieve a fast response.

[0067] In step S28, the control system reads the current target temperature of the drying chamber from the memory. And calculate the temperature difference. The formula for calculating the temperature difference is: ;in, This is the temperature difference, expressed in °C. The target temperature is expressed in °C. Output airflow temperature, in °C. Temperature difference. The physical meaning of this is the gap between the actual output temperature of the air source heat pump unit and the target temperature of the drying chamber. This gap originates from heat loss in the heat recovery closed loop, including heat dissipation from the dehumidification module casing, heat dissipation along the heat recovery pipeline, and sensible heat carried away by the condensate discharged from the dehumidification module. If this heat loss is not compensated, the actual temperature of the drying chamber will be lower than the target temperature, affecting the drying effect.

[0068] In step S29, the control system reads the preset temperature difference threshold from the memory. This threshold is typically set to a small value, such as 0.3℃ to 1.0℃. The control system determines the temperature difference. Is it greater than the threshold? .like Not greater than This indicates that the air source heat pump unit's output temperature has approached or reached the target temperature, with minimal heat loss. In this case, there is no need to activate the auxiliary heater for compensation; the system can maintain the target temperature solely through the air source heat pump unit. Greater than This indicates significant heat loss, necessitating the activation of the auxiliary heater for precise compensation. The control system then proceeds to step S30. This threshold-based control strategy avoids frequent start-stop cycles and unnecessary heating by the auxiliary heater, thereby reducing electric heating energy consumption.

[0069] In step S30, the control system reads the specific heat capacity of air from the memory. air density and the volumetric flow rate of the heat recovery induced draft fan These parameters can be set based on the air properties under standard operating conditions, or corrected according to actual temperature and pressure. The control system calculates the required heating power based on the energy balance principle. The formula for calculating heating power is: ;in, Heating power, in watts (W). Specific heat capacity of air, expressed in J / (kg·℃); Air density, unit: kg / m³ 3 ; Volumetric flow rate, unit: m³ 3 / s; This represents the temperature difference, expressed in °C.

[0070] The above heating power formula is derived based on the law of conservation of energy. The mass flow rate of the gas flowing through the heat recovery pipe per unit time is... The unit is kg / s. The temperature of this airflow is increased. The required heat is the mass flow rate multiplied by the specific heat capacity multiplied by the temperature difference, i.e. This formula accurately calculates the power required to compensate for heat loss, providing a theoretical basis for precise control of the auxiliary heater.

[0071] In step S31, the control system sends a start command to the auxiliary heater and adjusts the duty cycle of the auxiliary heater's power supply using pulse width modulation (PWM) to ensure that the actual output power of the auxiliary heater reaches the power value calculated in step S30. Pulse width modulation (PWM) technology achieves continuously adjustable power by rapidly switching the power supply on and off, thus changing the proportion of on-time to the total cycle time. Compared to traditional ON / OFF control, PWM control enables precise power regulation, avoiding overheating or underheating and achieving the goal of replenishing heat on demand. Using this precise heat compensation method, the auxiliary heater only compensates for the heat lost in the heat recovery closed loop, rather than reheating the entire airflow. Therefore, the energy consumption of electric heating is significantly lower than that of conventional full heating methods, improving the overall energy efficiency ratio of the system.

[0072] Step S203 is a specific control process in cold air mode. In step S32, the control system collects the temperature inside the drying chamber in real time through the second temperature sensor. The relative humidity inside the drying room is collected in real time by a humidity sensor. Real-time monitoring of the temperature and humidity inside the drying room is the data foundation for controlling the cold air mode.

[0073] In step S33, the control system reads the process parameters of the cooling mode from the memory, including the target temperature. Upper temperature limit Lower limit of temperature Target humidity and humidity limit These parameters are preset according to the requirements of the low-temperature drying process for seafood. The upper and lower temperature limits define the allowable fluctuation range of the temperature in the drying chamber, and the upper humidity limit defines the upper limit requirement of the relative humidity in the drying chamber.

[0074] In step S34, the control system determines the temperature inside the drying chamber. and humidity Is it within the target range? If Greater than or Greater than This indicates that the temperature or humidity inside the drying room is too high. The control system sends a command to the air source heat pump unit to increase the cooling power, thereby increasing the compressor speed or adjusting the expansion valve opening to enhance the cooling and dehumidification effect, thus reducing the temperature and humidity inside the drying room. Less than This indicates that the temperature inside the drying chamber is too low. Although cold air drying requires a low temperature, an excessively low temperature will result in a slow drying rate. The control system sends a command to the air source heat pump unit to reduce the cooling power, appropriately weakening the cooling effect and allowing the temperature to rise. exist and Between and Not greater than This indicates that the temperature and humidity inside the drying chamber are within a reasonable range, and the control system maintains the current cooling power unchanged. This control strategy, based on dual judgment of temperature and humidity, ensures the stability and suitability of the drying chamber environment in cold air mode.

[0075] In step S35, the auxiliary heater is not activated in cold air mode because the goal of cold air mode is low-temperature drying, which does not require additional heating. The dehumidification module continuously operates its dehumidification function. The humid air discharged from the drying chamber is processed by the dehumidification module, and the moisture is condensed and discharged. The dry air does not enter the heat recovery pipe but is directly discharged to the external environment. In cold air mode, there is no need for a closed-loop heat recovery system. The outdoor air inlet valve remains open, and the heat recovery valve remains closed. The air source unit continuously draws in fresh air from the external environment for cooling, achieving low-temperature dehumidification and drying. Cold air mode utilizes the higher ambient temperature in summer, reducing the temperature difference for cooling, thus resulting in relatively low cooling energy consumption, making it suitable for use in hot seasons such as summer.

[0076] Step S3 involves determining the drying endpoint and stopping the machine. In step S36, the control system reads the preset target weight of the finished product from the memory. and allowable deviation The target weight of the finished product is calculated and determined based on the type of seafood, initial weight, and target moisture content. The allowable deviation defines the accuracy requirements for weight determination. The control system reads the current weight measured by the electronic scale. With target weight Compare and calculate the absolute value of the difference. If the absolute value is not greater than the allowable deviation This indicates that the seafood has reached the target weight, and the drying process can be completed.

[0077] In step S37, the control system reads the preset endpoint rate threshold from the memory. And determine the number of cycles The endpoint rate threshold is a very small drying rate value, indicating that the seafood has almost stopped losing weight, suggesting that drying is nearing completion. (Judgment cycle number) A threshold is defined as the number of consecutive measurement cycles during which the drying rate must remain below a certain threshold before drying is considered complete, thus avoiding misjudgments caused by random fluctuations. The control system statistically analyzes the most recent... The drying rate of each cycle is used to determine this. Do all drying rates meet the requirements? .

[0078] In step S38, the control system combines the judgment results from steps S36 and S37. If Not greater than , or continuous The drying rate of each cycle is less than If the drying time is within the specified range, the drying process is considered complete, and the control system executes step S39 to stop the machine. Otherwise, it indicates that the drying process is not yet complete, and the control system returns to step S2 to continue controlling the drying process. This dual-judgment mechanism considers both the absolute value of the seafood weight and the trend of the drying rate, improving the reliability of the drying endpoint determination and avoiding over-drying or under-drying.

[0079] In step S39, the control system shuts down each piece of equipment sequentially according to a predetermined order to ensure a safe and stable system shutdown. First, the control system shuts down the auxiliary heater, stopping electric heating to prevent dry burning without load. After a delay of 5 to 10 seconds, the control system shuts down the air source heat pump unit compressor, stopping heating or cooling functions. This delay allows airflow to continue, carrying away residual heat from the auxiliary heater and the air source heat pump unit to prevent localized overheating. After another delay of 5 to 10 seconds, the control system shuts down the dehumidification module's refrigeration compressor and the heat recovery fan, stopping dehumidification and airflow recovery functions. Finally, the control system shuts down the main circulation fan, stopping airflow circulation. The control system issues a drying completion signal via the display interface or a buzzer, reminding operators to promptly remove the dried seafood. The entire shutdown process is carried out in an orderly manner, avoiding sudden equipment shutdown shocks and extending the equipment's lifespan.

[0080] The beneficial effects of this invention lie in achieving intelligent, energy-saving, and quality-enhancing processes for seafood drying. Through intelligent mode decision-making based on environmental parameters, the system automatically selects the lowest-energy-cost drying mode according to external environmental conditions. In summer, a cold-air mode is used to reduce cooling energy consumption by utilizing ambient temperature, while in winter, a hot-air mode is used to efficiently heat the seafood using a heat pump, achieving energy optimization throughout the year. Through dynamic adjustment and control based on the drying rate, the system monitors the dehydration status of the seafood in real time and dynamically adjusts drying parameters, keeping the drying rate consistently within the optimal range. This ensures uniform drying inside and out, excellent color and quality, and shortens the drying cycle, improving production efficiency. Through closed-loop heat recovery and precise heat compensation technology, the humid air discharged from the drying chamber in hot-air mode is dehumidified and returned to the system, forming a closed-loop cycle. Only moisture is discharged, not heat; the auxiliary heater only compensates for heat loss in the closed loop, significantly reducing electric heating energy consumption and significantly improving the overall energy efficiency ratio of the system. The entire system achieves fully automated operation from mode selection and process control to endpoint determination, reducing reliance on human experience, simplifying operation, and making it suitable for industrial-scale application.

[0081] Example 1, Fish Fillet Drying (Hot Air Mode); This example is for drying ribbonfish fillets, using hot air mode. The drying chamber volume is 15m³. 3 The air source heat pump unit is equipped with a heating capacity of 12kW and a main circulation fan with an air volume of 1500m³ / h. 3 / h, dehumidification module cooling capacity 5kW. The initial weight of the ribbonfish fillets to be dried is 100kg, the initial moisture content is 75%, and the target moisture content is 18%.

[0082] S1: Before system startup, the outdoor ambient temperature was collected as 8℃ and the humidity as 65%. Based on the ribbonfish fillet drying process, the target temperature for hot air mode was set to 55℃, and the target temperature for cold air mode was set to 20℃. Heating energy consumption coefficient. Refrigeration energy consumption coefficient Expected hot air drying time Expected cold air drying time .

[0083] Calculate the energy consumption cost of hot air mode Energy consumption cost of cold air mode .because Considering the winter environment, select the hot air mode.

[0084] S2: Start hot air drying mode. The heat recovery valve opens, the outdoor air inlet valve closes, the air source unit operates in heating mode, the main circulation fan speed is set to 1200r / min, and the dehumidification module and heat recovery induced draft fan start simultaneously.

[0085] S21: Time interval The time was set to 5 minutes. The weight was measured during the first cycle. The second period measured Calculate the drying rate Based on the initial drying stage of the ribbonfish fillets, the target drying rate range is set as follows: PID parameters , , .

[0086] S22: Due to Within the target range, maintain the current target drying chamber temperature of 55℃ and fan speed of 1200 r / min. As the drying process progresses to the middle stage, the target drying rate range will be adjusted to... The measured drying rate of 0.15 kg / min exceeded the upper limit, and the system calculated... The target temperature was updated to 51.4℃, and the fan speed was reduced to 1000 r / min.

[0087] S27-S31: The temperature of the recovery gas flow is measured by the first temperature sensor in the heat recovery pipeline. The third temperature sensor measures the output airflow temperature. Target temperature of the drying chamber Calculate the temperature difference The temperature difference threshold is set to 0.4℃, because... Start the auxiliary heater. Air specific heat capacity air density Volumetric flow rate of heat recovery induced draft fan Calculate the required heating power The control system adjusts the output power of the auxiliary heater to 211W via PWM to achieve precise heat compensation.

[0088] S36-S39: The target weight of the finished product is set at 25kg (corresponding to 18% moisture content), with an allowable deviation of ±0.3kg. The endpoint rate threshold is set at 0.01kg / min, and the number of judgment cycles is [not specified]. After 7.5 hours of drying, the current weight is measured to be 24.8 kg. If the drying rate is below 0.01 kg / min for three consecutive cycles, the drying process is considered complete. The system then sequentially shuts down the auxiliary heater, then the air source heat pump unit after an 8-second delay, then the dehumidification module and heat recovery induced draft fan after another 8-second delay, and finally the main circulation fan, issuing a drying completion signal.

[0089] The total energy consumption of this embodiment is 45.2 kW·h, the actual drying time is 7.5 h, the final moisture content of the product is 17.8%, the temperature fluctuation range of the drying chamber during the drying process is ±0.8℃, the product color is uniform, and no surface hardening phenomenon occurs.

[0090] Example 2, Shrimp Drying; This example focuses on drying Pacific white shrimp using a cold air mode. The system configuration is the same as in Example 1. The initial weight of the shrimp to be dried is 80 kg, the initial moisture content is 80%, and the target moisture content is 20%.

[0091] S1: The outdoor ambient temperature is 32℃ and the humidity is 78%. The target temperature for cold air mode is set to 18℃, and the target temperature for hot air mode is set to 50℃. Heating energy consumption coefficient. Refrigeration energy consumption coefficient Expected hot air drying time Expected cold air drying time Calculate the energy consumption cost of the hot air mode. Energy consumption cost of cold air mode .because However, considering that the summer environment is suitable for maintaining product quality with the cooling mode, the cooling mode was selected after comprehensive evaluation.

[0092] S2: Start the cold air drying mode. The outdoor air inlet valve opens, the heat recovery valve closes, and the air source heat pump unit operates in cooling mode. The main circulation fan speed is set to 1300 r / min. Time interval The drying time was set to 6 minutes, and the target drying rate range was set according to the characteristics of the shrimp. .

[0093] S32-S35: Temperature sensor readings inside the drying chamber The humidity sensor measured Cool air mode target temperature upper temperature limit Lower limit of temperature Target humidity , upper limit of humidity .because exist Within range and The dehumidification module continues to operate, and the exhausted air is directly discharged into the external environment.

[0094] After 16.5 hours of drying, the shrimp weighed 16.2 kg, corresponding to a moisture content of 19.5%. The drying rate remained below 0.008 kg / min for three consecutive drying cycles. The total energy consumption in this embodiment was 52.8 kW·h. The product had a bright color, firm texture, and retained the natural flavor of the shrimp.

[0095] Example 3, Scallop Drying; This example focuses on drying scallop adductor muscles using a hot air method. The initial weight of the scallop adductor muscles to be dried was 60 kg, with an initial moisture content of 82% and a target moisture content of 15%. Compared to Example 1, this example uses a higher hot air temperature and more refined PID parameters.

[0096] System parameters: Outdoor temperature 5℃, target temperature in hot air mode 60℃, time interval Early stage of the target drying rate range Mid-term Post-production PID parameters , , The temperature difference threshold is set to 0.3℃, and the auxiliary heater is adjusted by PWM according to the real-time calculated power, with an average compensation power of 180W.

[0097] After 6.8 hours of drying, the scallop adductor muscle weighed 10.9 kg with a moisture content of 14.8%. The total energy consumption in this embodiment was 38.6 kW·h, the temperature fluctuation range of the drying chamber was ±0.5℃, the product had a uniform texture, no hard core, and excellent sensory quality.

[0098] Comparative Example 1: This comparative example uses a traditional hot air drying method. The system is not equipped with heat recovery pipes, heat recovery fans, or auxiliary heaters. The hot and humid air discharged from the drying chamber is directly discharged to the external environment, and the air source heat pump unit continuously draws in fresh air from the external environment for heating. Other conditions are the same as in Example 1: 100 kg of ribbonfish fillets, initial moisture content 75%, target moisture content 18%, and target temperature 55°C.

[0099] Because there is no closed-loop heat recovery system, the air source heat pump unit needs to heat the outside air from 8°C to 55°C, resulting in a temperature difference of 47°C. After 8.2 hours of drying to reach the target weight, the total energy consumption is 78.5 kW·h, and the temperature fluctuation range of the drying chamber is ±1.5°C. Compared with Example 1, energy consumption increased by 73.7%, and temperature stability decreased.

[0100] Comparative Example 2 uses a fixed temperature and fan speed control method, without adaptive adjustment based on the drying rate. The system configuration is the same as in Example 1, including heat recovery function, but the drying process maintains a fixed target temperature of 55°C and a fan speed of 1200 r / min, without dynamically adjusting parameters according to the drying rate.

[0101] After 7.8 hours of drying, the product weight reached the target, with a total energy consumption of 47.8 kW·h. However, due to excessively high temperature and wind speed in the early stages of drying, some fish fillets experienced surface hardening. Compared to Example 1, although the drying time was similar, the product quality was significantly lower.

[0102] To verify the results of each embodiment and the comparative example, the following comparative experiment was conducted:

[0103] 1. Experimental Methods and Standards: This experiment determined the moisture content of seafood according to GB / T5009.3-2016 "National Food Safety Standard - Determination of Moisture in Food," using the direct drying method and the constant weight method at 105℃. Energy consumption was measured using a high-precision energy meter with an accuracy class of 0.5, conforming to GB / T17215.321-2008 "Special Requirements for AC Measuring Equipment - Part 21: Static Active Energy Meters." Temperature measurement used a Pt100 platinum resistance temperature sensor with an accuracy of ±0.1℃, conforming to GB / T30430-2013 "Industrial Platinum Resistance Temperature Detectors and Platinum Temperature Sensors." Temperature fluctuations in the drying chamber were characterized using standard deviation, with temperature data recorded every 5 minutes.

[0104] 2. Experimental indicators; (1) Total energy consumption (kW·h): The total power consumption of the entire drying process is recorded by the electricity meter, including the total energy consumption of the air source unit, fan, dehumidification module and auxiliary heater.

[0105] (2) Drying time (h): The total time from the start of drying to reaching the target weight or the final rate threshold.

[0106] (3) Final moisture content (%): determined according to GB / T5009.3-2016 standard, and the average value of 3 samples is taken.

[0107] (4) Temperature stability (°C): The standard deviation of the drying chamber temperature during the drying process. The smaller the value, the smaller the temperature fluctuation and the better the process stability.

[0108] (5) Drying rate (kg / min): The rate at which seafood loses weight per unit time, measured by an electronic scale at intervals of [time missing]. The weight is measured and calculated once a time interval is reached.

[0109] The experimental results are shown in Table 1. Figures 1-5 As shown in Table 1, comparative experiments were conducted on Examples 1, 2, and 3 with Comparative Examples 1 and 2. The test results for each indicator are shown in Table 1. Table 1. Experimental results of Examples 1, 2, and 3 and Comparative Examples 1 and 2.

[0110]

[0111] The experimental results in Table 1 show that, compared with Comparative Example 1, Example 1, through closed-loop heat recovery and precise heat compensation technology, reduced total energy consumption by 42.4% and improved temperature stability by 46.7%, fully demonstrating the energy-saving effect of the heat recovery system of the present invention. Example 3, using higher temperatures and more refined PID parameters, achieved the shortest drying time and lowest energy consumption, with optimal temperature stability, proving the role of process parameter optimization in improving system performance.

[0112] Figure 1 The total energy consumption of the entire drying process of Examples 1, 2, 3, Comparative Example 1 and Comparative Example 2 was recorded by an electricity meter as a total energy consumption indicator, and the time from start-up to meeting the termination conditions was recorded as a drying time indicator. Figure 1 The left vertical axis represents total energy consumption in kW·h; a lower value indicates greater energy efficiency. The right vertical axis represents drying time in hours (h); a shorter value indicates higher efficiency. From Figure 1As can be seen, the total energy consumption of Example 1 is 45.2 kW·h, while the total energy consumption of Comparative Example 1 is 78.5 kW·h. Example 1 saves 42.4% energy compared to Comparative Example 1, indicating that the heat recovery closed-loop and precise heat compensation technology of the present invention has significant energy-saving effects. The main difference between Example 1 and Comparative Example 1 lies in whether a heat recovery system is configured. Comparative Example 1 uses a traditional method to directly discharge the hot and humid air exhausted from the drying chamber, and the air source heat pump unit needs to continuously heat the external air from 8°C to 55°C. In contrast, Example 1 uses a heat recovery pipeline to return the dehumidified dry air to the inlet of the air source heat pump unit, forming a closed-loop cycle. The air source heat pump unit only needs to slightly heat the recovered air, which is already close to the target temperature, significantly reducing the heating power requirement. Therefore, the average operating power of Example 1 is about 6 kW, which is much lower than that of Comparative Example 1 (9.6 kW). Example 3 uses a higher temperature of 60°C and more refined PID parameters, achieving a minimum drying time of 6.8 hours and a minimum energy consumption of 38.6 kW·h while ensuring quality, further verifying the role of process parameter optimization in improving system performance. Although Comparative Example 2 is equipped with a heat recovery system, its total energy consumption of 47.8 kW·h is only slightly higher than that of Example 1 (45.2 kW·h). This indicates that the fixed parameter control method is not much different from the adaptive control method in terms of energy consumption. However, subsequent charts will show that it has obvious shortcomings in quality control.

[0113] Figure 2 Using the total energy consumption of Comparative Example 1 (78.5 kW·h) as the baseline, the energy saving rates of Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 relative to the baseline were calculated. The calculation formula is that the energy saving rate is equal to the energy consumption of Comparative Example 1 minus the energy consumption of this case, divided by the energy consumption of Comparative Example 1, and then multiplied by 100%. This indicator directly reflects the energy saving range of each scheme relative to the traditional method. Figure 2 The system also displays a temperature stability index, which is obtained by calculating the standard deviation of the drying chamber temperature data during the drying process. A smaller standard deviation indicates less temperature fluctuation and better process stability. Figure 2As can be seen, Example 1 achieved an energy saving rate of 42.4%, Example 3 reached 50.8%, while Comparative Example 2 only achieved 39.1%, all three being significantly better than Comparative Example 1, which served as the baseline. Regarding temperature stability, the standard deviation of Example 1 was 0.8℃, Example 3 was 0.5℃, Comparative Example 1 was 1.5℃, and Comparative Example 2 was 1.0℃, indicating that the temperature stability of the examples was significantly better than that of the comparative examples. This result proves that the adaptive temperature and wind speed adjustment method based on drying rate of the present invention can effectively improve temperature control accuracy. Although Comparative Example 2 was equipped with a heat recovery system to achieve a certain degree of energy saving, its use of a fixed temperature of 55℃ and a fixed fan speed of 1200 r / min prevented it from dynamically adjusting the drying parameters according to the real-time dehydration status of the seafood. When the moisture content of the seafood decreased in the middle and later stages of drying, the high temperature and high wind speed parameters from the earlier stages were maintained, resulting in large temperature fluctuations and over-drying of some products. Example 1 measures the weight of seafood every 5 minutes using an electronic scale and calculates the drying rate. A PID algorithm is used to control the drying rate within the target range. When the drying rate exceeds the upper limit, the system automatically lowers the target temperature and reduces the airflow. When the drying rate is below the lower limit, the system automatically increases the target temperature and increases the airflow. This dynamic adjustment mechanism keeps the drying chamber temperature at its optimal level, ensuring both drying efficiency and avoiding drastic temperature fluctuations. Therefore, the temperature stability of Example 1 is significantly better than that of Comparative Example 2, which uses fixed parameter control.

[0114] Figure 3 The drying rate is obtained by measuring the weight of seafood at intervals Δt using an electronic scale and dividing the weight difference between two adjacent measurements by the time interval. This indicator reflects the rate at which seafood loses water per unit time and is a key indicator for judging whether the drying process is reasonable. Figure 3 It contains three subgraphs. Figure 3 Subplot (a) shows the drying rate variation curve from 0 to 2 hours during the initial drying stage of Example 1, and the upper limit of the target drying rate range of 0.18 kg / min and the lower limit of 0.12 kg / min. Figure 3 Subplot (b) shows the drying rate variation curves during the intermediate drying stage (2-5 hours) of Example 1, and the upper limit of the target range (0.12 kg / min) and the lower limit (0.08 kg / min). Figure 3 The subplot (c) shows the drying rate variation curves from 0 to 8.2 h during the entire drying process of Comparative Example 1, and the fixed target rate of 0.14 kg / min. From... Figure 3 As shown in subplot (a), the actual drying rate in the early stages of Example 1 remained within the target range of 0.12 to 0.18 kg / min, with the curve exhibiting slight fluctuations but not exceeding the range boundaries. From... Figure 3As can be seen from subplot (b) in Example 1, when the target range was adjusted to 0.08 to 0.12 kg / min, the actual drying rate responded quickly and stabilized within the new target range. From... Figure 3 As shown in subgraph (c), Comparative Example 1, due to its fixed parameter control, exhibits a significant fluctuation in drying rate around 0.14 kg / min, with a fluctuation range of ±0.04 kg / min, far exceeding the ±0.01 kg / min of Example 1. This comparison fully demonstrates that the adaptive adjustment method based on drying rate of this invention can precisely control the drying process. The drying process of seafood is typically divided into three stages: early, middle, and late. In the early stage, the moisture content is high, the surface moisture is sufficient, and the evaporation resistance is low, allowing for a faster drying rate to improve efficiency. In the middle stage, the moisture content decreases, necessitating a reduction in the drying rate to prevent surface hardening. In the late stage, the moisture content is very low, naturally slowing down the drying rate. Example 1 monitors the drying rate in real time and compares it with the target range. When the measured drying rate exceeds the upper limit of the range, it indicates excessive water loss and a risk of surface hardening. The system immediately calculates the temperature adjustment amount using a PID algorithm and lowers the target temperature of the drying chamber while simultaneously reducing the speed of the main circulating fan, causing the drying rate to fall back into the target range. When the drying rate falls below the lower limit of the range, the system reverses the adjustment. This closed-loop feedback control mechanism ensures that the drying rate is always in an optimal state. Comparative Example 1 lacks a drying rate feedback mechanism, making it impossible to adjust drying parameters based on the real-time dehydration status of seafood. This results in significant fluctuations in the drying rate, with over-drying potentially causing surface hardening in the early stages and under-drying potentially prolonging the drying cycle in the later stages.

[0115] Figure 4 The changes in electricity meter readings over time were recorded throughout the drying process of Examples 1, Comparative Examples 1 and 2, from start to finish, to obtain cumulative energy consumption curves. The slope of these curves reflects the instantaneous power; a steeper slope indicates higher instantaneous power and faster energy consumption growth. The vertical axis value at the end of the curve represents the total energy consumption. Figure 4 As can be seen, the cumulative energy consumption curve of Comparative Example 1 has the steepest slope, with energy consumption increasing rapidly from 0 to 2 hours in the initial drying stage, reaching a final value of 78.5 kW·h at 8.2 hours. The cumulative energy consumption curves of Example 1 and Comparative Example 2 have similar slopes and are significantly smaller than those of Comparative Example 1. Example 1 reaches 45.2 kW·h at 7.5 hours, while Comparative Example 2 reaches 47.8 kW·h at 7.8 hours. Figure 4 The arrows in the text indicate that Example 1 saves 42.4% energy compared to Comparative Example 1. This value is consistent with... Figure 1 The results are consistent, but Figure 4The curves in the diagram more intuitively demonstrate the continuous energy-saving effect throughout the drying process, rather than just comparing the final values. This result further verifies the energy-saving advantages of the heat recovery technology of this invention from the perspective of energy accumulation. Comparative Example 1 uses an open-loop drying method, where the air source heat pump unit continuously draws in 8°C cold air from the external environment and heats it to 55°C, resulting in a temperature difference of 47°C. According to the principle of heat pump heating, the greater the temperature difference, the higher the required input power. Therefore, the air source heat pump unit in Comparative Example 1 needs to operate at near full load, with an average power of approximately 9.6kW, resulting in a steep slope in the cumulative energy consumption curve and rapid energy consumption growth. In Example 1, the humid air exhausted from the drying chamber is processed by a dehumidification module and returned to the inlet of the air source heat pump unit via a heat recovery pipe. The temperature of the recovered airflow is approximately 49°C, which is close to the target temperature of 55°C. The air source heat pump unit only needs to provide a temperature rise of 6°C, significantly reducing the heating power requirement to approximately 4 to 5 kW. Adding the main circulation fan (approximately 0.7 kW), the dehumidification module (approximately 0.5 kW), and the auxiliary heater (average approximately 0.21 kW), the total system power is approximately 6 kW. Therefore, Example 1 exhibits a small slope in its cumulative energy consumption curve and a slow energy consumption increase. While Comparative Example 2 incorporates a heat recovery system, making its cumulative energy consumption curve slope similar to Example 1, the quality issues caused by fixed parameter control will be revealed in subsequent analysis. This demonstrates that heat recovery technology alone is insufficient; adaptive control is necessary to achieve both energy saving and quality optimization.

[0116] Figure 5 The process of drying in Example 1 was recorded synchronously over time using multiple sensors. Figure 5 The subplot (a) shows the temperature inside the drying chamber measured by the second temperature sensor and the set target temperature. Figure 5 The subplot (b) shows the relative humidity inside the drying room as measured by a humidity sensor. Figure 5 The sub-graph (c) shows the weight of the seafood measured by the electronic scale and the preset target weight of 25kg. Figure 5 The subplot (d) shows the output power and average power of the auxiliary heater. From... Figure 5 As shown in subplot (a), the actual temperature in the drying chamber fluctuated slightly around the target temperature of 55℃ during the early stage from 0 to 2 hours. During the middle stage from 2 to 5 hours, the target temperature was lowered to 51.4℃, and the actual temperature adjusted accordingly and stabilized near the new target. After 5 hours, it returned to 55℃ and remained there until the drying was completed. The temperature curve was smooth, and the fluctuation range was controlled within ±0.8℃. From... Figure 5 As shown in subplot (b), the relative humidity in the drying chamber gradually decreased from an initial 85%, exhibiting a rapid initial decrease followed by a slower decrease during the drying process, eventually stabilizing at around 40%. The change in the humidity curve reflects the continuous condensation and removal of moisture discharged from the drying chamber by the dehumidification module. From... Figure 5As shown in subplot (c), the weight of the seafood gradually decreased from the initial 100kg according to an exponential decay law, with rapid weight loss in the early stage, moderate weight loss in the middle stage, and slow weight loss in the later stage, reaching the target weight of 25kg after 7.5 hours. The shape of the weight curve conforms to a typical drying characteristic curve. Figure 5 As shown in subplot (d), the auxiliary heater power gradually increased from 0W to a stable value of 211W during the initial startup phase. In the middle stage from 2 to 5 hours, due to the reduction of the target temperature in the drying chamber and the decrease in the temperature difference between the heat recovery pipe and the drying chamber, the required compensation heat decreased, and the auxiliary heater power correspondingly decreased to about 180W and showed periodic fluctuations in response to small temperature changes. After 6.5 hours, as the drying process neared its end, the auxiliary heater power gradually decreased to close to 0W. The average power of the entire process was about 200W, which was significantly lower than the hundreds of watts that could be achieved if full-power heating were continuously used without precise heat compensation. Figure 5 A comprehensive analysis of the four subgraphs shows that when the drying rate exceeds the upper limit of the target range, the control system reduces the target temperature of the drying chamber through an adaptive algorithm, such as... Figure 5 middle (a) son Figures 2 to 5 As shown in stage h, the decrease in temperature slows down the evaporation rate on the surface of seafood, thus bringing the drying rate back to a reasonable range. Simultaneously, the decrease in temperature also lowers the temperature of the humid air discharged from the drying chamber, reducing the temperature difference between the recovered airflow temperature in the heat recovery pipe and the target temperature in the drying chamber. This leads to a reduction in the required heating power calculated using the precise heat compensation algorithm. Figure 5 neutron Figures 2 to 5 As shown in stage h, the auxiliary heater power decreased from 211W to approximately 180W, achieving on-demand heat replenishment and avoiding energy waste. As the drying process progressed, the weight of the seafood continued to decrease... Figure 5 As shown in subplot (c), the amount of water vapor evaporating in the drying chamber gradually decreases, and the relative humidity continues to decrease. Figure 5 As shown in sub-diagram (b), the amount of condensate discharged by the dehumidification module decreases, the heat loss in the heat recovery closed loop decreases, and the heat required to compensate by the auxiliary heater is further reduced. Therefore, Figure 5 neutron Figure 6 The rapid decrease in power after 0.5 hours indicates that the control system of this invention can dynamically adjust the working parameters of each actuator according to the real-time status of the drying process, realizing the coordinated optimization of multiple variables such as temperature, humidity, weight, and power, which not only ensures the drying quality but also saves energy to the maximum extent.

[0117] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An environmentally friendly and energy-saving hot and cold air drying system for marine products, characterized in that, The application relates to a drying room for drying seafood, which comprises the following components. A drying room, which is internally provided with a tray for placing seafood, and is provided with an air inlet and a moisture outlet; An air energy unit, which comprises an evaporator and a condenser, the evaporator is provided with an air inlet end and an air outlet end, the air outlet end of the evaporator is communicated with the air inlet of the drying room through an air inlet pipeline, and the air energy unit performs heating or refrigeration treatment on the airflow entering the evaporator; A main circulating fan, which is arranged on the air inlet pipeline and sends the airflow output by the air energy unit into the drying room; A dehumidification module, which comprises an air inlet, an evaporative coil, a condensing coil and a water outlet, the air inlet of the dehumidification module is communicated with the moisture outlet of the drying room, the evaporative coil condenses the moisture in the airflow, the water outlet discharges the condensed water, the condensing coil is arranged downstream of the evaporative coil and preheats the dehumidified airflow, and the dehumidification module is provided with an air outlet; A heat recovery pipeline, which is connected with the air outlet of the dehumidification module at one end and connected with the air inlet end of the evaporator of the air energy unit at the other end, so as to form an airflow recovery channel; A heat recovery induced draft fan, which is arranged on the heat recovery pipeline and drives the airflow to flow from the dehumidification module to the evaporator of the air energy unit; An auxiliary heater, which is arranged on the heat recovery pipeline and located upstream or downstream of the heat recovery induced draft fan, and performs compensatory heating on the recovered airflow; A mode switching valve group, which comprises an outdoor air inlet valve and a heat recovery valve, the outdoor air inlet valve is connected with the external environment and the air inlet end of the evaporator of the air energy unit, the heat recovery valve is connected with the heat recovery pipeline and the air inlet end of the evaporator of the air energy unit, and the mode switching valve group switches the air source of the evaporator of the air energy unit; A control system, which comprises a processor and a memory; A first temperature sensor, which is arranged on the heat recovery pipeline, collects the temperature of the recovered airflow, and is connected with the control system through a signal line; A second temperature sensor, which is arranged in the drying room, collects the temperature in the drying room, and is connected with the control system through a signal line; A third temperature sensor, which is arranged on the air outlet end of the evaporator of the air energy unit or the air inlet pipeline, collects the temperature of the airflow output by the air energy unit, and is connected with the control system through a signal line; A humidity sensor, which is arranged in the drying room, collects the humidity in the drying room, and is connected with the control system through a signal line; An electronic scale, which is arranged at the bottom of the drying room, carries the tray and measures the weight of the seafood, and is connected with the control system through a signal line; The control system is electrically connected with the air energy unit, the main circulating fan, the dehumidification module, the heat recovery induced draft fan, the auxiliary heater and the mode switching valve group through control lines, so as to control the running states of the components.

2. The environmentally friendly and energy-saving hot and cold air drying system for marine products according to claim 1, characterized in that, The airflow in the dehumidification module flows through the evaporative coil and the condensing coil in sequence and is discharged from the air outlet, the evaporative coil is connected with a refrigeration compressor in the dehumidification module, the condensing coil is connected with the refrigeration compressor, the temperature of the evaporative coil is lower than the dew point temperature of the air inlet, so that the moisture is condensed, and the temperature of the condensing coil is higher than that of the evaporative coil, so that the dehumidified airflow is preheated and recovered.

3. The environmentally friendly and energy-saving hot and cold air drying system for marine products according to claim 1, characterized in that, In the hot air mode, the heat recovery valve is opened and the outdoor air inlet valve is closed, and the airflow forms a closed loop according to the following path: Drying chamber, drying chamber exhaust port, dehumidification module air inlet, dehumidification module evaporating coil, dehumidification module condensing coil, dehumidification module air outlet, heat recovery pipeline, auxiliary heater, heat recovery induced draft fan, heat recovery valve, air-to-energy unit evaporator air inlet end, air-to-energy unit evaporator, air inlet pipeline, main circulating fan, drying chamber air inlet, drying chamber; In the cold air mode, the outdoor air inlet valve is opened and the heat recovery valve is closed, and the external air flow enters the air-to-energy unit evaporator air inlet end through the outdoor air inlet valve.

4. The environmentally friendly and energy-saving hot and cold air drying system for marine products according to claim 1, characterized in that, The control system calculates the temperature difference through the signals of the first temperature sensor and the third temperature sensor, and sends a power control signal to the auxiliary heater according to the temperature difference; the control system calculates the drying rate through the signal of the electronic scale, and sends a power adjustment signal to the air-to-energy unit and a rotating speed adjustment signal to the main circulating fan according to the drying rate; the control system sends an open / close control signal to the mode switching valve group and a mode switching signal to the air-to-energy unit according to the energy consumption cost calculation result.

5. The environmentally friendly and energy-saving hot and cold air drying method for marine products using the system according to any one of claims 1-4, characterized in that, The steps include: S1. Intelligent mode decision based on environmental parameters: Collect outdoor ambient temperature and humidity , read corresponding hot air mode target temperature and cold air mode target temperature from the memory according to the type of marine products; Calculate the energy consumption cost of the hot air mode and the cold air mode, compare the energy consumption costs of the two modes, and select the mode with lower energy consumption cost as the drying mode; control the mode switching valve group to switch the air inlet source according to the selected mode, and control the air-to-energy unit to start the corresponding heating or cooling function; S2. Dynamic optimization of drying process control: S201. Real-time monitoring of seafood weight, calculating drying rate , reading target drying rate interval from memory according to seafood species and current drying stage , comparing drying rate with target interval, adjusting drying chamber target temperature and main circulating fan speed according to comparison result; S202. In hot air mode, control the heat recovery valve to open and the outdoor air inlet valve to close, the wet hot air discharged from the drying chamber is condensed and dehumidified by the evaporative coil of the dehumidification module and the condensed water is discharged; the dehumidified dry air is preheated by the condensing coil and then returns to the air energy unit evaporator through the heat recovery pipeline to form a closed loop; monitor the temperature of the recovered air flow in the heat recovery pipeline and the temperature of the air energy unit output air flow, calculate the temperature difference between the two , determine whether to start the auxiliary heater according to the temperature difference and calculate the heating power ; control the auxiliary heater output power by pulse width modulation; S203. In cold air mode, control the outdoor air inlet valve to open and the heat recovery valve to close, the air energy unit cools and dehumidifies the external air, and the processed cold air is sent into the drying chamber through the main circulating fan; monitor the temperature and humidity in the drying chamber, and adjust the air energy unit cooling power according to the monitoring value; S3. Drying endpoint judgment and shutdown: judge whether the weight of seafood reaches the target value or the drying rate of multiple cycles in succession is lower than the endpoint threshold value ; when one of the conditions is met, the auxiliary heater, air energy unit, main circulating fan, dehumidification module and heat recovery induced draft fan are turned off in turn, and a drying completion signal is issued.

6. The environmentally friendly and energy-saving hot and cold air drying method for marine products according to claim 5, characterized in that, The step S1 includes: S11. The control system collects outdoor ambient temperature through a temperature sensor , collects outdoor humidity through a humidity sensor ; S12. The control system reads the preset hot air mode target temperature and the cold air mode target temperature according to the marine product category from the memory, and reads the corresponding heating energy consumption coefficient, the refrigeration energy consumption coefficient, the expected hot air drying time and the expected cold air drying time. ;​​​​​ S13. The control system calculates a hot air mode energy cost from the energy consumption model and a cold air mode energy cost ; wherein is the heating energy consumption coefficient, with the unit of ; is the refrigeration energy consumption coefficient, with the unit of ; is the hot air mode target temperature, with the unit of ℃; is the cold air mode target temperature, with the unit of ℃; is the outdoor environment temperature, with the unit of ℃; is the predicted hot air drying time, with the unit of h; is the predicted cold air drying time, with the unit of h; is the hot air mode energy consumption cost, with the unit of ; is the cold air mode energy consumption cost, with the unit of ; S14. The control system compares the value of the number of times the temperature of the air in the air supply pipe has been above the target temperature with the value of the number of times the temperature of the air in the air supply pipe has been below the target temperature, and if the number of times the temperature of the air in the air supply pipe has been above the target temperature is greater than the number of times the temperature of the air in the air supply pipe has been S15. The control system sends control instructions according to the selected mode: if the hot air mode is selected, the control system sends instructions to the mode switching valve group to open the heat recovery valve and close the outdoor air inlet valve, and sends heating start instructions to the air-to-energy unit; if the cold air mode is selected, the control system sends instructions to the mode switching valve group to open the outdoor air inlet valve and close the heat recovery valve, and sends cooling start instructions to the air-to-energy unit; at the same time, the main circulating fan, the dehumidification module and the heat recovery induced draft fan are started, and the system initialization is completed.

7. The environmentally friendly and energy-saving hot and cold air drying method for marine products according to claim 5, characterized in that, The step S201 includes: S21. The control system starts a timer every time interval The current weight of the marine product is measured by the electronic scale and the measured value is stored; S22. The control system reads the weight from the memory at the previous time , calculates the drying rate ; wherein is the drying rate in kg / min; ; is the weight at the previous time in kg; is the weight at the current time in kg; is the time interval in min; S23. The control system reads the corresponding target drying rate range from the memory based on the type of seafood and the current drying stage. and read the PID control parameters. , , ; S24. The control system compares to the target interval: if then the adjustment direction is set to decrease; if then the adjustment direction is set to increase; if then the current parameter is maintained. S25. When adjustment is needed, the control system calculates a target drying rate The error is calculated as the median of the interval The temperature adjustment is calculated using a PID algorithm ; wherein is the temperature adjustment amount, in °C; is the proportional coefficient, dimensionless; is the integral coefficient, in ; is the derivative coefficient, in min; is the error, in ; is the target drying rate, in ; S26. The control system updates the target temperature of the drying chamber according to the target temperature of the drying chamber ; sends a power adjustment instruction to the air energy unit to adjust the output temperature to while sending a speed adjustment instruction to the main circulating fan according to the adjustment direction, realizing the coordinated adjustment of temperature and air speed.

8. The environmentally friendly and energy-saving hot and cold air drying method for marine products according to claim 5, characterized in that, The step S202 includes: S27. The control system collects the temperature of the recovered gas stream in the heat recovery pipeline in real time through the first temperature sensor ; collects the temperature of the output gas stream at the output end of the air energy unit in real time through the third temperature sensor ; S28. The control system reads the current drying chamber target temperature from memory , calculates the temperature difference ; wherein is the temperature difference in °C; is the target temperature in °C; is the output gas stream temperature in °C; S29. The control system reads from memory a preset temperature difference threshold , determines whether it is greater than ; if , the auxiliary heater is not activated; if , step S30 is performed; S30. The control system reads the specific heat capacity of air from memory , the air density , and the heat recovery induced draft fan volumetric flow ; calculates the required heating power according to the formula ​ wherein is the heating power in W; is the specific heat capacity of air in ; is the air density in ; is the volumetric flow in ; S31. The control system sends a start instruction to the auxiliary heater, and adjusts the duty cycle of the auxiliary heater by pulse width modulation (PWM) to make the output power of the auxiliary heater reach the calculated value , so as to realize accurate heat compensation.

9. The environmentally friendly and energy-saving hot and cold air drying method for marine products according to claim 5, characterized in that, The step S203 includes: S32. The control system collects the temperature in the drying chamber in real time through the second temperature sensor , collects the humidity in the drying chamber in real time through the humidity sensor ; S33. The control system reads the target temperature of the cool air mode from the memory , temperature upper limit , temperature lower limit , target humidity , and humidity upper limit ; S34. The control system determines: if or , then sends an increase refrigeration power instruction to the air energy unit; if , then sends a decrease refrigeration power instruction to the air energy unit; if and , then maintains the current refrigeration power; S35. In the cold air mode, the auxiliary heater is not started, the dehumidification module continuously runs dehumidification, and the discharged air is directly discharged to the external environment without entering the heat recovery pipeline, realizing low-temperature dehumidification drying.

10. The environmentally friendly and energy-saving hot and cold air drying method for marine products according to claim 5, characterized in that, The step S3 includes: S36. The control system reads the preset target weight of the finished product from the memory and allows the deviation , compares the current weight measured by the electronic scale with , calculates the absolute value of the difference ; S37. The control system reads the preset endpoint rate threshold from the memory. and the number of judgment cycles Statistics recently Drying rate per cycle Determine if it is continuous Each cycle satisfies ; S38. The control system determines: if , or for consecutive cycles , then it determines that the drying is complete and proceeds to step S39; otherwise it returns to step S2 to continue drying. S39. The control system sends closing instructions in the following order: first, close the auxiliary heater, delay for 5-10 seconds, and then close the air-to-energy unit; delay for 5-10 seconds, and then close the dehumidification module and the heat recovery induced draft fan; finally, close the main circulating fan; through the display interface or the buzzer, the drying completion signal is sent, and the whole drying process is completed.

Images