Ventilation and heat exchange systems and methods for underground cavern construction in frigid regions

Abstract

This invention discloses a ventilation and heat exchange system and method for underground cavern construction in frigid regions, relating to the field of ventilation technology for underground cavern construction. The system includes a heat recovery module, a temperature control module, and a power unit. The heat recovery module preheats the air supplied to the working face using ambient heat from the underground cavern. The temperature control module injects a cooling medium into the exhaust duct to reduce the temperature of the exhaust airflow. The supply duct outlet is located at the bottom of the cavern, and the exhaust duct inlet is located at the top, forming a bottom-supply, top-exhaust layout. The preheating and cooling processes are coordinated, increasing the supply air temperature to prevent freezing of the working face while simultaneously increasing the driving pressure difference across the exhaust duct by lowering the exhaust air temperature, thereby enhancing the overall ventilation efficiency of the system. This invention solves the problems of fresh air icing, wellhead icing, high energy consumption, and low sewage discharge efficiency in construction ventilation in frigid regions, achieving safe, energy-saving, and efficient ventilation and heat exchange.

Description

Technical Field

[0001] This invention belongs to the field of ventilation technology for underground cavern construction, and particularly relates to a ventilation and heat exchange system and method for underground cavern construction in extremely cold regions. Background Technology

[0002] Currently, in the construction of large underground caverns (such as underground oil depots and hydroelectric engineering caverns) in frigid regions, mechanical ventilation systems centered on air supply and exhaust shafts are commonly used. These systems utilize fans to deliver cold, fresh air (fresh air) to the working face and extract hot, polluted air (stale air) from the cavern to maintain a suitable working environment. However, in frigid climates such as high latitudes and high altitudes, external temperatures often drop below -20°C, while the temperature of the surrounding rock in deep underground caverns typically remains above 10°C, resulting in a temperature difference exceeding 30°C. Traditional ventilation methods face the following prominent contradictions in such environments:

[0003] (1) Icing problem caused by low air supply temperature: When the air supply fan is running, the low temperature fresh air is directly sent into the cavern, which can cause the seepage water in the well wall, working face and other areas to freeze quickly and form hanging ice columns. This not only worsens the working environment and affects the construction efficiency, but also poses a safety risk of ice falling and injuring people and damaging equipment.

[0004] (2) Hazard of ice formation caused by chimney effect during shutdown: After the ventilation fan stops working, the hot and humid air in the tunnel continues to be discharged from the tunnel and the working face under the drive of thermal pressure difference (chimney effect). When the hot and humid air meets the cold air outside the tunnel near the wellhead, the water vapor will condense and freeze, forming dangerous ice formations. The breakage of the ice formations increases the safety risks to personnel and equipment.

[0005] To address these issues, the conventional approach is to install an electric heating device at the air supply shaft inlet to preheat the incoming fresh air. While this method can alleviate localized icing, it has significant drawbacks: high energy consumption, requiring a continuous large amount of electricity and significantly increasing construction costs; failure to utilize geothermal resources, neglecting the heat reserves inside the tunnel and the surrounding rock itself; and low system energy efficiency, failing to optimize in conjunction with the chimney effect, resulting in limited overall ventilation and heat exchange efficiency.

[0006] Therefore, in response to the special ventilation needs of underground cavern construction in frigid regions, there is still a lack of an energy-saving ventilation and heat exchange system that can effectively utilize geothermal energy, synergistically enhance the chimney effect, and achieve energy recovery and temperature control. Summary of the Invention

[0007] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a ventilation and heat exchange system and method for underground cavern construction in frigid regions. This system aims to solve the problems of excessively low fresh air temperature leading to icing on the work surface, chimney effect causing icing at the wellhead during shutdown, and excessive energy consumption due to reliance on external electric heating in traditional ventilation systems in frigid regions. The invention provides an energy-saving ventilation and heat exchange system and method that can effectively recover and utilize geothermal energy from the surrounding rock of underground caverns, actively and collaboratively enhance the chimney effect, and achieve energy cascade utilization and precise temperature control.

[0008] This invention solves the above-mentioned technical problems through the following technical solution: a ventilation and heat exchange system for underground cavern construction in extremely cold regions, comprising:

[0009] A heat recovery module includes a heat-conducting structure disposed on an air supply duct, the heat-conducting structure being used to preheat the airflow supplied to the working face using the ambient heat of the underground cavern.

[0010] A temperature control module includes a cooling medium injection channel connected to an exhaust duct, the cooling medium injection channel being used to inject cooling medium into the exhaust duct to reduce the temperature of the exhaust airflow.

[0011] A power unit for providing auxiliary power to at least the airflow in the supply air duct and / or the exhaust air duct;

[0012] The outlet of the air supply duct is located at the bottom of the underground cavern construction space, and the inlet of the exhaust duct is located at the top of the underground cavern construction space.

[0013] The preheating function of the heat recovery module and the cooling function of the temperature control module are configured in synergy. By increasing the supply air temperature to prevent the working surface from freezing, the exhaust air temperature is reduced to increase the driving pressure difference at both ends of the exhaust duct, thereby jointly enhancing the overall efficiency of the system.

[0014] This invention utilizes a heat recovery module to actively extract and utilize stable geothermal resources stored in the surrounding rock and internal air of deep underground caverns to preheat the incoming extremely low-temperature fresh air in a non-consumptive manner. This preheating process, without relying on external high-grade electrical energy input, can significantly raise the temperature of the fresh air arriving at the working face to above freezing point. This physically blocks the path of phase change and freezing of leaking water upon contact with the low-temperature airflow, fundamentally eliminating the thermodynamic conditions for ice formation on the working face and well walls, and creating a stable and safe physical working environment for underground construction in frigid climates.

[0015] This invention utilizes a temperature control module to actively and controllably introduce low-temperature air from outside the cavern, using it as a natural cold source, into the exhaust duct via a cooling medium injection channel. This air is then forcibly mixed and undergoes heat and mass exchange with the hot, humid waste air to be discharged. This process pre-cools the waste air before it leaves the main cavern space, significantly reducing the dew point temperature difference when it encounters the outside cold air at the wellhead. This suppresses the phase change driving force that causes violent condensation and ice formation of water vapor, eliminating the long-term safety hazard of ice buildup at the wellhead from the source.

[0016] This invention constructs a geothermal-cold source energy synergistic exchange system: transforming underground waste heat, traditionally considered a disadvantage, and external cold into beneficial resources for preheating fresh air and enhancing ventilation, respectively. On the one hand, the system completely or partially replaces the electric heating load by recovering geothermal energy; on the other hand, it enhances the natural ventilation effect by introducing cold air, achieving direct substitution and indirect savings of high-grade electrical energy, forming a closed loop of temperature control and enhanced ventilation with significantly reduced additional energy consumption (only fan energy consumption).

[0017] The core objective of this invention lies in the dynamic synergy and coupled amplification effect of preheating and cooling functions: the preheating function not only improves the microclimate of the working face but also creates a greater potential for usable temperature difference for the cooling function; the cooling function not only prevents ice formation at the wellhead but also significantly enhances the natural driving force of the chimney effect by actively increasing the effective temperature difference between the inlet and outlet of the exhaust duct. This synergistic mechanism of "using heat to resist cold and using cooling to promote flow" achieves a fundamental shift from passive energy-consuming defense to actively utilizing environmental energy and enhancing the system's self-driving force, thereby improving the reliability, energy efficiency, and overall performance of ventilation in large underground cavern construction under frigid conditions.

[0018] Furthermore, the heat-conducting structure includes heat-conducting sheets coiled around the outside of the air supply duct wall.

[0019] The coiled heat-conducting fins can greatly expand the surface area of ​​the heat-conducting structure in a limited space. Through efficient heat conduction with the surrounding rock and the air inside the cave, the underground heat energy can be quickly and stably transferred to the air supply airflow. This significantly improves the preheating effect of fresh air with a lower cost and more reliable passive heat exchange method, and reduces the dependence on active heating components.

[0020] Furthermore, the temperature control module also includes an outer sleeve fitted on the outside of a section of the exhaust duct, and a closed interlayer is formed between the outer sleeve and the wall of the exhaust duct; a through hole is provided on the wall of the exhaust duct to connect its inner cavity and the interlayer, and the through hole is connected to a guide tube extending into the inner cavity of the exhaust duct.

[0021] The cooling medium injection channel is connected to the interlayer and is used to inject the cooling medium into the exhaust duct through the interlayer and the guide pipe.

[0022] The combined structure of the outer jacket and the guide tube provides a controlled delivery path and precise injection direction for the cooling medium. It can both preheat the cooling medium through the jacket to reduce the thermal shock to the pipe wall, and inject the cold flow in the same direction as the exhaust airflow into the main airflow through the guide tube. By utilizing the airflow ejection effect, the mixing efficiency is enhanced, thereby effectively reducing the exhaust air temperature, optimizing energy utilization and enhancing flow stability.

[0023] Furthermore, the total flow area of ​​the guide tube is determined according to the following formula:

[0024] ;

[0025] in, This indicates the total flow area of ​​the guide tube; Indicates the system's sewage discharge efficiency; This indicates the air volume supplied by the air supply duct; Indicates the average density of air; This indicates the specific heat capacity of air at constant pressure. It represents the convective heat transfer coefficient between the airflow at the outlet of the guide tube and the main airflow in the exhaust duct.

[0026] This invention uses a clear physical formula to quantitatively correlate the flow area of ​​the guide tube with the core operating parameters of the system (air volume, efficiency, and physical properties), thereby achieving precise design of the through-hole and guide tube and optimized matching of system performance. This not only ensures the synergy of the preheating and cooling processes and enhances operational reliability, but also elevates the technical level of the solution through scientific calculation methods.

[0027] Furthermore, the distance between the inlet of the exhaust duct and the working face is 1.5 meters. Up to 3 ,in This represents the area of ​​the working face; the distance between the outlet of the air supply duct and the working face is 4. Up to 5 .

[0028] This invention optimizes the airflow organization in the working face area by placing the outlet of the air supply duct further away (relative to the distance between the inlet of the exhaust duct and the working face) to form a sufficient airflow diffusion zone, and placing the inlet of the exhaust duct closer (relative to the distance between the outlet of the air supply duct and the working face) to quickly capture high-temperature polluted air. This distance configuration effectively separates the fresh air supply and polluted air extraction paths, enhancing sewage discharge efficiency while minimizing airflow short-circuiting and pollution backflow.

[0029] Furthermore, the power unit includes a blower installed in the air supply duct, an exhaust fan installed in the exhaust duct, and a compressor installed in the cooling medium injection channel.

[0030] By independently installing blowers, exhaust fans, and compressors in the air supply duct, exhaust duct, and cooling medium injection channel, precise and independent control of airflow and pressure in each branch is achieved. This ensures the system's basic ventilation capacity under extreme conditions and provides stable and adjustable dynamic matching for the three core processes of preheating, smoke exhaust, and cooling mixing, thereby significantly enhancing the reliability, adaptability, and overall energy efficiency of the entire system.

[0031] Furthermore, a heat insulation layer is provided on the outer side of the exhaust duct wall and on the outer side of the cooling medium injection channel.

[0032] This invention effectively blocks the unintended heat exchange between the low-temperature airflow inside the exhaust duct and the high-temperature environment outside the cavity by setting a heat insulation layer on the outside of the exhaust duct and the cooling medium injection channel. This ensures that the cooling capacity is efficiently used to reduce the exhaust temperature to enhance the chimney effect, while avoiding cooling capacity loss and thermal interference, thus ensuring the accuracy and stability of the system's core cooling and efficiency enhancement functions.

[0033] Furthermore, the injection air volume of the cooling medium injection channel is matched with the air supply air volume of the air supply duct.

[0034] This invention achieves a dynamic balance between the cooling demand on the exhaust side and the fresh air supply on the supply side by matching the injection air volume of the cooling medium with the supply air volume. This not only avoids energy waste and weakening of exhaust power caused by excessive cold source injection, but also prevents poor cooling effect caused by insufficient cooling capacity. Thus, it achieves the maximum synergistic enhancement of the chimney effect and the stability of the overall thermal performance of the system with optimal energy input.

[0035] Furthermore, the total contact area between the heat-conducting structure and the wall of the air supply duct satisfies the following relationship:

[0036] ;

[0037] in, This indicates the contact area between the heat-conducting structure and the wall of the air supply duct; This represents the coefficient that considers the influence of wind speed on the thermal conductivity of the heat-conducting structure; Indicates the wall thickness of the air supply duct; This represents the heat flow rate through the heat-conducting structure per unit time. Indicates the thermal conductivity of a thermally conductive structure; This indicates the temperature difference between the permitted operating temperature and the supply airflow temperature.

[0038] This invention scientifically quantifies the heat-conducting contact area using the above formula, achieving a leap from empirical estimation to precise calculation in the design of heat recovery modules. By systematically linking key parameters such as wind speed, pipe wall characteristics, material properties, and target temperature rise, it ensures that the heat-conducting structure can recover geothermal heat with optimal heat-conducting area and efficiency under any operating condition, thereby maximizing the energy efficiency ratio and optimizing construction costs while meeting the standard temperature requirements.

[0039] Based on the same concept, the present invention also provides a ventilation and heat exchange method for underground cavern construction in frigid regions, applied to the ventilation and heat exchange system for underground cavern construction in frigid regions as described above, the method comprising:

[0040] Start the power unit;

[0041] The heat recovery module utilizes the ambient heat of the underground cavern to preheat the airflow sent into the working face along the air supply duct.

[0042] The temperature control module injects cooling medium into the exhaust duct to reduce the temperature of the polluted hot air stream drawn from the working face.

[0043] The preheating and cooling processes work together to prevent the work surface from freezing while enhancing the exhaust power.

[0044] The method of this invention dynamically integrates geothermal recovery and cold source utilization into the same working cycle by coordinating the preheating and cooling processes. At the physical level, it simultaneously solves the problems of icing risk and insufficient exhaust power caused by low-temperature air supply. It not only achieves the safety guarantee of the working environment and the proactive improvement of ventilation efficiency, but also transforms the traditional "energy-consuming heat preservation" mode into an "energy-efficiency enhancement" mode through systematic energy recycling, which significantly reduces the overall ventilation energy consumption and operating cost of underground cavern construction in frigid regions.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This invention constructs a ventilation and heat exchange system that can synergistically utilize underground geothermal energy and external cold sources by incorporating a heat recovery module, a temperature control module, and a power unit, along with a "bottom-supply, top-exhaust" spatial layout. This solution effectively preheats the supply air to prevent icing on the work surface without relying on high-power electric heating, while simultaneously enhancing the system's natural ventilation dynamics (chimney effect) through cooling the exhaust air. Thus, it systematically solves the key challenges of ventilation during underground cavern construction in frigid regions in terms of safety, energy saving, and high efficiency. Attached Figure Description

[0047] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the plan structure of the ventilation and heat exchange system for underground cavern construction in extremely cold regions, as described in this embodiment of the invention.

[0049] Figure 2 This is a three-dimensional structural diagram of the ventilation and heat exchange system for underground cavern construction in frigid regions, as described in this embodiment of the invention.

[0050] Figure 3 This is a schematic diagram of the planar structure of the air supply duct and heat-conducting plate in an embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram of the three-dimensional structure of the heat-conducting sheet in an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the planar structure of the exhaust duct and cooling medium injection channel in an embodiment of the present invention;

[0053] Figure 6 This is an embodiment of the present invention. Figure 5 Section II-II view;

[0054] Figure 7 This is an embodiment of the present invention. Figure 5 Section I-I view;

[0055] Figure 8 This is a three-dimensional simulation result of a traditional forced ventilation scheme in an embodiment of the present invention;

[0056] Figure 9 This is a three-dimensional simulation result of the system of the present invention in an embodiment of the present invention;

[0057] Figure 10 This is a cross-sectional view of the simulation results of a traditional forced ventilation scheme in an embodiment of the present invention;

[0058] Figure 11 This is a cross-sectional view of the simulation results of the system of the present invention in an embodiment of the present invention;

[0059] Figure 12 This is a comparison chart of the CO concentration change over time at a distance of 30 meters from the working face in this embodiment of the invention;

[0060] Figure 13 This is a comparison graph of the CO concentration change over time at a distance of 40 meters from the working face in an embodiment of the present invention.

[0061] Explanation of reference numerals in the attached diagram: 1-Air supply duct, 11-Air supply duct inlet, 12-Air supply duct outlet, 13-Heat conduction plate, 14-Air supply fan, 2-Exhaust duct, 21-Exhaust duct outlet, 22-Exhaust duct inlet, 23-Compressed air duct, 24-Compressed air fan, 25-Outer jacket, 26-Guide pipe, 27-Exhaust fan, 28-Insulation layer, 3-Working face. Detailed Implementation

[0062] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0064] In the context of this invention, the term "severely cold region" has a specific engineering climatology definition, referring specifically to underground engineering construction environments that meet the following conditions:

[0065] Temperature benchmark: During the winter construction period at the project site, the average temperature of the coldest month will not exceed -10℃, and the extreme minimum temperature can reach below -20℃. Under these conditions, the temperature difference between the air inside the tunnel (construction work face) and the outside environment will normally exceed 25℃, and can easily reach over 30℃.

[0066] The core problem is characterized by the coupling of climate and geological environment, which leads to the following typical and interrelated engineering challenges for conventional ventilation methods: (1) Forced heat exchange contradiction: The fresh air sent into the tunnel to maintain air quality is extremely cold, which will directly cause or aggravate water leakage on the working face, tunnel wall and freezing of ventilation shaft wall (forming ice hangers), worsening working conditions; (2) Chimney effect side effect: During the shutdown period, the hot and humid air in the tunnel is discharged from the shaft under thermal pressure (chimney effect), and meets the extremely low temperature air at the wellhead. Water vapor condenses and freezes rapidly, forming high-risk ice hangers, threatening the wellhead structure and the safety of personnel and equipment.

[0067] The system and method provided by this invention are specifically designed to effectively alleviate the construction environment in frigid regions characterized by the aforementioned climatic parameters and engineering problems.

[0068] Example 1

[0069] like Figure 1 and Figure 2As shown, the ventilation and heat exchange system provided by the present invention mainly consists of two parts: an air supply system and an exhaust system, which work together in the working face area of ​​the underground cavern.

[0070] The air supply system utilizes the heat from the underground cavern environment to preheat the low-temperature fresh air (fresh air) outside the underground cavern before delivering it to the working area at the working face. For example... Figure 3 and Figure 4 As shown, the air supply system includes air supply ducts 1 (at least one, and possibly multiple), a blower 14 installed within the air supply ducts 1, and a heat recovery module. The air supply ducts 1 have an inlet 11 and an outlet 12. The inlet 11 connects to the environment outside the underground cavern (i.e., the outside world), and the outlet 12 is located at the bottom of the underground cavern construction space (or the working face area). The blower 14 is typically an axial flow fan, used to provide the power to draw outside air into the air supply ducts 1. The heat recovery module includes a heat-conducting structure, which is located at one end of the air supply ducts 1 near the working face 3. The heat-conducting structure recovers geothermal heat through heat exchange with the higher-temperature cavern air or surrounding rock, and then uses the recovered geothermal heat to preheat the airflow within the air supply ducts 1.

[0071] In this embodiment, the heat-conducting structure is a heat-conducting sheet 13 made of a metal material with good thermal conductivity (such as aluminum or copper). The heat-conducting sheet 13 is tightly attached to the outer wall of the air supply duct 1 in a coiled manner, which increases the heat-conducting surface area and improves the heat conduction and heat radiation capabilities.

[0072] The air supply preheating process of the system of the present invention is as follows: When the system is running, the extremely low temperature fresh air from the outside enters the air supply duct 1 from the inlet 11 of the air supply duct under the drive of the blower 14; when the cold air flows through the heat-conducting plate 13, the heat-conducting plate 13 continuously absorbs the heat in the cavern environment and conducts the heat to the air flow in the air supply duct 1 through the pipe wall, so that its temperature gradually increases; the preheated air flow is finally blown from the outlet 12 of the air supply duct to the working face 3.

[0073] The optimal distance between the outlet 12 of the air supply duct and the working face 3 is designed to be 4. Up to 5 ,in This indicates the area of ​​the working face 3, to ensure that the preheated airflow can fully diffuse and cover the working face without generating turbulent vortex zones.

[0074] To ensure effective preheating, the heat flow required to heat the supply airflow (i.e., the outside fresh air) to the target temperature must first be determined. Let the supply airflow of the blower 14 be... That is, per second The relationship between the fresh air volume per cubic meter, the supply air volume, and the heat flow rate that the heat conduction fin needs to transfer per unit time is determined by the following formula:

[0075] (1)

[0076] in, It represents the heat flow rate through a heat-conducting structure per unit time, that is, the heat passing through a certain area per unit time (unit: W). This indicates the temperature difference between the permitted operating temperature (e.g., 5℃, or 278.45K) and the supply airflow temperature, i.e., the difference between the permitted operating temperature and the ambient temperature, expressed in K. Indicates ventilation time; Indicates the average density of air; This indicates the specific heat capacity of air at constant pressure. This indicates the preheating time. Because the blower 14 continuously supplies air, the heat-conducting fin 13 maintains a constant thermal conductivity. Formula (1) can be simplified to:

[0077] (2)

[0078] In formula (2), the supply air volume can be calculated using existing formulas based on construction requirements (such as the required air volume for smoke exhaust after blasting). Therefore, the heat flow can be calculated using formula (2). .

[0079] Based on the quantitative analysis of heat conduction, in order to achieve the above-mentioned heat flow... The total effective heat transfer area required by the heat-conducting plate 13 for heat transfer. (That is, the total contact area between all heat-conducting plates 13 and the wall of the air supply duct 1) must satisfy the following formula:

[0080] (3)

[0081] in, This represents the influence coefficient of wind speed on the heat conduction effect of the heat conduction structure. It is usually taken as 5 to 10, and the specific value can be determined by simulation calculation. This indicates the wall thickness of air supply duct 1; This indicates the thermal conductivity of the heat-conducting plate 13.

[0082] According to formula (3), the total effective heat exchange area required for the heat-conducting plate 13 can be calculated, which is used to guide the determination of the number and specific arrangement size of the heat-conducting plate 13, so as to ensure that the preheating effect meets the engineering requirements.

[0083] The exhaust system is used to efficiently remove the polluted hot air (sewage) generated at the working face 3 from the underground cavern. For example... Figure 5 , Figure 6 and Figure 7As shown, the exhaust system includes an exhaust duct 2, an exhaust fan 27, an outer casing 25, a cooling medium injection channel, a guide pipe 26, and a heat insulation layer 28. The exhaust duct 2 has an inlet 22 and an outlet 21. The inlet 22 is located at the top of the underground cavern construction space (or the working face 3 area), and the outlet 21 is connected to the environment outside the underground cavern. The exhaust fan 27 is usually an axial flow fan, installed inside the exhaust duct 2 and near the outlet 21 of the exhaust duct, for actively extracting stale air. The outer casing 25 is fitted onto the outside of a section of the exhaust duct 2 near the working face 3 area, forming a closed interlayer (i.e., a hollow layer) between the outer casing 25 and the exhaust duct 2. Both ends of the outer casing 25 are sealed and welded to the outer wall of the exhaust duct 2.

[0084] The cooling medium injection channel includes a compressed air pipe 23 (at least one, and possibly multiple) and a compressed air fan 24 (such as an axial flow fan) installed inside the compressed air pipe 23. One end of the compressed air pipe 23 is connected to the environment outside the underground cavern (using outside cold air as the cooling medium), and the other end is connected to the interlayer. Multiple through holes are opened on the wall of the exhaust duct 2 inside the interlayer, and each through hole is connected to a guide pipe 26 extending into the inner cavity of the exhaust duct 2. The outlet direction of the guide pipe 26 is towards the outlet 21 of the exhaust duct.

[0085] In order to avoid the influence of the thermal environment inside the cave on the compressed air pipe 23, the cooling medium in the interlayer, and the sludge air in the exhaust pipe 2, a heat insulation layer 28 is laid on the outer surface of the exhaust pipe 2, the outer sleeve 25, and the compressed air pipe 23.

[0086] The exhaust cooling and efficiency enhancement process of the system of this invention is as follows: When the system is running, the high-temperature polluted air at the working face 3 is drawn into the exhaust duct 2 from the inlet 22 under the suction of the exhaust fan 27; at the same time, the compressor 24 is started, and the outside cold air (as a cooling medium) is forced into the interlayer between the outer jacket 25 and the exhaust duct 2 through the compressor pipe 23. After the cold air flows through the interlayer, it is sprayed into the inner cavity of the exhaust duct 2 in the same direction (co-current) as the main airflow through each guide pipe 26, and is forcibly mixed with the high-temperature polluted air, thereby significantly reducing the temperature of the polluted air.

[0087] This cooling process brings two core advantages: First, it lowers the temperature of the exhaust airflow, reducing the risk of condensation and freezing in the extreme low-temperature environment outside the tunnel; second, and more importantly, it increases the temperature difference between the interior of exhaust duct 2 (after cooling) and the high-temperature area near the working face 3. According to thermodynamic principles, a larger temperature difference means a stronger thermal pressure difference (chimney effect), thereby significantly enhancing the natural driving force of the system's exhaust airflow and achieving synergistic effects between mechanical and natural power.

[0088] The optimal distance between the exhaust duct inlet 22 and the working face 3 is designed to be 1.5 meters. Up to 3 ,in This indicates the area of ​​the working face 3, which is designed to facilitate the rapid capture and discharge of pollutants without generating turbulent eddy zones.

[0089] To ensure that the cooling effect matches the system airflow, the key parameters of the cooling medium injection structure need to be quantitatively designed. The core issue is determining the total flow area of ​​the guide pipe 26 on the exhaust duct 2.

[0090] The cooling medium injection channel aims to lower the temperature T1 (approximately equal to the air temperature inside the cavity) of the high-temperature waste air in exhaust duct 2. Assuming the target cooling time is t, the required total cooling capacity is... It can be represented as:

[0091] (4)

[0092] in, This indicates the total air volume within exhaust duct 2.

[0093] Total cooling capacity This is achieved through convective heat transfer between the cooling medium (outside cold air) and the high-temperature waste air within the cooling zone (i.e., the exhaust duct section enclosed by the outer casing 25 and with guide pipes 26). According to Newton's law of cooling:

[0094] (5)

[0095] in, Indicates the convective heat transfer coefficient; This represents the total effective heat exchange area of ​​all guide tube outlets.

[0096] Total air volume in exhaust duct 2 It consists of two parts: the volume of contaminated hot air drawn from the working face 3 (the main part) and the volume of cold air injected through the cooling medium injection channel. In engineering, the effective exhaust air volume and the supply air volume... and system sewage discharge efficiency Related. Sewage discharge efficiency This reflects the system's ability to capture and discharge contaminants from the working face; calibrated through experiments or simulations, its value is typically 0.7–0.8. Therefore, the total airflow within exhaust duct 2... It can be associated with:

[0097] (6)

[0098] in, This indicates the airflow rate of the cooling medium. To simplify design and ensure cooling effectiveness, the injected airflow rate is typically... With air volume Matching, that is ≈ .at this time, .

[0099] By combining equations (4) to (6), the formula for calculating the total flow area of ​​the guide tube required to ensure the desired cooling effect can be derived as follows:

[0100] (7)

[0101] According to formula (7), after determining the supply air volume, convective heat transfer coefficient (which is related to flow velocity and pipe surface characteristics), and selecting the sewage discharge efficiency, the following can be calculated: This, in turn, guides the design of the number of guide tubes 26 and the orifice size of a single guide tube.

[0102] The entire system of this invention adopts an optimized layout of bottom supply and top exhaust: the air supply duct outlet is located in the bottom area of ​​the cavern space, while the exhaust duct inlet is located in the top area. This conforms to the law of hot air rising, which can most effectively organize airflow, deliver fresh air to the work surface, and quickly exhaust the stale and hot air accumulated at the top.

[0103] This invention solves the coupled problems of "air supply icing" and "low exhaust efficiency and wellhead icing" in underground cavern construction in frigid regions by coordinating two functional modules: geothermal recovery preheating on the air supply side and active cold air injection cooling on the exhaust side. This not only eliminates the high energy consumption of traditional electric heating devices but also improves ventilation efficiency by enhancing the chimney effect, achieving a unified goal of safety, energy saving, and high efficiency.

[0104] To quantitatively evaluate the overall performance of the system of this invention, numerical simulation studies based on computational fluid dynamics (CFD) were conducted, and a comparative analysis was performed with traditional forced ventilation systems (i.e., systems without heat recovery modules and temperature control modules).

[0105] The simulation was based on a typical engineering cross section. After the blast, the blasting fumes (CO) filled the tunnel space 30 meters in front of the working face with an initial concentration of 1900 ppm.

[0106] The parameters of the system of this invention (i.e., the smoke exhaust duct ventilation system) are as follows: the outlet velocity of the air supply duct is 9.0 m / s, corresponding to an air supply volume of 15.79 m³ / s. 3 / s. During operation of the exhaust system, the measured average inlet wind speed reached 2.0 m / s, of which approximately 8 m³ / s was contributed by natural air intake due to the enhanced chimney effect. 3 / s.

[0107] Comparative solution: Use a traditional forced ventilation system with the same air volume, without heat recovery module and temperature control module.

[0108] The simulation results after 600 seconds (10 minutes) of ventilation are as follows: Figures 8 to 11As shown, the color bands represent pollutant concentrations (unit: ppm), with lighter colors indicating higher pollutant concentrations. Figures 8 to 11 It can be seen that the system of the present invention effectively guides the airflow direction due to the synergistic effect of the active suction (exhaust fan) of the exhaust duct and the significantly enhanced thermal pressure difference (temperature control module), which significantly reduces the range of the vortex zone behind the working face and promotes the directional replacement of fresh air and polluted air.

[0109] During the critical smoke extraction period after blasting (e.g., the first 5 minutes), the CO removal efficiency of the system of this invention was improved by approximately 90% compared to the control scheme. Specifically, when using the system of this invention, the average CO concentration within the first 40 meters of the construction tunnel was reduced to below 24 ppm (the allowable limit) within 600 seconds of ventilation; while in the control scheme, the average CO concentration still exceeded the allowable limit in the same area and time, and there was localized accumulation of pollutants.

[0110] Monitoring sections were set up at 30 meters and 40 meters from the working face to compare the CO concentration change curves over time (see...). Figure 12 and Figure 13 The results show:

[0111] When using the system of this invention, in the core working area 30 meters in front of the tunnel face, the CO concentration continuously decreased and stabilized within the allowable limit of 24 ppm within 580 seconds after ventilation began. At the same cross-section, the control scheme required a longer ventilation time to achieve the same safe concentration.

[0112] Quantitative data further confirms that when the system of the present invention runs for 600 seconds, the CO mass emission flux at the inlet section of the exhaust duct reaches 1193 mg / s, which is significantly higher than that under conventional ventilation conditions, directly reflecting its ability to enhance pollutant transport.

[0113] The above simulation comparison confirms that the system of the present invention not only effectively alleviates the risk of icing in low-temperature environments through geothermal recovery and active temperature control, but also significantly improves the efficiency of pollutant removal by optimizing the flow field and enhancing the ventilation driving force, providing an effective solution for safe, efficient and energy-saving construction ventilation for underground cavern projects in frigid regions.

[0114] Example 2

[0115] The ventilation and heat exchange system for underground cavern construction in frigid regions provided by this invention mainly includes the following steps: system layout, startup and operation, and coordinated control, as detailed below:

[0116] Step 1: System setup and parameter settings.

[0117] Before construction begins, the area of ​​the working face is determined. Spatial layout and key parameter presets for the system:

[0118] The outlet of the air supply duct is located at the bottom of the underground cavern construction space, and its distance from the working face is controlled at 4 km. Up to 5 Within the specified range. Simultaneously, the exhaust duct inlet will be located at the top of the underground cavern construction space, with its distance from the working face controlled at 1.5 meters. Up to 3 Within this range. This "bottom-up" layout is the basis for the method's effectiveness.

[0119] Heat recovery module preset: based on the air volume required for construction ventilation Target air supply temperature rise and the wall thickness of the air supply duct Thermal conductivity of heat-conducting sheet material The total effective heat transfer area required for the heat-conducting sheet is calculated using formula (3) in Example 1, based on the parameters. Based on the calculated area To configure the heat-conducting fins that are coiled around the outside of the air supply duct.

[0120] Temperature control module preset: Determines the injection airflow of the cooling medium. So that it matches the air supply volume Matching (i.e., both are equal). According to The air physical properties (density, specific heat capacity), sewage discharge efficiency and convective heat transfer coefficient are calculated and set by formula (7) to determine the number and size of the through holes.

[0121] Step 2: System startup and basic ventilation.

[0122] Start the power unit. Typically, the air supply fan in the air supply duct is started first to force in the low-temperature outside air; then the exhaust fan in the exhaust duct is started to create negative pressure suction in the working face area. During this basic ventilation stage, the heat recovery module and temperature control module are ready to operate.

[0123] Step 3: Preheating and cooling are carried out in a coordinated manner.

[0124] Preheating process: As cold air drawn in from the outside flows through the air supply duct, the heat-conducting fins coiled around the outside of the duct continuously absorb heat from the surrounding rock and the internal air of the cavern, and transfer the heat to the air inside the duct through heat conduction, effectively raising its temperature. The preheated airflow is delivered to the working face from the bottom outlet, fundamentally avoiding the freezing problem caused by the low-temperature airflow directly contacting the damp wall.

[0125] Exhaust cooling and efficiency enhancement process: After the exhaust fan is started, the compressor in the cooling medium injection channel is started immediately or in conjunction with it, forcing outside cold air through the compressor pipe into the outer layer of the exhaust duct (i.e., the hollow layer between the outer casing and the exhaust duct). This cold air is then injected into the main airflow of the exhaust duct through the guide pipe, where it is fully mixed with the high-temperature polluted air drawn from the working face, resulting in a significant temperature reduction.

[0126] The preheating process raises the ambient temperature of the work surface, while the cooling process actively increases the temperature difference between the exhaust duct inlet (high-temperature end) and outlet (low-temperature end) by lowering the temperature of the airflow within the exhaust duct. According to thermodynamic principles, this temperature difference directly determines the magnitude of the thermal pressure difference (chimney effect). Therefore, these two processes work synergistically to prevent the work surface from freezing while significantly enhancing the natural ventilation power driving the discharge of pollutants.

[0127] Step 4: Operation monitoring and adjustment.

[0128] During system operation, the system efficiency can be evaluated in real time by monitoring the temperature and air volume at key points in the supply and exhaust ducts. For example, the operating frequency of the supply fan, exhaust fan, and compressor fan can be adjusted to match the ventilation needs of different construction stages (such as drilling, blasting, and slag removal), ensuring that the preheating and cooling effects are always optimized, and achieving the comprehensive goals of safety, energy saving, and high efficiency.

[0129] The method of this invention, through the systematic implementation of the above steps, closely integrates geothermal recovery with cold source utilization, which not only eliminates the construction safety hazards under severe cold conditions, but also significantly improves the energy efficiency and sewage discharge capacity of the ventilation system, providing a reliable solution for underground engineering construction in similar environments.

[0130] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A ventilation and heat exchange system for underground cavern construction in extremely cold regions, characterized in that, The system includes: A heat recovery module includes a heat-conducting structure disposed on an air supply duct, the heat-conducting structure being used to preheat the airflow supplied to the working face using the ambient heat of the underground cavern. A temperature control module includes a cooling medium injection channel connected to an exhaust duct, the cooling medium injection channel being used to inject cooling medium into the exhaust duct to reduce the temperature of the exhaust airflow; the temperature control module also includes an outer sleeve fitted over a section of the exhaust duct, the outer sleeve forming a closed interlayer between the outer sleeve and the wall of the exhaust duct; a through hole is provided on the wall of the exhaust duct, connecting its inner cavity to the interlayer, and the through hole is connected to a guide tube extending into the inner cavity of the exhaust duct; the cooling medium injection channel is connected to the interlayer and is used to inject cooling medium into the exhaust duct through the interlayer and the guide tube; A power unit for providing auxiliary power to at least the airflow in the supply air duct and / or the exhaust air duct; The outlet of the air supply duct is located at the bottom of the underground cavern construction space, and the inlet of the exhaust duct is located at the top of the underground cavern construction space. The preheating function of the heat recovery module and the cooling function of the temperature control module are configured in synergy. By increasing the supply air temperature to prevent the working surface from freezing, the exhaust air temperature is reduced to increase the driving pressure difference at both ends of the exhaust duct, thereby jointly enhancing the overall efficiency of the system.

2. The ventilation and heat exchange system for underground cavern construction in frigid regions according to claim 1, characterized in that, The heat-conducting structure includes heat-conducting sheets coiled around the outside of the air supply duct wall.

3. The ventilation and heat exchange system for underground cavern construction in frigid regions according to claim 1, characterized in that, The total flow area of ​​the guide tube is determined according to the following formula: ； in, This indicates the total flow area of ​​the guide tube; Indicates the system's sewage discharge efficiency; This indicates the air volume supplied by the air supply duct; Indicates the average density of air; This indicates the specific heat capacity of air at constant pressure. It represents the convective heat transfer coefficient between the airflow at the outlet of the guide tube and the main airflow in the exhaust duct.

4. The ventilation and heat exchange system for underground cavern construction in frigid regions according to claim 1, characterized in that, The distance between the inlet of the exhaust duct and the working face is 1.5 meters. Up to 3 ,in This represents the area of ​​the working face; the distance between the outlet of the air supply duct and the working face is 4. Up to 5 .

5. The ventilation and heat exchange system for underground cavern construction in frigid regions according to claim 1, characterized in that, The power unit includes a blower installed in the air supply duct, an exhaust fan installed in the exhaust duct, and a compressor installed in the cooling medium injection channel.

6. The ventilation and heat exchange system for underground cavern construction in frigid regions according to claim 1, characterized in that, A heat insulation layer is provided on the outer side of the exhaust duct wall and the outer side of the cooling medium injection channel.

7. The ventilation and heat exchange system for underground cavern construction in frigid regions according to claim 1, characterized in that, The air volume injected into the cooling medium injection channel is matched with the air volume supplied by the air supply duct.

8. The ventilation and heat exchange system for underground cavern construction in frigid regions according to any one of claims 1 to 7, characterized in that, The total contact area between the heat-conducting structure and the wall of the air supply duct satisfies the following relationship: ； in, This indicates the contact area between the heat-conducting structure and the wall of the air supply duct; This represents the coefficient that considers the influence of wind speed on the thermal conductivity of the heat-conducting structure; Indicates the wall thickness of the air supply duct; This represents the heat flow rate through the heat-conducting structure per unit time. Indicates the thermal conductivity of a thermally conductive structure; This indicates the temperature difference between the permitted operating temperature and the supply airflow temperature.

9. A ventilation and heat exchange method for underground cavern construction in extremely cold regions, characterized in that, The method, applied to the ventilation and heat exchange system for underground cavern construction in frigid regions as described in any one of claims 1 to 8, comprises: Start the power unit; The heat recovery module utilizes the ambient heat of the underground cavern to preheat the airflow sent into the working face along the air supply duct. The temperature control module injects cooling medium into the exhaust duct to reduce the temperature of the polluted hot air stream drawn from the working face. The preheating and cooling processes work together to prevent the work surface from freezing while enhancing the exhaust power.

Images