A fire source safety exposure distance detection system and a detection method thereof

Abstract

The application discloses a fire source safety exposure distance detection system, comprising: a heat source simulation module, which is used for simulating the fire source condition when a fire breaks out and controlling the temperature to be stable at a set value; a fabric moving device, which is used for fixing the fabric of an experimental sample and adjusting the distance between the heat source and the fabric; and a data acquisition module, which is used for collecting the environmental temperature in the heat exposure process, collecting the size of the heat flux density reaching the sensor surface through the fabric and collecting information from the simulated skin. The application provides the fire source safety exposure distance detection system, confirms the fire source safety exposure distance under the safe condition, facilitates people to better collect data, is used for evaluating the safety exposure distance of the firefighter under the fire environment, and facilitates improving the fire extinguishing safety and working efficiency of the firefighter. The application also provides a detection method.

Description

Technical Field

[0001] This invention relates to the field of fire source safety exposure distance detection technology, and in particular to a fire source safety exposure distance detection system and its detection method. Background Technology

[0002] Due to the complexity of the fire environment, fire suits alone are insufficient to guarantee the safety of firefighters. The safety of firefighters depends more on the risk assessment of the fire environment. This has led to research on the safe distance for firefighters, with the aim of minimizing the occurrence of accidents such as heat stress and burns by controlling the distance between firefighters and flames.

[0003] The safe distance for firefighters is difficult to calculate through real-life experiments in a fire environment. Early researchers mainly relied on empirical summaries based on firefighters' descriptions of firefighting situations. However, due to the variability of the fire environment, it is difficult to accurately predict the safe distance for firefighters (Page WG, Butler B W. An empirically based approach to defining wildland firefighter safety and survival zone separation distances[J]. International Journal of Wildland Fire, 2017, 26(8):655-667). Subsequently, researchers attempted to use mathematical models to predict the safe distance for firefighters. However, the models focused on simulating heat transfer in the fire environment, simplifying the simulation of heat transfer in fire suits, the air layer under the suit, and human tissue (Yuan Jing, Song Wenhua, Zhang Ru, Xie Shujun. Study on safe distance for fire rescue in crude oil storage tank fire [J]. Fire Science and Technology, 2009, 28(2): 124-126; Liao Yufan, Chen Juanjuan, Fang Zheng. Safe rescue distance for firefighters in oil tank fire [J]. Fire Science and Technology, 2017 (1): 107-110.). At the same time, existing models cannot be directly used to predict human skin burns, and have problems such as large prediction errors and low applicability (Butler BW, Cohen J D. Firefighter safety zones: atheoretical model based on radiative heating [J]. International Journal of Wildland Fire, 1998, 8(2): 73-77).

[0004] Existing experimental testing devices are mainly used for evaluating the thermal protection performance of fire suits. The distance between the heat source and the test sample is kept constant. The impact of the heat transfer performance of the clothing on human burns under different heat source distances is not considered. At the same time, the existing thermal protection performance evaluation criteria are not applicable to the evaluation of safe exposure distance. Therefore, there is a lack of testing devices and evaluation methods for safe exposure distance, which cannot be used to evaluate the safe exposure distance of firefighters in firefighting operations. Summary of the Invention

[0005] The purpose of this invention is to provide a fire source safety exposure distance detection system, which confirms the detection of fire source safety exposure distance under safe conditions, facilitates better data collection, evaluates the safe exposure distance of firefighters in fire environments, and helps improve firefighters' firefighting safety and work efficiency.

[0006] The technical solution adopted by the fire source safety exposure distance detection system and detection method disclosed in this invention is as follows:

[0007] A fire source safety exposure distance detection system, comprising:

[0008] The heat source simulation module is used to simulate the fire source situation when a fire occurs and to control the temperature to be stable at a set value.

[0009] Fabric moving device, used to fix the fabric of the experimental sample, and to adjust the distance between the heat source and the fabric;

[0010] The data acquisition module is used to collect ambient temperature during heat exposure, the amount of heat flux density reaching the sensor surface through the fabric, and to collect information by simulating skin.

[0011] As a preferred embodiment, the heat source simulation module includes: a heat exposure simulation chamber, a heat radiation plate, and an intelligent temperature controller.

[0012] One side of the heat exposure simulation chamber is made of high-temperature resistant quartz glass, while the rest is made of high-temperature resistant polytetrafluoroethylene.

[0013] The heat radiation plate is fixed to one side of the heat exposure simulation box, and the heat radiation plate is made of nickel-chromium wire and ceramic. The nickel-chromium wire is cast into the ceramic and fired at high temperature. The heat radiation temperature of the heat radiation plate can be adjusted independently, and the temperature adjustment range is 200℃~550℃.

[0014] The intelligent temperature controller uses signal voltage triggering and is mainly used to control the temperature of the heat radiation plate to stabilize at the set value.

[0015] As a preferred embodiment, the ceramic is a far-infrared ceramic radiating plate with an emissivity as high as 0.9.

[0016] As a preferred embodiment, the fabric moving device comprises a fabric clamping device and a moving slide rail. The fabric clamping device is used to fix the fabric of the experimental sample and is located on one side of the heat radiation plate. The moving slide rail enables parallel forward and backward movement of the fabric to adjust the distance between the heat source and the fabric.

[0017] As a preferred embodiment, the data acquisition module includes a K-type thermocouple, a heat flux density sensor, and a data logger. The K-type thermocouple is placed 5 cm away from the heat source and the fabric, with a temperature measurement range of -260℃ to 260℃. The heat flux density sensor collects the amount of heat flux density reaching the sensor surface through the fabric. The sensor has an embedded simulated skin sensor to simulate skin for information collection. The data logger is used in conjunction with a data acquisition card and acquisition software to collect, record, view, and analyze the data collected by the K-type thermocouple and the heat flux density sensor. The data acquisition card can export the data to a computer system, facilitating user-defined data analysis. The data acquisition software allows users to view or control the status of the data logger.

[0018] As a preferred embodiment, the heat flux density sensor is equipped with a water cooling device on its back. The water cooling device includes a copper plate and a copper tube. The copper tube is placed on the back of the copper plate and is circulated and wound around it. The water flow rate and water temperature inside the copper tube can be adjusted according to experimental needs.

[0019] A detection method based on the above-mentioned fire source safety exposure distance detection system.

[0020] The degree of burns to human skin is calculated based on Henriques' skin burn integral model, as shown in Formula 1 below:

[0021] (1)

[0022] In the formula, Ω is the quantitative value of the degree of skin burn, which is dimensionless; ΔE is the skin activation energy, which is dimensionless; P is the frequency disruption factor, which is dimensionless; R is the ideal gas constant, with a value of 8.31 J / mol ℃; T is the absolute skin temperature; and t is the time (s) during which the absolute skin temperature T > 44℃.

[0023] When the Ω value at the junction of the epidermis and dermis satisfies 0.53≤Ω<1.0, a first-degree burn will be achieved in the epidermis.

[0024] When Ω ≥ 1.0, the skin is considered to have suffered a second-degree burn.

[0025] When the Ω value at the junction of the dermis and subcutaneous tissue is ≥1.0, the skin is considered to have suffered a third-degree burn.

[0026] When the fabric is at a safe exposure distance, the heat flux density received by the heat flux density sensor surface is approximately 0.7 kW / m². 2 The fabric was placed in a heat flux density of 0.7 kW / m². 2 The location of the heat source is determined, and the change in heat flux density at that distance is measured and collected. Substituting this data into the skin heat transfer equation, the temperature change at the interface between the epidermis and dermis can be calculated. Assuming that heat is transferred one-dimensionally along the skin thickness direction, according to Fourier's law, the skin epidermal heat transfer equation is shown in Equation 2:

[0027] (2)

[0028] Where t and x represent time and location, ρ and c represent the density and specific heat of the skin layer, k is the thermal conductivity, and T is the temperature value at the corresponding time and location;

[0029] Because the dermis and epidermis have different structures, there is an influence of blood perfusion heat transfer. Therefore, the heat transfer equation of the epidermis is as shown in formula (3):

[0030] (3)

[0031] in, For blood perfusion rate, Blood flow density, Blood flow is hotter than heat. The initial temperature;

[0032] To facilitate the calculation and solution of the skin heat transfer equation, the boundary conditions for the epidermis, dermis, and subcutaneous tissue are set as follows:

[0033] (4)

[0034] , (5)

[0035] , (6)

[0036] in, , , These are the thermal conductivity (W / m K) of the epidermis, dermis, and subcutaneous tissue, respectively. , These are the upper and lower surfaces of the dermis, respectively. , These are the upper and lower surfaces of the subcutaneous tissue, respectively. To measure the heat flux density reaching the skin surface, the heat transfer equation described above can be discretized and solved using the finite difference method to obtain the change in human skin temperature with heat exposure time.

[0037] As a preferred option, in order to predict the safe exposure distance of firefighters in a large-scale fire environment, it is necessary to further convert the data obtained from the experiment. The Origin software is used to perform nonlinear curve fitting to establish the functional relationship between fire source height, fire source temperature, heat source distance and heat flux density. The final fitted function is shown in formula (7):

[0038] (7)

[0039] in, The height of the fire source, The temperature of the fire source. Distance from the heat source For heat flux density, the correlation coefficient R of the fitted curve is... 2 =0.838, indicating a high degree of fit;

[0040] By measuring the heat source distance corresponding to different heat flux densities in small-scale fabric experiments, a fitting relationship between heat flux density and heat source distance under small-scale fabric experiments was established. The fitting equation is shown in formula (8).

[0041] (8)

[0042] in, The heat flux density is measured in small-scale fabric experiments. The distance (cm) of the heat source in the small-scale fabric experiment, and the correlation coefficient R of the fitted curve. 2 =0.999, indicating a high degree of fit;

[0043] Substituting formula (7) into formula (8), we can obtain the conversion relationship between the heat source distance in a large-scale fire environment and the heat source distance in a small-scale fabric experiment, as shown in formula (9):

[0044] (9)

[0045] When converting the distance of the heat source in a small-scale fabric experiment to the distance of the heat source in a large-scale fire environment, the height and temperature of the fire source must be set.

[0046] The beneficial effects of the fire source safety exposure distance detection system disclosed in this invention are as follows: Through the constructed safety exposure distance assessment device, the distance between firefighters and the fire environment can be simulated and adjusted, enabling human safety risk assessment at different exposure distances. A temperature threshold is established as the evaluation standard for determining the safety exposure distance, solving the problem of inconsistent heat flux density thresholds used in existing technologies. Simultaneously, the method of determining the safety exposure distance using a skin temperature threshold improves upon the shortcomings of the safe heat flux density method in simplifying the thermal protection performance of clothing, while more intuitively demonstrating the burn situation of human skin. A standardized evaluation method for safety exposure distance is proposed, enabling the measurement of safety exposure distance under small-scale experimental simulation environments. By utilizing the conversion relationship between safety exposure distance under small-scale experimental simulation environments and full-scale fire environments, it can be used to predict the safety exposure distance of firefighters in real firefighting operation environments. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the structure of a fire source safety exposure distance detection system according to the present invention.

[0048] Figure 2 This invention relates to the calibration of a safe exposure distance measurement device under empty plate conditions, which is a detection method of the present invention. Detailed Implementation

[0049] The present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings.

[0050] Please refer to Figure 1 A fire source safety exposure distance detection system, comprising:

[0051] The heat source simulation module is used to simulate the fire source situation when a fire occurs and to control the temperature to be stable at a set value.

[0052] The heat source simulation module includes: a heat exposure simulation chamber 3, a heat radiation plate 1, and an intelligent temperature controller 2. One side of the heat exposure simulation chamber 3 is made of high-temperature resistant quartz glass, and the rest is made of high-temperature resistant polytetrafluoroethylene. The heat radiation plate 1 is fixed to one side of the heat exposure simulation chamber 3 and is made of nickel-chromium wire and ceramic. The nickel-chromium wire is cast into the ceramic and fired at high temperature. The heat radiation temperature of the heat radiation plate 1 can be adjusted autonomously, with a temperature adjustment range of 200℃~550℃. The intelligent temperature controller 2 is triggered by a signal voltage and is mainly used to control the temperature of the heat radiation plate 1 to stabilize at the set value. The ceramic is a far-infrared ceramic radiation plate with an emissivity of up to 0.9.

[0053] The fabric moving device 4 is used to fix the fabric of the experimental sample and adjust the distance between the heat source and the fabric. The fabric moving device 4 consists of a fabric clamping device 5 and a moving slide rail 6. The fabric clamping device 5 is used to fix the fabric of the experimental sample and is located on one side of the heat radiation plate 1. The moving slide rail 6 enables the fabric to move back and forth in parallel to adjust the distance between the heat source and the fabric.

[0054] The data acquisition module is used to collect ambient temperature during heat exposure, the amount of heat flux density reaching the sensor surface through the fabric, and to collect information by simulating skin.

[0055] The data acquisition module includes a K-type thermocouple 10, a heat flux density sensor 7, and a data logger 11. The K-type thermocouple 10 is placed 5 cm away from the heat source and the fabric, and its temperature measurement range is -260℃ to 260℃. The heat flux density sensor 7 collects the amount of heat flux density reaching the sensor surface through the fabric. The sensor has a simulated skin sensor embedded inside to simulate skin for information collection. The data logger 11 is used in conjunction with the acquisition card and acquisition software to collect, record, view, and analyze the data collected by the K-type thermocouple 10 and the heat flux density sensor 7. The acquisition card can export the data to the computer system 12, which is convenient for users to perform customized data analysis. The acquisition software can be used to view or control the status of the data logger 11.

[0056] The heat flux density sensor 7 has a water cooling device 8 on its back. The water cooling device 8 includes a copper plate and a copper tube 9. The copper tube 9 is placed on the back of the copper plate and is wound in a loop. The water flow rate and water temperature inside the copper tube 9 can be adjusted according to the experimental needs.

[0057] A detection method based on the above-mentioned fire source safety exposure distance detection system.

[0058] Since heat flux density is measured because it affects the severity of skin burns, previous studies have largely used it as a criterion for evaluating safe exposure distance. This invention uses skin burns as a direct basis, replacing the heat flux density threshold with a skin temperature threshold as the evaluation criterion for safe exposure distance. This provides a more intuitive representation of human skin burn conditions and improves the accuracy of prediction results. To determine the severity of human skin burns, calculations are performed based on the Henriques skin burn integral model, as shown in the following formula:

[0059] (1)

[0060] In the formula, Ω is the quantitative value of the degree of skin burn, dimensionless; ΔE is the skin activation energy, dimensionless; P is the frequency disruption factor, dimensionless; R is the ideal gas constant, with a value of 8.31 J / mol ℃; T is the absolute skin temperature; and t is the time (s) for the absolute skin temperature T > 44℃. When the Ω value at the junction of the epidermis and dermis satisfies 0.53 ≤ Ω < 1.0, a first-degree burn will occur in the epidermis; when Ω ≥ 1.0, a second-degree burn will occur. When the Ω value at the junction of the dermis and subcutaneous tissue is ≥ 1.0, a third-degree burn will occur. The model shows that when the temperature at the junction of the epidermis and dermis remains above 44℃, a second-degree burn will occur and the burn will be irreversible. Therefore, this paper uses 44℃ as the skin temperature threshold to determine the safe exposure distance. When the stable temperature reaches 44℃, the distance between the heat source and the fabric is the safe exposure distance.

[0061] Preliminary experiments show that when the fabric is at a safe exposure distance, the heat flux density received by the heat flux density sensor surface is approximately 0.7 kW / m². 2 Therefore, the fabric was placed in a heat flux density of 0.7 kW / m². 2 The location of the heat source is determined, and the change in heat flux density at the distance from the heat source is measured and collected. The data is then substituted into the skin heat transfer equation to calculate the temperature change at the junction of the epidermis and dermis. Assuming that heat is transferred one-dimensionally along the skin thickness direction, according to Fourier's law, the skin epidermal heat transfer equation is shown in formula (2):

[0062] (2)

[0063] Where t and x represent time and location, ρ and c represent the density and specific heat of the skin layer, k is the thermal conductivity, and T is the temperature value at the corresponding time and location. Due to the different structures of the dermis and epidermis, there is an influence of blood perfusion heat transfer. Therefore, the heat transfer equation of the epidermis is as shown in formula (3):

[0064] (3)

[0065] in, For blood perfusion rate, Blood flow density, Blood flow is hotter than heat. The initial temperature is given. To facilitate the calculation and solution of the skin heat transfer equation, the boundary conditions for the epidermis, dermis, and subcutaneous tissue are set as follows.

[0066] (4)

[0067] , (5)

[0068] , (6)

[0069] in, , , These are the thermal conductivity (W / m K) of the epidermis, dermis, and subcutaneous tissue, respectively. , These are the upper and lower surfaces of the dermis, respectively. , These are the upper and lower surfaces of the subcutaneous tissue, respectively. To measure the heat flux density reaching the skin surface, the heat transfer equation described above can be discretized and solved using the finite difference method to obtain the change in human skin temperature with heat exposure time.

[0070] After obtaining the change value of human skin temperature each time, the stabilized skin temperature is compared with the temperature threshold of 44℃. If it is greater than 44℃, the distance to the heat source is increased and the test is repeated; otherwise, the distance to the heat source is decreased and the test is repeated. To ensure the operability of the experiment, the change in heat source distance is determined to be 0.5 m. Through continuous modification and testing, the heat source distance at which the skin temperature stabilizes at 44℃ can be finally obtained, which is the safe exposure distance.

[0071] Because the heat radiation panel used in small-scale fabric experiments to simulate heat sources differs significantly from the fire source in real fire situations, further calculations are needed to convert the data obtained from the experiments in order to predict the safe exposure distance for firefighters in large-scale fire environments.

[0072] During a fire, numerous factors influence the safe exposure distance of firefighters, such as terrain, fire source shape, and fire source temperature. Therefore, the conversion relationship of safe exposure distance under different conditions cannot be established using only a single variable. Heat flux density, as an important standard for evaluating the magnitude of thermal radiation, can reflect the fire environment to a certain extent. Therefore, heat flux density can be used as a correlation quantity to connect small-scale fabric experimental environments with large-scale fire environments, establishing a conversion equation. By reviewing the literature, we summarized and organized the data measured by researchers in large-scale fire environments, including fire source height, fire source temperature, heat source distance, and the corresponding heat flux density at that distance, as shown in Table 1.

[0073] Table 1. Specific information on large-scale fire experiments

[0074]

[0075] The Origin software was used to perform nonlinear curve fitting to establish the functional relationship between the fire source height, fire source temperature, heat source distance and heat flux density. The final fitted function is shown in formula (7):

[0076] (7)

[0077] in, The height of the fire source, The temperature of the fire source. Distance from the heat source The heat flux density is given. The correlation coefficient R of the fitted curve is given. 2 =0.838, indicating a high degree of fit.

[0078] By using the heat source distance corresponding to different heat flux densities measured in small-scale fabric experiments, a fitting relationship between heat flux density and heat source distance under small-scale fabric experiments is established. The fitting equation is shown in formula (8).

[0079] (8)

[0080] in, The heat flux density is measured in small-scale fabric experiments. The distance (cm) of the heat source in the small-scale fabric experiment, and the correlation coefficient R of the fitted curve. 2 =0.999, indicating a high degree of fit. Substituting formula (7) into formula (8), the conversion relationship between the heat source distance under large-scale fire conditions and the heat source distance under small-scale fabric experiments can be obtained, as shown in formula (9):

[0081] (9)

[0082] As the formula shows, when converting the heat source distance between small-scale fabric experiments and large-scale fire environments, the fire source height and temperature must be set. Considering that surface fires occur most frequently in real forest fires, accounting for approximately 94% of all forest fires, and that surface fires are typically low to medium intensity fires with a fire source height ranging from 0.5m to 3.0m, the fire source height is set to the maximum value of 3m for low to medium intensity fires. The fire source temperature is kept consistent with that of the small-scale fabric experiments, and is set to 450℃ to simulate a low-heat radiation environment.

[0083] The specific steps include the following: According to the test requirements, the experimental sample was cut into 150 mm × 150 mm pieces and placed under conditions of (20±2)℃ and 65%±5% relative humidity for 24 hours to allow it to humidify before sealing and removing it; the data logger was connected, the 2040 series 2F16 channel was selected, and the acquisition interval was set to once every 1 second; the heat source temperature was set using the intelligent temperature controller, the heat radiation plate was turned on for heating, and the water cooling device on the back of the heat flux density sensor was turned on for cooling; the fabric was fixed on the fabric clamping device, and after the heat radiation plate temperature rose to the set temperature, the heat exposure simulation chamber was opened, and the timer was started for 20 minutes of heat exposure. The safe exposure distance was measured according to the safe exposure distance evaluation method.

[0084] To ensure the reliability and accuracy of the experimental data obtained from the experimental setup, the setup needs to be calibrated according to ASTM F2731-11. First, the heat flux density under the condition of an empty plate (without fabric coverage) was measured. The heat source temperature was set to 450℃, and the heat exposure distance was 95 mm. The results are shown below. Figure 2 As shown in the figure. The results show that after an exposure time of 20 s, the heat flux density reaching the sensor surface tends to stabilize and the data stabilizes at 8 kW / m². 2 ~8.5 kW / m 2 The ASTM F2731-11 standard specifies that the calibrated heat flux density for radiant heat exposure is the average value over the last 50 seconds after stabilization. Therefore, the average heat flux density after three repeated experiments is calculated to be 8.44 kW / m³. 2 It conforms to the heat flux density range (8.5 ± 0.5 kW / m³) under ASTM F2731-11 standard. 2 In addition, the standard deviation and coefficient of variation of the experimental results under the three thermal radiation exposure calibrations were 0.026 kW / m². 2 The results of the three repeated measurements were 0.308%, indicating that the results had a small standard deviation and coefficient of variation, and the numerical fluctuation was small. Therefore, the safety exposure distance test device has good accuracy and stability.

[0085] Error analysis was then performed on the experimental testing device. Three repeated measurements were conducted under each of the three fabric conditions. The data in the table show that the standard deviation under all three conditions was less than 0.02 kW / m. 2 The dispersion index is between 0.445% and 1.326%, indicating that the experimental test results have low dispersion and small fluctuation under the three different conditions. Therefore, the test results of the safety exposure distance assessment device have good accuracy and repeatability.

[0086] Table 2 Error Analysis of Test Results of Safety Exposure Distance Measurement Device under Different Conditions

[0087]

[0088] Existing methods for evaluating safe exposure distance mainly include empirical prediction and numerical simulation. Empirical prediction is simple to calculate but has large deviations and limited applicability, while numerical simulation is complex in principle, difficult to solve, and hard to verify effectively. Currently, there is a lack of experimental evaluation methods and devices for safe exposure distance. The safe exposure distance measurement device and method developed in this invention have high accuracy and repeatability and can be used to evaluate the safe exposure distance of firefighters during firefighting operations.

[0089] This invention provides a fire source safety exposure distance detection system. Through the constructed safety exposure distance assessment device, it can simulate and adjust the distance between firefighters and the fire environment, realizing human safety risk assessment at different exposure distances. It establishes a skin temperature threshold as the evaluation standard for determining the safety exposure distance, solving the problem of inconsistent skin heat flux density thresholds used in existing technologies. Furthermore, the method of determining the safety exposure distance using the skin temperature threshold improves upon the shortcomings of the safe heat flux density method in simplifying the thermal protection performance of clothing, while providing a more intuitive display of human skin burn conditions. A standardized evaluation method for safety exposure distance is proposed, enabling the measurement of safety exposure distance in small-scale experimental simulation environments. By utilizing the conversion relationship between safety exposure distances in small-scale experimental simulation environments and full-scale fire environments, it can be used to predict the safety exposure distance of firefighters in real firefighting operation environments.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A detection method of a fire source safety exposure distance detection system, characterized by, Comprising a heat source simulation module for simulating the heat source condition when a fire occurs and controlling the temperature to be stable at a set value; a fabric moving device for fixing the fabric of the experimental sample and adjusting the distance between the heat source and the fabric; a data acquisition module for acquiring the ambient temperature during heat exposure, acquiring the heat flux density through the fabric to the sensor surface, and collecting simulated skin information; The degree of burn of human skin is calculated based on the Henriques skin burn integral model, and the calculation formula 1 is as follows: （1） In the formula, Ω is a quantitative value of the degree of skin burn, dimensionless; ΔE is the skin activation energy, dimensionless; P is a frequency damage factor, dimensionless; R is an ideal gas constant, the value is 8.31 J / mol ℃; is the absolute temperature of the skin; is the time (s) when the skin absolute temperature T> 44℃; When the value Ω located at the junction of the epidermis and the dermis satisfies 0.53≤Ω<1.0, first-degree burn will occur in the epidermis; When Ω≥1.0, the skin reaches the second-degree burn; When Ω≥1.0 at the junction of the dermis and the subcutaneous tissue, the skin reaches the third-degree burn; The heat flux density received by the heat flux density sensor surface is about 0.7 The fabric is placed at a position with a heat flux density of 0.7 The heat flux density change at the distance of the heat source is measured and collected, the data is substituted into the skin heat transfer equation, the temperature change at the junction of the epidermis and the dermis is calculated, it is assumed that the heat is transferred in one dimension along the thickness direction of the skin, and the skin epidermis heat transfer equation is shown in formula 2 according to the Fourier law: （2） Wherein, t, x respectively represent time and position, ρ, c respectively represent the density and specific heat of the skin layer, k is the thermal conductivity, T is the temperature value of the time and position; Due to the different structures of the dermis and the epidermis, there is a blood perfusion heat transfer effect, so the heat transfer equation of the epidermis is as shown in formula (3): （3） wherein, is the blood perfusion rate, is the blood density, is the blood specific heat, is the initial temperature; In order to facilitate the calculation and solution of the skin heat transfer equation, the boundary conditions of the epidermis, dermis and subcutaneous tissue are set as follows: （4） ， （5） ， （6） wherein, , , K are the thermal conductivities of the epidermis, dermis and subcutaneous tissue respectively (W / m K), , are the upper and lower surfaces of the dermis respectively, , are the upper and lower surfaces of the subcutaneous tissue respectively, The heat flux density reaching the skin surface is measured, and the change in the skin temperature of the human body with the heat exposure time is obtained by discretely solving the above heat transfer equations (2) and (3) by the finite difference method. The conversion relationship between the heat source distance in large-scale fire environment and the heat source distance in small-scale fabric experiment is as shown in formula (9): （9） is the heat source distance (cm) for small scale fabric experiments, is the fire height, is the fire temperature, is the heat source distance.

2. The detection method of a fire source safety exposure distance detection system according to claim 1, characterized in that, The heat source simulation module comprises a heat exposure simulation box, a heat radiation plate and an intelligent temperature controller: One side of the heat exposure simulation box is made of high-temperature resistant quartz glass plate, and the rest is made of high-temperature resistant polytetrafluoroethylene; The heat radiation plate is fixed on one side of the heat exposure simulation box, and the heat radiation plate is made of nichrome wire and ceramic, the nichrome wire is cast into the ceramic, and the heat radiation plate is made by high-temperature sintering, the heat radiation temperature of the heat radiation plate can be adjusted independently, and the temperature adjustment range is 200-550℃; The intelligent temperature controller uses signal voltage triggering, mainly used for controlling the temperature of the heat radiation plate to be stable at the set value.

3. A method of detecting a fire source safety exposure distance detection system as defined in claim 2, wherein, The ceramic is a far-infrared ceramic radiation plate with an emissivity of up to 0.

9.

4. The method of claim 1, wherein the method further comprises: determining the distance between the fire source and the object based on the detected distance between the fire source and the object and the determined distance between the fire source and the object. The fabric moving device is composed of a fabric clamping device and a moving slide rail, the fabric clamping device is used to fix the fabric of the experimental sample, the fabric clamping device is arranged on one side of the heat radiation plate, and the moving slide rail realizes the forward and backward parallel movement of the fabric, which is used to adjust the distance between the heat source and the fabric.

5. The method of claim 1, wherein the method further comprises: determining the distance between the fire source and the object based on the detected distance between the fire source and the object and the determined distance between the fire source and the object. The data acquisition module includes a K-type thermocouple, a heat flux density sensor and a data logger, the K-type thermocouple is placed at a position 5 cm away from the heat source between the heat source and the fabric, the temperature measurement range is-260-260℃, the heat flux density sensor acquires the heat flux density through the fabric to the sensor surface, the sensor is embedded with a simulated skin sensor to simulate the skin for information collection, the data logger is used with acquisition card and acquisition software, the data collected by the K-type thermocouple and the heat flux density sensor are collected, recorded, viewed and analyzed, the acquisition card can export data to the computer system, which is convenient for users to customize data analysis, and the acquisition software is used to view or control the state of the data logger.

6. The method of claim 1, wherein the method further comprises: determining the distance between the fire source and the detection system based on the detected temperature and the detected pressure. The heat flow density sensor back is provided with a water cooling device, the water cooling device includes a copper plate and a copper pipe, the copper pipe is placed in the copper plate back and circulates winding, the water flow velocity and water temperature inside the copper pipe can be adjusted according to the experiment needs. ​ 7. The detection method of a fire source safety exposure distance detection system according to claim 1, wherein, In order to predict the safety exposure distance of firefighters in large-scale fire environment, the data obtained by experiment need to be further converted, the origin software is used for nonlinear curve fitting, the functional relationship between the fire source height, fire source temperature, heat source distance and heat flow density is established, and the finally fitted function is shown as formula (7): （7） wherein, is the heat flux density, the correlation coefficient R2 of the fitted curve is 0.838, and the fitting degree is high; The heat source distance corresponding to different heat flow densities measured by small-scale fabric experiment is used to establish the fitting relationship between the heat flow density and the heat source distance under small-scale fabric experiment, and the fitting equation is shown as formula (8) （8） wherein, q is the heat flux (W / m2) for small scale fabric experiment, d is the heat source distance (cm) for small scale fabric experiment, the correlation coefficient R2=0.999 of the fitted curve is high, Substitute formula (7) into formula (8), the conversion relationship between the heat source distance in large-scale fire environment and the heat source distance under small-scale fabric experiment can be obtained, which is shown as formula (9): （9） When converting the heat source distance under small-scale fabric experiment and the heat source distance in large-scale fire environment, the fire source height and fire source temperature need to be set.

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