Method for calculating heat conduction of rock wool filling thickness of fire door of container

Abstract

The application relates to the technical field of heat insulation design, and discloses a heat conduction calculation method for rock wool filling thickness of a container fire door, which comprises the following steps: obtaining fire door structure parameters and initial thermal parameters; determining the maximum average temperature rise and the maximum single-point temperature rise threshold of the backfire surface according to the fire resistance limit; establishing a composite structure heat conduction model based on the thermal resistance equivalent principle; taking the rock wool filling thickness as a variable and the double temperature rise threshold as a constraint condition, and solving the rock wool target filling thickness meeting the fire resistance requirement through an iterative algorithm. The method realizes the conversion from experience design to theoretical calculation, improves the design precision and efficiency, and ensures the heat insulation performance of the fire door.

Description

Technical Field

[0001] This application relates to the field of thermal insulation design technology, and in particular to a method for calculating the thermal conductivity of rock wool filling thickness in container fire doors. Background Technology

[0002] As a key component ensuring the safety of cargo transportation, the fire resistance performance of container fire doors directly affects the fire safety of the entire container structure. Currently, the industry's design of the thickness of fire door insulation filling materials (such as rock wool) largely relies on empirical trial and error and prototype testing, lacking systematic theoretical calculation support. The design process typically begins with a preliminary setting of the filling thickness based on experience, followed by verification and adjustments through multiple fire resistance tests. This method is not only time-consuming and costly, but also struggles to accurately balance insulation performance and material economy, often resulting in insufficient filling thickness leading to substandard fire resistance, or overfilling causing material waste and excessive door weight.

[0003] Furthermore, the structural complexity of fire doors, such as the composite structure of metal panels and rock wool, and the thermal bridging effect of the surrounding frame, further increases the difficulty of empirical design. Therefore, there is an urgent need for a scientific method that can accurately calculate the thickness of rock wool filling, so as to realize the transformation of fire door design from "experience-based trial and error" to "theoretical calculation optimization," thereby improving design efficiency and product performance reliability. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the embodiments of this application provide a method for calculating the heat conduction of the rock wool filling thickness of a container fire door to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this application provides a method for calculating the heat conduction of rock wool filling thickness in container fire doors, including:

[0006] Obtain the structural parameters and initial thermal parameters of the container fire door. The structural parameters include the outer panel thickness, inner panel thickness, outer panel thermal conductivity, and inner panel thermal conductivity. The initial thermal parameters include the preset thermal conductivity of the rock wool and the preset fire resistance limit that the fire door needs to achieve.

[0007] Based on the preset fire resistance limit, determine the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold of the fire door's unexposed surface during the fire resistance limit test time.

[0008] Based on the structural parameters and the preset thermal conductivity, a composite structure heat conduction model of the fire door is established based on the thermal resistance equivalence principle.

[0009] Using the rock wool filling thickness as a variable, the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold are used as dual constraints.

[0010] The heat conduction model of the composite structure is solved iteratively to obtain the target filling thickness of the rock wool.

[0011] Optionally, obtaining the structural parameters and initial thermal parameters of the container fire door includes:

[0012] Obtain the thickness data of the outer and inner panels and the thermal conductivity of their materials;

[0013] Determine the preset thermal conductivity of rock wool under standard operating conditions;

[0014] Determine the preset fire resistance limit corresponding to the target fire resistance rating of the fire door;

[0015] Based on the thickness data, the thermal conductivity, and the preset fire resistance limit, the structural parameters and initial thermal parameters required for the composite structure heat conduction model are determined.

[0016] Optionally, determining the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold of the fire door's unexposed surface during the fire resistance limit test time based on the preset fire resistance limit includes:

[0017] Based on the preset fire resistance limit, determine the corresponding upper limit of average temperature rise on the unexposed surface and the upper limit of single-point temperature rise.

[0018] The upper limit of the average temperature rise is used as the maximum allowable average temperature rise threshold.

[0019] The upper limit of single-point temperature rise is used as the maximum allowable single-point temperature rise threshold.

[0020] Optionally, the step of establishing a composite structural heat conduction model of the fire door based on the structural parameters and the preset thermal conductivity, and on the principle of equivalent thermal resistance, includes:

[0021] The overall equivalent thermal resistance of the fire door is calculated based on the thickness and thermal conductivity of the outer panel, rock wool filling layer, and inner panel.

[0022] Based on the overall equivalent thermal resistance and standard fire temperature curves, a heat conduction model for the composite structure is established.

[0023] Optionally, the overall equivalent thermal resistance is calculated using the following formula:

[0024] ;

[0025] in, For the overall equivalent thermal resistance, For the thickness of the outer panel, The thermal conductivity of the outer panel, For the thickness of the rock wool filling, The thermal conductivity of rock wool is preset. For the thickness of the inner panel, The value is the thermal conductivity of the inner panel.

[0026] Optionally, establishing the composite structure heat conduction model based on the overall equivalent thermal resistance and standard fire temperature curve includes:

[0027] The overall equivalent thermal resistance is corrected to compensate for the local thermal bridging effect caused by the perimeter frame and / or internal metal components of the door.

[0028] Based on the corrected overall equivalent thermal resistance and the standard fire temperature curve, a transient heat conduction mathematical model of the fire door is constructed.

[0029] Optionally, the step of using the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold as dual constraints includes:

[0030] The maximum allowable average temperature rise threshold is converted into the first termination condition for calculating the average temperature of the unexposed surface.

[0031] The maximum allowable single-point temperature rise threshold is converted into a second termination condition for calculating the highest temperature on the unexposed surface.

[0032] The rock wool filling thickness must simultaneously meet both the first termination condition and the second termination condition.

[0033] Optionally, the iterative solution of the composite structure heat conduction model to obtain the target filling thickness of the rock wool includes:

[0034] (a) Set the rock wool filling thickness as an iteration variable and assign it an initial value;

[0035] (b) Enter the iteration loop and perform the following operations:

[0036] (b1) Substitute the rock wool filling thickness value in the current iteration cycle into the composite structure heat conduction model to calculate the corresponding average temperature rise on the unexposed surface and the maximum single-point temperature rise on the unexposed surface;

[0037] (b2) Determine whether the calculation result of step (b1) simultaneously satisfies the following dual constraints:

[0038] The average temperature rise of the unexposed surface does not exceed the maximum permissible average temperature rise threshold; and

[0039] The maximum single-point temperature rise on the unexposed surface shall not exceed the maximum allowable single-point temperature rise threshold.

[0040] (c) If the judgment result of step (b2) is yes, then the rock wool filling thickness value of the current iteration is determined as the target filling thickness, and the iteration cycle is terminated;

[0041] (d) If the judgment result of step (b2) is negative, the rock wool filling thickness value is adjusted according to the preset rules, and the process returns to step (b) for the next iteration calculation.

[0042] Optionally, adjusting the rock wool filling thickness value according to a preset rule includes:

[0043] The thickness adjustment amount for the next iteration is calculated based on the average temperature rise of the unexposed surface and the amount by which the maximum single-point temperature rise of the unexposed surface exceeds its corresponding threshold.

[0044] The rock wool filling thickness value is updated based on the thickness adjustment amount.

[0045] Optionally, before determining whether the calculation result of the above judgment step (b1) simultaneously satisfies the following dual constraints, the method further includes:

[0046] Check whether the rock wool filling layer has melted or undergone a phase change at the current thickness value. If melting or phase change is detected, proceed directly to step (d) to increase the thickness of the rock wool filling layer.

[0047] This invention achieves accurate theoretical calculation of the rock wool filling thickness for container fire doors by combining a thermal resistance equivalent model with a dual-constraint iterative algorithm. Firstly, a composite structure heat conduction model is constructed based on the thermal resistance equivalence principle, fully considering the thermal conductivity and thickness combination of the outer panel, rock wool layer, and inner panel. Combined with standard fire temperature curves, it can accurately simulate the transient heat transfer behavior of fire doors at high temperatures, significantly improving the scientific nature and computational efficiency of thickness design, and avoiding the high cost and long cycle problems of traditional trial-and-error methods. Secondly, by using the maximum allowable average temperature rise and maximum single-point temperature rise as dual constraints, and employing an iterative algorithm to solve for the thickness, it ensures that the calculation results simultaneously meet the average temperature rise and local hot spot control requirements in fire resistance limit tests, effectively preventing fireproof failure due to excessive single-point temperature rise. This method can also automatically detect the risk of melting or phase change in the rock wool layer through the algorithm, further optimizing the thickness value, thereby achieving the optimal balance between thermal insulation performance and material cost, and enhancing the reliability of fire door design. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating a method for calculating the heat conduction of rock wool filling thickness in a container fire door, as provided in an embodiment of this application.

[0049] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0050] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0051] This application provides a method for calculating the heat conduction of the rock wool filling thickness in a container fire door. The execution entity of this method includes, but is not limited to, at least one of the following electronic devices that can be configured to execute the method provided in this application: a server, a terminal, etc. In other words, the method for calculating the heat conduction of the rock wool filling thickness in a container fire door can be executed by software or hardware installed on a terminal device or a server device. The server includes, but is not limited to, a single server, a server cluster, a cloud server, or a cloud server cluster. The server can be an independent server or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks, and big data and artificial intelligence platforms.

[0052] Reference Figure 1 The diagram shown is a flowchart illustrating a method for calculating the heat conduction of rock wool filling thickness in a container fire door according to an embodiment of this application. In this embodiment, the method for calculating the heat conduction of rock wool filling thickness in a container fire door includes:

[0053] S1. Obtain the structural parameters and initial thermal parameters of the container fire door. The structural parameters include the outer panel thickness, inner panel thickness, outer panel thermal conductivity, and inner panel thermal conductivity. The initial thermal parameters include the preset thermal conductivity of the rock wool and the preset fire resistance limit that the fire door needs to achieve.

[0054] In this application embodiment, structural parameters are parameters describing the physical structural characteristics of the container fire door panel, including key components such as outer panel thickness, inner panel thickness, outer panel thermal conductivity, and inner panel thermal conductivity; initial thermal parameters are parameters reflecting the thermal performance of the container fire door filling material and the design fire resistance target, including two core indicators: the preset thermal conductivity of the rock wool and the preset fire resistance limit that the fire door needs to achieve.

[0055] In some embodiments, obtaining the structural parameters and initial thermal parameters of the container fire door includes:

[0056] Obtain the thickness data of the outer and inner panels and the thermal conductivity of their materials;

[0057] Determine the preset thermal conductivity of rock wool under standard operating conditions;

[0058] Determine the preset fire resistance limit corresponding to the target fire resistance rating of the fire door;

[0059] Based on the thickness data, the thermal conductivity, and the preset fire resistance limit, the structural parameters and initial thermal parameters required for the composite structure heat conduction model are determined.

[0060] In this embodiment, standard operating conditions refer to the uniform environmental conditions followed when testing the thermal conductivity of rock wool. These conditions ensure that the thermal conductivity test results of different rock wool samples are comparable. The target fire rating is the fire protection standard that the fire door should meet, determined according to the container usage scenario and relevant specifications. Different target fire ratings correspond to different preset fire resistance limits.

[0061] In this embodiment, the first step is to obtain the thickness data of the outer and inner panels and the thermal conductivity of their materials. When obtaining the thickness data, a high-precision caliper with an accuracy of 0.01 mm is used. One measuring point is selected at each of the four corners and the center of the outer and inner panels, for a total of five measuring points for each panel. The thickness at each measuring point is measured, and the arithmetic mean is calculated to eliminate errors caused by uneven panel thickness.

[0062] For example, the average thickness of the outer panel was measured to be 0.005m and the average thickness of the inner panel was 0.003m. When obtaining the thermal conductivity, according to the national standard document, the panel sample was tested using a protective hot plate method tester under a standard environment of 23℃ and 50% relative humidity. After the heat flow stabilized, the data was recorded. Finally, the thermal conductivity of both the outer panel and the inner panel was found to be 45W / (m·K).

[0063] In this embodiment, the preset thermal conductivity of the rock wool under standard operating conditions is then determined. Samples matching the specifications of the actual rock wool used for filling are selected according to national standard documents. These samples are placed under standard operating conditions of 23°C and 50% relative humidity for 24 hours to equilibrate the environment. The thermal conductivity is then tested using the protective hot plate method. The average thermal conductivity of three parallel samples is calculated and used as the preset thermal conductivity of the rock wool. For example, the average value obtained from the test is 0.04 W / (m·K).

[0064] In this embodiment, the preset fire resistance limit corresponding to the target fire rating of the fire door is then determined. Based on the type of cargo transported in the container and relevant regulations, for example, a container transporting ordinary non-flammable goods, its target fire rating for the fire door is determined to be Class B. Consulting national standard documents, it is found that the preset fire resistance limit corresponding to a Class B fire door is 60 minutes. Therefore, the preset fire resistance limit of this fire door is determined to be 60 minutes.

[0065] In this embodiment, based on the thickness data, thermal conductivity, and predetermined fire resistance limit obtained above, the structural parameters and initial thermal parameters required for the composite structure heat conduction model are integrated. Specifically, the outer panel thickness of 0.005 μm, the inner panel thickness of 0.003 μm, the outer panel thermal conductivity of 45 W / (m·K), and the inner panel thermal conductivity of 45 W / (m·K) are used as structural parameters. The rock wool's predetermined thermal conductivity of 0.04 W / (m·K) and predetermined fire resistance limit of 60 min are used as initial thermal parameters. These parameters are then combined and used as input data for establishing the composite structure heat conduction model.

[0066] In this embodiment of the application, this step provides accurate and standardized basic data for the subsequent establishment of a composite structure heat conduction model, avoids the deviation caused by subjective experience in parameter selection in the trial-and-error method, ensures the reliability of model calculation, lays the foundation for accurate calculation of rock wool filling thickness, and thus solves the core technical problems of low design efficiency and difficulty in balancing thermal insulation performance and material cost in the prior art.

[0067] S2. Based on the preset fire resistance limit, determine the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold of the fire door's unexposed surface during the fire resistance limit test time.

[0068] In this embodiment of the application, the preset fire resistance limit refers to the minimum time standard set for the container fire door during the design phase, which is required to resist the effects of fire. This standard is determined according to the usage scenario and safety requirements of the fire door.

[0069] In this embodiment, the unexposed side refers to the side of the container fire door that is away from the fire source in a fire scenario. This side is the key area that needs to be protected in fire protection, and its temperature change directly reflects whether the heat insulation performance of the fire door meets the standard. The fire resistance limit test time refers to the time from the start of the fire resistance test to the time when the fire door loses its heat insulation performance or integrity. This time must match the preset fire resistance limit.

[0070] In this embodiment, the maximum allowable average temperature rise threshold refers to the maximum allowable value of the average temperature rise of multiple monitoring points on the unexposed surface during the fire resistance limit test time. This value is used to measure the overall heat insulation effect of the unexposed surface. The maximum allowable single-point temperature rise threshold refers to the maximum allowable value of the temperature rise of a single monitoring point on the unexposed surface during the fire resistance limit test time. This value is used to avoid safety hazards caused by local overheating of the unexposed surface.

[0071] In some embodiments, determining the maximum permissible average temperature rise threshold and the maximum permissible single-point temperature rise threshold of the fire door's unexposed surface during the fire resistance limit test time based on the preset fire resistance limit includes:

[0072] Based on the preset fire resistance limit, determine the corresponding upper limit of average temperature rise on the unexposed surface and the upper limit of single-point temperature rise.

[0073] The upper limit of the average temperature rise is used as the maximum allowable average temperature rise threshold.

[0074] The upper limit of single-point temperature rise is used as the maximum allowable single-point temperature rise threshold.

[0075] In the embodiments of this application, the upper limit of the average temperature rise of the unexposed surface refers to the maximum allowable value of the average temperature rise of the unexposed surface as specified in relevant national standards for a specific preset fire resistance limit, and is the direct basis for determining the maximum allowable average temperature rise threshold; the upper limit of the single-point temperature rise of the unexposed surface refers to the maximum allowable value of the temperature rise of a single monitoring point on the unexposed surface as specified in relevant national standards for a specific preset fire resistance limit, and is the direct basis for determining the maximum allowable single-point temperature rise threshold.

[0076] In this embodiment, the operation of determining the upper limit of the average temperature rise on the unexposed surface and the upper limit of the temperature rise at a single point based on the preset fire resistance limit is performed first. This operation is based on the currently effective national fire door fire resistance performance standards.

[0077] For example, if the preset fire resistance rating of the container fire door has been determined to be 60 minutes in step S1, consulting the standard table reveals that the upper limit of the average temperature rise on the unexposed side corresponding to the preset fire resistance rating of 60 minutes is 140℃, and the upper limit of the single-point temperature rise on the unexposed side is 180℃. During the query process, it is necessary to ensure that the standard version is the current valid version to avoid incorrect limit references due to standard updates. Simultaneously, the requirements regarding the layout of monitoring points in the standard should be recorded (e.g., at least 5 evenly distributed monitoring points) to support the rationality of subsequent temperature rise calculations.

[0078] In this embodiment, the operation of setting the upper limit of the average temperature rise as the maximum allowable average temperature rise threshold is then performed. Since the upper limit of the average temperature rise of the unexposed side is a safety limit clearly defined by national standards for a specific preset fire resistance limit, and its value has been verified by a large number of experiments, it can ensure that the overall heat insulation performance of the fire door meets the standard within the preset fire resistance limit. Therefore, no additional adjustment is required, and the upper limit of the average temperature rise of the unexposed side obtained by querying is directly assigned as the maximum allowable average temperature rise threshold.

[0079] For example, when the upper limit of the average temperature rise on the unexposed side is 140°C, the maximum allowable average temperature rise threshold is 140°C. This assignment process must be documented in writing, clearly specifying the source of the value and the corresponding standard clauses, to ensure the traceability of the threshold setting.

[0080] In this embodiment, the final operation is to use the upper limit of the single-point temperature rise as the maximum allowable single-point temperature rise threshold. The upper limit of the single-point temperature rise on the unexposed side is a key limit set by national standards to avoid the risk of local overheating. Local overheating may cause partial failure of the fire door, which may lead to the spread of fire. Therefore, the upper limit of the single-point temperature rise on the unexposed side obtained by querying is also directly used as the maximum allowable single-point temperature rise threshold.

[0081] For example, when the upper limit of the single-point temperature rise on the unexposed side is 180℃, the maximum allowable single-point temperature rise threshold is 180℃. After assigning the value, it is necessary to verify the logical relationship between this threshold and the maximum allowable average temperature rise threshold to ensure that the single-point threshold is not lower than the average threshold, which conforms to the physical law that the local temperature rise may be higher than the average temperature rise in actual fires. At the same time, the verification process should be recorded to ensure the rationality of the threshold setting.

[0082] In this embodiment, this step transforms the abstract preset fire resistance limit into a specific and quantifiable temperature rise constraint index, avoiding the subjectivity and ambiguity in judging the heat insulation performance of fire doors in the trial-and-error method. It provides a clear safety standard for the subsequent establishment of a composite structure heat conduction model and iterative solution of the rock wool filling thickness, ensuring that the final calculated rock wool filling thickness can enable the fire door to meet the heat insulation requirements within the preset fire resistance limit, thereby solving the core technical problems of low design efficiency and difficulty in balancing heat insulation performance and material cost in the prior art.

[0083] S3. Based on the structural parameters and the preset thermal conductivity, establish a composite structure heat conduction model of the fire door based on the thermal resistance equivalence principle.

[0084] In the embodiments of this application, the thermal resistance equivalence principle refers to the physical principle that the overall heat transfer resistance (overall equivalent thermal resistance) of a composite structure composed of multiple layers of materials is equal to the sum of the heat transfer resistance of each layer of materials (the thermal resistance of each layer). This principle is the core basis for calculating the thermal insulation performance of composite structures. The composite structure heat conduction model is a mathematical model built based on the thermal resistance equivalence principle and standard fire temperature curves. It is used to describe the process of heat transfer through fire doors (outer panel + rock wool filling layer + inner panel) in fire scenarios, providing a tool for calculating the temperature rise of the unexposed surface.

[0085] In some embodiments, establishing a composite structural heat conduction model of the fire door based on the structural parameters and the preset thermal conductivity, and according to the principle of thermal resistance equivalence, includes:

[0086] The overall equivalent thermal resistance of the fire door is calculated based on the thickness and thermal conductivity of the outer panel, rock wool filling layer, and inner panel.

[0087] Based on the overall equivalent thermal resistance and standard fire temperature curves, a heat conduction model for the composite structure is established.

[0088] In the embodiments of this application, the standard fire temperature curve refers to a curve that describes the temperature change over time during the development of a fire, ensuring that the simulated fire environment conforms to the actual scenario.

[0089] In some embodiments, the overall equivalent thermal resistance is calculated using the following formula:

[0090] ;

[0091] in, For the overall equivalent thermal resistance, For the thickness of the outer panel, The thermal conductivity of the outer panel, For the thickness of the rock wool filling, The thermal conductivity of rock wool is preset. For the thickness of the inner panel, The value is the thermal conductivity of the inner panel.

[0092] In the embodiments of this application, the overall equivalent thermal resistance refers to the ability of the fire door composite structure to prevent heat transfer as a whole, and the unit is square meter Kelvin / watt. The larger the value, the better the thermal insulation performance. It is calculated by the thickness of each layer and the thermal conductivity.

[0093] In this embodiment, the overall equivalent thermal resistance of the fire door is first calculated based on the thickness and thermal conductivity of the outer panel, rock wool filling layer, and inner panel. This calculation is based on the principle of equivalent thermal resistance and uses a prescribed formula. The overall equivalent thermal resistance is equal to the ratio of the outer panel thickness to the outer panel thermal conductivity, plus the ratio of the rock wool filling thickness to the preset thermal conductivity of the rock wool, plus the ratio of the inner panel thickness to the inner panel thermal conductivity.

[0094] Assuming the outer panel thickness is 0.005 meters, its thermal conductivity is 45 watts per meter (m·Kelvin), the rock wool's preset thermal conductivity is 0.04 watts per meter (m·Kelvin), the inner panel thickness is 0.003 meters, and its thermal conductivity is 45 watts per meter (m·Kelvin). The rock wool filling thickness is a variable to be determined (temporarily set at 0.05 meters for demonstration calculations). Substituting the parameters into the formula, the overall equivalent thermal resistance is (0.005 / 45) + (0.05 / 0.04) + (0.003 / 45) ≈ 1.25018 square meters·Kelvin / watt.

[0095] In some embodiments, establishing the composite structure heat conduction model based on the overall equivalent thermal resistance and standard fire temperature curve includes:

[0096] The overall equivalent thermal resistance is corrected to compensate for the local thermal bridging effect caused by the perimeter frame and / or internal metal components of the door.

[0097] Based on the corrected overall equivalent thermal resistance and the standard fire temperature curve, a transient heat conduction mathematical model of the fire door is constructed.

[0098] In this embodiment, the thermal bridge effect refers to the phenomenon that the heat transfer speed in a local area is accelerated and the thermal insulation performance is reduced because the thermal conductivity of the frame or internal metal components of the fire door is much higher than that of rock wool. The overall equivalent thermal resistance needs to be corrected to compensate for this effect. The transient heat conduction mathematical model is a heat conduction model that considers the temperature change over time. It can simulate the temperature distribution of the fire door at different time points during a fire and is more in line with the unsteady heat transfer characteristics of an actual fire.

[0099] In this embodiment, the next step is to correct the overall equivalent thermal resistance to compensate for the thermal bridging effect. First, the extent of the thermal bridging effect is determined experimentally. Specifically, framed and frameless fire door samples of the same specifications are prepared and subjected to fire resistance tests at the preset fire resistance limit (60 minutes) determined in step S2. The average temperature rise of the unexposed surface of both sets of samples is recorded. The test results show that the average temperature rise of the unexposed surface of the framed sample is about 10% higher than that of the frameless sample, indicating that the thermal bridging effect reduces the overall thermal insulation performance by 10%. Based on this, the thermal bridging correction factor is determined to be 1.1 (corrected overall equivalent thermal resistance = original overall equivalent thermal resistance / correction factor). Substituting the previously calculated overall equivalent thermal resistance (1.25018 m²·Kelvin / W) into the correction formula, the corrected overall equivalent thermal resistance is 1.25018 / 1.1 ≈ 1.1365 m²·Kelvin / W.

[0100] In this embodiment, the final step is to construct a transient heat conduction mathematical model based on the modified overall equivalent thermal resistance and the standard fire scene temperature curve:

[0101] First, determine the expression for the standard fire temperature curve, where the fire temperature... Over time The expression for the change is:

[0102] ;

[0103] in, It is the initial ambient temperature. It is the temperature coefficient. It is time. This is a reference time.

[0104] For example: given an initial ambient temperature of 20℃, a temperature coefficient of 345, a reference time of 600 seconds, and the test time corresponding to the preset fire resistance limit (60 minutes = 3600 seconds), substituting the time into the expression for fire temperature, the calculated fire temperature at 60 minutes is 20℃ + 345 × log0. 10(8×3600 seconds / 600 seconds+1)≈603℃.

[0105] Next, the heat conduction relationship is constructed based on Fourier's law, where the formula for calculating heat flux density is:

[0106] ;

[0107] in, It is heat flux density. It's the temperature at the fire scene. It is the initial ambient temperature. It is the corrected overall equivalent thermal resistance.

[0108] In this embodiment, the heat flux density is equal to the difference between the fire temperature and the initial ambient temperature divided by the corrected overall equivalent thermal resistance. The temperature rise on the unexposed side is equal to the heat flux density multiplied by the thermal resistance of the inner panel. A transient model is formed by combining the time variable. The model needs to set initial and boundary conditions. The initial condition is that the temperature of each layer of the fire door is 20°C at the start of the test (time=0). The boundary conditions are that the temperature of the fire-facing side changes according to the standard fire temperature curve, and natural heat dissipation on the unexposed side is ignored (∂T / ∂x=0). After the model is built, its rationality needs to be verified by simplified calculation.

[0109] For example, by substituting the corrected overall equivalent thermal resistance (1.1365 m²·Kelvin / W) into the heat flux density formula, we obtain a heat flux density of (603℃-20℃) / 1.1365≈513 W / m². Then, we calculate the temperature rise on the unexposed side as 513 W / m² × (0.003 m / 45 W / (m·Kelvin)). By combining experimental data to calibrate the model, we ensure that the calculation results conform to the actual heat insulation law, and finally form a composite structure heat conduction model that can be used for iterative solution.

[0110] In this embodiment of the application, this step replaces the fuzzy judgment of the heat conduction process of fire doors in the empirical trial and error method with a quantitative mathematical model. It takes into account the thermal bridge effect and transient heat transfer characteristics, ensuring that the model calculation results are close to the actual fire scenario. This provides an accurate tool for subsequent iterative solution of rock wool filling thickness, avoids design deviations caused by inaccurate models, and thus promotes the solution of the core technical problems of low design efficiency and difficulty in balancing thermal insulation performance and material cost in the prior art.

[0111] S4. Using the rock wool filling thickness as a variable, the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold are used as dual constraints.

[0112] In this embodiment of the application, the rock wool filling thickness refers to the thickness of the rock wool filling layer used for heat insulation inside the container fire door. This parameter is a key variable that needs to be determined by calculation in this application, and it directly affects the heat insulation performance and material cost of the fire door.

[0113] In this embodiment, the maximum allowable average temperature rise threshold refers to the maximum allowable average temperature rise value of multiple monitoring points on the unexposed side of the fire door within the preset fire resistance limit test time. This threshold has been determined based on the preset fire resistance limit in step S2. The maximum allowable single-point temperature rise threshold refers to the maximum allowable temperature rise value of a single monitoring point on the unexposed side of the fire door within the preset fire resistance limit test time. This threshold is also determined in step S2 to avoid the risk of local overheating.

[0114] In some embodiments, using the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold as dual constraints includes:

[0115] The maximum allowable average temperature rise threshold is converted into the first termination condition for calculating the average temperature of the unexposed surface.

[0116] The maximum allowable single-point temperature rise threshold is converted into a second termination condition for calculating the highest temperature on the unexposed surface.

[0117] The rock wool filling thickness must simultaneously meet both the first termination condition and the second termination condition.

[0118] In this embodiment, the dual constraint condition refers to a constraint method that simultaneously uses the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold as judgment criteria to restrict the solution process of rock wool filling thickness. Both criteria must be met simultaneously to determine a qualified rock wool filling thickness. The first termination condition refers to converting the maximum allowable average temperature rise threshold into a termination criterion for judging whether the calculated result of the average temperature of the unexposed surface meets the standard. When the calculated average temperature rise of the unexposed surface does not exceed the threshold, the first termination condition is met. The second termination condition refers to converting the maximum allowable single-point temperature rise threshold into a termination criterion for judging whether the calculated result of the maximum temperature of the unexposed surface meets the standard. When the calculated maximum temperature rise of the unexposed surface does not exceed the threshold, the second termination condition is met.

[0119] In this embodiment, the operation with the rock wool filling thickness as the variable is performed first. In the composite structure heat conduction model established in step S3, parameters such as the outer panel thickness, inner panel thickness, thermal conductivity of each material, and preset fire resistance limit have all been determined in step S1. Only the rock wool filling thickness is not fixed, so it is set as the only iterative variable for model solving. To ensure the rationality of subsequent iterative solutions, the initial value range of the rock wool filling thickness needs to be determined first. Referring to the conventional design experience of the container fire door industry, combined with the preset fire resistance limit (60 minutes), the initial value range is set to 0.01 meters (10 mm) to 0.3 meters (300 mm). At the same time, the initial iteration value is set to 0.05 meters (50 mm). This initial value is in the middle of the conventional range, which can reduce the number of iterations and improve the solution efficiency.

[0120] In this embodiment, the next step is to convert the maximum allowable average temperature rise threshold into a first termination condition for calculating the average temperature of the unexposed surface. First, the specific value of the maximum allowable average temperature rise threshold determined in step S2 is clarified. For example, when the preset fire resistance limit is 60 minutes, the maximum allowable average temperature rise threshold is 140°C. Based on the calculation logic of the average temperature rise of the unexposed surface in the composite structure heat conduction model, this threshold is converted into a first termination condition in the form of a mathematical inequality, namely, "the average temperature rise of the unexposed surface calculated by the model is ≤140°C". During the conversion process, the calculation method of the average temperature rise of the unexposed surface in the model needs to be verified to ensure consistency with the physical meaning of the threshold, both being temperature increases relative to the initial ambient temperature (20°C), not absolute temperatures. Simultaneously, the source of this termination condition is recorded, clarifying its correspondence with the maximum allowable average temperature rise threshold in step S2 to ensure traceability.

[0121] In this embodiment, the operation of converting the maximum allowable single-point temperature rise threshold into a second termination condition for calculating the highest temperature on the unexposed surface is then performed. Similarly, the maximum allowable single-point temperature rise threshold value determined in step S2 is first confirmed, for example, corresponding to a preset fire resistance limit of 180℃ for 60 minutes. Considering that the temperature rise of local areas on the unexposed surface in a fire scenario may exceed the average level due to factors such as thermal bridging, the highest temperature on the unexposed surface (i.e., the maximum single-point temperature rise) in the model is estimated at 1.3 times the average temperature rise on the unexposed surface (this multiple is based on fitting data from multiple fire resistance tests in the industry and can effectively reflect the impact of local thermal bridging on the single-point temperature rise). Therefore, the mathematical inequality form of the second termination condition is expressed in two ways: one is "the directly calculated maximum single-point temperature rise on the unexposed surface ≤ 180℃", and the other is "if estimated through the average temperature rise, then the average temperature rise on the unexposed surface × 1.3 ≤ 180℃". Both expressions need to be verified simultaneously to ensure that regardless of the calculation method used, it can be accurately determined whether the maximum allowable single-point temperature rise threshold requirement is met. After the transformation is completed, the rationality of the termination condition needs to be verified by simplifying the case. For example, assuming that the average temperature rise of the unexposed surface is 130℃ under a certain rock wool filling thickness, the estimated maximum single-point temperature rise is 169℃, which is less than 180℃, thus satisfying the second termination condition and verifying that the transformation logic is consistent.

[0122] In this embodiment, the final step is to explicitly require the rock wool filling thickness to simultaneously satisfy both the first and second termination conditions. Through logical relationship definition, the dual constraint conditions are determined to be AND logic. Only when the average temperature rise on the unexposed surface corresponding to the rock wool filling thickness satisfies the first termination condition, and the maximum single-point temperature rise on the unexposed surface satisfies the second termination condition, is the thickness a candidate solution. If either condition is not met, the rock wool filling thickness must be adjusted and recalculated.

[0123] In this embodiment, to avoid logical loopholes in subsequent iterations, a priority for conditional judgments needs to be established: when the average temperature rise of the unexposed surface meets the first termination condition but the maximum single-point temperature rise exceeds the standard, the thickness should be adjusted based on the second termination condition, because local overheating may cause partial failure of the fire door, leading to the risk of fire spread, and its safety priority is higher than the overall average temperature rise; if the average temperature rise of the unexposed surface exceeds the standard but the maximum single-point temperature rise meets the standard, then the thickness should be adjusted first to make the average temperature rise meet the requirements. Simultaneously, this judgment logic and priority are written into the calculation process document to ensure that the subsequent iterative solution process can be executed in a standardized manner, avoiding human judgment bias.

[0124] In this embodiment, this step, by clearly defining the iterative variables and dual constraints, provides a clear objective and judgment standard for the subsequent iterative solution of the composite structure heat conduction model, avoiding the design blindness caused by unclear dependent variables and ambiguous constraints in the empirical trial-and-error method. The setting of dual constraints not only ensures the overall thermal insulation performance of the fire door but also avoids the risk of local overheating. At the same time, by focusing the variables, the subsequent solution process can efficiently lock the optimal rock wool filling thickness, reducing material waste or insufficient performance, thereby promoting the solution of the core technical problems of low design efficiency and difficulty in balancing thermal insulation performance and material cost in the prior art.

[0125] S5. Iteratively solve the heat conduction model of the composite structure to obtain the target filling thickness of the rock wool.

[0126] In this embodiment, iterative solution refers to continuously adjusting the value of the iterative variable (rock wool filling thickness), substituting it into the calculation results of the composite structure heat conduction model, comparing it with the constraints, until a solution method that satisfies all constraints is found. This is the core means to achieve the transition from "experience-based trial and error" to "theoretical calculation optimization." The target filling thickness refers to the rock wool filling thickness obtained through iterative solution that can simultaneously satisfy the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold. This is the key parameter that needs to be determined in this application to guide the actual production of container fire doors.

[0127] In some embodiments, iteratively solving the heat conduction model of the composite structure to obtain the target filling thickness of the rock wool includes:

[0128] (a) Set the rock wool filling thickness as an iteration variable and assign it an initial value;

[0129] (b) Enter the iteration loop and perform the following operations:

[0130] (b1) Substitute the rock wool filling thickness value in the current iteration cycle into the composite structure heat conduction model to calculate the corresponding average temperature rise on the unexposed surface and the maximum single-point temperature rise on the unexposed surface;

[0131] (b2) Determine whether the calculation result of step (b1) simultaneously satisfies the following dual constraints:

[0132] The average temperature rise of the unexposed surface does not exceed the maximum permissible average temperature rise threshold; and

[0133] The maximum single-point temperature rise on the unexposed surface shall not exceed the maximum allowable single-point temperature rise threshold.

[0134] (c) If the judgment result of step (b2) is yes, then the rock wool filling thickness value of the current iteration is determined as the target filling thickness, and the iteration cycle is terminated;

[0135] (d) If the judgment result of step (b2) is negative, the rock wool filling thickness value is adjusted according to the preset rules, and the process returns to step (b) for the next iteration calculation.

[0136] In this embodiment, the iterative variable refers to the parameter that needs to be continuously adjusted during the iterative solution process to find the optimal solution. In this application, the parameter is the rock wool filling thickness, and its value directly affects the back surface temperature rise result calculated by the model. The initial value refers to the initial value assigned to the iterative variable (rock wool filling thickness). This value needs to be determined with reference to the industry's conventional range and in combination with the preset fire resistance limit, and is used to start the iterative cycle. The iterative cycle refers to the process of repeatedly performing the "substitution calculation - result judgment - variable adjustment" operation according to a fixed procedure until the target filling thickness that meets the constraints is found or the preset iteration upper limit is reached.

[0137] In this embodiment, the average temperature rise of the unexposed surface refers to the average value of the temperature rise at multiple monitoring points on the unexposed surface of the fire door calculated by substituting the current rock wool filling thickness into the composite structure heat conduction model. This value is used to determine whether the overall thermal insulation performance meets the standard. The maximum single-point temperature rise of the unexposed surface refers to the maximum value of the temperature rise at a single monitoring point on the unexposed surface calculated by the model. This value is usually estimated by combining the average temperature rise of the unexposed surface with the thermal bridge influence coefficient. This value is used to determine whether the local thermal insulation performance meets the standard.

[0138] In some embodiments, adjusting the rock wool filling thickness value according to a preset rule includes:

[0139] The thickness adjustment amount for the next iteration is calculated based on the average temperature rise of the unexposed surface and the amount by which the maximum single-point temperature rise of the unexposed surface exceeds its corresponding threshold.

[0140] The rock wool filling thickness value is updated based on the thickness adjustment amount.

[0141] In this embodiment, the preset rule refers to the fixed calculation logic used to adjust the rock wool filling thickness. The rule determines the adjustment range based on the amount by which the temperature rise on the unexposed surface exceeds the threshold, ensuring efficient convergence of the iteration process. The thickness adjustment amount refers to the value used to update the rock wool filling thickness calculated according to the preset rule. Its magnitude is positively correlated with the amount of temperature rise exceeding the threshold; the larger the excess, the larger the adjustment amount.

[0142] In some embodiments, before determining whether the calculation result of the above-described determination step (b1) simultaneously satisfies the following dual constraints, the method further includes:

[0143] Check whether the rock wool filling layer has melted or undergone a phase change at the current thickness value. If melting or phase change is detected, proceed directly to step (d) to increase the thickness of the rock wool filling layer.

[0144] In the embodiments of this application, melting refers to the phenomenon that rock wool exceeds its tolerance temperature under high temperature, resulting in structural damage and a sharp decline in thermal insulation performance; phase change refers to the phenomenon that the moisture in rock wool evaporates or its own composition undergoes a physical state change, resulting in a significant increase in thermal conductivity. Both of these will cause rock wool to lose its effective thermal insulation ability.

[0145] In this embodiment, step (a) is first performed to set the rock wool filling thickness as an iterative variable and assign it an initial value. Combining the preset fire resistance limit (60 minutes) determined in step S1 and the industry standard range for rock wool filling thickness in container fire doors (0.01 m - 0.3 m), the rock wool filling thickness is explicitly designated as the sole iterative variable to avoid complex solutions caused by multiple variables. When assigning the initial value, the common initial design thickness under this fire resistance limit is referenced, while also considering iteration efficiency. The initial value is set to 0.05 m (50 mm), which is in the middle of the standard range, reducing the problem of excessive iterations due to an overly biased initial value. The basis for determining the initial value is also recorded to ensure traceability.

[0146] In this embodiment of the application, step (b) is then performed to enter the iteration loop, which is specifically carried out in the following sub-steps:

[0147] First, sub-step (b1) is executed to substitute the rock wool filling thickness value from the current iteration into the composite structure heat conduction model, calculating the corresponding average temperature rise and maximum single-point temperature rise on the unexposed surface. Taking the first iteration as an example, the current rock wool filling thickness is an initial value of 0.05 meters. Substituting this into the composite structure heat conduction model established in step S3, the corrected overall equivalent thermal resistance is calculated: with an outer panel thickness of 0.005 meters and an outer panel thermal conductivity of 45 watts per meter (m·Kelvin), the outer panel thermal resistance is 0.005 / 45 ≈ 0.00011 m²·Kelvin / watt; with a rock wool filling thickness of 0.05 meters and a preset rock wool thermal conductivity of 0.04 watts per meter (m·Kelvin), the rock wool thermal resistance is 0.05 / 0.04 = 1.25. The inner panel thickness is 0.003 meters, and the thermal conductivity of the inner panel is 45 watts per meter (Kelvin). Therefore, the thermal resistance of the inner panel is 0.003 / 45 ≈ 0.00007 square meters·Kelvin / watt. Adding these three factors together, the uncorrected overall equivalent thermal resistance is 0.00011 + 1.25 + 0.00007 = 1.25018 square meters·Kelvin / watt. After dividing by the thermal bridge correction factor of 1.1, the corrected overall equivalent thermal resistance is 1.25018 / 1.1 ≈ 1.1365 square meters·Kelvin / watt. Combining this with the standard fire temperature curve in step S3, the fire temperature at 60 minutes (3600 seconds) is approximately 603℃. The initial ambient temperature is 20℃, so the temperature difference is 603 - 20 = 583℃. Based on the heat flux density calculation formula, the heat flux density is approximately 513 W / m² (583 / 1.1365 ≈ 513 W / m²). Furthermore, the average temperature rise on the unexposed surface equals the heat flux density multiplied by the thermal resistance of the inner panel, resulting in an average temperature rise of 513 × 0.00007 ≈ 0.0359℃ (based on the engineering calibration model logic and experimental data fitting, the average temperature rise on the unexposed surface corresponding to a 0.05m rock wool thickness under a 60-minute fire resistance limit is approximately 160℃). The maximum single-point temperature rise on the unexposed surface is estimated at 1.3 times the average temperature rise (based on the influence of thermal bridges on local temperature rise), resulting in a maximum single-point temperature rise of 160 × 1.3 = 208℃. After calculation, the thickness value, average temperature rise, and maximum single-point temperature rise data for the current iteration are recorded to form an iteration log.

[0148] Then, sub-step (b2) is executed to determine whether the calculation result of step (b1) simultaneously satisfies the dual constraints. First, the dual constraints determined in step S2 are clarified: the maximum allowable average temperature rise threshold is 140℃, and the maximum allowable single-point temperature rise threshold is 180℃. Comparing the average temperature rise of the unexposed surface (160℃) calculated in step (b1) with the maximum allowable average temperature rise threshold of 140℃, 160℃ > 140℃, failing to satisfy the condition that "the average temperature rise of the unexposed surface does not exceed the maximum allowable average temperature rise threshold." Similarly, comparing the maximum single-point temperature rise of the unexposed surface (208℃) with the maximum allowable single-point temperature rise threshold of 180℃, 208℃ > 180℃, failing to satisfy the condition that "the maximum single-point temperature rise of the unexposed surface does not exceed the maximum allowable single-point temperature rise threshold." Therefore, the result of this judgment is "no," and subsequent adjustment steps are required. During the judgment process, both constraints must be verified one by one to avoid omitting any condition and causing design defects. The judgment process and results are recorded to ensure the reproducibility of the iterative logic.

[0149] In this embodiment of the application, if the judgment result of step (b2) is yes, then the target filling thickness is determined and the iteration operation is terminated in step (c). Taking a certain iteration as an example, assuming the current rock wool filling thickness is 0.064 meters, the average temperature rise on the unexposed surface is 139℃ (≤140℃), and the maximum single-point temperature rise on the unexposed surface is 181℃ (close to 180℃, which is satisfied because the iteration accuracy allows). At this time, the dual constraint conditions are satisfied, and the judgment result is "yes". Then, 0.064 meters is determined as the target filling thickness of the rock wool, and the iteration loop is terminated immediately to avoid excessive iteration and increased calculation cost. After determining the target thickness, the calculation result needs to be checked again by substituting it into the model to ensure that there is no calculation error. At the same time, the final thickness value and the corresponding temperature rise data are recorded as the basis for design output.

[0150] In this embodiment of the application, if the result of step (b2) is negative, the thickness is adjusted according to the preset rules and the iterative operation is returned. The adjustment process requires checking whether the rock wool has melted or undergone a phase change.

[0151] First, perform the inspection: According to the characteristics of rock wool products, its maximum withstand temperature is 700℃-800℃. When the temperature of the fire-facing surface of the rock wool exceeds 700℃, it will melt. Calculate the fire-facing surface temperature of the rock wool at the current thickness using the transient heat conduction model in step S3. For example, when the current thickness is 0.05 meters, the fire-facing surface temperature of the rock wool = fire temperature - (heat flux density × outer panel thermal resistance) ≈ 603℃ - (513 × 0.00011) ≈ 602.94℃ < 700℃, so there is no melting or phase change. If the thickness of a certain iteration is too thin (e.g., 0.03 meters), and the calculated fire-facing surface temperature of the rock wool is 720℃ > 700℃, then directly jump to step (d) to increase the thickness.

[0152] Next, the adjustment amount is calculated according to the preset rule: the preset rule is "thickness adjustment amount = current thickness × (maximum temperature rise excess / corresponding threshold)". Taking the first iteration as an example, the average temperature rise excess on the unexposed surface is 160-140=20℃, and the excess ratio is 20 / 140≈14.3%; the maximum single-point temperature rise excess on the unexposed surface is 208-180=28℃, and the excess ratio is 28 / 180≈15.6%. Taking the larger excess ratio of 15.6%, the adjustment amount is calculated as 0.05×15.6%≈0.0078 meters. Then, the thickness is updated according to the adjustment amount: the new thickness is 0.05+0.0078≈0.0578 meters, retaining 4 decimal places to ensure accuracy. After the update, return to step (b), and substitute 0.0578 meters as the new iteration thickness into the model to start the next loop. During the adjustment process, it is necessary to ensure that the adjustment amount is positive (because the thickness needs to be increased to improve the heat insulation when the temperature rise exceeds the standard). At the same time, the maximum adjustment amount in a single instance is set to not exceed 20% of the current thickness to avoid excessive adjustment range leading to iterative oscillation.

[0153] In this embodiment, this step replaces the traditional trial-and-error method of repeatedly creating samples and conducting tests with a standardized iterative solution process, significantly shortening the design cycle for the rock wool filling thickness of container fire doors and solving the problem of low design efficiency. Simultaneously, by accurately calculating the minimum target filling thickness that meets dual constraints, it avoids material cost waste caused by overfilling while ensuring the fire door's thermal insulation performance meets standards, achieving an optimal balance between thermal insulation performance and material cost, directly solving the core technical problem of existing technologies. Furthermore, the addition of a meltdown inspection step ensures that the target filling thickness can stably perform its thermal insulation function in actual fire scenarios, improving the safety and reliability of the design.

[0154] In the several embodiments provided in this application, it should be understood that the disclosed methods can be implemented in other ways.

[0155] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application.

[0156] The embodiments of this application can acquire and process relevant data based on artificial intelligence technology. Artificial intelligence is the theory, method, and technology that uses digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use that knowledge to obtain optimal results.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application 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 this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method for calculating the heat conduction of rock wool filling thickness in a container fire door, characterized in that, The method includes: Obtain the structural parameters and initial thermal parameters of the container fire door. The structural parameters include the outer panel thickness, inner panel thickness, outer panel thermal conductivity, and inner panel thermal conductivity. The initial thermal parameters include the preset thermal conductivity of the rock wool and the preset fire resistance limit that the fire door needs to achieve. Based on the preset fire resistance limit, determine the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold of the fire door's unexposed surface during the fire resistance limit test time. Based on the structural parameters and the preset thermal conductivity, a composite structure heat conduction model of the fire door is established based on the principle of equivalent thermal resistance. This includes: calculating the overall equivalent thermal resistance of the fire door based on the thickness and thermal conductivity of the outer panel, rock wool filling layer, and inner panel; and establishing the composite structure heat conduction model based on the overall equivalent thermal resistance and the standard fire temperature curve. The overall equivalent thermal resistance is calculated using the following formula: ； in, For the overall equivalent thermal resistance, For the thickness of the outer panel, The thermal conductivity of the outer panel, For the thickness of rock wool filling, The thermal conductivity of rock wool is preset. For the thickness of the inner panel, The thermal conductivity of the inner panel; Using the rock wool filling thickness as a variable, the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold are used as dual constraints. The heat conduction model of the composite structure is solved iteratively to obtain the target filling thickness of the rock wool.

2. The method for calculating the heat conduction of the rock wool filling thickness in a container fire door as described in claim 1, characterized in that, The acquisition of the structural parameters and initial thermal parameters of the container fire door includes: Obtain the thickness data of the outer and inner panels and the thermal conductivity of their materials; Determine the preset thermal conductivity of rock wool under standard operating conditions; Determine the preset fire resistance limit corresponding to the target fire resistance rating of the fire door; Based on the thickness data, the thermal conductivity, and the preset fire resistance limit, the structural parameters and initial thermal parameters required for the composite structure heat conduction model are determined.

3. The method for calculating the thermal conductivity of rock wool filling thickness in container fire doors as described in claim 1, characterized in that, The determination of the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold of the fire door's unexposed surface during the fire resistance limit test time based on the preset fire resistance limit includes: Based on the preset fire resistance limit, determine the corresponding upper limit of average temperature rise on the unexposed surface and the upper limit of single-point temperature rise. The upper limit of the average temperature rise is used as the maximum allowable average temperature rise threshold. The upper limit of single-point temperature rise is used as the maximum allowable single-point temperature rise threshold.

4. The method for calculating the heat conduction of the rock wool filling thickness in a container fire door as described in claim 1, characterized in that, The establishment of the composite structure heat conduction model based on the overall equivalent thermal resistance and standard fire temperature curve includes: The overall equivalent thermal resistance is corrected to compensate for the local thermal bridging effect caused by the perimeter frame and / or internal metal components of the door. Based on the corrected overall equivalent thermal resistance and the standard fire temperature curve, a transient heat conduction mathematical model of the fire door is constructed.

5. The method for calculating the heat conduction of the rock wool filling thickness in a container fire door as described in claim 1, characterized in that, The condition of using the maximum allowable average temperature rise threshold and the maximum allowable single-point temperature rise threshold as dual constraints includes: The maximum allowable average temperature rise threshold is converted into the first termination condition for calculating the average temperature of the unexposed surface. The maximum allowable single-point temperature rise threshold is converted into a second termination condition for calculating the highest temperature on the unexposed surface. The rock wool filling thickness must simultaneously meet both the first termination condition and the second termination condition.

6. The method for calculating the thermal conductivity of rock wool filling thickness in container fire doors as described in claim 1, characterized in that, The iterative solution of the composite structure heat conduction model to obtain the target filling thickness of the rock wool includes: (a) Set the rock wool filling thickness as an iteration variable and assign it an initial value; (b) Enter the iteration loop and perform the following operations: (b1) Substitute the rock wool filling thickness value in the current iteration cycle into the composite structure heat conduction model to calculate the corresponding average temperature rise on the unexposed surface and the maximum single-point temperature rise on the unexposed surface; (b2) Determine whether the calculation result of step (b1) simultaneously satisfies the following dual constraints: The average temperature rise of the unexposed surface does not exceed the maximum permissible average temperature rise threshold; and The maximum single-point temperature rise on the unexposed surface shall not exceed the maximum allowable single-point temperature rise threshold. (c) If the judgment result of step (b2) is yes, then the rock wool filling thickness value of the current iteration is determined as the target filling thickness, and the iteration cycle is terminated; (d) If the judgment result of step (b2) is negative, the rock wool filling thickness value is adjusted according to the preset rules, and the process returns to step (b) for the next iteration calculation.

7. The method for calculating the heat conduction of rock wool filling thickness in container fire doors as described in claim 6, characterized in that, The step of adjusting the rock wool filling thickness value according to preset rules includes: The thickness adjustment amount for the next iteration is calculated based on the average temperature rise of the unexposed surface and the amount by which the maximum single-point temperature rise of the unexposed surface exceeds its corresponding threshold. The rock wool filling thickness value is updated based on the thickness adjustment amount.

8. The method for calculating the thermal conductivity of rock wool filling thickness in container fire doors as described in claim 6, characterized in that, Before determining whether the calculation result of the above judgment step (b1) simultaneously satisfies the following dual constraints, the following steps are also included: Check whether the rock wool filling layer has melted or undergone a phase change at the current thickness value. If melting or phase change is detected, proceed directly to step (d) to increase the thickness of the rock wool filling layer.

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