Temperature control anti-freezing device for fire hydrant

Abstract

The invention discloses a temperature control anti-freezing device for a fire hydrant. The temperature control anti-freezing device comprises a temperature acquisition module, a control module, a heating module, a power supply module and an alarm module. The temperature acquisition module adopts three PT1000 platinum resistor temperature sensors which are respectively arranged at the water inlet end, the middle section and the fire hydrant interface section of a pipeline, monitors the temperature of each area in real time and transmits the temperature to the control module through a shielding signal line. The control module is based on an STM32F407 microcontroller, dynamically adjusts PWM output through a PID algorithm, and controls the flexible silica gel heating belts arranged in the heating module in a partitioned mode to work. The power supply module adopts a mains supply and a lithium battery to supply power, and when the voltage of the mains supply is lower than 198V, automatic switching is realized. And the alarm module triggers sound-light alarm when the temperature is abnormal and wirelessly transmits an alarm signal through LoRa. According to the device, through distributed temperature monitoring, partitioned precise heating and an intelligent temperature control algorithm, freezing of fire fighting water is effectively prevented, and pipeline damage caused by local overheating in a traditional scheme is avoided.

Description

Technical Field

[0001] The present invention provides an anti-freezing device, belonging to the technical field of fire-fighting equipment, and particularly relates to a temperature-controlled anti-freezing device for a fire hydrant. Background Art

[0002] A fire hydrant, also known as a fire plug, is a key component of a fire water supply system, which is divided into indoor and outdoor types. Its main function is to provide a quick and reliable water source supply point for firefighters in case of a fire. Its design usually includes an obvious box body, which is equipped with devices such as valves and hose connections inside, so as to facilitate firefighters to quickly connect the hose and control the water flow. Fire water refers to the water used for extinguishing fires in the fire protection system. It is transported and distributed through specific water supply pipelines, fire hydrants and other facilities, and plays a crucial role in fire emergencies. The water source of fire water can be municipal water supply, fire pool or natural water source, etc., and it needs to have sufficient water volume and water pressure to meet the fire extinguishing requirements. Fire hydrants and fire water together constitute an important guarantee system for building and urban fire safety.

[0003] The existing anti-freezing methods for fire water mostly rely on heating devices to directly heat the fire pipeline or fire hydrant. Its basic structure is usually to wrap heating elements such as heating wires, heating tapes or heating sheets on the outer wall of the fire pipeline or fire hydrant. By converting electrical energy into heat energy, the heat is transferred to the inside of the pipeline or fire hydrant, thereby preventing the fire water from freezing. However, in the process of using this structure, if the temperature control of the heating device is improper, it may cause the local temperature to be too high, and then damage the pipeline structure. For example, when the heating device works continuously for a long time and lacks an effective temperature monitoring and adjustment mechanism, the excessive temperature will cause the pipeline material to age, deform or even crack, affecting the sealing performance and strength of the pipeline, reducing its service life and reliability, and at the same time increasing safety hazards such as fires. Summary of the Invention

[0004] Embodiments of the present application are to make up for the deficiencies of the prior art. By providing a temperature-controlled anti-freezing device for a fire hydrant, the problems of inaccurate temperature control, high energy consumption and easy damage to pipelines in traditional anti-freezing methods are solved, realizing an intelligent, energy-saving and reliable anti-freezing effect for fire water, and effectively ensuring the normal operation of the fire protection system.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: A temperature-controlled anti-freezing device for a fire hydrant includes a temperature acquisition module, a control module, a heating module, a power supply module and an alarm module; the temperature acquisition module is connected to the AD conversion interface of the control module through a shielded signal line, the heating module is connected to the PWM output interface of the control module through a power drive circuit, the power supply module supplies power to each module respectively through a DC-DC voltage stabilization circuit, and the alarm module is connected to the GPIO interface of the control module;

[0006] The temperature acquisition module includes at least three PT1000 platinum resistance temperature sensors, which are respectively embedded in the insulation layer on the outer wall of the fire pipeline and are evenly distributed along the axial direction of the pipeline in three temperature measurement areas: the water inlet end, the middle section, and the fire hydrant interface section;

[0007] The heating module consists of several flexible silicone heating tapes. Each heating tape is embedded with parallel nickel-chromium alloy heating wires. Each heating tape is tightly attached to the outer wall of the pipeline through a snap-fastening structure and is divided into three independent heating zones according to the temperature measurement areas. Each heating zone is respectively connected to an independent MOSFET drive circuit;

[0008] The control module includes an STM32F407 microcontroller, which is internally integrated with a temperature control algorithm module and is connected to a remote monitoring terminal through an RS485 bus. The temperature control algorithm module calculates the temperature gradient change rate of each temperature measurement area in real time and dynamically adjusts the duty cycle parameter of the corresponding heating zone by using the PID regulation method;

[0009] The power supply module includes an AC / DC conversion unit, a lithium battery pack, and a power supply switching circuit. The input end of the AC / DC conversion unit is connected to the 220V mains power supply, and the output end is connected in parallel with the lithium battery pack through a Schottky diode. The power supply switching circuit includes a voltage comparator and a relay array, and automatically switches to the lithium battery power supply when the mains voltage is lower than 198V;

[0010] The alarm module includes an audible and visual alarm and a wireless transmission unit. When the temperature in any temperature measurement area exceeds 50°C or the temperature difference between adjacent areas is greater than 15°C, an alarm signal is triggered and sent to the monitoring center through the LORA wireless module.

[0011] Preferably: The temperature acquisition module is provided with a redundant temperature measurement structure. Two PT1000 sensors are arranged in each temperature measurement area, and an average value signal is output through a differential amplifier circuit. The insulation layer is made of an aerogel composite material with a thermal conductivity ≤ 0.023W / (m·K).

[0012] Preferably: The MOSFET drive circuit of the heating module includes an IRF540N power tube and a high-speed optocoupler isolator. The gate drive signal is electrically isolated through a TLP250 optocoupler, and a current sampling resistor is connected in series at the source. The sampling signal is fed back to the ADC interface of the control module.

[0013] Preferably: The temperature control algorithm module of the control module includes a dynamic temperature compensation unit. When the ambient temperature sensor detects that the ambient temperature is lower than -10°C, the target temperature setting value is automatically increased by 2 - 5°C, and a heat transfer model is established according to the pipeline diameter and flow rate: Q = K·πD·L·ΔT / (ln(r2 / r1)), where K is the comprehensive heat transfer coefficient, and the PID parameters are dynamically adjusted.

[0014] Preferably, the lithium battery pack of the power supply module is configured with a balanced charging management circuit, and the BQ76940 chip is used to monitor the voltage of each single battery and communicate with the control module through the I2C interface.

[0015] Preferably, a phase change energy storage layer is provided between the heating module and the outer wall of the pipeline. The phase change material is a paraffin-expanded graphite composite, with a phase change temperature range of 3-5 °C and a thickness of 2-3 mm, and it is bonded to the outer wall of the pipeline and the heating tape through hot melt adhesive.

[0016] Preferably, the control module has a built-in self-check program, which regularly performs heating circuit impedance detection and sensor calibration every day. When the impedance change of the heating tape is detected to exceed ±15%, it automatically marks the faulty area and starts the standby heating mode.

[0017] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0018] The fire-fighting water anti-freezing device for fire protection in the present application uses three PT1000 platinum resistance temperature sensors in the temperature acquisition module to continuously monitor the temperatures at the water inlet end, the middle section, and the fire hydrant interface section of the fire pipeline, and transmits the collected temperature signals to the AD conversion interface of the control module through shielded signal lines. The STM32F407 microcontroller in the control module analyzes the temperature gradient change rate of each temperature measurement area through the built-in temperature control algorithm module, and uses the PID regulation method to dynamically adjust the duty cycle parameter output by the PWM output interface, and then controls the heating power of the flexible silicone heating tape in the corresponding area of the heating module through the power drive circuit, realizing precise temperature control by area and time; the power supply module converts the 220V commercial power through the AC / DC conversion unit and supplies power in parallel with the lithium battery pack. When the commercial power voltage is lower than 198V, the power supply switching circuit automatically switches to lithium battery power supply to ensure the continuous operation of the system; the alarm module triggers the audible and visual alarm and sends an alarm signal to the monitoring center through the LORA wireless module when the temperature in any temperature measurement area exceeds 50 °C or the temperature difference between adjacent areas is greater than 15 °C. Therefore, it effectively avoids the problem of excessive local temperature caused by improper temperature control of the heating device in the traditional solution. Through the combination of distributed temperature measurement, dynamic PID regulation, and independent heating by area, while ensuring that the fire-fighting water does not freeze, it prevents the pipeline material from aging and damage due to overheating, improving the reliability and safety of the system.

[0019] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent description, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be learned from the practice of the present invention. Description of the Drawings

[0020] Figure 1 Schematic diagram of the structural framework relationship of a temperature-controlled anti-freezing device for a fire hydrant according to the present invention;

[0021] Figure 2 Schematic diagram of the secondary structural framework relationship of a temperature-controlled anti-freezing device for a fire hydrant according to the present invention;

[0022] Figure 3 General flowchart of a temperature-controlled anti-freezing device for a fire hydrant according to the present invention;

[0023] Figure 4 Drive circuit diagram of a temperature-controlled anti-freezing device for a fire hydrant according to the present invention;

[0024] Figure 5 Voltage stabilizing circuit diagram of a temperature-controlled anti-freezing device for a fire hydrant according to the present invention. Specific implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] It should be noted that the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation manner.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs; the terms used in the specification of the present invention herein are only for the purpose of describing specific implementation manners and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0028] As shown in the figure, a temperature-controlled anti-freezing device for a fire hydrant mainly consists of a temperature acquisition module, a control module, a heating module, a power supply module, and an alarm module. The temperature acquisition module is connected to the AD conversion interface of the control module through a shielded signal line. The heating module is connected to the PWM output interface of the control module through a power drive circuit. The power supply module supplies power to each module through a DC-DC voltage stabilization circuit. The alarm module is connected to the GPIO interface of the control module. The temperature acquisition module includes at least three PT1000 platinum resistance temperature sensors, which are embedded in the insulation layer on the outer wall of the fire pipeline and are evenly distributed along the pipeline axis in three temperature measurement areas: the water inlet end, the middle section, and the fire hydrant interface section. The heating module is composed of several flexible silicone heating tapes. Each heating tape is embedded with parallel nickel-chromium alloy heating wires. Each heating tape is tightly attached to the outer wall of the pipeline through a snap-fastening structure and is divided into three independent heating zones according to the temperature measurement areas. Each heating zone is respectively connected to an independent MOSFET drive circuit. The control module includes an STM32F407 microcontroller, which is internally integrated with a temperature control algorithm module. It is connected to a remote monitoring terminal through an RS485 bus. The algorithm module calculates the temperature gradient change rate of each temperature measurement area in real time and dynamically adjusts the duty cycle parameter of the corresponding heating zone by using the PID regulation method. The power supply module includes an AC / DC conversion unit, a lithium battery pack, and a power supply switching circuit. The input end of the AC / DC conversion unit is connected to the 220V mains electricity, and the output end is connected in parallel with the lithium battery pack through a Schottky diode. The power supply switching circuit includes a voltage comparator and a relay array, and automatically switches to lithium battery power supply when the mains voltage is lower than 198V. The alarm module includes an audible and visual alarm and a wireless transmission unit. When the temperature of any temperature measurement area exceeds 50°C or the temperature difference between adjacent areas is greater than 15°C, an alarm signal is triggered and sent to the monitoring center through the LORA wireless module.

[0029] In this implementation scheme, the temperature acquisition module uses a high-precision PT1000 platinum resistance temperature sensor, which has the characteristics of a wide measurement range (-50°C to 150°C), a fast response speed (<5 s), and good long-term stability. Combined with the embedded installation method and the aerogel insulation layer, it can not only accurately sense the temperature change of the pipeline but also effectively isolate the interference of the external environment. The control module selects the STM32F407 microcontroller. Its 168 MHz main frequency and floating-point operation unit can quickly process temperature data. The built-in PID algorithm can adjust the heating power in real time according to the temperature gradient change rate, and the temperature control accuracy can reach ±0.5°C. The RS485 bus communication ensures reliable transmission for remote monitoring. The heating module uses a flexible silicone heating tape with a nickel-chromium alloy heating wire, which has the advantages of high temperature resistance (up to 200°C), good flexibility, and uniform heat generation. The MOSFET drive circuit with independent zone control can achieve precise temperature zone management and avoid local overheating. The power supply module is powered by both AC / DC conversion and a lithium battery pack, and the voltage comparator is used to achieve automatic switching in milliseconds to ensure the continuous operation of the system in extreme weather. The alarm module integrates audible and visual alarms and LoRa wireless transmission, which has the characteristics of a long transmission distance (>5 km) and strong anti-interference ability, and can give real-time warnings of system abnormalities. Through optimized design, each module forms a synergistic effect and can work stably within the environmental temperature range of -30°C to 50°C, saving more than 30% energy compared with the traditional scheme, effectively solving the dual needs of fire water antifreeze and pipeline protection.

[0030] As shown in the figure, the fire water anti-freezing device has multiple innovative designs and advantages. The temperature acquisition module is equipped with a redundant temperature measurement structure. Two PT1000 sensors are arranged in each temperature measurement area, and an average value signal is output through a differential amplification circuit. Moreover, the insulating layer uses aerogel composite material with an extremely low thermal conductivity, effectively improving the temperature measurement accuracy and heat preservation effect. The MOSFET drive circuit of the heating module includes an IRF540N power tube and a high-speed optocoupler isolator. The gate drive signal is electrically isolated through the TLP250 optocoupler. A current sampling resistor is connected in series at the source, and the sampling signal is fed back to the ADC interface of the control module to ensure the stability and safety of the heating process. The temperature control algorithm module of the control module includes a dynamic temperature compensation unit. When the ambient temperature sensor detects that the ambient temperature is lower than -10°C, the target temperature setting value is automatically increased, and a heat transfer model is established based on the pipe diameter and flow rate to dynamically adjust the PID parameters to achieve precise temperature control. The lithium battery pack of the power module is configured with a balanced charging management circuit. The BQ76940 chip is used to monitor the voltage of each single battery and communicate with the control module through the I2C interface to ensure the reliability and long-term performance of the power supply. In addition, a phase change energy storage layer is provided between the heating module and the outer wall of the pipe. The phase change material is a paraffin-expanded graphite composite, with a phase change temperature range of 3 - 5°C and a thickness of 2 - 3 mm. It is bonded to the outer wall of the pipe and the heating tape through hot melt adhesive, which can effectively store and release heat, further enhancing the anti-freezing effect. The control module also has a built-in self-check program, which regularly performs heating circuit impedance detection and sensor calibration every day. When it detects that the impedance change of the heating tape exceeds ±15%, it automatically marks the faulty area and activates the standby heating mode to ensure the long-term stable operation and reliability of the device.

[0031] Meanwhile,

[0032] Traditional fire anti-freezing devices usually adopt a single temperature sensor or uniform heating method, which is prone to cause uneven local temperature. In this solution, at least three PT1000 platinum resistance temperature sensors are respectively deployed at the water inlet end, the middle section, and the fire hydrant interface section of the fire pipeline, and divided into three independent heating zones to achieve precise regional temperature control.

[0033] Each temperature measurement area adopts a redundant configuration of two PT1000 sensors, and an average value signal is output through a differential amplification circuit to improve data reliability. The temperature measurement accuracy of PT1000 is ±0.1°C, and the measurement range covers -50°C to 150°C, meeting the requirements of extreme environments.

[0034] Traditional PID control relies on fixed parameters and is difficult to adapt to complex environmental changes. In this solution, a temperature control algorithm module is built into the STM32F407 microcontroller to calculate the temperature gradient change rate of each area in real time and dynamically adjust the PID parameters.

[0035] The integrated heat transfer model of the algorithm module is Q = K·πD·L·ΔT / (ln(r2 / r1)), where the comprehensive heat transfer coefficient K is calibrated experimentally to be 1.2 - 1.8 W / (m 2 ·K), and it is applicable to scenarios with different pipe diameters (DN50 - DN200) and flow velocities (0.5 - 3 m / s).

[0036] In the traditional heating belt, it is in direct contact with the pipeline, and the heat loss is fast. In this solution, a paraffin-expanded graphite composite phase change layer with a thickness of 2 - 3 mm and a phase change temperature of 3 - 5 °C is added between the heating module and the outer wall of the pipeline, which can absorb excess heat and release it at low temperatures.

[0037] The thermal conductivity of the phase change material is increased to 5.6 W / (m·K), and the heat storage density reaches 180 kJ / kg. It is bonded to the pipeline through hot melt adhesive, and the peel strength ≥ 2 MPa.

[0038] The traditional solution relies on single mains power supply and is prone to failure during power outages. This solution uses an AC / DC conversion unit in parallel with a lithium battery pack, and realizes automatic switching through a voltage comparator (LM393) and a relay array (HF46F).

[0039] The lithium battery pack is a 48V / 20Ah ternary lithium battery, and a BQ76940 chip is configured to achieve balanced management. The monomer voltage error ≤ 10 mV; when the mains voltage is lower than 198 V, it switches to battery power supply, and the switching delay < 20 ms.

[0040] Other implementation key points and quantization parameters are as follows:

[0041] 1. Temperature acquisition module

[0042] Sensor model: PT1000 platinum resistance (Heraeus M222), accuracy ±0.1 °C, response time < 5 seconds;

[0043] Installation structure: Embedded installation in the aerogel insulation layer (Aske Aerogel-1000), thermal conductivity 0.023 W / (m·K), compressive strength ≥ 0.5 MPa.

[0044] 2. Heating module

[0045] Heating belt parameters: Flexible silicone heating belt (Omega SRFG), rated power 30 W / m, diameter of nickel-chromium alloy heating wire 0.3 mm, resistivity 1.1 Ω / m;

[0046] Drive circuit: IRF540N MOSFET is paired with a TLP250 optocoupler for isolation, the peak drive current is 20 A, and the switching frequency is 10 kHz.

[0047] 3. Control module

[0048] Main control chip: STM32F407 microcontroller, with a main frequency of 168 MHz and an internal 12-bit ADC (sampling rate 1 MHz);

[0049] Communication protocol: RS485 bus (MAX3485 chip), baud rate 115200 bps, transmission distance ≥ 1200 m.

[0050] 4. Power supply module

[0051] AC / DC converter: Mean Well LRS-350-48, input 220V ± 15%, output 48V / 7.3A, efficiency ≥ 90%;

[0052] Lithium battery management: BQ76940 supports 16-series battery monitoring, balancing current 100 mA, communication interface I2C (rate 400 kHz).

[0053] Wireless transmission: LoRa module (Semtech SX1278), frequency band 433 MHz, transmission power 20 dBm, transmission distance ≥ 5 km;

[0054] Acoustic-optic alarm: Omron E2K-X15ME1, sound pressure level ≥ 85 dB, flash frequency 2 Hz.

[0055] In a feasible embodiment,

[0056] 1. Extreme environment test

[0057] Scenario: A fire station in Heilongjiang (average winter temperature -30°C);

[0058] Result: In an environment of -35°C for 72 consecutive hours, the pipeline did not freeze, the maximum heating temperature was 48°C, and there was no local overheating (temperature difference < 10°C).

[0059] 2. Energy consumption comparison experiment

[0060] Traditional solution: Constant power heating, daily power consumption 15.6 kWh;

[0061] This solution: Time-sharing PID regulation + phase change energy storage, daily power consumption 9.8 kWh, energy saving rate 37.2%.

[0062] 3. Fault self-diagnosis verification

[0063] Simulated fault: Manually disconnect the MOSFET drive circuit of a certain heating zone;

[0064] System response: The self-check program detected an impedance anomaly (change +18%) within 30 seconds, activated the standby heating mode and sent an alarm signal to the monitoring center.

[0065] During use, after installation, connect to the 220V mains power supply. The AC / DC conversion unit of the power module starts to work and supplies power to the system. At the same time, the lithium battery pack enters the charging state. After the system starts, the STM32F407 microcontroller of the control module collects the temperature signals of each temperature measurement area in real time through the AD conversion interface. The temperature control algorithm module calculates the temperature gradient change rate and dynamically adjusts the PWM output to the duty cycle parameters of each heating zone using the PID regulation method. When the temperature of a certain area approaches the freezing point, the heating belt of the corresponding zone starts to work. The power supply switching circuit continuously monitors the mains voltage and automatically switches to the lithium battery pack for power supply when the detected voltage is lower than 198V. During use, if the temperature of any temperature measurement area exceeds 50°C or the temperature difference between adjacent areas is greater than 15°C, the alarm module immediately triggers the audible and visual alarm and sends an alarm signal to the monitoring center through the LoRa wireless module. During daily operation, the control module automatically performs heating circuit impedance detection and sensor calibration every day to ensure the long-term stable operation of the system.

[0066] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with this technology can make various modifications and decorations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A temperature-controlled anti-freezing device for a fire hydrant, characterized in that, It includes a temperature acquisition module, a control module, a heating module, a power supply module and an alarm module; the temperature acquisition module is connected to the AD conversion interface of the control module through a shielded signal line, the heating module is connected to the PWM output interface of the control module through a power drive circuit, the power supply module supplies power to each module through a DC-DC voltage stabilization circuit, and the alarm module is connected to the GPIO interface of the control module; The temperature acquisition module includes at least three PT1000 platinum resistance temperature sensors, which are respectively embedded in the insulation layer on the outer wall of the fire pipeline and are evenly distributed along the pipeline axis in three temperature measurement areas: the water inlet end, the middle section and the fire hydrant interface section; The heating module is composed of several flexible silicone heating tapes. Each heating tape is embedded with parallel nickel-chromium alloy heating wires. Each heating tape is tightly attached to the outer wall of the pipeline through a snap-fastening structure and is divided into three independent heating zones according to the temperature measurement areas. Each heating zone is connected to an independent MOSFET drive circuit; The control module includes an STM32F407 microcontroller, which is internally integrated with a temperature control algorithm module and is connected to a remote monitoring terminal through an RS485 bus. The temperature control algorithm module calculates the temperature gradient change rate of each temperature measurement area in real time and dynamically adjusts the duty cycle parameter of the corresponding heating zone by using the PID regulation method; The power supply module includes an AC / DC conversion unit, a lithium battery pack and a power supply switching circuit. The input end of the AC / DC conversion unit is connected to the 220V mains power supply, and the output end is connected in parallel with the lithium battery pack through a Schottky diode. The power supply switching circuit includes a voltage comparator and a relay array, and automatically switches to lithium battery power supply when the mains voltage is lower than 198V; The alarm module includes an audible and visual alarm and a wireless transmission unit. When the temperature of any temperature measurement area exceeds 50°C or the temperature difference between adjacent areas is greater than 15°C, an alarm signal is triggered and sent to the monitoring center through the LORA wireless module.

2. The temperature-controlled anti-freezing device for a fire hydrant according to claim 1, wherein: The temperature acquisition module is provided with a redundant temperature measurement structure. Dual PT1000 sensors are arranged in each temperature measurement area, and an average value signal is output through a differential amplification circuit. The insulation layer is made of aerogel composite material, and the thermal conductivity is ≤0.023W / (m·K).

3. The anti-freezing device for fire fighting water according to claim 1, wherein: The MOSFET drive circuit of the heating module includes an IRF540N power tube and a high-speed optocoupler isolator. The gate drive signal is electrically isolated through a TLP250 optocoupler. A current sampling resistor is connected in series at the source electrode, and the sampling signal is fed back to the ADC interface of the control module.

4. A temperature-controlled anti-freezing device for a fire hydrant according to claim 1, characterized in that: The temperature control algorithm module of the control module includes a dynamic temperature compensation unit. When the ambient temperature sensor detects that the ambient temperature is lower than -10°C, the target temperature setting value is automatically increased by 2-5°C, and a heat transfer model is established according to the pipeline diameter and flow rate: Q = K·πD·L·ΔT / (ln(r2 / r1)), where K is the comprehensive heat transfer coefficient, and the PID parameters are dynamically adjusted.

5. The temperature-controlled anti-freezing device for a fire hydrant according to claim 1, characterized in that: The lithium battery pack of the power supply module is configured with a balanced charging management circuit, which uses a BQ76940 chip to monitor the voltage of each single battery and communicates with the control module through an I2C interface.

6. The temperature-controlled anti-freezing device for a fire hydrant according to claim 1, wherein: A phase change energy storage layer is provided between the heating module and the outer wall of the pipeline. The phase change material is a paraffin-expanded graphite composite with a phase change temperature range of 3 - 5°C and a thickness of 2 - 3 mm, which is bonded to the outer wall of the pipeline and the heating tape through hot melt adhesive.

7. The temperature-controlled anti-freezing device for a fire hydrant according to claim 1, characterized in that: The control module has a built-in self-check program that regularly performs heating circuit impedance detection and sensor calibration every day. When the detected impedance change of the heating tape exceeds ±15%, it automatically marks the faulty area and activates the standby heating mode.

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