A heat dissipation method and system for the inner circle of concrete-filled steel tube

Abstract

The present invention belongs to the technical field of heat dissipation design for concrete-filled steel tubes, and particularly relates to a method and a system for dissipating heat from the inner circle of a concrete-filled steel tube. The method for dissipating heat from the inner circle of the concrete-filled steel tube according to the present invention comprises the following steps: after a spiral heat dissipation coil with a specific heat dissipation radius is pre-arranged in an outer steel tube, the concrete is then poured; the axis of the spiral cylindrical structure formed by the spiral heat dissipation coil is coaxial with the outer steel tube. The method for dissipating heat from the inner circle of the concrete-filled steel tube according to the present invention can effectively ensure the balanced heat dissipation effect of the temperature inside the concrete-filled steel tube, can greatly reduce the maximum temperature difference across the cross section, so as to reduce and even avoid the temperature cracking phenomenon occurring after the formation of large-diameter concrete-filled steel tube members.

Description

Technical Field

[0001] The invention belongs to the technical field of heat dissipation design of steel tube concrete, and particularly relates to a heat dissipation method and a heat dissipation system for an inner ring of a steel tube concrete. Background Art

[0002] With the rapid development of infrastructure, large-volume steel tube concrete construction is increasing, such as cable towers, piers and foundations of cable-stayed bridges, box foundations or raft foundations of high-rise buildings, transmission towers, etc.; and as the diameter of steel tube concrete gradually increases, large-diameter steel tube concrete components with a diameter of more than one meter are becoming more and more common, and the following problems are often common: on the one hand, with the increase in component size, the volume of concrete inside the steel tube increases, and the influence of hydration heat on the concrete inside the steel tube gradually becomes prominent. Due to the good thermal conductivity of the steel tube, the outer circle concrete dissipates heat quickly while the inner circle concrete dissipates heat slowly, which easily causes uneven temperature distribution; under the condition of internal and external constraints, large temperature stress will be generated inside the concrete and cracks are likely to occur. At the same time, since the temperature will increase with the expansion of volume, it is also very easy to cause the steel tube concrete to be hollowed out, which will eventually bury serious quality risks for the engineering structure. On the other hand, although steel tube concrete is more solid than traditional structures, it is also necessary to monitor its structural status during use to grasp the safety of the structure in a timely manner. However, due to the existence of steel pipes, the traditional external monitoring method is not very applicable. Take the steel tube concrete transmission tower as an example. If it is hit by a rare earthquake after it is built, the power department is more inclined to demolish and rebuild it due to the difficulty in nondestructive testing. In addition to the huge expenses incurred by such reconstruction projects themselves, the collateral losses caused by the interruption of the power network are even greater and need to be solved urgently. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for heat dissipation of the inner ring of steel tube concrete, which can effectively ensure the balanced heat dissipation effect of the temperature inside the steel tube concrete, and can greatly reduce the maximum temperature difference of the cross section, so as to reduce or even avoid the temperature cracking phenomenon that occurs after the large diameter steel tube concrete component is formed.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A heat dissipation method for an inner ring of a steel tube concrete, characterized by comprising the following steps:

[0006] The concrete is poured after the spiral heat dissipation coil is pre-placed in the outer steel pipe; the axis of the spiral cylindrical structure formed by the spiral heat dissipation coil is coaxial with the outer steel pipe;

[0007] The heat dissipation radius R of the spiral tube structure 散 Obtained by the following formula:

[0008]

[0009] Wherein:

[0010] R 散 is the heat dissipation radius of the spiral cylindrical structure;

[0011] D is the diameter of the concrete-filled steel tube member;

[0012] t s is the thickness of the outer steel tube;

[0013] k is the intermediate coefficient;

[0014] ξ is the equivalent heat conduction coefficient;

[0015] λ is the thermal conductivity of the concrete;

[0016] c w is the specific heat capacity of the cooling water in the spiral cooling coil;

[0017] ρ w is the density of the cooling water in the spiral cooling coil;

[0018] q w is the flow rate of the cooling water in the spiral cooling coil.

[0019] Preferably, for the heat dissipation system, which adopts the above-mentioned heat dissipation method for the inner ring of the concrete-filled steel tube, it is characterized in that: a bottom support block is installed in the outer steel tube, a central rod is fixed at the bottom support block, the central rod is coaxially installed in the cavity of the spiral cylindrical structure formed by the spiral cooling coil, and the central rod and the tube body of the spiral cooling coil are connected to each other through inclined support rods.

[0020] Preferably, the spiral cooling coil is of a double-spiral structure. Two ports at the bottom of the spiral cooling coil respectively form a water inlet end and a water outlet end, and the top ports of the spiral cooling coil are communicated with each other to form a communicating water path.

[0021] Preferably, through holes are arranged in a penetrating manner on the bottom support block; one end of the through hole is in plug-in fit with the water inlet end and the water outlet end of the spiral cooling coil respectively, and the other end of the through hole is connected to a water source; a central positioning hole for inserting the central rod is also recessed at the bottom support block.

[0022] Preferably, the central positioning hole also constitutes a signal line access hole; the signal line extends through the cavity of the central positioning hole to the rod cavity of the sleeve-shaped central rod, and is led out through an avoidance groove opened on the outer wall of the central rod, and finally connected to a sensor located on the inclined support rod.

[0023] Preferably, the sensor is fixed on the inclined support rod by a clip; the clip includes a "C"-shaped positioning section and two clamping arms for clamping the inclined support rod, and the clamping arms are fastened by a tension bolt; the cylindrical cavity of the positioning section forms an installation cavity for the sensor to be inserted and fixed.

[0024] Preferably, along the extending direction of the tube body of the spiral cooling coil, the spiral cooling coil is formed by coaxially inserting two or more tube segments with each other.

[0025] Preferably, a dovetail-shaped convex rib is convexly provided on the inner wall of the outer steel pipe, and the length direction of the convex rib is parallel to the axial direction of the outer steel pipe; the bottom support block is rectangular in shape and concave with dovetail positioning grooves at both ends, and the dovetail positioning grooves are clamped into the convex ribs to position the bottom support block.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1), Through the above scheme, the present invention adopts the most mature and stable cooling coil technology to form a spiral cooling coil, thereby improving the cooling efficiency. More importantly, by proposing the above calculation formula for the cooling radius R 散 of the spiral cooling coil, it is convenient to adjust the design size according to actual needs subsequently, and finally effectively ensures the optimal balanced cooling effect of the temperature inside the concrete-filled steel tube.

[0028] Actual measurement proves that the present invention can reduce the maximum cross-sectional temperature difference to the greatest extent, and can reduce and even avoid the temperature cracking phenomenon that occurs after the formation of large-diameter concrete-filled steel tube members.

[0029] 2), On the basis of the above scheme, the present invention further provides a cooling system based on the above calculation formula, including a bottom support block and a central rod, and uses inclined support rods to ensure the three-dimensional support effect on the spiral cooling coil for subsequent pouring. At the same time, the existence of the inclined support rods also facilitates fixing the spiral cooling coil and can carry sensors such as temperature sensors or crack sensors according to actual needs, and it is convenient to arrange signal lines along the inclined support rods until they are connected to the central rod, so as to achieve the data transmission of the signal lines while realizing the purpose of erecting the signal lines. At the same time, the existence of the inclined support rods and the central rod can also effectively avoid the physical damage problem of the signal lines caused by the throwing phenomenon during concrete pouring, killing multiple birds with one stone.

[0030] 3), As described above, the inclined support rods have both the function of supporting the spiral cooling coil and the effect of fixing the sensors. When fixing the sensors, by using a unique clip, the stable and reliable on-line positioning function of the sensors can be ensured, and their actual positions can be adjusted at any time according to needs before pouring, which is very flexible and convenient to use.

[0031] 4) During actual design, the spiral heat dissipation coil can be replaced with a relatively rigid hose instead of a steel pipe, which is convenient for laying and subsequent entry of workers. Of course, it can also adopt a structure of sleeving in sections to facilitate the extension of the pipe body according to requirements. Both the water inlet end and the water outlet end of the spiral heat dissipation coil are located at the bottom, which is conducive to the introduction and export of water sources, ensuring water flow supply and guaranteeing the established heat dissipation effect.

[0032] 5) A chute clamping structure is adopted between the bottom support block and the outer sleeve steel pipe to ensure the modular assembly effect, and is conducive to improving the on-site assembly efficiency while ensuring its assembly stability and reliability. Description of the Drawings

[0033] Figure 1 and Figure 2 is a schematic perspective view of one embodiment of the present invention;

[0034] Figure 3 is an installation state diagram of the spiral heat dissipation sleeve relative to the outer sleeve steel pipe;

[0035] Figure 4 is Figure 1 a data comparison diagram of the measured curve and the calculated curve of the temperature difference at three points in the cross-section during the hydration reaction after pouring of the structure shown;

[0036] Figure 5 is a front view of the assembly state of the bottom support block relative to the outer sleeve steel pipe;

[0037] Figure 6 is a schematic perspective view of the bottom support block;

[0038] Figure 7 and Figure 8 is a schematic perspective view of the cooperation state of the spiral heat dissipation coil and the center rod;

[0039] Figure 9 is Figure 7 a top view of the structure shown;

[0040] Figure 10 is a schematic perspective view of the clip.

[0041] The actual corresponding relationship between the reference numerals and the component names of the present invention is as follows:

[0042] 10 - Outer sleeve steel pipe; 11 - Convex rib;

[0043] 20 - Spiral heat dissipation coil;

[0044] 30 - Bottom support block; 31 - Water passing hole; 32 - Central positioning hole; 33 - Dovetail positioning groove;

[0045] 40 - Center rod; 41 - Avoidance groove;

[0046] 50 - Clamp; 51 - Positioning section; 52 - Clamping arm; 53 - Tensioning bolt;

[0047] 60 - Inclined support rod. Detailed implementation manner

[0048] For easy understanding, in combination with Figures 1 - 10 , the specific structure and working mode of the present invention are further described as follows:

[0049] Assume that the cross - section of the spiral cooling coil 20 on the cross - section of the outer steel pipe 10 is approximately a circular cross - section, as Figure 3 shown. According to the data, after the concrete - filled steel tube with a diameter of more than 1000 mm is poured, the temperature difference between the core concrete and the edge concrete can reach more than 25 degrees Celsius. At the same time, the heat dissipation effect of the spiral cooling coil 20 mainly depends on the thermal conductivity of the concrete, the cooling water flow rate and the specific heat capacity, and has nothing to do with parameters such as the thermal conductivity of the steel pipe. Based on this, the present invention proposes a heat dissipation radius calculation formula for the spiral cooling coil 20 arranged inside the large - diameter concrete - filled steel tube, aiming to optimize the balanced heat dissipation effect of the temperature inside the concrete - filled steel tube while ensuring simple calculation. The actual measurement proves that the present invention can reduce the maximum cross - section temperature difference to the greatest extent and can reduce and even avoid the temperature cracking phenomenon that occurs after the large - diameter concrete - filled steel tube member is formed.

[0050] The heat dissipation formula for the inner circle of the concrete - filled steel tube proposed by the present invention, that is, Figure 3 the heat dissipation radius R of the spiral cylindrical structure shown 散 can be obtained by the following formula:

[0051]

[0052] Where:

[0053] R 散 is the heat dissipation radius of the spiral cylindrical structure;

[0054] D is the diameter of the concrete - filled steel tube member;

[0055] t s is the thickness of the outer steel pipe 10;

[0056] k is the intermediate coefficient;

[0057] ξ is the equivalent temperature - conduction coefficient;

[0058] λ is the thermal conductivity of the concrete;

[0059] c w is the specific heat capacity of the cooling water in the spiral cooling coil 20;

[0060] ρ wis the density of the cooling water in the spiral cooling coil 20;

[0061] q w is the flow rate of the cooling water in the spiral cooling coil 20.

[0062] Based on the above formula, the present invention further proposes one of the embodiment structures as shown in Figures 1 - 2 and Figures 5 - 10 shown. Among them:

[0063] In design, the material of the spiral cooling coil 20 can be steel or hard plastic pipe, etc., as long as it can achieve the water conduction function; during installation, the axis of the spiral cylindrical structure formed by the spiral cooling coil 20 and the outer sleeve steel pipe 10 are coaxial with each other.

[0064] The spiral cooling coil 20 can adopt a segmented combined structure, that is, it is formed by splicing several pipe segments as shown in Figures 7 - 8 shown. In addition, the spiral cooling coil 20 can be designed as a double spiral structure, and of course other multi-spiral structures with other numbers can be used; during use, the bottom end of the spiral cooling coil 20 is provided with an inlet end and an outlet end, and the top end of the spiral cooling coil 20 is connected to each other through corresponding connecting pipes to ensure the water cooling effect.

[0065] To ensure the installation effect of the spiral cooling coil 20, on the one hand, as shown in Figures 1 - 3 shown, a dovetail-shaped convex rib 11 is provided on the inner wall of the outer sleeve steel pipe 10, so as to cooperate with the dovetail positioning groove 33 at the end of the square block-shaped bottom support block 30, so as to achieve the position locking effect of the bottom support block 30. On the other hand, a central positioning hole 32 is provided on the bottom support block 30, so as to insert the central rod 40, and rely on the inclined support rod 60 extending outward from the central rod 40, so as to achieve the three-dimensional support function of the spiral cooling coil 20 as shown in Figures 7 - 9 shown.

[0066] During the installation process of the bottom support block 30, corresponding central positioning holes 32 and water passing holes 31 are pre-set on the bottom support block 30, aiming to specifically supply the bottom of the central rod 40 and the spiral cooling coil 20 for insertion, so as to achieve many functions of positioning and water passing or wire passing. The water passing function is obvious. The water at the water source enters the spiral cooling coil 20 through one of the water passing holes 31, and then returns to the other water passing hole 31 and then flows back to the water source or external water receiving equipment. The wire passing function is used to provide information flow for the sensor as shown in Figures 7 - 10 shown. More specifically, the central positioning hole 32 also constitutes a signal wire access hole. When threading, the signal wire extends through the hole cavity of the central positioning hole 32 to the rod cavity of the sleeve-shaped central rod 40, and is led out through the avoidance groove 41 opened on the outer wall of the central rod 40 as shown in Figure 7 shown, and finally connected to the sensor located on the inclined support rod 60.

[0067] As for the sensor itself, a crack sensor or the like can be used, and it can be specifically used according to the actual situation as appropriate. The sensor is fixed on the inclined support rod 60 through a clamp 50.

[0068] The clamp 50 includes a "C"-shaped positioning section 51 and two clamping arms 52 for clamping the inclined support rod 60. As shown in the reference Figure 10 figure, the clamping arms 52 are fastened by a tension bolt 53. During actual operation, such as a temperature sensor, etc., it can adjust the cooling water temperature more precisely according to the temperature change of the core concrete of the concrete-filled steel tube member to reduce temperature cracks. The crack sensor can, while detecting the quality of the member completion, quickly evaluate the damage result after the building reaches its service life or experiences natural disasters.

[0069] During the construction process, it is necessary to first assemble the bottom support block 30 and the joint pipelines of the corresponding water circuit and signal circuit. After the spiral cooling coil 20 is laid, along the internal dovetail-shaped convex rib 11, the assembled bottom support block 30 is placed inside the outer steel pipe 10, and then the signal line and water pipe are connected, and then concrete is poured. All joint pipelines can adopt a modular unit design to facilitate subsequent adjustment of the design size and specifications according to actual needs.

[0070] Embodiment:

[0071] I. Calculation process:

[0072] When the present invention is actually measured, the parameters of the concrete-filled steel tube member are:

[0073] Diameter D = 1500 mm, steel pipe thickness t s = 30 mm, and the thermal conductivity of the concrete is 8.928 KJ / (m·h·°C).

[0074] The spiral cooling coil 20 is selected with a conventional diameter, that is, 15 mm.

[0075] Generally, the specific heat capacity of the cooling water c w = 4.187 KJ / (kg·°C); density ρ w = 1000 kg / m 3 ; flow rate q w = 100 m 3 / h.

[0076] By substituting the above parameters into the calculation formula of the heat dissipation radius R 散 of the spiral cylindrical structure, it can be calculated that R 散 = 0.366 m.

[0077] II. Verification process:

[0078] Modeling was carried out using the finite element analysis software Midas for structural design. In addition to setting three main data collection points, namely the center point a, the 1 / 2 radius point b, and the point c near the outer side of the concrete, the points where the cross-section of the spiral heat dissipation coil 20 described in the present invention is located were also added, and its heat dissipation radius R 散 Calculated according to the proposed formula is 0.366 m, and the specific position is as shown in Figure 3 shown.

[0079] During the test, a room temperature of 20 °C was used as the external boundary condition of the model, and based on the curves of the temperatures at points a, b, and c changing with time, the calculated results are as shown in Figure 4 shown. Figure 4 It shows the temperature change conditions of several measuring points in the test, where the abscissa represents time and the ordinate represents the temperature value.

[0080] From Figure 4 the solid line part in it can be seen that: in the initial stage of concrete solidification, the hydration heat is released and the temperature rises rapidly. The core measuring point a reaches the highest value of 74 °C 27 h after pouring, and other measuring points also reach the maximum value almost simultaneously; after that, the temperatures of each measuring point gradually decrease smoothly.

[0081] Figure 4 The dotted line part in it represents the data obtained through Midas analysis. It can be found by observation that: the overall trend of its temperature change is basically consistent with the test data, and the temperatures of each measuring point reach the peak within 25 - 27 h after pouring.

[0082] Thus, it can be known that: compared with the test data, after using the spiral heat dissipation coil 20 with a fixed heat dissipation radius designed by the present invention, the highest temperature at point a drops from 74 °C to 59 °C, the highest temperature at point b drops from 67 °C to 49 °C, and the highest temperature at point c drops from 54 °C to 45 °C. The maximum temperature drop at point b reaches 18 °C, which is higher than 15 °C at point a and 9 °C at point c. This is because the position of the spiral heat dissipation coil 20 in the component is closest to point b. At the same time, since point c is adjacent to the outer steel pipe 10, the heat dissipation effect is mainly related to the ambient temperature, so the temperature drop amplitude is relatively low.

[0083] Subsequently, the value of the heat dissipation radius R 散 was increased or decreased at intervals of 0.1 m, and multiple calculation simulations were carried out. It was found that the heat dissipation effect is the most ideal when the heat dissipation radius is controlled within the range of ±0.2 m. If the heat dissipation radius is too large, the heat release of the hydration reaction in the inner circle of the core concrete cannot be effectively controlled, and if the heat dissipation radius is too small, the overall temperature of the core concrete cannot be effectively reduced. That is, the heat dissipation radius value calculated by the present invention is always the optimal value.

[0084] Through the verification of the above embodiments, it can be known that: for the concrete-filled steel tube members designed by the present invention, in the hydration reaction with intense heat release after pouring, the maximum cross-sectional temperature difference is reduced from 27°C to 19°C; that is, the present invention can minimize the maximum cross-sectional temperature difference, and can indeed reduce or even avoid the temperature crack phenomenon generated after the formation of large-diameter concrete-filled steel tube members, with remarkable results.

[0085] Certainly, for those skilled in the art, the present invention is not limited to the details of the above exemplary embodiments, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0086] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0087] The technologies, shapes, and structures not detailed in the present invention are all well-known technologies.

Claims

1. A heat dissipation method for the inner ring of concrete-filled steel tube, characterized in that It includes the following steps: After a spiral cooling coil (20) is pre - placed in an outer steel pipe (10), concrete is poured; the axis of the spiral cylindrical structure formed by the spiral cooling coil (20) is coaxial with the outer steel pipe (10). The heat dissipation radius R of the spiral tubular structure 散 is obtained by the following formula: Wherein: R 散 is the heat dissipation radius of the spiral tubular structure; D is the diameter of the concrete - filled steel tube member; t s is the thickness of the outer steel pipe (10); k is an intermediate coefficient; ξ is the equivalent thermal diffusivity; λ is the thermal conductivity of concrete; c w is the specific heat capacity of the cooling water in the spiral cooling coil (20); ρ w is the density of the cooling water in the spiral cooling coil (20); q w is the flow rate of the cooling water in the spiral cooling coil (20).

2. Heat dissipation system, which adopts a heat dissipation method for the inner circle of concrete-filled steel tube as described in claim 1, characterized in that: A bottom support block (30) is installed in the outer steel pipe (10), a central rod (40) is fixed at the bottom support block (30), the central rod (40) is coaxially installed in the cavity of the spiral cylindrical structure formed by the spiral cooling coil (20), and the central rod (40) and the pipe body of the spiral cooling coil (20) are connected to each other by an inclined support rod (60).

3. The heat dissipation system according to claim 2, wherein: The spiral cooling coil (20) is of a double - spiral structure. Two ports at the bottom of the spiral cooling coil (20) respectively form a water inlet end and a water outlet end, and the top ports of the spiral cooling coil (20) are communicated with each other to form a communicating waterway.

4. The heat dissipation system according to claim 3, characterized in that: Water - passing holes (31) are arranged in a penetrating manner on the bottom support block (30); one end of the water - passing hole (31) is in plug - in fit with the water inlet end and the water outlet end of the spiral cooling coil (20) respectively, and the other end of the water - passing hole (31) is connected to a water source; a central positioning hole (32) for inserting the central rod (40) is also recessed at the bottom support block (30).

5. The heat dissipation system according to claim 4, wherein: The central positioning hole (32) also constitutes a signal line access hole; the signal line extends through the cavity of the central positioning hole (32) to the rod cavity of the sleeve - shaped central rod (40), and is led out through an avoidance groove (41) opened on the outer wall of the central rod (40), and finally connected to a sensor located on the inclined support rod (60).

6. The heat dissipation system according to claim 5, wherein: The sensor is fixed on the inclined support rod (60) by a clamp (50); the clamp (50) includes a "C" - shaped positioning section (51) and two clamping arms (52) for clamping the inclined support rod (60), and the clamping arms (52) are tightened by a tension bolt (53); the cavity of the positioning section (51) constitutes an installation cavity for inserting and fixing the sensor.

7. The heat dissipation system according to claim 2 or 3 or 4 or 5 or 6, characterized in that: Along the extending direction of the pipe body of the spiral cooling coil (20), the spiral cooling coil (20) is formed by coaxially plug - connecting two or more pipe segments with each other.

8. The heat dissipation system according to claim 2 or 3 or 4 or 5 or 6, characterized in that: A dovetail - shaped convex rib (11) is convexly provided on the inner wall of the outer steel pipe (10), and the length direction of the convex rib (11) is parallel to the axial direction of the outer steel pipe (10); the outer shape of the bottom support block (30) is rectangular, and dovetail positioning grooves (33) are recessed at both ends, and the dovetail positioning grooves (33) are clamped into the convex rib (11) to position the bottom support block (30).

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