A method, system and medium for constructing a heat removal coefficient calculation model considering the size of a side smoke exhaust port

Abstract

The application discloses a heat exhaust coefficient calculation model construction method and system considering side exhaust port size and a medium, relates to the technical field of smoke exhaust design, and constructs a heat exhaust test device with adjustable side exhaust port size, provides a heat exhaust coefficient calculation model based on the heat exhaust test device with adjustable side exhaust port size, considers the influence of the length-width ratio of the exhaust port, constructs a heat exhaust coefficient function about entrainment influence variables, tunnel geometric variables, environmental variables and physical environmental variables, and carries out dimension analysis on the heat exhaust coefficient function, fits out a dimensionless heat release quantity, and an expression relationship between the dimensionless heat release quantity and the heat exhaust coefficient, so that the accuracy of heat exhaust coefficient estimation of the smoke exhaust system of the curved tunnel is ensured.

Description

Technical Field

[0001] This invention relates to the field of smoke exhaust design technology, specifically to a method, system, and medium for constructing a heat exhaust coefficient calculation model that takes into account the size of the side smoke exhaust outlet. Background Technology

[0002] In tunnel fires, the primary goal of smoke extraction systems is to create and maintain a smoke-free, low-temperature safe environment for personnel evacuation and fire rescue. The heat extraction coefficient is a direct and crucial indicator of whether a smoke extraction system can effectively control the fire's thermal environment. Overestimating the heat extraction coefficient results in an insufficient system heat extraction capacity, making it unable to effectively control smoke and heat during a fire and potentially causing safety accidents. Conversely, underestimating the heat extraction coefficient leads to an overly conservative design, selecting excessively powerful fans and too much equipment, resulting in huge construction costs and high energy consumption during operation, ultimately causing waste.

[0003] Urban underground transportation is evolving from simple point-to-line structures to more complex network structures. Due to their unique geometric characteristics, these tunnels exhibit significantly different smoke flow characteristics compared to straight tunnels under fire conditions, posing new challenges to tunnel fire safety research. When using centralized top smoke extraction, smoke is confined to a localized area and extracted. This mechanism of zoned control and on-site removal can more precisely suppress smoke diffusion, providing better support for personnel escape and fire rescue. However, centralized top smoke extraction requires reserving a large space for smoke extraction ducts in the superstructure, which significantly increases the tunnel's excavation depth and cross-sectional dimensions, especially in shallow urban areas, greatly increasing engineering difficulty and civil engineering costs.

[0004] Furthermore, in curved tunnels, smoke moves along the outer arch wall due to centrifugal force, deviating from the tunnel's crown centerline. This makes it difficult for the top smoke vents to capture the smoke. Installing smoke vents on the outer wall of the tunnel can overcome the adverse effects of centrifugal force and is more conducive to smoke extraction. However, the presence of centrifugal force in curved tunnels alters the flow field structure, temperature distribution, and mixing mechanism of fire smoke with fresh air. When smoke flows through curved sections, it is subjected to the coupled effects of buoyancy, the suction force of the smoke vents, and centrifugal force, making the flow field characteristics more complex, and conventional heat dissipation coefficient relationships can no longer accurately represent it.

[0005] Therefore, it is urgent to propose an experimental device and calculation method for the heat dissipation coefficient of the side smoke exhaust ramp, especially considering the influence of the length-to-width ratio of the smoke exhaust outlet, so as to provide a scientific basis for optimizing the design of emergency ventilation strategies and ensuring the safety of personnel. Summary of the Invention

[0006] The technical problem this invention aims to solve is that the smoke exhaust system of curved tunnels has smoke exhaust vents set on the outer wall of the tunnel, and conventional heat exhaust coefficient relationships can no longer accurately represent this. The purpose of this invention is to provide a method, system, and medium for constructing a heat exhaust coefficient calculation model that considers the size of the side smoke exhaust vents. It provides a heat exhaust test device with adjustable side smoke exhaust vent sizes for the smoke exhaust system of curved tunnels, and based on this device, a heat exhaust coefficient calculation model is provided. Considering the influence of the length-to-width ratio of the smoke exhaust vents, a heat exhaust coefficient function is constructed considering the entrainment influence variable, tunnel geometric variables, environmental variables, and physical environmental variables. Dimensional analysis is performed on the heat exhaust coefficient function to fit the dimensionless heat release quantity, and the dimensionless heat release quantity expression relationship of the heat exhaust coefficient is obtained, ensuring the accuracy of the heat exhaust coefficient estimation for the smoke exhaust system of curved tunnels.

[0007] This invention is achieved through the following technical solution:

[0008] This solution provides a method for constructing a heat dissipation coefficient calculation model that considers the size of the side flue gas outlet. The method includes:

[0009] Construct a heat dissipation test device with adjustable side exhaust port size;

[0010] Smoke exhaust experiments were conducted in the target experimental tunnel under different working conditions, with the length-to-width ratio of the smoke exhaust outlet, heat release rate, and smoke exhaust velocity as variables affecting entrainment. The heat exhaust coefficient under different working conditions was calculated.

[0011] A heat exhaust coefficient function is constructed based on the influencing variables of suction, tunnel geometry, environmental variables, and physical environmental variables. Dimensional analysis is then performed on the heat exhaust coefficient function to fit the dimensionless heat release quantity, and the dimensionless heat release quantity expression relationship of the heat exhaust coefficient is obtained. The dimensionless heat release quantity expression relationship is related to the aspect ratio of the smoke exhaust outlet.

[0012] The dimensionless heat release quantity based on the heat dissipation coefficient guides the design of tunnel smoke exhaust.

[0013] A further optimized solution is that the heat dissipation test device includes: a main exhaust duct, an exhaust duct connecting duct, and an exhaust ramp;

[0014] The side wall of the exhaust ramp is provided with side exhaust outlets that correspond one-to-one with the exhaust duct connecting passages; the length-to-width ratio of the side exhaust outlets is adjustable.

[0015] A further optimization is that the exhaust ramp is a curved pipe with a gradually changing cross-sectional area, and the cross-sectional area of ​​the exhaust ramp is larger the closer it is to the main exhaust duct.

[0016] A further optimization scheme is that the calculation method for the heat dissipation coefficient includes:

[0017] The thickness of the flue gas layer and the upstream flue gas velocity of the heat dissipation test device were calculated by combining the structural parameters of the target experimental tunnel and the flue gas monitoring parameters.

[0018] The heat carried by the flue gas discharged from the exhaust port of the heat dissipation test device is characterized by the flue gas monitoring parameters. The heat carried by the flue gas flow upstream of the heat dissipation test device is characterized by substituting the flue gas layer thickness and the flue gas flow velocity upstream of the heat dissipation test device into the gas temperature formula.

[0019] The heat dissipation coefficient at the current exhaust velocity is characterized by the ratio of the heat carried by the flue gas discharged from the exhaust port to the heat carried by the upstream flue gas flow.

[0020] A further optimized solution is that the upstream flue gas velocity u of the heat dissipation test device... cs Calculate according to the following formula:

[0021] ;

[0022] Where g represents the acceleration due to gravity; This represents the difference between the density of the smoke gas and the density of the surrounding air. Indicates ambient air density; The geometric height of the target experimental tunnel is represented by α; the velocity coefficient is represented by α.

[0023] A further optimized solution is that the method for calculating the thickness of the flue gas layer includes:

[0024] Using the height of the flue gas layer interface as an unknown variable, calculate the flue gas temperature integral ratio of the upper tunnel layer and the flue gas temperature integral ratio of the lower tunnel layer respectively.

[0025] The height of the flue gas layer interface is determined by solving for the minimum sum of the flue gas temperature integral ratio of the upper layer and the flue gas temperature integral ratio of the lower layer of the tunnel, and the thickness of the flue gas layer is then determined.

[0026] A further optimized scheme is as follows: the dimensionless heat release quantity Q* is represented as:

[0027] Q*= ;

[0028] Where d represents the hydraulic diameter of the flue gas outlet; Q represents the heat release rate; V e Indicates the exhaust velocity; H represents the tunnel's geometric height H; T a Indicates air temperature; ρ a The density of air is represented by g; g represents the acceleration due to gravity; c represents the air density. p This indicates specific heat capacity.

[0029] A further optimized scheme is that the dimensionless heat release quantity of the heat dissipation coefficient is expressed as follows:

[0030] ;

[0031] Where E represents the heat dissipation coefficient, Q* represents the dimensionless heat release quantity, A represents the coefficient of the dimensionless heat release quantity, which has a first linear relationship with the length-to-width ratio of the flue gas outlet, and B represents the constant term, which has a second linear relationship with the length-to-width ratio of the flue gas outlet.

[0032] This solution also provides a system for constructing a heat dissipation coefficient calculation model that considers the size of the side flue gas outlet, used to implement the above-mentioned method for constructing a heat dissipation coefficient calculation model that considers the size of the side flue gas outlet. The system includes:

[0033] A building module is used to construct a heat dissipation test device with adjustable side exhaust port size;

[0034] The test module is used to conduct smoke exhaust experiments under different working conditions in the target test tunnel, using the length-to-width ratio of the smoke exhaust outlet, the heat release rate, and the smoke exhaust velocity as variables affecting the entrainment effect, and to calculate the heat exhaust coefficient under different working conditions.

[0035] The analysis and fitting module is used to construct a heat release coefficient function for the influencing variables of entrainment, tunnel geometry, environmental variables, and physical environmental variables, and to perform dimensional analysis on the heat release coefficient function to fit a dimensionless heat release quantity, as well as the dimensionless heat release quantity representation relationship of the heat release coefficient; the dimensionless heat release quantity representation relationship is related to the length-to-width ratio of the exhaust port;

[0036] The application module uses a dimensionless heat release quantity representation based on the heat dissipation coefficient to guide the design of tunnel smoke exhaust.

[0037] This solution also provides a computer-readable medium having a computer program stored thereon, which, when executed by a processor, enables the construction of a heat dissipation coefficient calculation model considering the size of the side exhaust outlet, as described above.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] This invention provides a method, system, and medium for constructing a heat exhaust coefficient calculation model that considers the size of the side exhaust outlet. It constructs a heat exhaust test device with adjustable side exhaust outlet size and provides a heat exhaust coefficient calculation model based on this device. Considering the influence of the exhaust outlet's aspect ratio, a heat exhaust coefficient function is constructed, relating to suction effects, tunnel geometry, environmental variables, and physical environmental variables. Dimensional analysis is performed on the heat exhaust coefficient function to fit a dimensionless heat release quantity, and the dimensionless heat release quantity expression relationship of the heat exhaust coefficient is obtained, ensuring the accuracy of heat exhaust coefficient estimation for curved tunnel exhaust systems. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0041] Figure 1 A schematic diagram illustrating the process of constructing a model for calculating the heat dissipation coefficient while considering the size of the side flue gas outlet;

[0042] Figure 2 A schematic diagram showing the calculation results of flue gas layer thickness under different operating conditions;

[0043] Figure 3 A schematic diagram showing the variation of the heat transfer coefficient under different length-to-width ratios of the flue gas outlets and different flue gas velocities.

[0044] Figure 4 A schematic diagram showing the variation of the heat release coefficient under different heat release rates and different exhaust air velocities.

[0045] Figure 5 Dimensional analysis fitting curve for the smoke exhaust outlet with an aspect ratio of n=1;

[0046] Figure 6 Dimensional analysis fitting curve for the smoke exhaust outlet with an aspect ratio of n=6;

[0047] Figure 7 Dimensional analysis fitting curves for different exhaust port aspect ratios and heat release rates;

[0048] Figure 8 A schematic diagram comparing the difference between the dimensionless heat release quantity relationship of the heat dissipation coefficient and the experimental test results;

[0049] Figure 9 A schematic diagram comparing the dimensionless heat release quantity relationship of the heat dissipation coefficient with the experimental test results;

[0050] Figure 10 A schematic diagram of the system architecture for constructing a heat dissipation coefficient calculation model that takes into account the size of the side flue gas outlet;

[0051] Figure 11 This is a schematic diagram of a heat dissipation test device with an adjustable side exhaust port size.

[0052] The attached diagram shows the markings and corresponding component names:

[0053] 1-Main exhaust duct; 2-Exhaust duct ramp; 3-Exhaust duct connecting passage; 4-Side exhaust outlet; 5-Fireproof glass; 6-Variable frequency fan; 7-Frequency tuner; 8-Hollow rectifier tube; 9-Exhaust fan; 10-Exhaust duct; 11-Liquefied propane; 12-Pressure reducing valve; 13-Gas flow controller; 14-Gas pipe; 15-Porous combustion chamber; 16-Thermocouple; 17-Temperature data acquisition module; 18-Data acquisition and analysis instrument; 19-Shielded cable; 20-Thermocouple tree; 21-High temperature hot-wire anemometer probe; 22-Anemometer data transmission line; 23-Fractional acquisition and analysis instrument. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0055] The smoke exhaust system of curved tunnels has smoke exhaust outlets set on the outer wall of the tunnel, and the conventional heat exhaust coefficient relationship can no longer accurately represent it; in view of this, this solution provides the following embodiments to solve the above-mentioned technical problems.

[0056] Example 1

[0057] This embodiment provides a method for constructing a heat dissipation coefficient calculation model that considers the size of the side exhaust outlet, such as... Figure 1 As shown, the method includes:

[0058] Step 1: Construct a heat dissipation test device with adjustable side exhaust port size;

[0059] Specifically, in step one, the heat dissipation test device includes: a main flue, a flue connecting duct, and a flue ramp; the side walls of the flue ramp are provided with side flue outlets that correspond one-to-one with the flue connecting ducts; the length-to-width ratio of the side flue outlets is adjustable. The flue ramp is a curved pipe with a gradually changing cross-sectional area; the closer to the main flue, the larger the cross-sectional area of ​​the flue ramp. The detailed structure of the heat dissipation test device is described in Example 2.

[0060] Step 2: Using the length-to-width ratio of the smoke exhaust outlet, the heat release rate, and the smoke exhaust velocity as variables affecting the entrainment, smoke exhaust experiments were conducted under different working conditions in the target experimental tunnel, and the heat exhaust coefficient under different working conditions was calculated.

[0061] In step two, the calculation method for the heat dissipation coefficient includes:

[0062] S21, the thickness of the flue gas layer and the upstream flue gas velocity of the heat dissipation test device are calculated by combining the structural parameters of the target experimental tunnel and the flue gas monitoring parameters;

[0063] In step S21, the upstream flue gas velocity u of the heat dissipation test device csCalculate according to the following formula:

[0064] ;

[0065] Where g represents the acceleration due to gravity; This represents the difference between the density of the smoke gas and the density of the surrounding air. Indicates ambient air density; The geometric height of the target experimental tunnel is represented by α; α represents the flow velocity coefficient, which is 0.613 in this embodiment.

[0066] In step S21, the method for calculating the thickness of the flue gas layer includes:

[0067] S211, using the height of the flue gas layer interface as an unknown variable, calculate the flue gas temperature integral ratio of the upper tunnel layer and the flue gas temperature integral ratio of the lower tunnel layer respectively.

[0068] S212, calculate the height of the flue gas layer interface when the sum of the flue gas temperature integral ratio of the upper layer and the flue gas temperature integral ratio of the lower layer of the tunnel is minimized, and determine the thickness of the flue gas layer.

[0069] The integral ratio method is a commonly used method for estimating smoke layer thickness. This method uses mathematical techniques to locate the significant and relatively stable temperature jump between the hot smoke layer formed by a fire and the lower cold air layer. By calculating the integral ratio of the upper and lower smoke temperatures separately, the position corresponding to the minimum integral ratio is found, thereby determining the smoke layer thickness *l*. The specific calculation relationship is expressed as follows:

[0070] ; ;

[0071] ;

[0072] Where T(z) represents the vertical temperature distribution function; r u This represents the integral ratio of flue gas temperature in the upper layer of the tunnel; r l The integral ratio of flue gas temperature in the lower tunnel layer is represented by z; the distance between the thermocouple and the tunnel arch is represented by r. i H represents the sum of the integral ratios of flue gas temperature in the upper and lower layers of the tunnel; H represents the geometric height of the target experimental tunnel; H int This indicates the height of the flue gas layer interface.

[0073] like Figure 2As shown, in this embodiment, under the conditions of an exhaust outlet aspect ratio n=2 and a heat release rate HRR=34kW, the thickness of the flue gas layer under different exhaust velocities is calculated. The point where the sum of the integral ratios under different conditions is the lowest is the flue gas stratification interface. When the exhaust velocity is 0, the calculated flue gas layer interface height is 0.53m, and the corresponding flue gas layer thickness is 0.1m. As the exhaust velocity increases, more high-temperature flue gas is discharged, and the flue gas layer thickness gradually decreases. When the exhaust velocity is 3m / s, the flue gas layer interface height is 0.58m, and the corresponding flue gas layer thickness is 0.05m. Since the distance between the exhaust outlet and the tunnel top is 0.05m, the temperature difference of the thermocouples closest to the tunnel top at the exhaust outlet is not significant under different n values. Starting from the second thermocouple from the top, the temperature difference under different n values ​​begins to become significant due to the influence of the exhaust outlet.

[0074] S22, based on flue gas monitoring parameters, characterize the heat carried by the flue gas discharged from the exhaust port of the heat exhaust test device, and substitute the flue gas layer thickness and the upstream flue gas flow velocity of the heat exhaust test device into the gas temperature formula to characterize the heat carried by the upstream flue gas flow of the heat exhaust test device.

[0075] S23, the heat dissipation coefficient E at the current exhaust gas velocity is characterized by the ratio of the heat carried by the flue gas discharged from the exhaust port to the heat carried by the upstream flue gas flow.

[0076] ;

[0077] ;

[0078] ;

[0079] in, This indicates the heat carried by the flue gas discharged from the exhaust port; This indicates the heat carried by the upstream flue gas flow; This indicates the mass flow rate of the flue gas discharged from the exhaust port; This indicates the mass flow rate of the upstream flue gas; This indicates the temperature rise of the flue gas at the exhaust port; This indicates the temperature rise of the upstream flue gas; ρ es ρ represents the density of the flue gas at the exhaust port. cs Indicates the upstream flue gas density; u es Indicates the velocity of the flue gas at the exhaust port; u cs denoted by , A represents the upstream flue gas velocity; A represents the cross-sectional area of ​​the flue gas outlet; w represents the geometric width of the target experimental tunnel.

[0080] The heat dissipation coefficient E under different operating conditions was calculated using the above method. The variation law of the heat dissipation coefficient under different flue gas velocities is as follows: Figure 3 and Figure 4As shown, the heat dissipation coefficient E increases with the increase of the exhaust gas velocity Ve. This is because the increase in exhaust gas velocity significantly enhances the ability of the exhaust port to draw in high-temperature flue gas; when the exhaust gas velocity is low, the suction force of the exhaust port is weak, and it may only be able to draw in a portion of the flue gas near the exhaust port. The flue gas further away mainly relies on its own buoyancy and propagation speed to flow forward, and may not be drawn away in time before flowing past the exhaust port, resulting in flue gas loss. When the exhaust gas velocity is increased, it can effectively discharge high-temperature flue gas from the ceiling over a larger area.

[0081] The variation of the heat dissipation coefficient under different length-to-height ratios n of the flue gas outlet (n=1, n=2, n=4, n=6) is shown in Figure 3. The heat dissipation coefficient gradually increases with increasing n. When n=1, the flue gas outlet is square, and its effective range is limited to the upper half of the outlet. When n=6, the flue gas outlet becomes elongated, covering a wider area of ​​the flue gas propagation path, thus drawing more high-temperature flue gas into the outlet and increasing the amount of heat dissipated. The length-to-height ratio n of the flue gas outlet significantly affects the heat dissipation efficiency. In practical engineering, increasing the length-to-height ratio n can improve the heat dissipation efficiency.

[0082] The variation of the heat removal coefficient under different heat release rates (HRRs) is shown in Figure 4. When the exhaust velocity is less than 1.5 m / s, the difference in heat removal coefficients under different HRRs is not significant. This is because when the exhaust velocity is low (<1.5 m / s), the suction force of the exhaust port is weak. Regardless of the size of the fire, the exhaust system can only remove a portion of the smoke, and the amount of smoke removed is relatively fixed, so the HRR has little effect on the heat removal coefficient. However, when the exhaust velocity is greater than 1.5 m / s, the heat removal coefficient E gradually decreases as the HRR increases. This is because the suction capacity of the exhaust port is enhanced after the exhaust velocity increases. For a smaller HRR, the smoke layer is thinner, the smoke temperature is lower, and the smoke can be effectively removed. For a larger HRR, the smoke layer is thicker, the flow rate is faster, and it is more difficult to intercept and change the direction of the high-speed smoke flow, resulting in the loss of a large amount of high-temperature smoke and a decrease in the heat removal coefficient.

[0083] As can be seen from the above analysis, the heat dissipation coefficient E is related to the size of the flue gas outlet, the heat release rate, and the flue gas velocity.

[0084] Step 3: Construct a heat release coefficient function for the influencing variables of suction, tunnel geometry, environmental variables, and physical environmental variables, and perform dimensional analysis on the heat release coefficient function to fit the dimensionless heat release quantity, as well as the dimensionless heat release quantity representation relationship of the heat release coefficient; the dimensionless heat release quantity representation relationship is related to the length-to-width ratio of the exhaust port;

[0085] In step three, the heat dissipation coefficient function is expressed as: ;

[0086] Choose H, ρ a, c p and T a Dimensionless analysis is performed using these as basic parameters:

[0087] ;

[0088] in, Indicates temperature; ~ Indicates the first dimensionless coefficient; ~ Indicates the second dimensionless coefficient; ~ Indicates the third dimensionless coefficient; ~ This indicates the fourth dimensionless quantity; ~ The fifth dimensionless quantity is represented by L; the length is represented by T; the mass is represented by M.

[0089] The dimensionless coefficients are obtained by solving for:

[0090] ;

[0091] Then we get

[0092] ;

[0093] The heat dissipation coefficient function can then be written as: ;right By performing multiplication and division operations between the terms to eliminate terms, the heat dissipation coefficient E can be calculated using the following formula:

[0094] ;

[0095] In step three, the dimensionless heat release quantity Q* is expressed as: Q*= ;

[0096] Where d represents the hydraulic diameter of the flue gas outlet; Q represents the heat release rate; V e Indicates the exhaust velocity; H represents the tunnel's geometric height H; T a Indicates air temperature; ρ a The density of air is represented by g; g represents the acceleration due to gravity; c represents the air density. p This indicates specific heat capacity.

[0097] In step three, the dimensionless heat release quantity of the heat dissipation coefficient is expressed as follows:

[0098] ;

[0099] Where E represents the heat dissipation coefficient, Q* represents the dimensionless heat release quantity, A represents the coefficient of the dimensionless heat release quantity, which has a first linear relationship with the length-to-width ratio of the flue gas outlet, and B represents the constant term, which has a second linear relationship with the length-to-width ratio of the flue gas outlet.

[0100] Specifically, the heat dissipation coefficient values ​​under different operating conditions are fitted according to the heat dissipation coefficient E relationship, such as... Figure 5 and Figure 6 As shown, it was found that the heat dissipation coefficient under different operating conditions exhibits a logarithmic function relationship with the dimensionless heat release quantity, satisfying y=blnx+c, where b and c are coefficients; the values ​​of coefficients b and c differ under different heat release rates; for example... Figure 5 As shown, under the condition that the aspect ratio of the exhaust outlet n=1, when the heat release rate HRR=18kW, y=-0.25lnx+0.85. As the heat release rate HRR increases, coefficient b gradually increases, and coefficient c gradually decreases. When the heat release rate HRR=42kW, y=-0.18lnx+0.5. The fitting results are good under different heat release rates HRR, and the coefficient of determination R0 is high. 2 Not less than 0.94.

[0101] like Figure 6 As shown, under the condition that the aspect ratio of the exhaust outlet is n=6, when the heat release rate HRR=18kW, y=-0.42lnx+1.24. With the increase of the heat release rate HRR, the coefficient b gradually increases, and the coefficient c gradually decreases. When the heat release rate HRR=42kW, y=-0.32lnx+0.7. The fitting results are good under different heat release rates HRR, and the coefficient of determination R0 is high. 2 Not less than 0.94. It can be seen that when the length-to-height ratio of the exhaust outlet increases, the coefficients b and c change more drastically. The logarithmic function relationship is also satisfied under the conditions of n=2 and n=4, which will not be listed here individually.

[0102] like Figure 7 As shown, the coefficients b and c obtained under different operating conditions are analyzed. Coefficient b increases linearly with increasing n, while coefficient c decreases linearly, indicating good linear fitting results, although the magnitude of change varies. The expressions for the heat dissipation coefficient E obtained under different n values ​​are shown in Table 1. The heat dissipation coefficient for different flue gas outlet sizes can be calculated using Table 1.

[0103] Table 1. Formulas for calculating the heat transfer coefficient E under different n values.

[0104] The length-to-height ratio of the smoke exhaust outlet is n Heat dissipation coefficient E 1 2 4 6

[0105] Based on the given data on the heat transfer coefficient E under different exhaust outlet length-to-height ratios n, each equation is a linear function of y with respect to ln(x), in the form y = d * ln(x) + e, where d and e are linear functions of Q. However, to further simplify the formula and make the prediction formula more universal, the exhaust outlet length-to-height ratio n is also included in the prediction formula, and d and e are expressed as functions of n and Q. Assuming that d(n,Q) and e(n,Q) are both linear functions of n and Q, that is:

[0106] ;

[0107] ;

[0108] Where C1~C4 and D1~D4 are coefficients in the expression. The values ​​of each coefficient were obtained through linear regression analysis, and finally, the heat dissipation coefficient calculation model of this embodiment was obtained:

[0109] ;

[0110] The heat dissipation coefficient calculation model described above can be used to predict the heat dissipation coefficient E under different fire source power, smoke exhaust velocity, and smoke exhaust outlet size. This embodiment compares the E predicted using the above heat dissipation coefficient calculation model with experimental test values. Figure 8 and Figure 9 As shown, when the exhaust gas velocity is low (Ve=0.5m / s), the heat transfer coefficient E is very small, almost around 0.1. When both the predicted and measured values ​​are small, the relative error will be significantly amplified, leading to a misleading judgment on the model's reliability. Therefore, using absolute error instead of relative error as the evaluation standard is more reasonable. Thus, when the exhaust gas velocity is low (Ve=0.5m / s), comparing the predicted and experimental values ​​using absolute error, the difference in E under different operating conditions is less than 0.1. When the exhaust gas velocity Ve>0.5m / s, the relative error between the predicted and experimental values ​​under different operating conditions is almost always within 20%. The results predicted using this formula agree well with the experimental test values, verifying the reliability of the prediction formula.

[0111] Step four: The dimensionless heat release quantity relationship based on the heat dissipation coefficient guides the tunnel smoke exhaust design.

[0112] Example 2

[0113] This embodiment provides a system for constructing a heat dissipation coefficient calculation model that considers the size of the side flue gas outlet. Its characteristic is that it is used to implement the heat dissipation coefficient calculation model construction method considering the size of the side flue gas outlet described in Embodiment 1, such as... Figure 10 As shown, the system includes:

[0114] A building module is used to construct a heat dissipation test device with adjustable side exhaust port size;

[0115] The test module is used to conduct smoke exhaust experiments under different working conditions in the target test tunnel, using the length-to-width ratio of the smoke exhaust outlet, the heat release rate, and the smoke exhaust velocity as variables affecting the entrainment effect, and to calculate the heat exhaust coefficient under different working conditions.

[0116] The analysis and fitting module is used to construct a heat release coefficient function for the influencing variables of entrainment, tunnel geometry, environmental variables, and physical environmental variables, and to perform dimensional analysis on the heat release coefficient function to fit a dimensionless heat release quantity, as well as the dimensionless heat release quantity representation relationship of the heat release coefficient; the dimensionless heat release quantity representation relationship is related to the length-to-width ratio of the exhaust port;

[0117] The application module uses a dimensionless heat release quantity representation based on the heat dissipation coefficient to guide the design of tunnel smoke exhaust.

[0118] Specifically, such as Figure 11 As shown, the heat dissipation test device in this scheme includes: a main exhaust duct 1, an exhaust ramp 2, an exhaust duct connecting passage 3, side exhaust outlets 4 on the side walls of the exhaust ramp that correspond one-to-one with the exhaust duct connecting passage, a main tunnel air supply system, a ramp exhaust system, a fire source combustion system, a temperature measurement system, and a wind speed measurement system.

[0119] The main exhaust duct 1 is made of fireproof board with a thickness of more than 10cm. It is fixed and assembled with a steel frame, and the joints are sealed with fireproof glue. The ratio of the main exhaust duct 1 is generally 1:10. One side of the main exhaust duct 1 is made of fireproof glass 5, which can be used to observe the flow of smoke and the thickness of the smoke layer.

[0120] Similar to the main smoke exhaust duct 1, the smoke exhaust ramp 2 is made of fireproof board and fireproof glass, fixed with a steel frame and sealed with fireproof glue. The smoke exhaust ramp 2 is interconnected with the main smoke exhaust duct 1. The model ramp 2 has a certain curvature, and its curve radius is determined according to the actual tunnel. A certain number (e.g., 3) of side smoke exhaust ports 4 are opened at equal intervals on the side of the model ramp 2. The spacing of the side smoke exhaust ports 4 is determined according to actual needs. In the actual tunnel, the spacing is generally 40m-60m. In the event of an actual fire, 1-3 smoke exhaust ports will be opened for smoke exhaust. Each side smoke exhaust port 4 is connected to the main smoke exhaust duct 1 and the smoke exhaust ramp 2 through the smoke exhaust duct connecting passage 3.

[0121] The main tunnel ventilation system includes: a variable frequency fan 6, a frequency converter 7, and a hollow rectifier tube 8; the hollow rectifier tube 8 covers the entire cross section at the end of the main exhaust duct 1, making the airflow in the main exhaust duct 1 stable and uniform; the wind speed in the main exhaust duct 1 can be controlled by adjusting the frequency of the variable frequency fan 6.

[0122] The ramp smoke exhaust system includes: smoke exhaust fan 9, frequency converter 7, and smoke exhaust duct 10. The smoke exhaust fan 9 is located in the middle of the smoke exhaust duct 10. The smoke exhaust duct 10 is made of stainless steel. The exhaust port of the smoke exhaust fan 9 is welded to the smoke exhaust duct 10. The smoke exhaust duct connecting the smoke exhaust duct 10 and the smoke exhaust duct connecting the smoke exhaust duct 3 to each side smoke exhaust port 4 are also welded.

[0123] In this embodiment, the side smoke exhaust vent 4 is 0.6m in both length and width (scaled to 1:10, and this scale will be followed thereafter). Generally, the width of the smoke exhaust vent 4 is 0.2m-0.6m, and the height is 0.1m-0.4m. To change the area and aspect ratio of the side smoke exhaust vent 4, this embodiment uses a 5cm thick fireproof board to seal it. The fireproof board is bolted to the side wall of the model ramp 2 and sealed with fireproof adhesive. Changing the area and aspect ratio of the fireproof board used for sealing allows for control over the area and aspect ratio of the side smoke exhaust vent 4.

[0124] The combustion system includes: liquefied propane 11, a pressure reducing valve 12, a gas flow controller 13, a gas pipe 14, and a porous combustion chamber 15. The pressure reducing valve 12 is connected to both the liquefied propane 11 and the gas flow controller 13 via the gas pipe 14. The outlet of the gas flow controller 13 is connected to the porous combustion chamber 15 via the gas pipe 14. By pre-setting the output flow rate of the gas flow controller 13, the heat release rate of propane combustion can be controlled. The heat of combustion of propane is approximately 46.4 kJ / g, and the product of the propane mass flow rate and its heat of combustion is the heat release rate of propane combustion at the current mass flow rate.

[0125] The temperature measurement system includes thermocouples 16, a temperature data acquisition module 17, and a data acquisition and analysis instrument 18. The 1mm diameter thermocouples 16 are evenly arranged on the top of the model ramp 2 at 10cm intervals. The thermocouples 16 and the temperature data acquisition module 17 are connected by shielded wires 19 to monitor the temperature rise of the flue gas upstream of the tunnel arch. A thermocouple tree 20 is installed at each smoke exhaust outlet. These thermocouple trees 20 are composed of thermocouples 16 evenly arranged along the height of the model ramp 2 with a spacing of 2 cm to monitor the temperature rise of the side smoke exhaust outlet 4. And calculate the thickness l of the flue gas layer.

[0126] The wind speed measurement system includes a high-temperature hot-wire anemometer 21, a wind speed data transmission line 22, and a fractional acquisition and analysis instrument 23. High-temperature hot-wire anemometers 20 are arranged in the main exhaust duct 1 and the exhaust ramp 2. Following typical tunnel cross-sectional dimensions, four high-temperature hot-wire anemometers 21 are evenly distributed across each wind speed monitoring section. By changing the wind speeds of the main exhaust duct 1 and the side exhaust vents 4 at different fan frequencies, the wind speed-frequency relationship between the variable frequency fan 6 and the exhaust fan 9 can be calibrated. When different numbers of side exhaust vents 4 are opened, the exhaust wind speed of the side exhaust vents 4 needs to be calibrated separately; the smoke velocity u at the side exhaust vents 4 can be obtained through the aforementioned wind speed measurement system. es And the upstream flue gas velocity u of model ramp 2 cs .

[0127] Example 3

[0128] This embodiment provides a computer-readable medium storing a computer program. The computer program, executed by a processor, can implement the heat dissipation coefficient calculation model construction method considering the side exhaust port size as described in Embodiment 1; specifically, it performs the following steps:

[0129] Step 1: Construct a heat dissipation test device with adjustable side exhaust port size;

[0130] Step 2: Using the length-to-width ratio of the smoke exhaust outlet, the heat release rate, and the smoke exhaust velocity as variables affecting the entrainment, smoke exhaust experiments were conducted under different working conditions in the target experimental tunnel, and the heat exhaust coefficient under different working conditions was calculated.

[0131] Step 3: Construct a heat release coefficient function for the influencing variables of suction, tunnel geometry, environmental variables, and physical environmental variables, and perform dimensional analysis on the heat release coefficient function to fit the dimensionless heat release quantity, as well as the dimensionless heat release quantity representation relationship of the heat release coefficient; the dimensionless heat release quantity representation relationship is related to the length-to-width ratio of the exhaust port;

[0132] Step four: The dimensionless heat release quantity relationship based on the heat dissipation coefficient guides the tunnel smoke exhaust design.

[0133] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing a heat dissipation coefficient calculation model considering the size of the side flue gas outlet, characterized in that, The method includes: Construct a heat dissipation test device with adjustable side exhaust port size; Smoke exhaust experiments were conducted in the target experimental tunnel under different working conditions, with the length-to-width ratio of the smoke exhaust outlet, heat release rate, and smoke exhaust velocity as variables affecting entrainment. The heat exhaust coefficient of the heat exhaust test device under different working conditions was calculated. A heat exhaust coefficient function was constructed considering the influencing variables of suction, tunnel geometry, environmental variables, and physical environmental variables. Dimensional analysis was then performed on the heat exhaust coefficient function using smoke exhaust experimental data to obtain the dimensionless heat release quantity and the dimensionless heat release quantity representation relationship between the heat exhaust coefficient and the smoke exhaust outlet. This dimensionless heat release quantity representation relationship is related to the length-to-width ratio of the smoke exhaust outlet. The dimensionless heat release quantity based on the heat dissipation coefficient guides the design of tunnel smoke exhaust.

2. The method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet according to claim 1, characterized in that, The heat dissipation test device includes: a main flue, a flue connecting duct, and a flue ramp; The side wall of the exhaust ramp is provided with side exhaust outlets that correspond one-to-one with the exhaust duct connecting passages; the length-to-width ratio of the side exhaust outlets is adjustable.

3. The method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet according to claim 2, characterized in that, The exhaust ramp is a curved pipe with a gradually changing cross-sectional area; the closer it is to the main exhaust duct, the larger its cross-sectional area.

4. The method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet according to claim 1, characterized in that, The method for calculating the heat dissipation coefficient includes: The thickness of the flue gas layer and the upstream flue gas velocity of the heat dissipation test device were calculated by combining the structural parameters of the target experimental tunnel and the flue gas monitoring parameters. The heat carried by the flue gas discharged from the exhaust port of the heat dissipation test device is characterized by the flue gas monitoring parameters. The heat carried by the flue gas flow upstream of the heat dissipation test device is characterized by substituting the flue gas layer thickness and the flue gas flow velocity upstream of the heat dissipation test device into the gas temperature formula. The heat dissipation coefficient at the current exhaust velocity is characterized by the ratio of the heat carried by the flue gas discharged from the exhaust port to the heat carried by the upstream flue gas flow.

5. The method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet according to claim 4, characterized in that, The upstream flue gas velocity u of the heat dissipation test device cs Calculate according to the following formula: ； Where g represents the acceleration due to gravity; This represents the difference between the density of the smoke gas and the density of the surrounding air. Indicates ambient air density; The geometric height of the target experimental tunnel is represented by α; the velocity coefficient is represented by α.

6. The method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet according to claim 4, characterized in that, The method for calculating the thickness of the flue gas layer includes: Using the height of the flue gas layer interface as an unknown variable, calculate the flue gas temperature integral ratio of the upper tunnel layer and the flue gas temperature integral ratio of the lower tunnel layer respectively. The height of the flue gas layer interface is determined by solving for the minimum sum of the flue gas temperature integral ratio of the upper layer and the flue gas temperature integral ratio of the lower layer of the tunnel, and the thickness of the flue gas layer is then determined.

7. The method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet according to claim 1, characterized in that, The dimensionless heat release quantity Q* is represented as: Q*= ； Where d represents the hydraulic diameter of the flue gas outlet; Q represents the heat release rate; V e Indicates the exhaust velocity; H represents the tunnel's geometric height H; T a Indicates air temperature; ρ a The density of air is represented by g; g represents the acceleration due to gravity; c represents the air density. p This indicates specific heat capacity.

8. The method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet according to claim 1 or 7, characterized in that, The dimensionless heat release quantity of the heat dissipation coefficient is expressed as follows: ； Where E represents the heat dissipation coefficient, Q* represents the dimensionless heat release quantity, A represents the coefficient of the dimensionless heat release quantity, which has a first linear relationship with the length-to-width ratio of the flue gas outlet, and B represents the constant term, which has a second linear relationship with the length-to-width ratio of the flue gas outlet.

9. A system for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet, characterized in that, The system is used to construct a heat dissipation coefficient calculation model considering the size of the side flue gas outlet as described in any one of claims 1-8, the system comprising: A building module is used to construct a heat dissipation test device with adjustable side exhaust port size; The test module is used to conduct smoke exhaust experiments under different working conditions in the target test tunnel, using the length-to-width ratio of the smoke exhaust outlet, the heat release rate, and the smoke exhaust velocity as variables affecting the entrainment effect, and to calculate the heat exhaust coefficient under different working conditions. The analysis and fitting module is used to construct a heat release coefficient function for the influencing variables of entrainment, tunnel geometry, environmental variables, and physical environmental variables, and to perform dimensional analysis on the heat release coefficient function to fit a dimensionless heat release quantity, as well as the dimensionless heat release quantity representation relationship of the heat release coefficient; the dimensionless heat release quantity representation relationship is related to the length-to-width ratio of the exhaust port; The application module uses a dimensionless heat release quantity representation based on the heat dissipation coefficient to guide the design of tunnel smoke exhaust.

10. A computer-readable medium having a computer program stored thereon, characterized in that, The computer program, when executed by a processor, can implement the method for constructing a heat dissipation coefficient calculation model considering the size of the side exhaust outlet as described in any one of claims 1-8.

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