A method for relieving heat stress of sows based on underground temperature reduction and wet curtain collaborative control

Abstract

This invention discloses a method for alleviating heat stress in sows based on the coordinated control of underground cooling and evaporative cooling pads, belonging to the field of intelligent environmental control technology in livestock farming. The invention constructs a coordinated cooling system consisting of underground pre-cooling, evaporative cooling pads, precise air supply, intelligent control, and monitoring units. A PLC controller is at the core, and temperature, humidity, and wind speed sensors collect real-time environmental data from the pigsty. This invention employs a two-stage cooling mode with underground air ducts and evaporative cooling pads connected in series. Based on the appropriate temperature and humidity thresholds for sows at different physiological stages, the operating parameters of fans and water pumps are adjusted accordingly. Differentiated directional air supply is provided for pregnant sows, lactating sows, and piglets, and a closed-loop feedback control and remote manual intervention mechanism is established. This invention overcomes the shortcomings of traditional cooling equipment, such as poor cooling effect in high-temperature and high-humidity environments, temperature and humidity imbalance, and uneven air supply that easily causes cold stress. At an ambient temperature of 35℃, the system can stably maintain a pigsty temperature of 20-25℃ and a relative humidity of 50%-65%, improving cooling efficiency by 40% compared to traditional solutions and reducing the annual operating cost per farrowing house by more than 500 yuan. This solution features a high degree of automation, low energy consumption, and stable operation. It can effectively alleviate heat stress in sows and maintain their production performance, making it suitable for large-scale application in sow farrowing pens.

Description

Technical Field

[0001] This invention relates to the field of intelligent control technology for livestock breeding environment, specifically to a method for alleviating heat stress in sows based on the coordinated control of ground cooling and evaporative cooling pads. Background Technology

[0002] Sows are a type of livestock highly sensitive to environmental temperature, humidity, and airflow speed, and are extremely prone to heat stress in hot summer weather. When sows experience heat stress, they exhibit a significant decrease in feed intake, reduced lactation performance, and disrupted estrous cycles. Pregnant sows also experience a significantly increased probability of abortion and stillbirth, severely impairing their reproductive performance and directly reducing the profitability of large-scale pig farms. Therefore, developing stable, precise, and energy-efficient cooling technologies for sow houses has become a key development direction in the field of large-scale pig farming.

[0003] Currently, the mainstream cooling technologies for sow houses in China are divided into two main categories: single cooling modes and simple combination cooling modes. Among them, the evaporative cooling pad-fan single cooling system is the most widely used. This system relies on the evaporation and heat absorption of the water film to cool the house. However, in the hot and humid areas of southern my country, the relative humidity of the air can quickly reach saturation, and the evaporative cooling efficiency drops sharply. At the same time, the continuous operation of the evaporative cooling pad will cause humidity overload in the house, which can easily induce limb and hoof diseases and skin diseases in sows, and will also accelerate the mold growth of feed and bedding in the house, leading to secondary breeding risks.

[0004] Existing technologies include combined cooling solutions using underground ventilation ducts and evaporative cooling pads. However, these systems typically operate independently in parallel without intelligent collaborative control logic. This prevents dynamic matching of the two devices' operating power and start / stop status based on real-time environmental parameters such as temperature, humidity, and wind speed within the pigsty. Consequently, problems arise such as poor operating condition matching, high overall energy consumption, imbalanced temperature and humidity control, and inadequate management of air delivery points and wind speed. Traditional ventilation systems often employ a pervasive, all-area airflow approach, failing to differentiate their design for the environmental needs of different breeding zones, such as pregnant sows, lactating sows, and piglets. Direct cold airflow can easily cause cold stress in pigs, and the airflow precision is insufficient.

[0005] In summary, existing cooling technologies for sow houses have several technical shortcomings, including unstable cooling effects, difficulty in balancing temperature and humidity, high equipment energy consumption, crude air supply control, and a tendency to cause stress in livestock and poultry. The industry urgently needs a synergistic cooling method that can achieve graded pre-cooling, coordinated temperature and humidity control, and precise air supply to different zones, so as to effectively alleviate heat stress in sows while ensuring a stable indoor environment and reducing system operating energy consumption. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing sow house cooling technologies, such as large fluctuations in cooling effect, temperature and humidity imbalance, high equipment energy consumption, low air delivery accuracy, and easy induction of livestock and poultry stress. This invention provides a method for alleviating heat stress in sows based on the coordinated control of underground cooling and evaporative cooling pads. This invention adopts a tiered cooling approach of pre-cooling through underground air ducts + secondary fine cooling through evaporative cooling pads. Combined with a PLC intelligent control system and a zoned precise air delivery structure, the operating status of the equipment is dynamically adjusted according to the environmental tolerance thresholds of sows and piglets at different physiological stages. This achieves coordinated control of multiple parameters, including temperature, humidity, and air velocity in the pig house. While effectively alleviating heat stress in sows, this invention optimizes system energy consumption, avoids cold and heat stress in livestock and poultry, and improves the precision of environmental management in sow houses. Technical solution

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for alleviating heat stress in sows based on the coordinated control of ground cooling and evaporative cooling pads, comprising six steps: system construction, parameter preset, real-time environmental monitoring, graded coordinated cooling, zoned precise air supply, and dynamic feedback adjustment. The specific steps are as follows: Step 1: Overall Construction of the Collaborative Cooling System An integrated, coordinated cooling system is constructed, consisting of a buried pre-cooling unit, a wet curtain cooling unit, a precision air supply unit, an intelligent control unit, and a monitoring unit. The buried pre-cooling unit includes a buried air duct, an intake fan, and an air filter. The buried air duct uses an 800mm diameter U-shaped high-density polyethylene pipe, buried 2m below the ground surface, utilizing the constant temperature of the underground soil for natural air pre-cooling. The air filter is installed at the air inlet of the buried air duct to filter dust and impurities, ensuring the cleanliness of the incoming air. The wet curtain cooling unit includes a 150mm thick polymer wet curtain, a variable frequency water pump, and a water collection tray. The wet curtain cooling unit and the buried pre-cooling unit are arranged in series. The airflow pre-cooled by the buried air duct flows directly through the polymer wet curtain for secondary cooling. The water collection tray is located at the bottom of the wet curtain to collect the returned water. The precision air supply unit includes a main ventilation duct, branch ducts, and directional air outlets. The branch ducts are structurally designed differently according to the environmental needs of different functional areas of the pigsty and pigs at different physiological stages, achieving zoned and directional air supply. The intelligent control unit is based on a PLC controller, serving as the central hub for command issuance, logic operations, and data interaction for the entire system. The monitoring unit integrates temperature sensors, humidity sensors, and wind speed sensors, with each type of sensor correspondingly located at the underground air duct outlet, inside each functional area of ​​the pigsty, and at the air supply terminal, completing the collection of environmental parameters at all points.

[0008] Step 2: Presetting System Operating Parameters The PLC controller's human-machine interface allows for the pre-entry of suitable environmental parameter thresholds for sows and piglets at different physiological stages. Simultaneously, the collaborative operation logic parameters for the underground pre-cooling unit and the evaporative cooling unit are set. Basic environmental parameter standards for each zone are as follows: 1. Pregnant sow area: ambient temperature 20-22℃, relative humidity 50%-65%, air supply velocity 2-2.5m / s; 2. Lactating sow area (farming room): Ambient temperature 22-25℃, relative humidity 50%-65%, air supply velocity 1.8-2.2m / s; 3. Piglet activity area: ambient temperature 28~32℃, air supply speed less than 1m / s.

[0009] The collaborative operation logic parameters include: the start-up temperature threshold of the underground precooling unit, the intervention temperature difference threshold of the wet curtain fine cooling unit, the air humidity linkage control threshold, and the equipment delay operation duration parameter.

[0010] Step 3: Real-time monitoring of the environment at all locations After the system is running normally, the monitoring unit continuously collects three types of core parameters: temperature T1 at the outlet of the underground air duct, ambient temperature T2 in the target functional area of ​​the pig house, relative humidity RH in the pig house, and real-time wind speed V at the air supply terminal. All collected data are transmitted to the PLC controller in real time through signal lines, and the PLC controller completes data storage and comparison calculation.

[0011] Step 4: Synergistic cooling through underground pre-cooling and wet curtain fine cooling. The PLC controller compares real-time monitoring data with preset parameter thresholds and dynamically switches the start / stop status and operating power of the underground precooling unit and the wet curtain cooling unit according to the hierarchical control logic to achieve hierarchical cooling. The specific control logic is as follows: 1. Standby mode: When the temperature T2 in the gestation ward is ≤22℃, the temperature T2 in the lactation ward is ≤25℃, and the RH in the ward is ≤65%, the entire system enters standby mode, with only the monitoring unit continuing to perform inspections, and the rest of the equipment stops operating; 2. Single-stage precooling operation: When the temperature in the gestation house is 22℃ < T2 ≤ 25℃ and the temperature in the lactation house is 25℃ < T2 ≤ 28℃, and the RH ≤ 65%, the underground precooling unit is started separately, and the air intake fan runs at 60% to 80% of the rated speed; the outside air is precooled to 18 to 20℃ through the underground air duct and then sent into the pig house to complete the initial cooling. 3. Dual-stage synergistic cooling mode: After the underground pre-cooling unit has been running for 30 minutes, if the temperature of the pregnancy room T2 is still >25℃ and the temperature of the lactation room T2 is still >28℃, and the RH inside the room is <60%, the PLC controller starts the wet curtain fine cooling unit, and the variable frequency water pump supplies water at 40% to 60% of the rated flow rate. The pre-cooled air flows through the wet curtain to complete the secondary fine cooling. After the airflow temperature drops to 16 to 18℃, it is sent into the room. 4. Humidity linkage regulation mode: If the RH inside the building is ≥60% during the underground pre-cooling operation, in order to avoid humidity overload, the speed of the air intake fan in the underground air duct should be increased to 100% of the rated speed, and the flow rate of the wet curtain variable frequency water pump should be reduced to 20%~30% of the rated flow rate to strictly control the humidity inside the building. 5. Extreme high temperature full load condition: When the temperature of the pig house functional area T2 is greater than 30℃ (extreme high temperature environment), the underground pre-cooling unit and the wet curtain cooling unit will operate at full load. At the same time, the negative pressure fan of the pig house will be activated to enhance the air convection in the house and quickly reduce the environmental parameters to a suitable range.

[0012] Step 5: Precise Air Supply Control by Zone The PLC controller performs differentiated control of the precision air supply unit according to the wind speed and direction requirements of different functional areas of the pigsty: 1. Gestation area: Air is supplied by the main ventilation duct and general branch ducts, and the air velocity is stably controlled at 2-2.5 m / s. The directional air outlets are arranged at a 30° horizontal angle, and the cold air covers the back area of ​​the sows in a directional manner to ensure the cooling effect while avoiding direct airflow stress. 2. Delivery room area: A point-to-point branch pipeline layout is adopted, with one set of directional air outlets configured for every two delivery beds. The air outlets are installed at a height of 2.2 to 2.3 meters above the ground, and the air supply speed is strictly controlled at 1.8 to 2.2 m / s to achieve fixed-point, low-speed air supply in the delivery bed area.

[0013] Step Six: Dynamic Feedback and Closed-Loop Adjustment The PLC controller completes a round of environmental data acquisition and parameter verification at all locations every 5 minutes, forming a closed-loop dynamic adjustment mechanism. 1. When the monitored temperature T2 is 5% lower than the preset lower limit, gradually reduce the flow rate of the evaporative pump in the evaporative cooling pad and then reduce the speed of the air intake fan in the underground air duct in the order of "adjusting the evaporative cooling pad first and then adjusting the fan" to prevent the temperature inside the building from being too low. 2. When the relative humidity (RH) of the monitored air is 5% higher than the preset upper limit of humidity, immediately shut down the wet curtain cooling unit and keep only the underground pre-cooling unit running independently until the humidity in the building returns to the suitable range of 50% to 65%. 3. All system operating data and equipment adjustment commands are synchronously uploaded to the remote monitoring platform. Administrators can use remote terminals to correct parameters and manually start and stop equipment, thus achieving remote operation and maintenance. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of the synergistic cooling system of the present invention; Figure 2 This is a flowchart of the control logic of the PLC controller in the present invention, taking a pregnancy room as an example; Figure 3This is a schematic diagram of the precision air supply structure in the delivery room area of ​​the present invention; In the diagram, 1 is the underground ventilation duct, 2 is the air intake fan, 3 is the filter screen, 4 is the polymer wet curtain, 5 is the variable frequency water pump, 6 is the water collection pan, 7 is the main ventilation duct, 8 is the branch duct, 9 is the negative pressure fan (directional air outlet), 10 is the PLC controller, 11 is the temperature sensor, 12 is the humidity sensor, 13 is the wind speed sensor, and 14 is the electric air volume regulating valve. Detailed Implementation

[0015] This embodiment is applied to the farrowing and gestation pens of sows in large-scale pig farms. The overall system is constructed according to the method described in this invention, and the specific implementation process is as follows: 1. The system is constructed by excavating underground trenches in the breeding area and laying 800mm diameter U-shaped high-density polyethylene buried air ducts at a uniform burial depth of 2m. Air filters and intake fans are installed at the air inlets of the buried air ducts, and 150mm thick polymer wet curtains are connected in series at the air outlets. A water collection tray is installed at the bottom of the wet curtains, and a variable frequency water pump is installed to form a water circulation loop. Main ventilation ducts are laid inside the pigsty, with differentiated branch ducts branched according to functional areas. Point-to-point branch ducts are used in the farrowing area, with one set of directional air outlets for every two farrowing beds, 2.25m above the ground. Universal branch ducts are used in the gestation area, with air outlets arranged at a 30° horizontal angle. Temperature, humidity, and wind speed sensors are installed at the buried air duct outlets, gestation area, farrowing area, piglet area, and each air supply terminal, respectively. A PLC controller is sealed and installed in a separate equipment room outside the pigsty. All sensor circuits and equipment power circuits are connected to the PLC controller to complete the system network.

[0016] 2. Parameter presets are entered into the PLC controller to set the environmental thresholds for each zone: gestation house temperature 20–22℃, humidity 50%–65%, wind speed 2–2.5 m / s; farrowing house temperature 22–25℃, humidity 50%–65%, wind speed 1.8–2.2 m / s; piglet area temperature 28–32℃, wind speed <1 m / s. Simultaneously, preset logical parameters such as a 30-minute equipment delay, a humidity linkage threshold of 60%, and a temperature deviation of 5%.

[0017] 3. During normal operation in spring and autumn, when the ambient temperature is low, the temperature in the gestation ward is kept below 22℃ and the temperature in the delivery room is kept below 25℃, and the humidity inside the ward is ≤65%. The system remains on standby, with only the sensors continuously collecting data.

[0018] 4. Summer High-Temperature Tiered Operation: When the ambient temperature rises in summer, with the maternity ward temperature reaching 23℃ and the delivery room temperature reaching 26℃, and humidity ≤65%, the underground pre-cooling unit is activated. The intake fan operates at 70% speed, and the air is pre-cooled to 19℃ through the underground ventilation duct before being sent into the ward. After 30 minutes of continuous operation, if the ward temperature continues to rise and the humidity is <60%, the evaporative cooling pad unit is automatically activated, and the variable frequency water pump supplies water at 50% flow rate, further cooling the airflow to 17℃. If the ward humidity rises to 60% or higher during operation, the system automatically increases the fan speed to 100% and reduces the water pump flow rate to 25% to prevent further humidity increases. When extreme high temperatures occur and the ward temperature exceeds 30℃, the underground unit and evaporative cooling pad unit operate at full load, while the negative pressure fan is activated to enhance ventilation and quickly control the temperature.

[0019] 5. Air Supply and Dynamic Adjustment: The air outlets in the maternity ward supply air in a directional manner at a speed of 2.3 m / s, while the air outlets in the delivery room maintain a stable speed of 2.0 m / s. The PLC controller collects data every 5 minutes. If the temperature is 5% below the lower limit, the water pump flow rate and fan speed are gradually reduced. If the humidity exceeds the standard, the wet curtain is immediately shut off. All data is uploaded to a remote platform in real time, allowing management personnel to monitor and intervene remotely.

[0020] This embodiment operated continuously for 6 months, resulting in a reduction of over 90% in the heat stress incidence rate of sows, maintaining normal levels of milk production and feed intake, keeping indoor humidity within a reasonable range, and preventing large-scale hoof diseases and feed mold. The system operated stably, with controllable energy consumption, and fully met the summer environmental management needs of large-scale sow houses.

Claims

1. A method for alleviating heat stress in sows based on the coordinated control of underground cooling and evaporative cooling pads, comprising the steps of constructing a coordinated cooling system, presetting operating parameters, real-time environmental monitoring, graded coordinated cooling, zoned precise air supply, and dynamic feedback adjustment; the coordinated cooling system includes an underground pre-cooling unit, an evaporative cooling pad precision cooling unit, a precise air supply unit, an intelligent control unit, and a monitoring unit, wherein the intelligent control unit is based on a PLC controller, and the monitoring unit includes a temperature sensor, a humidity sensor, and a wind speed sensor; characterized in that, The method employs a series-stage cooling mode combining pre-cooling via underground air ducts with secondary fine cooling via evaporative cooling pads. It dynamically adjusts the operation of each unit based on real-time environmental parameters in different functional areas of the pigsty, while simultaneously combining zoned differentiated air supply strategies and a periodic closed-loop feedback mechanism to achieve refined environmental management of the sowsty. The underground pre-cooling unit includes underground air ducts, an intake fan, and a filter; the evaporative cooling pad unit includes polymer evaporative cooling pads, a variable frequency water pump, and a water collection tray, arranged in series with the underground air ducts. The precise air supply unit includes a main ventilation duct, branch ducts, and directional air outlets, with the branch ducts designed differently based on the different physiological stages of sows. Temperature sensors, humidity sensors, and wind speed sensors are respectively deployed at the underground air duct outlet, different functional areas of the pigsty, and the air supply terminals. The preset operating parameters include environmental parameter thresholds corresponding to different physiological stages of sows, the underground pre-cooling start threshold, the evaporative cooling pad intervention temperature difference, and the humidity linkage threshold. In the real-time environmental monitoring step, the monitoring unit continuously collects the underground air duct outlet temperature T1, the target area temperature T2 of the pigsty, and the pigsty humidity RH. The system monitors the air velocity V at the air supply terminal and transmits the collected data to the PLC controller in real time. In the dynamic feedback adjustment step, the PLC controller collects monitoring data at fixed intervals and adjusts the equipment operating parameters according to the deviation of environmental parameters from the threshold. The system operating data and equipment adjustment instructions can be uploaded to the remote monitoring platform and support manual intervention.

2. The method for alleviating heat stress in sows based on the synergistic control of ground cooling and evaporative cooling pads according to claim 1, characterized in that, The underground ventilation duct is a U-shaped high-density polyethylene pipe, with a burial depth of 1.5m to 2m; the thickness of the polymer wet curtain is 150mm.

3. The method for alleviating heat stress in sows based on the synergistic control of ground cooling and evaporative cooling pads according to claim 1, characterized in that, The specific environmental parameter thresholds for sows and piglets at different physiological stages are as follows: temperature 20℃~22℃, relative humidity 50%~65%, and air velocity 2m / s~2.5m / s in the gestation sow area; temperature 22℃~25℃, relative humidity 50%~65%, and air velocity 1.8m / s~2.2m / s in the lactation sow area; and temperature 28℃~32℃ and air velocity less than 1m / s in the piglet area.

4. The method for alleviating heat stress in sows based on the synergistic control of ground cooling and evaporative cooling pads according to claim 1, characterized in that, The specific control logic of the graded coordinated cooling is as follows: (1) When the temperature of the gestation house T2 ≤ 22℃, the temperature of the lactation house T2 ≤ 25℃, and the relative humidity of the pig house RH ≤ 65%, the system enters the standby state, and only the monitoring unit performs real-time inspection operations; (2) When 22℃ < T2 ≤ 25℃ (gestation house) or 25℃ < T2 ≤ 28℃ (lactation house), and RH ≤ 65%, the underground pre-cooling unit is started, and the air intake fan is controlled to run at 60% to 80% of the rated speed. The outside air is pre-cooled to 18℃ to 20℃ through the underground air duct and then sent into the pig house; (3) After the underground pre-cooling unit has been running continuously for 30 minutes, if the temperature of the gestation house T2 > 25℃ or the temperature of the lactation house T2 > 28℃, and RH < 60%, the wet curtain cooling unit is started, and the variable frequency water pump is controlled to run at 40% to 60% of the rated flow. The pre-cooled air is cooled to 16℃ to 18℃ through the wet curtain. If RH≥60% at this time, the speed of the air intake fan will be increased to 100% of the rated speed, and the flow rate of the wet curtain variable frequency water pump will be reduced to 20%~30% of the rated flow rate; (4) When the temperature of the target area of ​​the pig house T2>30℃, the underground pre-cooling unit and the wet curtain fine cooling unit will both be running at full load, and the negative pressure fan of the pig house will be started to enhance the air circulation in the house.

5. The method for alleviating heat stress in sows based on the synergistic control of ground cooling and evaporative cooling pads according to claim 1, characterized in that, The precise air supply control method for the zones is as follows: In the gestation area, air is supplied through the main ventilation duct in conjunction with general branch ducts, and the air supply velocity is controlled at 2m / s to 2.5m / s, with the directional air outlets set at a 30° horizontal angle; In the farrowing area, a point-to-point branch duct layout is adopted, with one set of directional air outlets corresponding to every two farrowing beds, and the air outlets are installed at a height of 2.2m to 2.3m above the ground, with the air supply velocity controlled at 1.8m / s to 2.2m / s; The piglet area is equipped with infrared heating lamps, which automatically turn on when the temperature in the piglet area is below 28℃.

6. The method for alleviating heat stress in sows based on the synergistic control of ground cooling and evaporative cooling pads according to claim 1, characterized in that, The specific rules for dynamic feedback adjustment are as follows: the PLC controller completes a round of monitoring data acquisition every 5 minutes; when the temperature T2 in the pig house is 5% lower than the preset lower limit, the flow rate of the evaporative cooling pad variable frequency pump is reduced first, and then the speed of the air intake fan of the underground pre-cooling unit is gradually reduced; when the relative humidity RH in the pig house is 5% higher than the preset upper limit, the evaporative cooling pad unit is immediately shut down, and only the underground pre-cooling unit is kept running until the relative humidity in the pig house returns to the preset suitable range.

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