Quantitative evaluation method and device for gas diffusion characteristics of building group with pseudo heat island effect

Abstract

This invention relates to the fields of environmental science and fluid mechanics, and proposes a method and apparatus for quantitatively assessing the gas diffusion characteristics of building complexes with simulated heat island effects. By constructing a scaled-down model of the building complex with temperature-variable functionality and a ventilation system, the residual concentration of a baseline gas is measured under no-temperature-difference conditions. Keeping the ventilation conditions constant, the model temperature is adjusted to create a series of surface-environment temperature differences to simulate the evolution of heat island intensity, and the residual gas concentration is measured at each temperature difference. Based on experimental data, a nonlinear mathematical correction model including thermal hindrance and thermal penetration terms is established to obtain the heat island effect correction coefficient. Finally, this model is applied to quantitatively assess and predict the gas diffusion under actual heat island effects. This invention reproduces the nonlinear abrupt change process of gas concentration first increasing and then decreasing with temperature difference, realizing the calculation and prediction of harmful gas concentrations in urban building complexes and complex terrains under different surface-environment temperature differences, providing a scientific basis for environmental safety management and emergency response plan development.

Description

Technical Field

[0001] This invention relates to the fields of environmental science and fluid mechanics, and in particular to a method and apparatus for quantitatively assessing the gas diffusion characteristics of building complexes with pseudo-heat island effects. Background Technology

[0002] The urban heat island effect significantly impacts the diffusion and retention of pollutants within building complexes by altering local flow field structure and turbulence characteristics, posing a severe challenge to urban public safety and environmental risk assessment. Existing methods for assessing gas diffusion characteristics under the heat island effect primarily rely on computational fluid dynamics (CFD) numerical simulations or field observations based on a limited number of monitoring points. However, numerical simulation methods often face challenges such as model simplification, high computational costs, and inaccurate parameterization of key physical processes when dealing with nonlinear problems involving complex building complexes coupled with thermal buoyancy. Field observations, on the other hand, are constrained by uncontrollable environmental conditions and limited spatiotemporal resolution, making it difficult to systematically reveal the quantitative evolution of gas diffusion behavior under different heat island intensities.

[0003] An existing invention patent application with application number CN112347711A discloses a numerical simulation method for the impact of street valley horizontal ventilation on the urban heat island effect. This method uses a combination of Gauss-Seidel iterative algorithm and Newton iterative algorithm to solve for the airflow and pressure values ​​at the street valley intersection, aiming to improve the computational convergence speed and accuracy of CFD models in multi-street valley scenarios, thereby reducing the computational burden of large-scale simulations.

[0004] However, current technologies for assessing the risk of gas diffusion under the urban heat island effect mainly rely on numerical simulation and field observation. Numerical simulation is highly dependent on the setting of parameters such as boundary conditions and turbulence models, and often oversimplifies the urban underlying surface and building disturbances, leading to deviations between simulation results and actual diffusion behavior. Field observation is limited by the density of monitoring points, observation duration, and instantaneous meteorological changes, making it difficult to fully capture the spatiotemporal evolution of diffusion, and resulting in insufficient data representativeness and continuity. Both methods focus on qualitative or semi-quantitative analysis, lacking a quantitative assessment system that deeply couples controllable physical experiments with high-fidelity mathematical models. This makes it impossible to accurately quantify the dynamic impact of key driving factors such as heat island circulation and temperature stratification on pollutant diffusion paths, concentration distribution, and exposure risks, thus hindering the improvement of urban environmental safety early warning and refined governance capabilities, and failing to provide direct and reliable technical guidance for specific practical operations in urban environmental safety and refined governance. Summary of the Invention

[0005] In view of this, the present invention proposes a quantitative assessment method and device for the gas diffusion characteristics of building clusters under the pseudo-heat island effect, which can quantitatively assess gas diffusion under the heat island effect through controlled experiments and mathematical models, in order to solve the problem that existing schemes rely on simulation and observation and cannot quantitatively assess the risk of heat island diffusion.

[0006] The technical solution of this invention is implemented as follows: On the one hand, this invention provides a method for quantitatively evaluating the gas diffusion characteristics of building complexes with a pseudo-heat island effect, comprising the following steps: Construct a scaled-down model of a building complex with temperature control and ventilation systems; Under constant ventilation conditions without temperature difference, the scaled-down model of the building complex was subjected to constant ventilation, and the residual concentration of the reference gas in the scaled-down model of the building complex was measured. Keeping ventilation conditions constant, the temperature of the scaled-down model of the building complex was adjusted to create a series of surface-environment temperature differences, simulating the evolution of the heat island intensity, and measuring the residual gas concentration at each temperature difference; Based on the baseline gas residual concentration and gas residual concentration data at various temperature differences, a nonlinear mathematical correction model including thermal hindrance and thermal penetration terms is established to obtain the heat island effect correction coefficient. The heat island effect correction coefficient is applied to the analysis of gas diffusion characteristics under the actual heat island effect to achieve quantitative assessment and risk prediction.

[0007] Based on the above technical solutions, the preferred steps for determining the residual concentration of the reference gas within the scaled-down model of the building complex include: Under no temperature difference conditions, the building complex scale model was ventilated at a constant wind speed and the background gas concentration was measured after the flow field stabilized. A quantitative tracer gas was introduced into the scaled model of the building complex, and after the concentration stabilized, the total gas concentration was measured. The difference between the background gas concentration and the total gas concentration is calculated to obtain the baseline gas residual concentration.

[0008] Based on the above technical solutions, the preferred steps for measuring the residual gas concentration at various temperature differences include: The areas in the flow field where pollutants are easily deposited or whose concentrations are abnormally increased due to the influence of surface thermal buoyancy are designated as thermal retention sensitive areas. The residual gas concentration at various temperature differences in the heat retention sensitive area is measured using a sensor array.

[0009] Based on the above technical solutions, the preferred nonlinear mathematical correction model is: ; ; in, The baseline gas residual concentration; This is the urban heat island correction factor; The temperature difference between the Earth's surface and the surrounding airflow; The growth coefficient is the resistance factor, which characterizes the resistance strength of weak thermal buoyancy to the horizontal ventilation flow field. It is a natural constant; The temperature difference representing the maximum retardation characteristic is the temperature difference threshold when the thermal retardation effect is most significant. The turbulence penetration factor characterizes the ability of strong thermal buoyancy to clean up dead zone structures; The critical penetration temperature difference is the temperature difference that characterizes the transition from flow field structure dominated by stagnation to flow field structure dominated by penetration. This is the turbulence index.

[0010] Based on the above technical solutions, preferably, the heat retention sensitive area includes the leeward backflow area of ​​the building, the bottom of the street canyon, and the geometric center area of ​​the building complex in the scaled-down model of the building complex; The residual gas concentration exhibits a non-monotonic abrupt change characteristic as the temperature difference changes: when the temperature difference is less than the maximum hindrance characteristic temperature difference, it is in the thermal hindrance stage, and the concentration increases as the temperature difference increases; when the temperature difference is greater than the critical penetration temperature difference, it is in the thermal penetration stage, and the concentration decreases sharply as the temperature difference increases.

[0011] Based on the above technical solutions, the preferred approach to quantitative assessment and risk prediction specifically includes the following steps: Obtain the actual ground surface temperature and ambient air temperature in the scaled-down model of the building complex, and calculate the actual temperature difference; Substitute the actual temperature difference into the nonlinear mathematical correction model to calculate the heat island effect correction coefficient; The risk level is determined based on the value of the heat island effect correction coefficient: if the heat island effect correction coefficient is greater than 1, it is determined to be a high-risk blocking period; if the heat island effect correction coefficient is less than 1 and the value is significantly lower than 1, it is determined to be a low-risk penetration period.

[0012] On the other hand, the present invention provides a quantitative detection device for a method of quantitatively evaluating the gas diffusion characteristics of building complexes that realizes the above-mentioned pseudo-heat island effect, comprising: An environmental simulation chamber system is used to house scaled-down models of building complexes and provide a controlled experimental environment. The heat island environment construction subsystem includes a variable-temperature heat source base plate set at the bottom of the scaled-down model of the building complex, which is used to simulate surface heat sources of different intensities and generate controllable temperature differences. A flow field dynamics subsystem is used to generate and maintain a stable horizontal background wind field within the environmental simulation chamber. The nonlinear feature monitoring array consists of gas concentration sensors distributed in multiple heat retention sensitive areas within the scaled model of the building complex, and is used to monitor gas concentration changes in real time. The data analysis module is communicatively connected to the monitoring array and is used to receive and process concentration data, and to perform parameter fitting and calculation of the nonlinear mathematical correction model.

[0013] Based on the above technical solutions, preferably, the variable temperature heat source base plate is used to provide a continuously adjustable temperature difference of 0 degrees Celsius to 60 degrees Celsius relative to the ambient airflow.

[0014] Based on the above technical solutions, preferably, the gas concentration sensor is arranged in the heat retention sensitive area within the scaled-down model of the building complex.

[0015] Based on the above technical solutions, preferably, the heat retention sensitive area includes the backflow area on the leeward side of the building, the bottom of the street canyon, and the geometric center area of ​​the building complex.

[0016] The method and apparatus for quantitatively evaluating the gas diffusion characteristics of building complexes exhibiting a simulated heat island effect, as described in this invention, have the following advantages over existing technologies: (1) By constructing a quantitative assessment system based on physical experiments and mathematical models, the shortcomings of oversimplification in numerical simulation and incomplete field observation data in existing technologies are effectively overcome. This system uses controllable physical experiments to obtain real boundary conditions and key parameters, calibrates and drives mathematical models, and realizes accurate quantification of gas diffusion paths and concentration distribution under complex environments such as heat island circulation and temperature stratification. This significantly improves the accuracy and reliability of risk assessment and provides direct technical support for urban environmental safety early warning.

[0017] (2) By setting up a scaled-down model of the building complex, various meteorological scenarios and leakage conditions can be reproduced, and transient diffusion data that is difficult to capture by traditional field observations can be obtained efficiently. These experimental data provide reliable verification and input for the mathematical model, reduce the simulation's dependence on empirical parameters, make the evaluation results closer to reality, and enhance the applicability and robustness of the technology in complex urban environments.

[0018] (3) By establishing a coupling mechanism for real-time interaction between physical experimental data and mathematical models, dynamic and continuous simulation of the diffusion process was achieved. This mechanism can assimilate observation data in real time and dynamically correct model parameters, thereby accurately predicting the spatiotemporal evolution trend of pollutants under the influence of the heat island effect. This supports rapid simulation and comparison of different risk scenarios, providing dynamic and visualized decision-making basis for emergency response and long-term planning.

[0019] (4) Based on accurate diffusion simulation results, the system can output quantitative risk maps and exposure assessment reports, clearly identifying high-risk areas and affected populations. This breaks through the limitations of traditional qualitative or semi-quantitative analysis, which helps environmental management departments to formulate precise prevention and control measures and evacuation plans based on specific data, thereby improving the refinement and scientific level of urban public safety management. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart of the method for quantitatively evaluating the gas diffusion characteristics of building complexes with pseudo-heat island effect according to the present invention; Figure 2 This is a schematic diagram showing the relationship between residual concentration under different temperature differences and residual concentration without temperature difference in a typical thermal retardation to thermal penetration process measured by the quantitative evaluation method of gas diffusion characteristics of building complexes with pseudo-heat island effect of the present invention. Figure 3 This is a fitting iterative diagram of the correction coefficient and initial temperature difference for the quantitative evaluation method of the gas diffusion characteristics of building complexes with the pseudo-heat island effect of the present invention. Figure 4 The correction coefficients of the quantitative evaluation method for the gas diffusion characteristics of building complexes with the pseudo-heat island effect of the present invention are fitted to the final heat island model based on the temperature difference. Figure 5 This is a structural diagram of the quantitative detection device of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0024] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0028] like Figures 1-4As shown, the quantitative assessment method for gas diffusion characteristics of building clusters under simulated heat island effects of the present invention includes the following steps: constructing a scaled-down model of the building cluster with temperature-changing function and ventilation system; performing constant ventilation on the scaled-down model of the building cluster under no temperature difference conditions and measuring the baseline gas residual concentration within the scaled-down model of the building cluster; keeping the ventilation conditions unchanged, adjusting the temperature of the scaled-down model of the building cluster to form a series of surface-environment temperature differences, simulating the evolution process of heat island intensity, and measuring the gas residual concentration under each temperature difference; based on the baseline gas residual concentration and the gas residual concentration data under each temperature difference, establishing a nonlinear mathematical correction model including thermal hindrance terms and thermal penetration terms to obtain heat island effect correction coefficients; applying the heat island effect correction coefficients to the analysis of gas diffusion characteristics under actual heat island effects to achieve quantitative assessment and risk prediction.

[0029] As described above, firstly, within a controllable environmental simulation chamber system, a scaled-down model of a building complex with typical urban layout characteristics is constructed at a certain scale (e.g., 1:200). The model has a variable-temperature heat source base plate integrated at its bottom for accurately simulating surface heat sources; the model is placed within a flow field dynamics subsystem capable of generating a stable horizontal background wind field.

[0030] At the start of the experiment, the temperature of the variable-temperature heat source base plate was set to match the ambient airflow temperature, establishing a zero-temperature-difference condition (ΔT=0). The ventilation system was activated and a constant airflow velocity (e.g., 1.0 m / s) was maintained. After the flow field stabilized sufficiently, the residual concentration C0 of the reference gas was measured. Subsequently, while keeping the ventilation conditions strictly constant, the temperature of the variable-temperature heat source base plate was gradually adjusted through program control to create a series of controllable surface-ambient temperature differences (ΔT_i), for example, varying from 0°C to 60°C in 5°C intervals, thereby simulating the evolution process from a weak heat island to a strong heat island.

[0031] At each set temperature difference, after the system reaches a new thermodynamic and flow equilibrium, the residual gas concentration in key areas of the building complex model is measured using a nonlinear feature monitoring array. After obtaining a series of concentration data at different temperature differences, a nonlinear fitting is performed using a data analysis module to establish a nonlinear mathematical correction model driven by physical mechanisms.

[0032] The core of this model is the heat island effect correction coefficient. Its expression is: ; ; in, The baseline gas residual concentration; This is the urban heat island correction factor; The temperature difference between the Earth's surface and the surrounding airflow; The growth coefficient is the resistance factor, which characterizes the resistance strength of weak thermal buoyancy to the horizontal ventilation flow field. It is a natural constant; The temperature difference representing the maximum retardation characteristic is the temperature difference threshold when the thermal retardation effect is most significant. The turbulence penetration factor characterizes the ability of strong thermal buoyancy to clean up dead zone structures; The critical penetration temperature difference is the temperature difference that characterizes the transition from flow field structure dominated by stagnation to flow field structure dominated by penetration. This is the turbulence index.

[0033] This includes thermal hindrance terms that describe how weak thermal buoyancy hinders ventilation. And the thermal penetration term describing the cleaning of dead zone structures by strong thermal buoyancy After determining the characteristic parameters—the stagnation growth coefficient, the maximum stagnation characteristic temperature difference, the turbulence penetration factor, the critical penetration temperature difference, and the turbulence exponent—through fitting, the correction coefficient function can be obtained. Finally, the model is applied to a real-world scenario: the actual surface temperature and ambient air temperature of the target area are obtained through meteorological monitoring, the actual temperature difference is calculated, and this difference is substituted into the calibrated... The function calculates the correction coefficient under the current heat island intensity, and then corrects the predicted concentration under the baseline diffusion scenario to achieve quantitative assessment and risk warning.

[0034] This model is the core mathematical tool for achieving quantitative assessment in this invention. The model decomposes the effects of the heat island effect into two competing physical processes: thermal hindrance and thermal penetration. The thermal hindrance term... This describes how, when temperature differences are small, the weak thermal buoyancy generated by surface heating weakens the momentum of horizontal flows, leading to streamline curvature and reduced wind speed. This results in more stable vortices, particularly in building leeward areas and street canyons, making it difficult for pollutants to be carried away and causing increased concentrations. This item follows... Increases first, then strengthens and then weakens. = The temperature reaches its peak at this point, which is the "maximum resistance characteristic temperature difference". (Heat penetration term) Describes when temperature difference Exceeding the critical value Subsequently, strong thermal buoyancy is sufficient to trigger the mixing of the thermal plume and enhanced turbulence. This buoyancy-driven turbulence can penetrate and "cleanse" poorly ventilated building dead zones and stagnation areas, significantly promoting the vertical and lateral diffusion of pollutants, leading to a decrease in concentration. The turbulence exponent n reflects the nonlinear intensity of the penetration effect. A series of data obtained through experiments are used to analyze (…). , ), then by A series of correction coefficients under the surface-environment temperature difference can be obtained. Using a nonlinear regression algorithm (the heat island correction model in this invention) By tuning and fitting the above model, a unique set of optimal parameters can be determined. , , , , This model successfully provides a concise and accurate mathematical description of complex nonlinear diffusion behavior.

[0035] The specific steps for determining the residual concentration of the reference gas in a scaled-down model of a building complex include: ventilating the scaled-down model of the building complex at a constant wind speed under no temperature difference conditions and after the flow field stabilizes, measuring the background gas concentration in the scaled-down model of the building complex; introducing a quantitative tracer gas into the scaled-down model of the building complex and after its concentration stabilizes, measuring the total gas concentration; calculating the difference between the background gas concentration and the total gas concentration to obtain the residual concentration of the reference gas.

[0036] Among them, the residual concentration of the reference gas Accurate determination of the background gas concentration is the benchmark for all subsequent quantitative comparisons. In practice, under conditions of no temperature difference and constant ventilation, a high-precision gas sensor is first used to measure the background gas concentration in the background air within the model. .

[0037] Then, a known amount of tracer gas, such as carbon dioxide, is released at a constant rate through a quantitative release device located upwind of the model. Once the gas has fully mixed among the buildings downwind and reached dynamic equilibrium (i.e., the inlet release rate equals the outlet discharge rate), and the concentration within the model no longer changes over time, the total gas concentration within the model is measured again. Reference gas residual concentration That is, the difference between the total concentration and the background concentration. = - This concentration value reflects the inherent retention capacity of the building complex structure for pollutants under purely mechanical ventilation conditions without thermal buoyancy interference, providing an accurate benchmark for subsequent assessment of the enhancement or reduction of the heat island effect.

[0038] Specifically, the steps for measuring the residual gas concentration at various temperature differences include: dividing the area in the flow field where pollutants are easily deposited or their concentrations abnormally increased due to the influence of surface thermal buoyancy into thermal retention sensitive areas; and measuring the residual gas concentration at various temperature differences in the thermal retention sensitive areas using a sensor array.

[0039] The heat island effect exhibits significant spatial nonuniformity in the flow field. To accurately capture its nonlinear effects, it is crucial to monitor areas sensitive to thermal stagnation. These areas are where pollutants are most likely to accumulate due to the interaction between thermal buoyancy and the flow around the building.

[0040] In practical implementation, the area needs to be divided based on the results of flow field simulation or pre-experimentation. This typically includes: the leeward recirculation zone of buildings (low wind speed in the wake area, prone to forming stable vortices), the bottom of street canyons (areas with poor ventilation between buildings on both sides), and the geometric center of the building complex (far from the incoming flow boundary, with the most complex ventilation paths). High spatiotemporal resolution gas concentration sensor arrays are deployed at these key locations. At each set temperature difference... Under experimental conditions, after the system reaches steady state, the concentration readings of all sensors in the array are recorded synchronously. The spatial average or maximum concentration of each sensitive area is taken as the representative residual gas concentration at that temperature difference. This approach avoids the randomness of single-point measurements and can more comprehensively and accurately reflect the impact of thermal buoyancy on the overall diffusion pattern and local concentration peaks.

[0041] The heat retention sensitive area includes the leeward recirculation area of ​​the buildings, the bottom of the street canyon, and the geometric center of the building complex in the scaled model of the building complex; the residual gas concentration shows a non-monotonic abrupt change characteristic of first rising and then falling with the temperature difference: when the temperature difference is less than the maximum hindrance characteristic temperature difference, it is in the heat hindrance stage, and the concentration increases with the increase of the temperature difference; when the temperature difference is greater than the critical penetration temperature difference, it is in the heat penetration stage, and the concentration decreases sharply with the increase of the temperature difference.

[0042] This feature clarifies the specific location of the sensitive area and reveals the physical laws governing concentration changes with temperature difference. The leeward recirculation zone of buildings, the bottom of street canyons, and the geometric center of building complexes are the areas most sensitive to the thermal buoyancy effect, as determined by flow field analysis. The experimentally observed concentration-temperature difference relationship exhibits a significant non-monotonic "first rise then fall" characteristic, which directly verifies the dominance shift between the two mechanisms of thermal retardation and thermal penetration.

[0043] During the thermal hysteresis stage ( < ), thermal hindrance terms dominate. With Increase from 0 to Ventilation efficiency continued to decrease, and pollutants accumulated in the sensitive area, leading to a decrease in the measured residual gas concentration. It continued to rise and gradually exceeded the baseline concentration. (Right now >1. This stage corresponds to a weak to moderate heat island effect in the city, where pollutant dispersion conditions deteriorate and risks increase.

[0044] During the heat penetration stage ( > The heat penetration effect begins to outweigh the blocking effect. Intense thermal turbulence significantly improves ventilation efficiency and concentration. Follow The concentration increases and then decreases rapidly, significantly lower than the baseline concentration (i.e., <1). This stage corresponds to a strong heat island or extreme high temperature weather. g and These are two key characteristic temperature difference thresholds, the specific values ​​of which are determined by factors such as the layout, density, and wind speed of the building complex, and are obtained through model fitting.

[0045] The quantitative assessment and risk prediction process includes the following steps: Obtain the actual surface temperature and ambient air temperature in the scaled-down model of the building complex, and calculate the actual temperature difference; substitute the actual temperature difference into the nonlinear mathematical correction model to calculate the heat island effect correction coefficient; determine the risk level based on the value of the heat island effect correction coefficient: if the heat island effect correction coefficient is greater than 1, it is determined to be a high-risk blocking period; if the heat island effect correction coefficient is less than 1 and the value is significantly lower than 1, it is determined to be a low-risk penetration period.

[0046] This step is the operational procedure for applying the laboratory-calibrated model to a real urban environment for risk assessment. For the target building complex area, a network of deployed temperature sensors is used to acquire real-time data on actual surface temperatures (such as road surface and roof temperatures) and ambient air temperatures (such as the air temperature inside a Stevenson screen), and the actual temperature difference is calculated. . This Substitute the value into the correction factor that has been calibrated through the scaling experiment. The current heat island effect correction coefficient can be calculated from this.

[0047] Risk level is determined based on this value: when A value greater than 1 indicates that the current heat island intensity is in the "thermal stagnation stage," meaning that actual diffusion conditions are worse than the baseline without a heat island, and pollutants are more likely to accumulate. At this point, the system should identify it as a high-risk stagnation period and issue a warning, indicating potential air quality deterioration or hazardous gas accumulation, requiring the activation of emergency monitoring or protective measures.

[0048] when <1, and its value is much smaller than 1 (e.g. When the value is <0.7, it indicates that the "heat penetration stage" is underway, and the diffusion conditions are better than the baseline. Although the weather is hot, the pollutants diffuse relatively quickly, and the short-term exposure risk is relatively low, which can be identified as a low-risk penetration period. This method achieves a direct and quantitative mapping from physical mechanisms to risk management decisions. For example, in the specific application scenario of the disclosure document: Scenario 1 (summer afternoon, =18°C) Calculated (18)≈1.739>1, judged as a high-risk blocking period; Scenario 2 (chemical leak, =55°C) Calculated (55)≈0.17<1, which is considered a low-risk penetration period (but we need to be wary of rapid long-distance spread).

[0049] like Figure 5 As shown, the quantitative detection device for the quantitative assessment method of gas diffusion characteristics of building clusters to realize the above-mentioned simulated heat island effect in this invention includes: an environmental simulation chamber system for accommodating a scaled-down model of the building cluster and providing a controllable experimental environment; a heat island environment construction subsystem, including a variable-temperature heat source base plate set at the bottom of the scaled-down model of the building cluster, for simulating surface heat sources of different intensities and generating a controllable temperature difference; a flow field dynamics subsystem for generating and maintaining a stable horizontal background wind field in the environmental simulation chamber; a nonlinear characteristic monitoring array, composed of gas concentration sensors distributed in multiple heat retention sensitive areas within the scaled-down model of the building cluster, for real-time monitoring of gas concentration changes; and a data analysis module, communicatively connected to the monitoring array, for receiving and processing concentration data, and performing parameter fitting and calculation of the nonlinear mathematical correction model.

[0050] This device is the hardware system for implementing the aforementioned evaluation methods. The environmental simulation chamber system is a sealed or semi-sealed chamber where the internal environment (such as temperature and humidity) can be precisely controlled to eliminate external interference. The core of the heat island environment construction subsystem is a variable-temperature heat source base plate, located below the scaled-down model of the building complex. It can employ technologies such as electric heating films and circulating liquid heat exchangers to achieve uniform and programmable heating / cooling. The flow field dynamics subsystem typically includes fans, honeycomb structures, damping nets, and contraction sections, used to generate a uniform, stable, and low-turbulence horizontal background wind field within the simulation chamber to simulate urban background wind. The nonlinear characteristic monitoring array consists of multiple high-sensitivity, fast-response gas concentration sensors (such as laser spectrometers and electrochemical sensor probes), which are deployed at key locations within the model based on the results of flow field simulations or pre-experiments. The data analysis module is a computing unit integrating software and hardware. It collects concentration data in real time, automatically performs preprocessing such as background subtraction and data smoothing, and calls the built-in nonlinear fitting algorithm to fit the experimental data with the above-mentioned mathematical model, outputting model parameters and goodness of fit. It can also be used as an application terminal for risk assessment.

[0051] Specifically, the variable-temperature heat source base plate is used to provide a continuously adjustable temperature difference from 0 to 60 degrees Celsius relative to the ambient airflow. This continuously adjustable temperature difference range comprehensively covers most real-world scenarios, from no heat island to extreme urban heat islands (e.g., the temperature difference between asphalt pavement and the air above can reach over 50°C in hot summer weather). Continuously adjustable means that the temperature difference can be precisely and continuously varied through program control (e.g., in 1°C increments), thereby obtaining high-resolution concentration-temperature difference curves, ensuring the accuracy and reliability of model fitting, and accurately capturing the critical point of the transition between thermal hindrance and thermal penetration effects.

[0052] Specifically, gas concentration sensors are placed within the heat retention sensitive area of ​​the building complex's scaled-down model. The heat retention sensitive area includes the leeward recirculation zone of the buildings, the bottom of the street canyon, and the geometric center of the building complex.

[0053] The sensor deployment strategy directly determines whether the core nonlinear characteristics of the heat island effect can be effectively captured. As mentioned above, sensors should be preferentially deployed in the following heat retention sensitive areas determined by flow field analysis: 1. The leeward backflow area of ​​buildings: Areas with low wind speeds and a tendency to form stable vortices in the downstream wake of buildings, which are typical locations for pollutant retention. 2. The bottom of street canyons: The bottom of the street space between buildings on both sides, with poor ventilation conditions, is prone to forming local high-concentration areas due to thermal buoyancy. 3. The geometric center of building clusters: Within dense building clusters, areas far from the incoming flow boundary, with the longest and most complex ventilation paths, resulting in significant heat accumulation effects. Through intensive monitoring of these key areas, the device can accurately capture the nonlinear concentration abrupt change signal caused by thermal buoyancy, providing sufficient data support for establishing a reliable quantitative model.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for quantitatively evaluating gas diffusion characteristics of a building group in pseudo-urban heat island effect, characterized by, Includes the following steps: Construct a scaled-down model of a building complex with temperature control and ventilation systems; Under constant ventilation conditions without temperature difference, the scaled-down model of the building complex was subjected to constant ventilation, and the residual concentration of the reference gas in the scaled-down model of the building complex was measured. Keeping ventilation conditions constant, the temperature of the scaled-down model of the building complex was adjusted to create a series of surface-environment temperature differences, simulating the evolution of the heat island intensity, and measuring the residual gas concentration at each temperature difference; Based on the baseline gas residual concentration and gas residual concentration data at various temperature differences, a nonlinear mathematical correction model including thermal hindrance and thermal penetration terms is established to obtain the heat island effect correction coefficient. The heat island effect correction coefficient is applied to the analysis of gas diffusion characteristics under the actual heat island effect to achieve quantitative assessment and risk prediction.

2. The method of quantitative evaluation of gas diffusion characteristics of a building complex simulating heat island effect according to claim 1, wherein The specific steps for determining the residual concentration of the reference gas within the scaled-down model of the building complex include: Under no temperature difference conditions, the building complex scale model was ventilated at a constant wind speed and the background gas concentration was measured after the flow field stabilized. A quantitative tracer gas was introduced into the scaled model of the building complex, and after the concentration stabilized, the total gas concentration was measured. The difference between the background gas concentration and the total gas concentration is calculated to obtain the baseline gas residual concentration.

3. The method of quantitative evaluation of gas diffusion characteristics of a building group simulating heat island effect according to claim 2, wherein The specific steps for measuring the residual gas concentration at various temperature differences include: The areas in the flow field where pollutants are easily deposited or whose concentrations are abnormally increased due to the influence of surface thermal buoyancy are designated as thermal retention sensitive areas. The residual gas concentration at various temperature differences in the heat retention sensitive area is measured using a sensor array.

4. The method of quantitative evaluation of gas diffusion characteristics of a building group simulating heat island effect according to claim 3, wherein The nonlinear mathematical correction model is as follows: ; ； in, The baseline gas residual concentration; This is the urban heat island correction factor; The temperature difference between the Earth's surface and the surrounding airflow; The growth coefficient is the resistance factor, which characterizes the resistance strength of weak thermal buoyancy to the horizontal ventilation flow field. It is a natural constant; The temperature difference representing the maximum retardation characteristic is the temperature difference threshold when the thermal retardation effect is most significant. The turbulence penetration factor characterizes the ability of strong thermal buoyancy to clean up dead zone structures; The critical penetration temperature difference is the temperature difference that characterizes the transition from flow field structure dominated by stagnation to flow field structure dominated by penetration. This is the turbulence index.

5. The method for quantitatively evaluating the gas diffusion characteristics of building clusters exhibiting a pseudo-heat island effect as described in claim 4, characterized in that: The heat retention sensitive area includes the leeward backflow area of ​​the buildings, the bottom of the street canyon, and the geometric center area of ​​the building complex in the scaled-down model of the building complex. The residual gas concentration exhibits a non-monotonic abrupt change characteristic as the temperature difference changes: when the temperature difference is less than the maximum hindrance characteristic temperature difference, it is in the thermal hindrance stage, and the concentration increases as the temperature difference increases; when the temperature difference is greater than the critical penetration temperature difference, it is in the thermal penetration stage, and the concentration decreases sharply as the temperature difference increases.

6. The method for quantitatively evaluating the gas diffusion characteristics of building complexes exhibiting a pseudo-heat island effect as described in claim 5, characterized in that, The quantitative assessment and risk prediction process includes the following steps: Obtain the actual ground surface temperature and ambient air temperature in the scaled-down model of the building complex, and calculate the actual temperature difference; Substitute the actual temperature difference into the nonlinear mathematical correction model to calculate the heat island effect correction coefficient; The risk level is determined based on the value of the heat island effect correction coefficient: if the heat island effect correction coefficient is greater than 1, it is determined to be a high-risk blocking period; if the heat island effect correction coefficient is less than 1 and the value is significantly lower than 1, it is determined to be a low-risk penetration period.

7. A quantitative detection device for implementing the quantitative evaluation method of the gas diffusion characteristics of a building group simulating the heat island effect according to any one of claims 1 to 6, characterized by, include: An environmental simulation chamber system is used to house scaled-down models of building complexes and provide a controlled experimental environment. The heat island environment construction subsystem includes a variable-temperature heat source base plate set at the bottom of the scaled-down model of the building complex, which is used to simulate surface heat sources of different intensities and generate controllable temperature differences. A flow field dynamics subsystem is used to generate and maintain a stable horizontal background wind field within the environmental simulation chamber. The nonlinear feature monitoring array consists of gas concentration sensors distributed in multiple heat retention sensitive areas within the scaled model of the building complex, and is used to monitor gas concentration changes in real time. The data analysis module is communicatively connected to the monitoring array and is used to receive and process concentration data, and to perform parameter fitting and calculation of the nonlinear mathematical correction model.

8. The quantitative test device of claim 7, wherein: The variable-temperature heat source base plate is used to provide a continuously adjustable temperature difference of 0 degrees Celsius to 60 degrees Celsius relative to the ambient airflow.

9. The quantitative test device of claim 7, wherein: The gas concentration sensor is arranged in the heat retention sensitive area within the scaled-down model of the building complex.

10. The quantitative test device of claim 9, wherein: The heat retention sensitive areas include the backflow area on the leeward side of the building, the bottom of the street canyon, and the geometric center area of ​​the building complex.

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