Cable tray temperature control system and cable tray design method

Abstract

This invention belongs to the field of temperature control technology for measurement and transmission cables, specifically relating to a temperature control system and design method for cable troughs. The temperature control system of this invention includes a temperature-controlled cable trough with a hollow inner cavity. A heat exchange tube is inserted into the cavity wall of the temperature-controlled cable trough to maintain a constant temperature environment within the hollow cavity. Both ends of the heat exchange tube extend out of the temperature-controlled cable trough and are connected to the inlet and outlet ends of a temperature-controlled pipeline, respectively. This invention achieves a constant temperature effect on the temperature-controlled cable trough. By optimizing the water distribution and collection structure, and by simulating and optimizing the insulation thickness and water pipe arrangement, it ensures that the temperature field uniformity within the cable trough always meets the actual temperature control requirements for long-distance measurement and transmission cables of 300 meters or more. For cable troughs of 300 meters or more, the temperature gradient within the cavity from beginning to end is less than ±1℃, and the control accuracy is controlled within ±0.1℃.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation technology for measurement and transmission cables, specifically relating to a constant temperature system for cable trays and a design method for cable trays. Background Technology

[0002] For measurement transmission cables of precision sensors, the ambient temperature has a significant impact on the measurement results; temperature fluctuations affect the cable's operating point and signal transmission. In general, air conditioning is commonly used to maintain a constant temperature in the area where precision sensors are located. However, measurement transmission cables, which connect to external equipment, frequently pass through low- or high-temperature environments, causing their temperature to fluctuate accordingly. Therefore, in the context of energy conservation and low carbon emissions, there is a strong desire to optimize the temperature control of measurement transmission cables over distances of 300 meters and above. This requires ensuring that the temperature of the constant-temperature cable tray remains within the applicable range for the measurement transmission cable, and that the temperature gradient within the cable tray does not exceed ±1℃, the temperature uniformity does not exceed ±0.1℃, and the temperature control accuracy does not exceed ±0.1℃, to meet the requirements of measurement transmission cables over distances of 300 meters and above.

[0003] Therefore, to address the high requirements for temperature variation gradient, temperature uniformity, and temperature control accuracy within thermostatic cable trays, the traditional solution is typically to install a water jacket on the outside of the cable tray to ensure the constant temperature requirement. However, while this solution can guarantee the high-parameter constant temperature requirement of temperature uniformity within the cable tray being no greater than ±0.1℃, it also presents the following technical challenges:

[0004] (1) Long-distance water jacket series water supply, the water temperature inside the water jacket will generate heat leakage with the direction of water flow, the temperature gradient is relatively large, and the water jacket itself is the channel of water flow. The shape and structure of the water jacket are very different. Therefore, it is very difficult to ensure that the water temperature gradient is reduced by covering the insulation layer, and it is very easy to generate cold bridge.

[0005] (2) The shape and processing technology of the water jacket for external water-jacketed constant temperature cable troughs, whether rectangular or circular, need to be determined based on parameters such as the number of cables inside and the flow rate of the water jacket. The connection methods between the water jacket and the cable trough vary greatly, and the material and heat transfer method of the water jacket also place high demands on processing and manufacturing. Therefore, the processing of water jackets for constant temperature cable troughs is very difficult and costly.

[0006] (3) Given the aforementioned difficulties in processing the water jacket and the complexity of the assembly process, if a problem occurs with the water jacket constant temperature cable tray, its replaceability and maintainability are very poor. For example, if the local heat conduction effect is poor, only most of the water jacket can be inspected and replaced. If the cable has a problem and needs to be repaired and replaced, the external sealing water jacket is very difficult to disassemble and assemble.

[0007] In addition, cable troughs with insulation layers are also used to ensure the constant temperature requirements of measurement transmission cables. However, when the cable trough's structural dimensions (length, width, and height) are fixed: on the one hand, as the insulation layer thickness increases, the temperature inside the cable trough is less affected by external factors, and the temperature field uniformity inside the cable trough is better. However, increasing the insulation layer thickness will encroach on the space inside the trough, and it certainly cannot be increased indefinitely. On the other hand, the spacing between the inlet and outlet heat exchange pipes inside the trough also has a significant impact on the temperature field inside the trough. How to find a reasonable spacing between the inlet and outlet heat exchange pipes while keeping the insulation layer as small as possible to ensure that the temperature field uniformity inside the trough meets the requirements is the key to the rational design of cable troughs, and there is currently no practical and effective solution. Furthermore, how to ensure that the temperature change gradient inside the constant temperature cable trough is no more than ±1℃ over long distances of 300 meters and above requires a segmented modular solution to ensure the high parameter requirements of temperature change gradient over long distances, simplify the manufacturing process, and facilitate the installation and maintenance of measurement transmission cables. Currently, there is no relevant solution for this either. Therefore, this issue urgently needs to be addressed. Summary of the Invention

[0008] One objective of this invention is to overcome the shortcomings of the prior art and provide a constant temperature cable tray system. This system innovatively utilizes the necessary air conditioning system and the waste heat inevitably generated by the outdoor unit, thereby achieving a constant temperature effect on the cable tray. Ultimately, it ensures that the temperature field uniformity within the tray consistently meets the actual constant temperature requirements of the measurement and transmission cables, and possesses advantages such as energy saving, environmental protection, low cost, and ease of implementation. Another objective of this invention is to provide a cable tray design method for the constant temperature cable tray system, thereby facilitating and efficiently optimizing the design of the constant temperature cable tray.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A constant temperature cable tray system includes a constant temperature cable tray, which is composed of constant temperature tray frame units sequentially assembled along its length. The assembled cable tray has a through-hole hollow cavity, which serves as a housing for measurement and transmission cables. A heat exchange tube is inserted through the cavity wall of the cable tray to maintain a constant temperature environment within the housing. Both ends of the heat exchange tube extend out of the cable tray and are connected to the inlet and outlet ends of a constant temperature pipeline, respectively. The constant temperature pipeline includes pipes sequentially arranged along the flow direction of the heat exchange medium. The system includes an inlet end, a cold source heat exchanger for absorbing heat from the air conditioner evaporator, a heat source heat exchanger for absorbing heat from the air conditioner outlet, an expansion tank, an air heat exchanger, a three-way regulating valve TWV, a water pump, and a pipe outlet end. The inlet and outlet of the heat source heat exchanger are bridged by a first bridging pipe with a first switching valve V1, and the inlet and outlet of the cold source heat exchanger are bridged by a second bridging pipe with a second switching valve V2. The pipe inlet end and the bypass outlet of the three-way regulating valve TWV are bridged to each other through a regulating pipe.

[0011] Preferably, the constant temperature heat exchanger unit includes a square-shaped wire trough shell and a wire trough cover plate covering the wire trough shell. A layer of heat insulation cotton is arranged in the space enclosed by the wire trough shell and the wire trough cover plate, and the space enclosed by the heat insulation cotton forms the hollow inner cavity. The heat insulation cotton at the bottom wall of the hollow inner cavity is recessed with a placement groove for placing heat exchange tubes, and a reinforcing layer for covering the placement groove is arranged on the bottom wall of the hollow inner cavity. The wire trough shells of adjacent constant temperature heat exchanger units are connected to each other by connectors.

[0012] Preferably, the reinforcing layer is a metal wire mesh, and the reinforcing layer extends in the same direction as the constant temperature cable groove.

[0013] Preferably, the bottom of the placement trough is provided with insulation cotton of the same thickness as the wall of the wire trough shell, and a wooden pad is arranged at the bottom of the placement trough, with the length of the wooden pad parallel to the extension direction of the heat exchange tube in order to support the heat exchange tube.

[0014] Preferably, the cold source heat exchanger and the heat source heat exchanger are arranged in the same heat exchange box, and an external fan for forced convection is also provided outside the heat exchange box.

[0015] Preferably, the heat exchange tubes are arranged sequentially along the length of the constant temperature cable trough, and the outlets of each heat exchange tube are connected to the inlet end of the pipeline by a water collector. A water distributor is provided at the outlet end of the pipeline to connect to the inlet of each heat exchange tube. Insulation sections are arranged at the water distributor, water collector and the connection with the heat exchange tube, and the temperature change gradient of the water distributor along the direction of heat exchange medium travel is not greater than 1℃.

[0016] Preferably, the heat exchange tube is U-shaped, N-shaped, S-shaped, or W-shaped.

[0017] Preferably, each heat exchange tube is arranged in a constant temperature tank unit or simultaneously arranged in two or more adjacent constant temperature tank units, and covers the entire constant temperature tank unit.

[0018] Preferably, a temperature sensor T1 for real-time temperature monitoring is arranged in the hollow inner cavity.

[0019] Preferably, a cable tray design method for the cable tray constant temperature system described above is characterized by comprising the following steps:

[0020] S1. Set the structural dimensions of the constant temperature cable tray and the U-shaped heat exchange tubes arranged symmetrically about the axis of the constant temperature cable tray, and establish a CFD simulation model.

[0021] S2. Set the inlet water temperature T of the heat exchanger tubes. in The ambient temperature T of the constant temperature cable tray am Temperature field uniformity J in the hollow cavity;

[0022] S3. Set the insulation cotton thickness δ=0m, and the spacing increment Δδ between the two parallel sections of the U-shaped heat exchange tube;

[0023] S4. Set the distance between two adjacent heat exchange tubes L = 0m, the maximum value of L L', and the increment of L ΔL;

[0024] S5, let δ n+1 =δ n +Δδ, n≥0 and are integers;

[0025] S6, Let L n+1 =L n +ΔL;

[0026] S7. The structural dimensions of the constant temperature cable tray and heat exchange tube, T in δ n+1 L n+1 、T am As input parameters for the CFD simulation model;

[0027] S8. Solve the temperature field inside the constant temperature cable trough based on the CFD simulation model obtained in step S7, and compare the temperature field uniformity.

[0028] S9. Determine if the temperature field uniformity is less than J. If not, proceed to step S10; if yes, the calculation ends, and the current δ is output. n+1 L n+1 ;

[0029] S10. Determine if L is true. n+1 >L'? If not, proceed to step S6; if yes, proceed to step S5.

[0030] The beneficial effects of this invention are as follows:

[0031] 1) Through the above solution, this invention solves the problem of the measurement transmission cable trough changing with ambient temperature, and aligns with the concept of energy conservation and low carbon emissions. By utilizing the waste heat from the outdoor unit of the air conditioner, the internal temperature of the constant-temperature cable trough can be maintained within a certain constant temperature range. In this way, the ambient temperature of the measurement transmission cable can be kept constant, and the measured values ​​can be minimized from external influences, which has a profound impact on the accuracy of the measurement data. At the same time, the overall structure directly utilizes the readily available air conditioning system on site, making the structure simple and easy to implement, with extremely low replacement costs and significant benefits.

[0032] 2) Based on the above structure, this invention also adds an air heat exchanger, allowing the liquid in the heat exchange tubes to undergo preliminary heat exchange with room temperature within the air heat exchanger before heating or cooling, thereby achieving temperature control. This ensures that the water temperature in the thermostatic pipeline undergoes an initial adjustment process before subsequent commissioning, further improving the efficiency of thermostatic operation. The expansion tank is designed to balance the water flow rate in the thermostatic pipeline during heating or cooling.

[0033] 3) Under normal conditions, when constant temperature is achieved without the need for heat exchange between cold and heat sources, the constant temperature pipeline can be directly adjusted to achieve self-circulation function, thereby ensuring temperature uniformity within the temperature field.

[0034] 4) In the actual design of constant temperature cable trays, it is necessary to obtain values ​​for the insulation cotton thickness, the parallel segment spacing of a single heat exchange tube, and the spacing between adjacent heat exchange tubes. The updated information, including the insulation cotton thickness, the parallel segment spacing of a single heat exchange tube, and the spacing between adjacent heat exchange tubes, should be input into the CFD simulation model to calculate the temperature field uniformity and determine whether the temperature field uniformity meets the requirements under the input insulation cotton thickness and heat exchange tube spacing conditions. The optimal solution is to use the minimum insulation cotton thickness and appropriate spacing and number of heat exchange tubes to meet the temperature field requirements within the constant temperature cable tray. Through simulation calculations, the insulation cotton thickness, heat exchange tube inlet and outlet, and the spacing between adjacent heat exchange tubes can be reasonably optimized, ultimately meeting the required temperature uniformity requirements within the constant temperature cable tray.

[0035] 5) This invention solves the problem of water temperature gradient in traditional devices. Due to the complexity of the manufacturing process, water jackets cannot be made into parallel structures, and each cable tray unit cannot have its own dedicated water path, thus temperature gradients are unavoidable. In contrast, the water pipes, i.e., heat exchange pipes, in this invention can be standard products, configured one-to-one with the thermostatic tank unit, or multiple thermostatic tank units can share a single water pipe, connected via a distributor and a collector. The entire water pipeline and distributor / collector structure are standard, and insulation is very simple. According to calculations and simulations, under normal temperature conditions, with an overall insulation layer thickness of 30mm, the parallel water pipeline of this invention can ensure that the temperature difference between the inlet and outlet of the water entering each unit does not exceed ±0.1℃.

[0036] 6) This invention solves the problem of difficult maintenance and upkeep in traditional constant-temperature cable tray devices. The water pipes and manifolds have standardized structures, making procurement and manufacturing easy, significantly reducing costs. The heat exchange tubes of this invention are arranged on the bottom surface of the constant-temperature cable tray, without affecting the original cable tray's cable-holding cavity, thus facilitating assembly and strong replaceability. Inspection and maintenance of the cables only require opening the cable tray cover normally. When the cable tray and cables need to be replaced, the heat exchange tubes, acting as the cold and heat source water pipes, can also be partially replaced and repaired, making it highly flexible and convenient to use.

[0037] 7) This invention can guarantee that the temperature uniformity in the constant temperature cable tray is no greater than ±0.1℃, the temperature change gradient is no greater than ±1℃, and the temperature control accuracy is no greater than ±0.1℃, which meets the requirements for long-distance measurement and transmission cables of 300 meters and above. Attached Figure Description

[0038] Figure 1 This is a diagram showing the arrangement of the present invention;

[0039] Figure 2 This is a cross-sectional view of a constant temperature cable tray.

[0040] Figure 3 This is a schematic diagram of one possible arrangement of heat exchange tubes;

[0041] Figure 4 This is a flowchart of the design method of the present invention;

[0042] Figure 5 , Figure 6 , Figure 7 This is a schematic diagram of three other arrangements of heat exchange tubes.

[0043] The actual correspondence between the reference numerals and component names in this invention is as follows:

[0044] 10-Thermostatic cable tray; 10a-Thermostatic cable tray frame unit; 11-Cable tray housing; 12-Cable tray cover; 13-Insulation cotton; 14-Reinforcing layer; 15-Wooden pad; 16-Insulation slot;

[0045] 20 - Heat exchanger tube; 21 - Water collector; 22 - Water distributor;

[0046] 30a-First bridge pipeline; 30b-Second bridge pipeline; 30c-Regulating pipeline; 31-Water pump; 32-Air heat exchanger; 33-Expansion tank; 34-Heat source heat exchanger; 35-Cold source heat exchanger; 36-Heat exchange box; 37-External fan. Detailed Implementation

[0047] For ease of understanding, the specific structure and operation of the present invention will be further described below with reference to the accompanying drawings:

[0048] Figure 1-3 The invention discloses a specific implementation structure; wherein, the total length of the constant temperature cable tray 10 is 1000m, which can be formed by splicing several sections of constant temperature tray frame units 10a through connectors. Each section of the constant temperature tray frame unit 10a is 6m long, and a total of 167 sections are cut and assembled. The constant temperature tray frame units 10a can be arbitrarily combined to form an assembly. Each section of the constant temperature tray frame unit 10a is connected to each other with fasteners or other connectors, making it simple and easy to disassemble. After connection, insulation cotton is applied to the inner wall and the inside of the top cover of each section of the constant temperature tray frame unit 10a. Specifically, as shown in the figure... Figure 1 As shown, the wire trough housing 11 and wire trough cover plate 12 that constitute each section of the constant temperature rack unit 10a are all as shown in the diagram. Figure 1-2 The cable tray 10 is covered with a layer of insulation cotton 13, which is 20mm thick, to minimize heat exchange between the cable and the external environment. Simultaneously, heat exchange tubes 20 are arranged within the constant-temperature cable tray 10, and the heat exchange tubes 20 are positioned as follows: Figure 2-3 The installation groove 16 shown is supported by wooden blocks 15 and covered with a layer of metal wire mesh that forms a reinforcing layer 14.

[0049] In actual design, the placement and material selection of heat exchange tubes 20 can be simulated and calculated using simulation software, including but not limited to N, W, U, and S types. See details... Figure 3 and Figure 5-7 As shown.

[0050] The metal wire mesh serves to support the measurement transmission cable and prevent the weight of the measurement transmission cable from pressing on the heat exchange tube 20; galvanized steel wire mesh is preferred.

[0051] Figure 3 The arrangement of the heat exchange tubes 20 shows that there are two or more heat exchange tubes arranged sequentially along the length of the constant temperature cable trough 10. The outlets of each heat exchange tube 20 are connected to the inlet end of the pipeline via a water collector 21. A water distributor 22 is installed at the outlet end of the pipeline to connect to the inlet of each heat exchange tube 20, thereby achieving the purpose of water collection and distribution. In actual design, the water collector 21 and the water distributor 22 are designed as follows: Figure 3 The cavity structure shown is sufficient; its structure is quite common and will not be described in detail here. The water distributor 22, water collector 21, and the connection points with the heat exchange tube 20 should be insulated. The thickness of the insulation should be determined based on simulation and calculation, ensuring that the temperature gradient of the water distributor 22 extending along the length of the constant temperature cable trough 10 is at least no greater than 1℃. In specific design, by optimizing the water distribution and collection structures, it can be ensured that the temperature field uniformity within the constant temperature cable trough 10 always meets the actual constant temperature requirements of long-distance measurement transmission cables of 300 meters or more.

[0052] Furthermore, the water in the heat exchange tube 20 undergoes convective heat exchange through a constant-temperature pipeline, thereby dissipating the heat from the water in the heat exchange tube 20 into the cable tray housing 11. Specifically, the hot water in the heat exchange tube 20 is circulated by a water pump 31. The heat exchange medium, i.e., the water, in the constant-temperature pipeline passes through the heat source heat exchanger 34 and the outdoor unit of the air conditioner, and then passes through the air heat exchanger 32 and the expansion tank 33. The exhaust air temperature of the outdoor unit of the air conditioner is T1, which serves as the heat source for the water. The heat exchange tube 20 can also cool the water through the evaporator of the air conditioner, at which point the evaporator of the air conditioner forms a cold source heat exchanger 35 with a temperature of T3. To further meet the energy-saving requirements, an air heat exchanger 32 is also added to the constant-temperature pipeline for heat exchange between the water in the heat exchange tube 20 and the air; the air heat exchanger 32 is usually placed in the outdoor environment as a water conditioning source with a temperature of T2. In addition, an expansion tank 33 is also installed in the constant-temperature pipeline to regulate water pressure. In addition, the inlet and outlet of the heat source heat exchanger 34 are bridged by a first bridging pipe 30a with a first switching valve V1, the inlet and outlet of the cold source heat exchanger 35 are bridged by a second bridging pipe 30b with a second switching valve V2, and the outlet end of the pipe is bridged to the bypass outlet of the three-way regulating valve TWV through a regulating pipe 30c.

[0053] exist Figure 1-3 In the illustrated embodiment, the specifications of the constant temperature cable tray are 400mm × 200mm; the insulation cotton 13 is a 20mm thick rubber-plastic insulation cotton 13. The heat exchange tube 20 is a 6mm outer diameter copper tube, bent into the shape shown. Figure 3 The U-shape is shown. The heat exchange tube 20 is 170mm from the axis of the constant temperature cable tray. The temperature sensor T1 is positioned as shown... Figure 3 As shown.

[0054] Therefore, the advantages of this invention are as follows:

[0055] 1. The constant temperature cable tray 10 is filled with insulation cotton 13, and heat exchange pipes 20 are introduced. Hot or cold water in the heat exchange pipes 20 can be used to control the air inside the constant temperature cable tray 10, ensuring a constant temperature effect inside the constant temperature cable tray 10. Compared with traditional hollow cable trays and fan cooling technologies, the replacement cost is lower, it better protects the measurement and transmission cables, is safer, and the temperature is more uniform and stable.

[0056] 2. The heat exchange tube 20 mentioned above can be made of simple and readily available materials such as copper tubes. Hot water comes from the waste heat of the outdoor unit of the air conditioner, while cold water comes from the evaporator, resulting in very low cost. Compared with the traditional electric heater plus cold source control method, it is more energy-efficient and low-carbon.

[0057] 3. A temperature sensor is installed inside the constant temperature cable tray 10, which can dynamically adjust the water volume according to the internal temperature. The water volume can be adjusted through the three-way regulating valve TWV.

[0058] 4. The heat exchanger 34 and the cold source heat exchanger 35 formed by the condenser of the air conditioner are both concentrated in a large heat exchange box 36 to complete heat exchange, and the heat exchange completion can be increased by forced convection through an external fan 37.

[0059] Based on the above structure, such as Figure 4 As shown, the present invention also provides a cable tray design method for the cable tray constant temperature system described above, comprising the following steps:

[0060] S1. Set the structural dimensions of the constant temperature cable tray 10 and the U-shaped heat exchange tube 20 arranged symmetrically about the axis of the constant temperature cable tray 10, and establish a CFD simulation model.

[0061] S2. Set the inlet water temperature T of the heat exchanger tubes. in The ambient temperature T of the constant temperature cable tray am Temperature field uniformity J in the hollow cavity;

[0062] S3. Set the insulation cotton thickness δ=0m, and the spacing increment Δδ between the two parallel sections of the U-shaped heat exchange tube;

[0063] S4. Set the distance between two adjacent heat exchange tubes L = 0m, the maximum value of L L', and the increment of L ΔL;

[0064] S5, let δ n+1 =δ n +Δδ, n≥0 and are integers;

[0065] S6, Let L n+1 =L n +ΔL;

[0066] S7. Determine the structural dimensions of the constant temperature cable tray 10 and the heat exchange tube 20, T in δ n+1 L n+1 、T am As input parameters for the CFD simulation model;

[0067] S8. Solve the temperature field inside the constant temperature cable trough 10 based on the CFD simulation model obtained in step S7, and compare the temperature field uniformity.

[0068] S9. Determine if the temperature field uniformity is less than J. If not, proceed to step S10; if yes, the calculation ends, and the current δ is output. n+1 L n+1 ;

[0069] S10. Determine if L is true. n+1 >L'? If not, proceed to step S6; if yes, proceed to step S5.

[0070] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0071] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0072] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A constant temperature system for cable trays, characterized in that: The system includes a constant temperature cable tray (10), which is composed of constant temperature tray frame units (10a) arranged sequentially along the length direction. After assembly, the constant temperature cable tray (10) has a through hollow inner cavity, which constitutes a cable cavity for accommodating measurement transmission cables. A heat exchange tube (20) for maintaining a constant temperature environment in the cable tray (10) is installed inside the cavity wall of the constant temperature cable tray (10). The two ends of the heat exchange tube (20) extend out of the constant temperature cable tray (10) and are connected to the inlet end and outlet end of the constant temperature pipeline, respectively. The constant temperature pipeline includes a pipeline inlet end, a cold source heat exchanger (35) for absorbing heat from the air conditioner evaporator, a heat source heat exchanger (34) for absorbing heat from the hot air at the air conditioner outlet, and an expansion joint arranged in sequence along the flow direction of the heat exchange medium. The water tank (33), air heat exchanger (32), three-way regulating valve TWV, water pump (31) and pipeline outlet are connected to the inlet and outlet of the heat source heat exchanger (34) by a first bridging pipeline (30a) with a first switching valve V1, and the inlet and outlet of the cold source heat exchanger (35) are connected to a second bridging pipeline (30b) with a second switching valve V2. The pipeline inlet and the bypass outlet of the three-way regulating valve TWV are connected to each other by a regulating pipeline (30c). The constant temperature rack unit (10a) includes a square groove-shaped wire groove shell (11) and a wire groove cover plate (12) covering the wire groove shell (11). A layer of heat insulation cotton (13) is arranged in the space enclosed by the wire groove shell (11) and the wire groove cover plate (12). The space enclosed by the heat insulation cotton (13) forms the hollow inner cavity. The heat insulation cotton (13) at the bottom wall of the hollow inner cavity is recessed with a placement groove (16) for placing heat exchange tubes (20). A reinforcing layer (14) for covering the placement groove (16) is arranged on the bottom wall of the hollow inner cavity. The wire groove shells (11) of adjacent constant temperature rack units (10a) are connected to each other by connectors.

2. The cable tray constant temperature system according to claim 1, characterized in that: The reinforcing layer (14) is a metal wire mesh, and the extension direction of the reinforcing layer (14) is the same as that of the constant temperature cable groove (10).

3. The cable tray constant temperature system according to claim 1, characterized in that: The bottom of the placement trough (16) is provided with insulation cotton (13) of the same thickness as the wall thickness of the wire trough shell (11), and a pad (15) is arranged at the bottom of the placement trough (16). The length direction of the pad (15) is parallel to the extension direction of the heat exchange tube (20) so as to support the heat exchange tube (20).

4. A cable tray constant temperature system according to claim 1, 2, or 3, characterized in that: The cold source heat exchanger (35) and the heat source heat exchanger (34) are both arranged in the same heat exchange box (36), and an external fan (37) for forced convection is also provided outside the heat exchange box (36).

5. A cable tray constant temperature system according to claim 1, 2, or 3, characterized in that: The heat exchange tubes (20) are arranged sequentially along the length of the constant temperature cable trough (10). The outlets of each heat exchange tube (20) are connected to the inlet end of the pipeline by a water collector (21). A water distributor (22) is provided at the outlet end of the pipeline to connect to the inlet of each heat exchange tube (20). Insulation sections are arranged at the water distributor (22), the water collector (21) and the connection with the heat exchange tubes (20), and the temperature change gradient of the water distributor (22) along the direction of heat exchange medium travel is not greater than 1℃.

6. A cable tray constant temperature system according to claim 1, 2, or 3, characterized in that: The heat exchange tube (20) is U-shaped, N-shaped, S-shaped or W-shaped.

7. The cable tray constant temperature system according to claim 6, characterized in that: Each heat exchange tube (20) is arranged in a constant temperature rack unit (10a) or simultaneously in two or more adjacent constant temperature rack units (10a), and covers the constant temperature rack unit (10a) where it is located.

8. A cable tray constant temperature system according to claim 1, 2, or 3, characterized in that: A temperature sensor T1 for real-time temperature monitoring is arranged in the hollow inner cavity.

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