A district heating mixed flow tank based on spoiler structure optimization

Abstract

The application belongs to the technical field of heat supply equipment, and provides a regional heat supply mixing tank based on turbulence structure optimization, which comprises a first turbulence component and a second turbulence component arranged in a tank body along a water flow direction; the first turbulence component is located behind a low-temperature water inlet and behind a high-temperature water inlet, and is used for blocking the channel of cold water sticking to the bottom and actively inducing to the middle or upper part of the tank body; the second turbulence component is located in front of a medium-temperature water outlet, and is used for forcibly turning and cutting the mixed fluid about to flow out, so as to realize the thermal deviation homogenization of the mixed fluid. The mixing tank is used for hydraulic decoupling and heat mixing of a primary circuit and a secondary circuit of a heat network, and the internal turbulence structure is additionally arranged and optimized to eliminate the thermal stratification phenomenon in the tank, and then the temperature uniformity of the water outlet is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of centralized district heating equipment, and relates to a mixing tank, specifically a district heating mixing tank based on turbulence structure optimization. Background Technology

[0002] In centralized district heating systems, the mixing tank is a key component for achieving hydraulic decoupling and heat mixing between the primary heating network (heat source side) and the secondary heating network (user side). Its main function is to mix the supply and return water from the primary and secondary loops within the tank, balancing water temperature and pressure, thus enabling the two circulation systems to operate relatively independently and stably. However, existing mixing tanks have significant drawbacks in actual operation. When the mixing effect inside the mixing tank is poor, severe temperature stratification (i.e., thermal stratification) is highly likely to occur. Specifically, because the high-temperature hot water (e.g., 90°C) entering from the primary side has a lower density, its momentum tends to concentrate at the top of the tank, making it difficult to sink; while the low-temperature return water (e.g., 40°C) entering from the secondary side has a higher density and tends to flow close to the bottom of the tank after entering. This flow pattern prevents sufficient mixing of hot and cold water, forming a typical "hot on top, cold on bottom" thermal deviation pattern. This "hot on top, cold on bottom" stratification structure causes the low-temperature return water at the bottom to form a "cold flow short circuit," rapidly discharging from the outlet without effective heating. This directly leads to significant temperature differences at different outlets of the mixing tank. Under certain high-load or high-flow-ratio operating conditions, the maximum temperature difference at the lateral outlets can even exceed 20°C. This severe uneven heating not only makes the outlet temperature extremely unstable, affecting the end-point balance and control capability of the heating system and reducing the heating quality, but may also cause engineering hazards such as pipeline thermal stress. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a district heating mixing tank based on optimized turbulence structure. This mixing tank is used for hydraulic decoupling and heat mixing of the primary and secondary loops of the heating network. By adding and optimizing the internal combined turbulence structure, the thermal stratification phenomenon inside the tank is eliminated, thereby improving the temperature uniformity of the outlet water.

[0004] A district heating mixing tank based on turbulence structure optimization includes a first turbulence component and a second turbulence component arranged inside the tank along the water flow direction;

[0005] The first turbulence-inducing component is located behind the low-temperature water inlet and the high-temperature water inlet, and is used to block the channel for cold water to flow straight along the bottom and actively induce it to the middle or upper part of the tank.

[0006] The second turbulence-inducing component is located in front of the medium-temperature water outlet and is used to forcibly turn and cut the mixed fluid that is about to flow out, so as to achieve the homogenization of the thermal deviation of the mixed fluid.

[0007] Furthermore, the first turbulence-disrupting component is an inclined turbulence-disrupting pipe assembly.

[0008] Furthermore, the turbulence-disrupting pipe assembly comprises four sets of pipe rows, each set of pipe rows having multiple turbulence-disrupting pipes with horizontally parallel and coplanar axes.

[0009] Furthermore, the four sets of pipes are arranged at an angle in the direction of water flow, and all of them are at the same angle.

[0010] Furthermore, the first group of pipes is tilted in a different direction than the remaining three groups of pipes, and the remaining three groups of pipes are tilted against the direction of water flow at the same angle, while the first group of pipes is tilted in the direction of water flow.

[0011] Furthermore, the four sets of pipe banks are composed of Φ159 steel pipes and Φ108 steel pipes arranged in an interlaced manner.

[0012] Furthermore, the second flow-dispersing component is an outlet flow-dispersing pipe and an inclined outlet flow-dispersing pipe array.

[0013] The first turbulence-disrupting component is a vertically arranged turbulence-disrupting plate extending downward from the upper wall of the tank.

[0014] The second turbulence component is a vertically arranged turbulence plate or water outlet turbulence pipe extending upward from the lower wall of the tank.

[0015] In summary, this application provides an optimized internal combined turbulence structure that can effectively break the "cold flow short circuit" at the bottom of the tank and the "hot flow slip" at the top under the premise of low additional pressure drop, eliminate thermal stratification by constructing a persistent entrainment and mixing path, and thus significantly improve the temperature uniformity of the outlet.

[0016] The advantages of this application compared to the prior art are:

[0017] 1. Flow field reconstruction eliminates "cold flow short circuit": By setting the first turbulence component at an angle in the front and middle section of the mixing tank, a strong windward obstruction and leeward separation effect is generated on the low-temperature return water entering from the bottom. This geometric guidance forces the cold water to rise, completely cutting off the channel through which the cold water easily flows straight close to the bottom of the tank, fundamentally eliminating the "short circuit" risk of insufficiently heated cold water being discharged directly from the outlet.

[0018] 2. Scale-based eddy current enhancement for deep mixing and breaking down thermal stratification: An innovative approach employs a staggered arrangement of large-diameter and small-diameter steel pipes. The large-diameter pipes primarily provide macroscopic flow obstruction and form large-scale wake vortices, significantly extending the residence and contact time of hot and cold fluids within the tank; the small-diameter pipes, on the other hand, are responsible for microscopic high-frequency cutting of the local flow field. The synergistic effect of the large and small pipe diameters creates intense momentum and heat exchange within the tank without causing excessive pressure drop, effectively breaking down the stubborn thermodynamic boundary layer where high-temperature water is on top and low-temperature water is below.

[0019] 3. Reverse flow at the end ensures uniform water temperature: A second flow-disrupting component with a reverse angle is added near the outlet area to forcibly reverse the flow direction and perform secondary disturbance and cutting of the mixed heat medium about to flow out. This design performs a final deep homogenization of local residual thermal deviations, ensuring that the temperature of the supplied hot water discharged from multiple medium-temperature outlets is highly consistent, greatly improving the heating quality and end-point equalization capability of the heating system's secondary side.

[0020] 4. Stable operation of the status monitoring support system: Pressure gauges and thermometers are integrated at the top of the stable zone at the end of the mixing tank. After the fluid has completed the entire mixing process, the temperature and pressure status of the final output heat medium can be accurately and in real time monitored, providing reliable closed-loop data support for the hydraulic decoupling judgment, precise heat control and abnormal status early warning of the entire district heating system. Attached Figure Description

[0021] Figure 1 This is a structural diagram of the district heating mixing tank based on turbulence structure optimization in Example 1;

[0022] Figure 2 This is a structural diagram of the district heating mixing tank based on turbulence structure optimization in Example 3;

[0023] Figure 3 This is a structural diagram of the district heating mixing tank based on turbulence structure optimization in Example 5.

[0024] In the diagram: 1. High-temperature inlet; 2. Low-temperature inlet; 3. Medium-temperature outlet; 4. First group of pipes; 5. Second group of pipes; 6. Third group of pipes; 7. Fourth group of pipes; 8. Ф159 steel pipe; 9. Ф108 steel pipe; 10. Outlet baffle pipe; 11. Outlet baffle pipe; 13. Pressure gauge; 14. Thermometer; 15. Tank body; 20. First baffle; 21. Second baffle. Detailed Implementation

[0025] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise stated, the technical or scientific terms used in this application have the ordinary meaning as understood by those skilled in the art.

[0026] Example 1, Reference Figure 1 This embodiment of a district heating mixed flow tank based on turbulence structure optimization includes a first turbulence component and a second turbulence component arranged in the tank body. Along the water flow direction, the denser low-temperature return water enters the tank body 15 through the low-temperature water inlet 2, while the less dense high-temperature hot water is injected downward into the tank body 15 through the two high-temperature water inlets 1 at the top.

[0027] The first flow-disrupting component is a flow-disrupting pipe group, and the second flow-disrupting component is a flow-disrupting pipe row 10 or a flow-disrupting pipe 11. The flow-disrupting pipe group includes a first group of pipe rows 4, a second group of pipe rows 5, a third group of pipe rows 6, and a fourth group of pipe rows 7. Each group of pipe rows has multiple flow-disrupting pipes with horizontally parallel and coplanar axes. The four groups of pipe rows are arranged at an angle along the direction of water flow, and the acute angle α of the inclination is 60º. During the mixing process of the fluid flowing dominantly towards the outlet side, it first encounters the first group of pipe rows 4, the second group of pipe rows 5, the third group of pipe rows 6, and the fourth group of pipe rows 7, which are arranged at an angle α of 60°. These four sets of inclined arrays block the straight path of cold water along the bottom, forcing the cold water at the bottom to rise along the pipe wall and actively induce it to the upper middle part of the tank 15. The first set of pipes 4 consists of two Φ159 steel pipes 8 and one Φ108 steel pipe 9 arranged in an interlaced pattern; the second set of pipes 5 consists of four Φ108 steel pipes 9; the third set of pipes 6 consists of three Φ159 steel pipes 8; and the fourth set of pipes 7 consists of four Φ108 steel pipes 9. The above-mentioned turbulence-inducing pipe groups are composed of interlaced Φ159 steel pipes 8 and Φ108 steel pipes 9. Among them, the larger diameter Φ159 steel pipes 8 generate a strong fluid obstruction effect and a large-scale wake vortex, which significantly prolongs the residence time of the water flow in the tank; the smaller diameter Φ108 steel pipes 9 subdivide and cut the local flow field, generating high-frequency micro vortices. The synergistic combination of large and small pipe diameters promotes intense momentum and heat exchange between hot and cold fluids in the front and middle sections of the tank, effectively breaking the inherent upper and lower thermal stratification boundaries within the tank.

[0028] Before the mixed fluid continues its journey to the right-side outlet region, it encounters a second flow-disrupting component arranged at a reverse inclination angle θ of 120°. This consists of an outlet flow-disrupting pipe array 10 and two outlet flow-disrupting pipes 11, respectively positioned in front of the second and third medium-temperature outlets 3. The reverse inclination angle is defined as θ = 120° between a radial diameter line passing through the center of one outlet flow-disrupting pipe 11 and the bottom surface of the tank 15. This reverse pipe bundle in this region forces a deflection and secondary cutting disturbance to the outflowing mixed fluid, ultimately homogenizing any remaining local thermal deviations.

[0029] Finally, the thoroughly mixed hot water is smoothly discharged from the three medium-temperature outlets 3 at the bottom, effectively eliminating the temperature difference between the outlets. The pressure gauge 13 and thermometer 14 located at the top of the end of the tank 15 are used to monitor the final pressure and temperature of the heat medium inside the tank 15 in real time to ensure the stable output of the overall hydraulic and thermal conditions of the system.

[0030] Example 2: Based on the scheme of Example 1, this example uses the decoupling link of the primary and secondary networks in a typical intelligent centralized heating system heat exchange station in a frigid region of northern my country. This heat exchange station undertakes the winter heating task for a large number of surrounding buildings (such as mixed residential and commercial buildings). In the complex heat pipe network in actual operation, due to the significant differences in the hydraulic conditions between the primary heat source and the secondary user side, the system has extremely high requirements for the optimization of thermo-hydraulic coupling.

[0031] Before the system upgrade, the station used a conventional hollow mixed-flow tank for hydraulic decoupling. Due to the extremely uneven mixing of fluids inside the tank, severe uneven heating and cooling frequently occurred in the terminal outlet water network. This not only reduced the heating comfort of users but also caused ineffective high-frequency regulation of the secondary network circulating water pump and forced excessive compensation on the heat source side, resulting in significant energy waste. This embodiment will detail the application process of a district heating mixed-flow tank based on turbulence structure optimization after replacing the original traditional mixed-flow tank, and the verification of its actual performance and thermodynamic indicators.

[0032] 1. Initial operating conditions and input parameters

[0033] The heat exchange station is set to operate under high-load rated operation conditions during a typical winter heating season. At this time, high-temperature hot water from the primary side of the heat source and low-temperature return water from the secondary side of the user side are simultaneously injected into tank 15 of the mixing tank according to the system's predetermined scheduling instructions for hydraulic decoupling and deep heat mixing. To accurately reflect the thermo-hydraulic characteristics of the equipment under this operating condition, the specific boundary condition parameters of the inlet are extracted in this embodiment as shown in Table 1:

[0034] Table 1. Parameters of the inlet of the hot water mixing tank

[0035] Inlet name Temperature ℃ <![CDATA[Flow rate m 3 / h]]> Mass flow rate kg / s High temperature water inlet (left) 90 2600 720.8 High temperature water inlet (right) 90 3000 831.7 Low temperature water inlet 40 1000 277.2

[0036] 2. Operational Results of Traditional Unturbulent Mixing Tanks

[0037] Under the aforementioned boundary conditions, if a standard cavity mixing tank without any internal turbulence-causing components is used, due to the density difference, the 40°C low-temperature return water flows straight along the bottom, forming a "cold flow short circuit," while the 90°C high-temperature hot water floats on top, forming a "thermal stratification." The actual outlet temperatures (for ease of explanation, the three medium-temperature outlets in all embodiments are divided into the first outlet (left side), the second outlet (middle side), and the third outlet (right side), the same below), and monitoring data are shown in Table 2:

[0038] Table 2. Outlet temperature of ordinary mixing tanks without mixing devices.

[0039] Outlet location Outlet temperature ℃ The first water outlet (left) 58 Second outlet (middle) 71 The third outlet (right) 79

[0040] As shown in Table 2, the maximum temperature difference between different outlets under traditional conditions is as high as 21℃. In order to ensure that the heat users connected to outlet 1 are not in an "overly cold" state, the heating station is often forced to increase the overall heating temperature or increase the circulation pump flow rate, resulting in a large amount of ineffective heat source energy consumption and pump consumption.

[0041] 3. Operational performance of the mixed flow tank in this embodiment

[0042] The equipment is replaced with the mixing tank described in this embodiment, which internally incorporates a combined first and second turbulence component (including a 60° inclined cross turbulence pipe array and a 120° reverse inclined outlet turbulence pipe array and an outlet turbulence pipe, and uses a combination of Φ159 and Φ108 variable diameter components). Specific design parameters are as follows: the first group of pipe arrays 4 consists of two interlaced Φ159 steel pipes 8 and one Φ108 steel pipe 9; the second group of pipe arrays 5 consists of four Φ108 steel pipes 9; the third group of pipe arrays 6 consists of three Φ159 steel pipes 8; and the fourth group of pipe arrays 7 consists of four Φ108 steel pipes 9. All four groups of pipe arrays are inclined in the direction of water flow, with an acute angle α of 60°. The distances between the top and bottom surfaces of the tank and the center of the pipes, as well as the center distances between the upper and lower pipes, are as follows: Figure 1 As shown; where H=450mm, h1=200mm, h2=350mm, the baffle pipe 10 at the water outlet is arranged at an angle against the water flow direction, and the reverse inclination angle θ is 120º. The two pipes of this pipe are Φ108 steel pipes. The two water outlet baffle pipes 11 are respectively arranged in front of the second medium temperature water outlet 3 and the third medium temperature water outlet 3. The radial diameter line of the water outlet baffle pipe 11 passing through the center of the circle is defined to have an angle θ of 120° with the bottom surface of the tank body 15, which is set in the opposite direction. The distance from the intersection of this diameter line and the bottom surface of the tank body 15 to the edge of the medium temperature water outlet 3 is L, and L is 100mm. The water outlet baffle pipe 11 corresponding to the second medium temperature water outlet 3 is Φ159 steel pipe, and the water outlet baffle pipe 11 corresponding to the third medium temperature water outlet 3 is Φ108 steel pipe. With the input parameters completely unchanged, the thermal stratification was completely broken by utilizing the multi-scale eddy currents of the aforementioned internal turbulence tank assembly. The outlet temperature monitoring data are shown in Table 3.

[0043] Table 3 shows the outlet temperature of the mixing tank in this embodiment.

[0044] Outlet location Outlet temperature ℃ The first water outlet (left) 74.6 Second outlet (middle) 75.5 The third outlet (right) 73.4

[0045] 4. Calculation of temperature uniformity index

[0046] To intuitively quantify the beneficial effects of this embodiment, a maximum temperature deviation is introduced. With temperature non-uniformity coefficient As an evaluation indicator, the specific calculation formula is as follows:

[0047] Average outlet temperature:

[0048]

[0049] Temperature non-uniformity coefficient:

[0050]

[0051] (1) Calculation of indexes for conventional ordinary mixing tanks without mixing devices:

[0052] According to the test data in Table 2, the temperatures of the three medium-temperature water outlets are as follows: the temperature of the first water outlet is 58℃, the temperature of the second water outlet is 71℃, and the temperature of the third water outlet is 79℃.

[0053] Calculate the average temperature:

[0054] ℃

[0055] Calculate the temperature non-uniformity coefficient:

[0056]

[0057] (2) Calculation of the parameters of the mixing tank in this embodiment:

[0058] According to the test data in Table 3, after deep mixing by the internal combined turbulence structure, the temperatures of the three outlets are as follows: the temperature of the first outlet is 74.6℃, the temperature of the second outlet is 75.5℃, and the temperature of the third outlet is 73.4℃.

[0059] Calculate the average temperature:

[0060] ℃

[0061] Calculate the temperature non-uniformity coefficient:

[0062]

[0063] Through the detailed quantitative calculations and comparisons above, it can be seen that the structural innovation of this embodiment reduces the maximum temperature deviation at the outlet of the mixing tank from 21℃ to 2.1℃, a reduction of up to 90%; the temperature non-uniformity coefficient, representing the system's dispersion, decreases significantly from 0.303 to 0.028, a reduction of a whole order of magnitude. In actual engineering heating scheduling, the system often uses the "most unfavorable user" (i.e., the branch with the lowest water temperature, such as the first outlet in traditional equipment) as a benchmark for overall heat source temperature compensation. This optimized structure allows the temperature of the first outlet to jump from 58℃ to 74.6℃, eliminating the "system bottleneck effect" caused by "cold flow short circuit". The system no longer needs to forcibly raise the unfavorable branch at 58℃ to a qualified temperature, resulting in ineffective excessive heating of the entire system. Based on the typical operating experience of "eliminating overheat compensation losses" in centralized heating networks, this improvement in temperature uniformity can reduce the overall heat transmission and distribution energy consumption of the heating system by approximately 8% to 12%.

[0064] Example 3, Reference Figure 2 This embodiment of a district heating mixed flow tank based on turbulence structure optimization includes a first turbulence component and a second turbulence component arranged in the tank body. Along the water flow direction, the denser low-temperature return water enters the tank body 15 through the low-temperature water inlet 2, while the less dense high-temperature hot water is injected downward into the tank body 15 through the two high-temperature water inlets 1 at the top.

[0065] The first flow-disrupting component is a flow-disrupting pipe group, and the second flow-disrupting component is a flow-disrupting pipe row 10 or a flow-disrupting pipe 11. The flow-disrupting pipe group includes a first group of pipe rows 4, a second group of pipe rows 5, a third group of pipe rows 6, and a fourth group of pipe rows 7. Each group of pipe rows has multiple flow-disrupting pipes with horizontally parallel and coplanar axes, forming a trapezoidal structure that is narrower at the top and wider at the bottom. The first group of pipe rows 4 is inclined in the direction of water flow, while the second group of pipe rows 5, the third group of pipe rows, and the fourth group of pipe rows 7 are all inclined against the direction of water flow. During the mixing process in which the fluid flows dominant towards the outlet side, it first encounters the first group of pipe rows 4, which is arranged at an inclination angle of α of 60°, and then actively induces the flow. In the upper middle part of tank 15, the trapezoidal structure of the flow-disrupting pipe assembly completely blocks the straight-flowing channel of cold water along the bottom. This flow-disrupting pipe assembly is composed of interlaced Φ159 steel pipes 8 and Φ108 steel pipes 9. The first group of pipes 4 consists of two interlaced Φ159 steel pipes 8 and one Φ108 steel pipe 9. The second group of pipes 5 consists of three Φ108 steel pipes 9 and one Φ159 steel pipe 8, with one Φ108 steel pipe shared with the first group of pipes 4. The third group of pipes 6 consists of two Φ159 steel pipes 8, and the fourth group of pipes 7 consists of five Φ108 steel pipes 9. The larger-diameter Φ159 steel pipes 8 generate a strong fluid obstruction effect and large-scale wake vortices, significantly extending the residence time of the water flow inside the tank. The smaller-diameter Φ108 steel pipes 9 subdivide and cut the local flow field, generating high-frequency micro-vortices. The synergistic combination of large and small pipe diameters promotes intense momentum and heat exchange between hot and cold fluids in the front and middle sections of the tank, effectively breaking the inherent upper and lower thermal stratification boundaries within the tank.

[0066] Before the mixed fluid continues its journey to the right-side outlet region, it encounters two second flow-disrupting components arranged at a reverse inclination angle θ of 120°. These are two outlet flow-disrupting pipes 11, positioned in front of the second and third medium-temperature outlets 3, respectively. The angle θ between a radial diameter line of one of the outlet flow-disrupting pipes 11 passing through its center and the bottom surface of the tank 15 is defined as the reverse inclination angle. This reverse-flowing pipe bundle in this region forces a deflection and secondary cutting disturbance to the outflowing mixed fluid, ultimately homogenizing any remaining local thermal deviations.

[0067] Finally, the thoroughly mixed hot water is smoothly discharged from the three medium-temperature outlets 3 at the bottom, effectively eliminating the temperature difference between the outlets. The pressure gauge 13 and thermometer 14 located at the top of the end of the tank 15 are used to monitor the final pressure and temperature of the heat medium inside the tank 15 in real time to ensure the stable output of the overall hydraulic and thermal conditions of the system.

[0068] Example 4: Based on the scheme of Example 3, this example uses the decoupling link of the primary and secondary networks in a typical intelligent centralized heating system heat exchange station in a frigid region of northern my country. This heat exchange station undertakes the winter heating task for a large number of surrounding buildings (such as mixed residential and commercial buildings). In the complex heat pipe network in actual operation, due to the significant differences in the hydraulic conditions between the primary heat source and the secondary user side, the system has extremely high requirements for the optimization of thermo-hydraulic coupling.

[0069] Before the system upgrade, the station used a conventional hollow mixed-flow tank for hydraulic decoupling. Due to the extremely uneven mixing of fluids inside the tank, severe uneven heating and cooling frequently occurred in the terminal outlet water network. This not only reduced the heating comfort of users but also caused ineffective high-frequency regulation of the secondary network circulating water pump and forced excessive compensation on the heat source side, resulting in significant energy waste. This embodiment will detail the application process of a district heating mixed-flow tank based on turbulence structure optimization provided by the present invention after replacing the original traditional mixed-flow tank, and the verification of its actual performance and thermodynamic indicators.

[0070] 1. Initial operating conditions and input parameters

[0071] The heat exchange station is set to operate under high-load rated operation conditions during a typical winter heating season. At this time, high-temperature hot water from the primary side of the heat source and low-temperature return water from the secondary side of the user side are simultaneously injected into tank 15 of the mixing tank according to the system's predetermined scheduling instructions for hydraulic decoupling and deep heat mixing. To accurately reflect the thermo-hydraulic characteristics of the equipment under this operating condition, the specific boundary condition parameters of the inlet are extracted in this embodiment as shown in Table 1:

[0072] Table 1. Inlet parameters of hot water mixing tank

[0073] Inlet name Temperature ℃ <![CDATA[Flow rate m 3 / h]]> Mass flow rate kg / s High temperature water inlet (left) 90 2600 720.8 High temperature water inlet (right) 90 3000 831.7 Low temperature water inlet 40 1000 277.2

[0074] 2. Operational Results of Traditional Unturbulent Mixing Tanks

[0075] Under the aforementioned boundary conditions, if a standard hollow mixing tank without any internal flow-disrupting components is used, due to the density difference, the 40°C low-temperature return water flows straight along the bottom, forming a "cold flow short circuit," while the 90°C high-temperature hot water floats on top, forming a "thermal stratification." The actual outlet temperature monitoring data is shown in Table 2.

[0076] Table 2. Outlet temperature of ordinary mixing tanks without mixing devices.

[0077] Outlet location Outlet temperature ℃ First outlet 58 Second outlet 71 Third outlet 79

[0078] As shown in Table 2, the maximum temperature difference between different outlets under traditional conditions is as high as 21℃. In order to ensure that the heat user connected to the first outlet is not in an "overly cold" state, the heating station is often forced to increase the overall heating temperature or increase the circulation pump flow, resulting in a large amount of ineffective heat source energy consumption and pump consumption.

[0079] 3. Operational performance of the mixed flow tank in this embodiment

[0080] Replace the equipment with the mixing tank described in this embodiment, which is equipped with a combined first and second turbulence components (including a first group of pipes 4 with a 60° inclination angle, a second group of pipes 5, a third group of pipes 6, and a fourth group of pipes 7 with a 120° opposite inclination angle, and an outlet turbulence pipe, and adopts a combination of Φ159 and Φ108 variable diameters). The specific design parameters are as follows: The first group of pipes 4 consists of two interlaced Φ159 steel pipes 8 and one Φ108 steel pipe 9, with an overall inclination angle of 60º (acute angle α). The second group of pipes 5 consists of three Φ108 steel pipes 9 and one Φ159 steel pipe 8, with one Φ108 steel pipe shared with the first group of pipes 4. The third group of pipes 6 consists of two Φ159 steel pipes 8. The fourth group of pipes 7 consists of five Φ108 steel pipes 9. Except for the first group of pipes, the reverse inclination angle of the other three groups of pipes is 120º. The four groups of pipes form a trapezoidal structure that is narrower at the top and wider at the bottom. The distance L from the intersection of the coplanar centerline of the fourth group of pipes with the bottom surface of the tank 15 to the edge of the first outlet (left side position) is 100mm. The distances between the top and bottom surfaces of the tank and the center of the pipes, as well as the center distances between the upper and lower pipes, are as follows: Figure 2 As shown, H=450mm, h1=200mm, h2=350mm. The baffle pipe array 10 at the water outlet is arranged at an angle against the water flow direction, with a reverse inclination angle θ of 120º. The two pipes in this array are Φ108 steel pipes. Two outlet baffle pipes 11 are respectively arranged in front of the second outlet 3 (middle position) and the third outlet (right position). The radial diameter line of one outlet baffle pipe 11 passing through the center is defined as having an angle θ of 120º with the bottom surface of the tank 15, and is set in the opposite direction. The distance from the intersection of this diameter line and the bottom surface of the tank 15 to the edge of the medium-temperature outlet 3 is L, and L is 100mm. The outlet baffle pipe 11 corresponding to the second outlet is a Φ159 steel pipe, and the outlet baffle pipe 11 corresponding to the third outlet is a Φ108 steel pipe. With the input parameters completely unchanged, the multi-scale vortex of the internal baffle pipe array completely breaks down thermal stratification. The outlet temperature monitoring data are shown in Table 3:

[0081] Table 3 shows the outlet temperature of the mixing tank in this embodiment.

[0082] Outlet location Outlet temperature ℃ First outlet 66.2 Second outlet 73.3 Third outlet 74

[0083] 4. Calculation of temperature uniformity index

[0084] To intuitively quantify the beneficial effects of this solution, a maximum temperature deviation is introduced. With temperature non-uniformity coefficient As an evaluation indicator, the specific calculation formula is as follows:

[0085] Average outlet temperature:

[0086]

[0087] Temperature non-uniformity coefficient:

[0088]

[0089] (1) Calculation of indexes for conventional ordinary mixing tanks without mixing devices:

[0090] According to the test data in Table 2, the temperatures of the three outlets are as follows: the temperature of the first outlet is 58℃, the temperature of the second outlet is 71℃, and the temperature of the third outlet is 79℃.

[0091] Calculate the average temperature:

[0092] ℃

[0093] Calculate the temperature non-uniformity coefficient:

[0094]

[0095] (2) Calculation of the parameters of the mixing tank in this scheme:

[0096] According to the test data in Table 3, after deep mixing by the internal combined turbulence structure, the temperatures of the three outlets are as follows: the temperature of the first outlet is 74.6℃, the temperature of the second outlet is 75.5℃, and the temperature of the third outlet is 73.4℃.

[0097] Calculate the average temperature:

[0098] ℃

[0099] Calculate the temperature non-uniformity coefficient:

[0100]

[0101] Through the detailed quantitative calculations and comparisons above, it can be seen that the structural innovation of this invention reduces the maximum temperature deviation at the outlet of the mixing tank from 21℃ to 7.8℃, a reduction of 63%; the temperature non-uniformity coefficient, representing the system's dispersion, decreases from 0.303 to 0.110. In actual engineering heating scheduling, the system often uses the "most unfavorable user" (i.e., the branch with the lowest water temperature, such as the first outlet in traditional equipment) as a benchmark for overall heat source temperature compensation. The optimized structure of this invention allows the temperature at the first outlet to jump from 58℃ to 66.2℃, alleviating the "system bottleneck effect" caused by "cold flow short circuit".

[0102] Example 5: A district heating mixing tank based on turbulence structure optimization in this example includes a first turbulence component and a second turbulence component arranged in the tank body. Along the water flow direction, the denser low-temperature return water enters the tank body 15 through the 2 low-temperature water inlets 2, while the less dense high-temperature hot water is injected downward into the tank body 15 through the two high-temperature water inlets 1 at the top.

[0103] The first turbulence-inducing component is a vertically arranged first turbulence-inducing plate 20 extending downward from the upper wall of the tank, and the second turbulence-inducing component is a vertically arranged second turbulence-inducing plate 21 or turbulence-inducing pipe 11 extending upward from the lower wall of the tank. The first turbulence-inducing plate 20 is arranged behind the high-temperature water inlet 1 and behind the low-temperature water inlet, respectively, blocking the channel for cold water to flow straight along the bottom and forcing the cold water at the bottom to be induced to the middle of the tank 15. The coordinated combination of the vertically arranged first turbulence-inducing pipes 20 causes intense momentum and heat exchange between the hot and cold fluids in the front and middle section of the tank, effectively breaking the inherent upper and lower thermal stratification boundary inside the tank. Before the mixed fluid continues its journey to the outlet region, it first encounters an upward-extending second baffle 21, followed by a second baffle component positioned at a reverse inclination angle θ of 120°. These are outlet baffle pipes 11, which are respectively arranged in front of the second and third medium-temperature outlets 3. The reverse inclination angle is defined as θ = 120° between a radial diameter line of the outlet baffle pipe 11 passing through the center and the bottom surface of the tank 15. The reverse pipes in this region force a deflection and secondary cutting disturbance to the outflowing mixed fluid, and perform final depth homogenization of any remaining local thermal deviations.

[0104] Example 6: Based on the scheme of Example 5, this example uses the decoupling link of the primary and secondary networks in a typical intelligent centralized heating system heat exchange station in a frigid region of northern my country. This heat exchange station undertakes the winter heating task for a large number of surrounding buildings (such as mixed residential and commercial buildings). In the complex heat pipe network in actual operation, due to the significant differences in the hydraulic conditions between the primary heat source and the secondary user side, the system has extremely high requirements for the optimization of thermo-hydraulic coupling.

[0105] Before the system upgrade, the station used a conventional hollow mixed-flow tank for hydraulic decoupling. Due to the extremely uneven mixing of fluids inside the tank, severe uneven heating and cooling frequently occurred in the terminal outlet water network. This not only reduced the heating comfort of users but also caused ineffective high-frequency regulation of the secondary network circulating water pump and forced excessive compensation on the heat source side, resulting in significant energy waste. This embodiment will detail the application process of a district heating mixed-flow tank based on turbulence structure optimization after replacing the original traditional mixed-flow tank, and the verification of its actual performance and thermodynamic indicators.

[0106] 1. Initial operating conditions and input parameters

[0107] The heat exchange station is set to operate under high-load rated operation during a typical winter heating season. At this time, high-temperature hot water from the primary side of the heat source and low-temperature return water from the secondary side of the user side are simultaneously injected into the main tank of the mixing tank according to the system's predetermined scheduling instructions for hydraulic decoupling and deep heat mixing. To accurately reflect the thermo-hydraulic characteristics of the equipment under this operating condition, the specific boundary condition parameters of the inlet are extracted in this embodiment as shown in Table 1:

[0108] Table 1. Parameters of the inlet of the hot water mixing tank

[0109] Inlet name Temperature ℃ <![CDATA[Flow rate m 3 / h]]> Mass flow rate kg / s High temperature water inlet (left) 90 2600 720.8 High temperature water inlet (right) 90 3000 831.7 Low temperature water inlet 40 1000 277.2

[0110] 2. Operational Results of Traditional Unturbulent Mixing Tanks

[0111] Under the aforementioned boundary conditions, if a standard hollow mixing tank without any internal flow-disrupting components is used, due to the density difference, the 40°C low-temperature return water flows straight along the bottom, forming a "cold flow short circuit," while the 90°C high-temperature hot water floats on top, forming a "thermal stratification." The actual outlet temperature monitoring data is shown in Table 2.

[0112] Table 2. Outlet temperature of a standard mixing tank without a mixing device.

[0113] Outlet location Outlet temperature ℃ First outlet 58 Second outlet 71 Third outlet 79

[0114] As shown in Table 2, the maximum temperature difference between different outlets under traditional conditions is as high as 21℃. In order to ensure that the heat users connected to outlet 1 are not in an "overly cold" state, the heating station is often forced to increase the overall heating temperature or increase the circulation pump flow rate, resulting in a large amount of ineffective heat source energy consumption and pump consumption.

[0115] 3. Operational performance of the mixed flow tank in this embodiment

[0116] Replace the equipment with the mixing tank described in this embodiment, which internally includes a combined first and second baffle plate. Specific design parameters include the heights of the first baffle plate 20 and the second baffle plate 21, and their respective distances from the inlet or outlet, as shown below. Figure 2As shown, h3=725mm, h4=100mm, h5=550mm, L=100mm. The outlet baffle pipe 11 is arranged at an angle against the water flow direction, with a reverse inclination angle θ of 120º. Two outlet baffle pipes 11 are respectively arranged in front of the second outlet 3 (middle position) and the third outlet (right position). The radial diameter line of the outlet baffle pipe 11 passing through the center is defined as having an angle θ of 120º with the bottom surface of the tank body 15, indicating a reverse arrangement. The distance from the intersection of this diameter line and the bottom surface of the tank body 15 to the edge of the medium-temperature outlet 3 is L, and L is 100mm. The outlet baffle pipe 11 corresponding to the second outlet is a Φ159 steel pipe, and the outlet baffle pipe 11 corresponding to the third outlet is a Φ108 steel pipe. With the input parameters completely unchanged, the internal baffle component's multi-scale eddy current completely breaks up thermal stratification. The outlet temperature monitoring data is shown in Table 3.

[0117] Table 3. Temperature of the mixing tank outlet in this embodiment.

[0118] Outlet location Outlet temperature ℃ First outlet 65.5 Second outlet 71.7 Third outlet 70.9

[0119] 4. Calculation of temperature uniformity index

[0120] To intuitively quantify the beneficial effects of this solution, a maximum temperature deviation is introduced. With temperature non-uniformity coefficient As an evaluation indicator, the specific calculation formula is as follows:

[0121] Average outlet temperature:

[0122]

[0123] Temperature non-uniformity coefficient:

[0124]

[0125] (1) Calculation of indexes for conventional ordinary mixing tanks without mixing devices:

[0126] According to the test data in Table 2, the temperatures of the three outlets are as follows: the temperature of the first outlet is 58℃, the temperature of the second outlet is 71℃, and the temperature of the third outlet is 79℃.

[0127] Calculate the average temperature:

[0128] ℃

[0129] Calculate the temperature non-uniformity coefficient:

[0130]

[0131] (2) Calculation of the parameters of the mixing tank in this embodiment:

[0132] According to the test data in Table 3, after deep mixing by the internal combined turbulence structure, the temperatures of the three outlets are as follows: the temperature of the first outlet is 74.6℃, the temperature of the second outlet is 75.5℃, and the temperature of the third outlet is 73.4℃.

[0133] Calculate the average temperature:

[0134] ℃

[0135] Calculate the temperature non-uniformity coefficient:

[0136]

[0137] Through the detailed quantitative calculations and comparisons above, it can be seen that the structural innovation of this invention reduces the maximum temperature deviation at the outlet of the mixing tank from 21 ℃ to 6.4 ℃, a reduction of 70%; the temperature non-uniformity coefficient, representing the system's dispersion, is significantly reduced from 0.303 to 0.089, a decrease of a full order of magnitude. In actual engineering heating scheduling, the system often uses the "most unfavorable user" (i.e., the branch with the lowest water temperature, such as the first outlet in traditional equipment) as a benchmark for overall heat source temperature compensation. The optimized structure of this embodiment allows the temperature of the first outlet to jump from 58 ℃ to 69.4 ℃, significantly reducing the "system bottleneck effect" caused by "cold flow short circuit".

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions created by the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions created by the present invention without departing from the essence and scope of the technical solutions created by the present invention.

Claims

1. A district heating mixing tank based on turbulence structure optimization, characterized in that: It includes a first turbulence-disrupting component and a second turbulence-disrupting component arranged inside the tank, along the direction of water flow; The first turbulence-inducing component is located behind the low-temperature water inlet and the high-temperature water inlet, and is used to block the channel for cold water to flow straight along the bottom and actively induce it to the middle or upper part of the tank. The second turbulence-inducing component is located in front of the medium-temperature water outlet and is used to forcibly turn and cut the mixed fluid that is about to flow out, so as to achieve the homogenization of the thermal deviation of the mixed fluid.

2. The district heating mixing tank based on turbulence structure optimization according to claim 1, characterized in that: The first turbulence-disrupting component is an inclined turbulence-disrupting pipe assembly.

3. The district heating mixing tank based on turbulence structure optimization according to claim 2, characterized in that: The turbulence-disrupting pipe group comprises four sets of pipe rows, each set of pipe rows having multiple turbulence-disrupting pipes with horizontally parallel and coplanar axes.

4. A district heating mixing tank based on turbulence structure optimization according to claim 3, characterized in that: The four sets of pipes are arranged at an angle in the direction of water flow, and all angles are the same, all being 60º.

5. A district heating mixing tank based on turbulence structure optimization according to claim 3, characterized in that: The first group of pipes is tilted in a different direction than the remaining three groups of pipes. The remaining three groups of pipes are tilted against the direction of water flow, and the angles are all the same. The first group of pipes is tilted in the direction of water flow.

6. A district heating mixing tank based on turbulence structure optimization according to claim 5, characterized in that: The first pipe bank is installed immediately after the low-temperature water inlet and the high-temperature water inlet, with an inclination angle of 60º; the remaining three pipe banks are all inclination angles of 120º.

7. A district heating mixing tank based on turbulence structure optimization according to claim 4 or 5, characterized in that: The four sets of pipes are composed of Φ159 steel pipes and Φ108 steel pipes arranged in an interlaced pattern.

8. A district heating mixing tank based on turbulence structure optimization according to claim 2, characterized in that: The second flow-dispersing component is an outlet flow-dispersing pipe and an inclined outlet flow-dispersing pipe array.

9. A district heating mixing tank based on turbulence structure optimization according to claim 1, characterized in that: The first turbulence-disrupting component is a vertically arranged turbulence-disrupting plate extending downward from the upper wall of the tank.

10. A district heating mixing tank based on turbulence structure optimization according to claim 9, characterized in that: The second turbulence component is a vertically arranged turbulence plate or water outlet turbulence pipe extending upward from the lower wall of the tank.

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