Underground Engineering Air Conditioning Cascade Cooling and Heat Dissipation System

Abstract

The present invention discloses a cascade cooling and heat dissipation system for air conditioning in underground engineering, including an air conditioning area, a primary reservoir and a secondary reservoir, the outlet of the primary reservoir is connected to the secondary reservoir, when the temperature of the primary reservoir exceeds a set value, the water in the primary reservoir can flow into the secondary reservoir, the outlet of the secondary reservoir is connected to the water inlet of the primary cooling tower, the outlet of the primary cooling tower is connected to the water inlet of the primary reservoir, the water in the secondary reservoir can be transported to the primary reservoir after being cooled by the primary cooling tower to reduce the temperature of the primary reservoir. The cascade cooling and heat dissipation system for air conditioning in underground engineering of the present invention realizes the independent setting of air conditioning circulation cooling and heat dissipation and overall heat dissipation of the engineering by setting a graded cooling reservoir, so as to meet the negative problems such as the increase of engineering construction scale and operation and maintenance cost when the exhaust air is taken out of the engineering to meet the heat dissipation of the entire engineering by exhaust air. It effectively guarantees the energy-saving and concealment requirements of special engineering.

Description

Technical Field

[0001] The invention relates to the field of underground engineering heat removal, and in particular to an underground engineering air conditioning cascade cooling and heat dissipation system. Background Art

[0002] my country has a vast territory, rich geological types and complex conditions. Therefore, underground engineering occupies an important position in my country's engineering construction field and is widely used in railways, water conservancy, mining, military, highways, subways, undersea tunnels, residential and other fields.

[0003] Usually, underground projects need to maintain the ambient temperature and relative humidity within a certain range. However, a large amount of heat will be generated when the cooling equipment of underground projects is in operation, so the air conditioning condensation heat dissipation is huge. The commonly used heat dissipation method is to set up an air conditioning cooling reservoir for water cooling. When the water temperature of the reservoir rises to the set value, it will be discharged. The water demand is very large, and the engineering guarantee is difficult. At present, some underground projects have also introduced water-saving measures such as evaporative cooling technology, but only solve the heat dissipation problems of the fresh air air conditioning load at the mouth and the diesel generator set of the backup power supply. Especially for underground projects located in the southern region with high wall temperature and large volume, there are geothermal gradients at different burial depths, that is, the greater the burial depth, the higher the initial ground temperature, and the air conditioning cooling load of the enclosure structure accounts for a large proportion. Such projects are highly dependent on external water sources and cannot meet the energy-saving needs of underground projects. Summary of the invention

[0004] The present invention provides an underground engineering air conditioning cascade cooling and heat dissipation system, which has the effect of improving the engineering water saving rate and reducing the difficulty of engineering support. The specific technical solution is as follows:

[0005] An underground engineering air-conditioning cascade cooling and heat dissipation system comprises an air-conditioning area, a primary reservoir and a secondary reservoir. The air-conditioning area is provided with an air-conditioner. The air-conditioning area and the primary reservoir are arranged at a location with a greater burial depth and a higher ground temperature. The primary reservoir is used to provide cooling water for the air-conditioner. The secondary reservoir is arranged at a location with a smaller burial depth and a lower ground temperature. The water outlet of the primary reservoir is connected with the secondary reservoir. When the temperature of the primary reservoir exceeds a set value, the water in the primary reservoir can flow into the secondary reservoir. The water outlet of the secondary reservoir is connected with the water inlet of a primary cooling tower. The water outlet of the primary cooling tower is connected with the water inlet of the primary reservoir. The water in the secondary reservoir can be cooled by the primary cooling tower and then transported to the primary reservoir to reduce the temperature of the primary reservoir.

[0006] Furthermore, the outlet of the secondary reservoir is connected to the primary reservoir, and the low-temperature water in the secondary reservoir can be directly transported to the primary reservoir to assist in lowering the temperature of the primary reservoir.

[0007] Furthermore, the outlet of the secondary reservoir is connected to the outlet pipe of the secondary reservoir, a water pump is provided on the outlet pipe of the secondary reservoir, the outlet of the water pump is respectively connected to the second control valve and the third control valve, the outlet of the primary cooling tower is connected to the outlet pipe of the primary cooling tower, the outlet pipe of the primary cooling tower is connected to the primary reservoir, the outlet of the second control valve is connected to the outlet pipe of the primary cooling tower; the outlet of the third control valve is connected to the water inlet of the primary cooling tower.

[0008] Furthermore, the first-stage cooling tower outlet pipe is connected to the fourth control valve and the fifth control valve respectively, the outlet of the fourth control valve is connected to the first-stage water reservoir, and the outlet of the fifth control valve is connected to the second-stage water reservoir.

[0009] Furthermore, the secondary reservoir and the primary reservoir are respectively connected to external water supply pipelines, and the external water supply can be directly transported to the secondary reservoir or the primary reservoir.

[0010] Furthermore, the external water supply pipeline is connected to the sixth control valve and the seventh control valve respectively, the water outlet of the sixth control valve is connected to the secondary water reservoir, and the water outlet of the seventh control valve is connected to the primary water reservoir.

[0011] Furthermore, the water outlet of the first-level reservoir is connected to the temperature sensor and the eighth control valve, and the water outlet of the eighth control valve is connected to the second-level reservoir. When the temperature sensor detects that the temperature of the first-level reservoir exceeds the set value, the eighth control valve opens and the water in the first-level reservoir can flow into the second-level reservoir.

[0012] Furthermore, the secondary water reservoir is connected to the diesel engine reservoir, which provides cooling water for the diesel engine unit. The diesel engine reservoir is connected to the secondary cooling tower, whose air inlet is connected to the air outlet of the primary cooling tower, whose air outlet is connected to the outside of the project. The secondary cooling tower can cool the diesel engine reservoir.

[0013] Furthermore, the water outlet of the diesel engine reservoir is connected to the temperature sensor and the ninth control valve, and the water outlet of the ninth control valve is connected to the second water pump. The second water pump can transport the water in the diesel engine reservoir to the secondary cooling tower for cooling. The water outlet of the secondary cooling tower is connected to the water inlet of the diesel engine reservoir.

[0014] Furthermore, a tenth valve is provided between the secondary water reservoir and the diesel engine water reservoir, and a temperature sensor is provided at the water inlet of the diesel engine water reservoir. When the temperature sensor detects that the return water temperature of the secondary cooling tower exceeds the set value, the tenth valve opens, the secondary water reservoir replenishes water into the diesel engine water reservoir, and the diesel engine water reservoir discharges high-temperature water to the outside of the project.

[0015] The underground engineering air conditioning cascade cooling and heat dissipation system of the present invention realizes the independent setting of air conditioning circulation cooling and heat dissipation and overall heat dissipation of the engineering by setting up cooling water reservoirs in a graded manner. The first-level cooling water reservoir is designed and operated according to the 5-degree temperature difference requirement of the air conditioning equipment, and the second-level cooling water reservoir can maximize the use of the engineering exhaust evaporation potential and design and operate according to the large temperature difference working condition, so as to meet the requirements of all heat dissipation of the engineering by exhausting the air to the outside of the engineering, without additionally increasing the engineering exhaust volume, resulting in negative problems such as increased engineering construction scale and operation and maintenance costs. In addition, by utilizing the energy storage link of the air conditioning cooling water reservoir and controlling the operating frequency of the cooling tower exhaust fan, the relative independence of air conditioning refrigeration and heat dissipation and engineering heat emission is achieved, so that the time period most conducive to the heat dissipation of the engineering can be selected for heat dissipation according to the outdoor meteorological conditions. The requirements of energy saving and concealment of special engineering are effectively guaranteed.

[0016] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0018] Figure 1 It is a schematic diagram of the underground engineering air conditioning cascade cooling and heat dissipation system of the present invention. DETAILED DESCRIPTION

[0019] In order to better understand the purpose, function and specific design scheme of the present invention, the underground engineering air conditioning cascade cooling and heat dissipation system of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0020] like Figure 1As shown, the underground engineering air conditioning cascade cooling and heat dissipation system of the present invention comprises an air conditioning area 9, a primary reservoir 1 and a secondary reservoir 2. The air conditioning area 9 is provided with an air conditioner. The air conditioning area 9 and the primary reservoir 1 are arranged at a location with a large burial depth and a high ground temperature. The primary reservoir 1 is used to provide cooling water for the air conditioner. The secondary reservoir 2 is arranged at a location with a small burial depth and a low ground temperature. The water outlet of the primary reservoir 1 is connected to the secondary reservoir 2. When the temperature of the primary reservoir 1 exceeds the set value, the water in the primary reservoir 1 can flow into the secondary reservoir 2. The water outlet of the secondary reservoir 2 is connected to the water inlet of the primary cooling tower 3. The water outlet of the primary cooling tower 3 is connected to the water inlet of the primary reservoir 1. The water in the secondary reservoir 2 can be cooled by the primary cooling tower 3 and then transported to the primary reservoir 1 to reduce the temperature of the primary reservoir 1. The air inlet of the primary cooling tower 3 is connected to the total exhaust air of the project, and the heat of the water is taken away by the exhaust air of the project.

[0021] Preferably, the outlet of the secondary reservoir 2 is connected to the primary reservoir 1, and the low-temperature water in the secondary reservoir 2 can be transported to the primary reservoir 1. When the return water temperature of the primary cooling tower 3 cannot meet the demand of the primary reservoir 1, the low-temperature water in the secondary reservoir 2 is directly transported to the primary reservoir 1 to assist in lowering the temperature of the primary reservoir 1.

[0022] Specifically, the outlet of the secondary reservoir 2 is connected to the outlet pipe of the secondary reservoir 2, a first water pump 41 is arranged on the outlet pipe of the secondary reservoir 2, a first control valve 51 is arranged between the secondary reservoir 2 and the first water pump 41, the outlet of the first water pump 41 is connected to the second control valve 52 and the third control valve 53 respectively, the outlet of the primary cooling tower 3 is connected to the outlet pipe of the primary cooling tower 3, the outlet pipe of the primary cooling tower 3 is connected to the primary reservoir 1, the outlet of the second control valve 52 is connected to the outlet pipe of the primary cooling tower 3; the outlet of the third control valve 53 is connected to the water inlet of the primary cooling tower 3. When the third control valve 53 is opened and the second control valve 52 is closed, the water in the secondary reservoir 2 can be cooled by the primary cooling tower 3 and then transported to the primary reservoir 1 to reduce the temperature of the primary reservoir 1. This is the first mode, i.e., the primary cooling tower 3 is circulated for cooling. When the second control valve 52 is opened and the third control valve 53 is closed, the water in the secondary reservoir 2 is directly transported to the primary reservoir 1 to reduce the temperature of the primary reservoir 1. This is the second method, that is, direct cooling of the secondary reservoir 2. When the first method cannot meet the needs of the primary reservoir 1, the second method is adopted.

[0023] It is worth noting that the water outlet pipe of the primary cooling tower 3 is connected to the fourth control valve 54 and the fifth control valve 55 respectively, the water outlet of the fourth control valve 54 is connected to the primary water reservoir 1, and the water outlet of the fifth control valve 55 is connected to the secondary water reservoir 2. When the fourth control valve 54 and the second control valve 52 are closed, and the fifth control valve 55 and the third control valve 53 are opened, the primary cooling tower 3 can cool the water in the secondary water reservoir 2 alone to prepare for the subsequent use of the primary water reservoir 1.

[0024] Preferably, the secondary reservoir 2 and the primary reservoir 1 are respectively connected to an external water supply pipeline, and the external water supply can be directly transported to the secondary reservoir 2 or the primary reservoir 1. Specifically, the external water supply pipeline is respectively connected to the sixth control valve 56 and the seventh control valve 57, the outlet of the sixth control valve 56 is connected to the secondary reservoir 2, and the outlet of the seventh control valve 57 is connected to the primary reservoir 1. When the water level in the secondary reservoir 2 is lower than the preset value, the sixth control valve 56 is opened, and the external water supply enters the secondary reservoir 2 to replenish the water in the secondary reservoir 2. When the circulating cooling of the primary cooling tower 3 and the direct cooling of the secondary reservoir 2 cannot meet the water temperature demand of the primary reservoir 1, the seventh control valve 57 is opened, and the external water supply enters the primary reservoir 1 to cool the primary reservoir 1. At the same time, the high-temperature water in the primary reservoir 1 flows into the secondary reservoir 2, which can reduce the temperature of the primary reservoir 1 more quickly on the one hand, and prevent the water level in the primary reservoir 1 from being too high on the other hand.

[0025] The outlet of the primary reservoir 1 of this embodiment is connected to the temperature sensor 6 and the eighth control valve 58, and the outlet of the eighth control valve 58 is connected to the secondary reservoir 2. When the temperature sensor 6 detects that the temperature of the primary reservoir 1 exceeds the set value, the eighth control valve 58 opens, and the water in the primary reservoir 1 can flow into the secondary reservoir 2. Since the geographical location of the primary reservoir 1 is higher than that of the secondary reservoir 2, the water in the primary reservoir 1 can flow to the secondary reservoir 2 along the slope of the project.

[0026] The secondary water reservoir 2 is also connected to the diesel engine water reservoir 7, which provides cooling water for the diesel engine set 71, and the diesel engine set 71 provides power for the underground project. The diesel engine water reservoir 7 is connected to the secondary cooling tower 8, which can cool the diesel engine water reservoir 7. The air inlet of the secondary cooling tower 8 is connected to the air outlet of the primary cooling tower 3, and the air outlet of the secondary cooling tower 8 is connected to the outside of the project, so that the high-temperature and high-humidity exhaust air can be directly discharged outside the project.

[0027] Specifically, the water outlet of the diesel engine water reservoir 7 is connected to the temperature sensor 6 and the ninth control valve 59, and the water outlet of the ninth control valve 59 is connected to the second water pump 42. The second water pump 42 can transport the water in the diesel engine water reservoir 7 to the secondary cooling tower 8 for cooling. The water outlet of the secondary cooling tower 8 is connected to the water inlet of the diesel engine water reservoir 7. When the temperature sensor 6 detects that the water temperature in the diesel engine water reservoir 7 exceeds the preset value, the ninth control valve 59 opens, and the second water pump 42 transports the water in the diesel engine water reservoir 7 to the secondary cooling tower 8 for cooling, and then transports it back to the diesel engine water reservoir 7 to cool the water in the diesel engine water reservoir 7.

[0028] It is worth noting that a tenth valve 510 is provided between the secondary water reservoir 2 and the diesel engine water reservoir 7, and a temperature sensor 6 is provided at the water inlet of the diesel engine water reservoir 7. When the temperature sensor 6 detects that the return water temperature of the secondary cooling tower 8 exceeds the set value, the tenth valve 510 opens, the secondary water reservoir 2 replenishes water into the diesel engine water reservoir 7, and the diesel engine water reservoir 7 discharges high-temperature water to the outside of the project, so that the water temperature in the diesel engine water reservoir 7 meets the requirements of the diesel engine unit 71.

[0029] When the present invention is actually applied, the initial water temperature of the primary reservoir 1 is close to the ground temperature of about Y degrees, and the air conditioning equipment is selected and designed according to the designed water inlet temperature of A degrees. When the air conditioning is running and the cooling water is circulated, the water temperature of the primary reservoir 1 gradually rises to C degrees, and the eighth control valve 58 is opened, and the high-temperature cooling water flows to the secondary reservoir 2 by gravity, and the water is circulated to the primary reservoir 1 after being cooled by the primary cooling tower 3. When the outlet water temperature of the air conditioning cooling water is higher than C degrees, it is no longer circulated, but is directly discharged to the secondary reservoir 2 by gravity pipeline.

[0030] According to the set water level limit of the primary reservoir 1, method one can open the first control valve, the third control valve 53 and the fourth control valve 54, and close the second control valve 52 and the fifth control valve 55 at the same time, operate the first water pump 41 and the primary cooling tower 3, and evaporate and cool the cooling water stored in the secondary reservoir 2 before replenishing the primary reservoir 1 with water; method two can open the first control valve, the second control valve 52 and the fourth control valve 54, and close the third control valve 53 and the fifth control valve 55 at the same time, and operate the first water pump 41 to directly replenish the cooling water stored in the secondary reservoir 2 to the primary reservoir 1; method three can directly replenish the primary reservoir 1 with external water supply, at this time, open the seventh control valve 57 and close the sixth control valve 56.

[0031] The three water replenishment methods can be flexibly selected or combined according to the actual project. The general principle is to give priority to method one, that is, to fully tap the exhaust evaporation potential and reduce dependence on external water sources; when the natural cooling and heat dissipation of the secondary reservoir 2 and the Z degree difference between high and low ground temperatures can balance the air conditioning condensation heat dissipation, or the primary cooling tower 3 needs to be overhauled, method two can be used; when the primary cooling tower 3 needs to be overhauled or method one, two or a combination of the two cannot meet the water replenishment of the primary reservoir 1, method three is used.

[0032] The initial water temperature of the secondary reservoir 2 is close to the ground temperature of about YZ degrees. The air conditioning equipment used for cooling the power station is selected and designed according to the designed inlet water temperature of B degrees. When the air conditioning is running and the cooling water is circulated, the water temperature of the secondary reservoir 2 gradually rises. At the same time, the high-temperature cooling water exceeding C degrees from the primary reservoir 1 and the high-temperature cooling water exceeding C degrees directly discharged from the air conditioning are merged into the secondary reservoir 2. When the water temperature of the secondary reservoir 2 exceeds D degrees, the first control valve is opened, the first water pump 41 and the primary cooling tower 3 are operated, and the heat is discharged out of the project through exhaust air through evaporative cooling. The cooling water after cooling can be directly replenished to the primary reservoir 1 by opening the third control valve 53 and the fourth control valve 54, and closing the second control valve 52 and the fifth control valve 55 at the same time; the cooling water can be recirculated to the secondary reservoir 2 by opening the third control valve 53 and the fifth control valve 55, and closing the second control valve 52 and the fourth control valve 54 at the same time.

[0033] The two cooling water circulation routes can be flexibly selected according to the actual project. In general, the first method is preferred, which is to directly replenish the primary reservoir 1. Therefore, in the specific implementation, the capacity of the primary reservoir 1 and the secondary reservoir 2 should be reasonably determined according to factors such as the scale and nature of the project.

[0034] When the diesel engine 71 is running, if the temperature of the diesel engine reservoir 7 exceeds the preset value, the ninth control valve 59 is opened, the second water pump 42 is operated, and the secondary cooling tower 8 meets the cooling and heat dissipation needs of the diesel engine 71, and the second water pump 42 can be operated with variable frequency according to the set return water temperature. When the return water temperature cannot meet the cooling needs of the diesel engine 71, the tenth valve 510 is opened, and the water of the secondary water reservoir 2 is added to the diesel engine reservoir 7, and at the same time, the high-temperature water in the diesel engine reservoir 7 is discharged outside the project.

[0035] Taking an underground project as an example, the total air intake volume is calculated to be 480,000 cubic meters per hour, the total exhaust volume is 420,000 cubic meters per hour, the initial wet-bulb temperature of the exhaust air is 27 degrees, the initial ground temperature of the first-level reservoir 1 is Y=30 degrees, and the initial ground temperature of the second-level reservoir 2 is 25 degrees (ie Z=5 degrees); the total air conditioning condensation heat dissipation is calculated to be 15,000 kilowatts, of which the air conditioning condensation heat dissipation that needs to run continuously is 4,000 kilowatts, and the rest of the air conditioning load is intermittent operation, with a startup time of 12 hours per day; the capacity of the diesel unit 71 designed to run simultaneously is 10,000 kilowatts.

[0036] According to the traditional design method, the air conditioning cooling water is used in two cycles with 2 degrees of redundancy, that is, A = 37 degrees. According to the 5-degree temperature difference requirement of the air conditioning equipment, the primary cooling tower 3 must also be selected according to the 5-degree temperature difference and the heat dissipation capacity needs to be designed according to the maximum heat dissipation of the air conditioning condensation. When all the air conditioning condensation heat, that is, 15,000 kilowatts, is carried by the primary cooling tower 3, the minimum exhaust volume required by the cooling tower is about 750,000 cubic meters per hour, and the total intake and discharge volume of the project must be greatly increased accordingly.

[0037] When selecting according to this system, since the air conditioning refrigeration and air conditioning heat dissipation systems are relatively independent, the air conditioning cooling tower can be calculated based on continuous operation, and the maximum heat dissipation capacity only needs 4000+(15000-4000) / 2=9500 kilowatts. When the operating temperature difference of the first-level cooling tower 3 increases to 8 degrees, the original design engineering exhaust volume of 420,000 cubic meters per hour can ensure that the first-level cooling tower 3 meets all air conditioning condensation and heat dissipation needs.

[0038] Considering that the allowable range of the inlet water temperature of the diesel generator set 71 is generally 40 to 60 degrees, and the maximum allowable inlet and outlet water temperature difference can be up to 25 degrees, the exhaust air still has sufficient evaporation potential after passing through the primary cooling tower 3 to carry the heat dissipation of the diesel generator set 71. Therefore, the selection process of the secondary cooling tower 8 is not listed in detail here.

[0039] The underground engineering air conditioning cascade cooling and heat dissipation system of the present invention realizes the independent setting of air conditioning circulation cooling and heat dissipation and overall heat dissipation of the engineering by setting up cooling water reservoirs in a graded manner. The first-level cooling water reservoir is designed and operated according to the 5-degree temperature difference requirement of the air conditioning equipment, and the second-level cooling water reservoir can maximize the use of the engineering exhaust evaporation potential and design and operate according to the large temperature difference working condition, so as to meet the requirements of all heat dissipation of the engineering by exhausting the air to the outside of the engineering, without additionally increasing the engineering exhaust volume, resulting in negative problems such as increased engineering construction scale and operation and maintenance costs. In addition, by utilizing the energy storage link of the air conditioning cooling water reservoir and controlling the operating frequency of the cooling tower exhaust fan, the relative independence of air conditioning refrigeration and heat dissipation and engineering heat emission is achieved, so that the time period most conducive to the heat dissipation of the engineering can be selected for heat dissipation according to the outdoor meteorological conditions. The requirements of energy saving and concealment of special engineering are effectively guaranteed.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An underground engineering air conditioning cascade cooling and heat dissipation system, It is characterized in that It includes an air-conditioning area, a primary reservoir and a secondary reservoir. The air-conditioning area is provided with air-conditioning. The air-conditioning area and the primary reservoir are arranged at a location with a greater burial depth and a higher ground temperature. The primary reservoir is used to provide cooling water for the air-conditioning. The secondary reservoir is arranged at a location with a smaller burial depth and a lower ground temperature. The outlet of the primary reservoir is connected with the secondary reservoir. When the temperature of the primary reservoir exceeds the set value, the water in the primary reservoir flows into the secondary reservoir. The outlet of the secondary reservoir is connected with the inlet of the primary cooling tower. The outlet of the primary cooling tower is connected with the inlet of the primary reservoir. The water in the secondary reservoir is cooled by the primary cooling tower and then transported to the primary reservoir to reduce the temperature of the primary reservoir. The outlet of the secondary reservoir is connected with the primary reservoir. When the return water temperature of the primary cooling tower cannot meet the demand of the primary reservoir, the low-temperature water in the secondary reservoir is directly transported to the primary reservoir to assist in reducing the temperature of the primary reservoir.

2. The underground engineering air conditioning cascade cooling and heat dissipation system according to claim 1, It is characterized in that The outlet of the secondary reservoir is connected to the outlet pipe of the secondary reservoir. A water pump is arranged on the outlet pipe of the secondary reservoir. The outlet of the water pump is connected to the second control valve and the third control valve respectively. The outlet of the primary cooling tower is connected to the outlet pipe of the primary cooling tower. The outlet pipe of the primary cooling tower is connected to the primary reservoir. The outlet of the second control valve is connected to the outlet pipe of the primary cooling tower; the outlet of the third control valve is connected to the water inlet of the primary cooling tower.

3. The underground engineering air conditioning cascade cooling and heat dissipation system as claimed in claim 2, It is characterized in that The first-stage cooling tower outlet pipe is connected to the fourth control valve and the fifth control valve respectively, the outlet of the fourth control valve is connected to the first-stage water reservoir, and the outlet of the fifth control valve is connected to the second-stage water reservoir.

4. The underground engineering air conditioning cascade cooling and heat dissipation system according to claim 1, It is characterized in that The secondary reservoir and the primary reservoir are respectively connected to external water supply pipelines, and the external water supply can be directly transported to the secondary reservoir or the primary reservoir.

5. The underground engineering air conditioning cascade cooling and heat dissipation system as claimed in claim 4, It is characterized in that The external water supply pipeline is connected to the sixth control valve and the seventh control valve respectively, the water outlet of the sixth control valve is connected to the secondary water reservoir, and the water outlet of the seventh control valve is connected to the primary water reservoir.

6. The underground engineering air conditioning cascade cooling and heat dissipation system according to claim 1, It is characterized in that The outlet of the first-level reservoir is connected to the temperature sensor and the eighth control valve, and the outlet of the eighth control valve is connected to the second-level reservoir. When the temperature sensor detects that the temperature of the first-level reservoir exceeds the set value, the eighth control valve opens and the water in the first-level reservoir flows into the second-level reservoir.

7. The underground engineering air conditioning cascade cooling and heat dissipation system according to claim 1, It is characterized in that The secondary water reservoir is connected to the diesel engine reservoir, which provides cooling water for the diesel engine unit. The diesel engine reservoir is connected to the secondary cooling tower, whose air inlet is connected to the air outlet of the primary cooling tower, whose air outlet is connected to the outside of the project. The secondary cooling tower can cool down the diesel engine reservoir.

8. The underground engineering air conditioning cascade cooling and heat dissipation system as claimed in claim 7, It is characterized in that The water outlet of the diesel engine reservoir is connected to the temperature sensor and the ninth control valve, and the water outlet of the ninth control valve is connected to the second water pump. The second water pump can transport the water in the diesel engine reservoir to the secondary cooling tower for cooling. The water outlet of the secondary cooling tower is connected to the water inlet of the diesel engine reservoir.

9. The underground engineering air conditioning cascade cooling and heat dissipation system as claimed in claim 7, It is characterized in that A tenth valve is installed between the secondary water reservoir and the diesel engine water reservoir. A temperature sensor is installed at the water inlet of the diesel engine water reservoir. When the temperature sensor detects that the return water temperature of the secondary cooling tower exceeds the set value, the tenth valve opens, the secondary water reservoir replenishes water into the diesel engine water reservoir, and the diesel engine water reservoir discharges high-temperature water to the outside of the project.

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