Structure and method for reducing pressure drop in u-tube cooling channels

Abstract

The application discloses a method for reducing pressure drop of a U-shaped tube in a cooling channel, characterized by fitting in a coordinate system, wherein a coordinate origin is a center point of an original U-shaped tube bending, the U-shaped tube is composed of an inner curve and an outer curve, the outer curve and the inner curve of the U-shaped tube to be optimized are divided into four curves by a y-axis, a straight line with a specific slope is used as a starting line, a three-dimensional curved surface with a flat surface with a specific slope is obtained by sweeping a curve composed of the intersection of the four curves as a guide line, the three-dimensional curved surface is an outer curved surface and an inner curved surface, and the outer curved surface and the inner curved surface are combined into an optimized U-shaped tube. The structure and the method for reducing pressure drop of the U-shaped tube in the cooling channel can reduce pressure drop of the U-shaped tube by optimizing geometric curves of the U-shaped tube, effectively reduce pressure loss and energy loss of the U-shaped tube, and improve heat transfer performance and flow control precision of the U-shaped tube.

Description

Technical Field

[0001] This invention relates to the field of U-tube technology, specifically to a structure and method for reducing the pressure drop of a U-tube in a cooling channel. Background Technology

[0002] In the current field of fluid mechanics and heat transfer, cooling channels play a crucial role in many important industrial applications, such as heat dissipation for aircraft engines, heat exchangers, and electronic equipment.

[0003] In these applications, the U-shaped bend in a continuous channel plays a key role as a common flow control device in cooling channels. It can effectively guide the cooling fluid from one direction to another, thereby achieving the cooling effect.

[0004] Due to their special geometry, they have areas of strong pressure and energy loss. When the cooling fluid passes through the U-shaped bend, strong rotation and eddies occur, which reduces the fluid flow velocity, resulting in pressure loss and resistance.

[0005] In addition, the geometry and dimensions of the U-bend also affect its flow performance, such as parameters like the bending radius and bending angle. If these parameters are not designed properly, they will further increase pressure loss and resistance, reducing the cooling efficiency of the entire system. This is especially noticeable when the radius ratio (average bend radius / pipe hydraulic diameter) is small. In this case, the bend area accounts for up to 25% of the pressure loss in the entire multi-channel cooling system.

[0006] For applications such as heat transfer and flow control, these pressure and energy losses will seriously affect their performance and efficiency, and will have a significant impact on the flow rate, pressure drop and heat transfer performance of the cooling channel.

[0007] Current research on U-shaped bends mainly focuses on how to optimize their flow performance, reduce pressure loss and resistance, and improve cooling efficiency.

[0008] Currently, some researchers are using complex flow control structures and devices to reduce these pressure and energy losses. However, these methods often require more complex processing and manufacturing processes, increasing production costs and manufacturing difficulties, thus limiting their widespread application in industrial settings. Research methods include numerical simulation, experimental measurement, and structural optimization. These methods can help engineers better understand the flow characteristics inside U-bends and provide a basis for improved design. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a structure and method for reducing the pressure drop of a U-shaped tube in a cooling channel, with the aim of solving the aforementioned problems.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A structure for reducing the pressure drop of a U-shaped tube in a cooling channel includes an optimized U-shaped tube, the optimized U-shaped tube being composed of an outer curved surface and an inner curved surface;

[0012] The outer surface contains two outer curves, and the inner surface contains two inner curves.

[0013] Preferably, the two ends of the U-shaped pipe are respectively connected to an upstream straight pipe section and a downstream straight pipe section.

[0014] A method for reducing the pressure drop of a U-shaped tube in a cooling channel is characterized by fitting a coordinate system, where the origin of the coordinate system is the center point of the bend in the original U-shaped tube, the inner curve and the outer curve form the U-shaped tube in the coordinate system, and the outer curve and the inner curve of the U-shaped tube to be optimized are divided into four curves by the y-axis, namely the outer curve on the left side of the y-axis, the outer curve on the right side of the y-axis, the inner curve on the left side of the y-axis, and the inner curve on the right side of the y-axis.

[0015] Each curve is defined by a polynomial with several parameters;

[0016] The outer curved surface of the U-shaped pipe is obtained by sweeping the curve formed by splicing two outer curves to the end line of the outer curved surface.

[0017] The inner curved surface of the U-shaped pipe is obtained by sweeping the curve formed by splicing two inner curves to the end line of the inner curved surface.

[0018] The outer curved surface and the inner curved surface are combined to form a three-dimensional optimized U-shaped tube, and the optimized U-shaped tube in the cooling channel is obtained based on this optimized U-shaped tube.

[0019] Preferably, the fitting function for the outer curve to the left of the y-axis is:

[0020] y∈[-13.925, 9.616], z=0;

[0021] Where: p1 = -11.59744363; p2 = -0.01409116; p3 = 1.32042011; p4 = -0.19860287; p5 = 6.78044764E-8; p6 = -1.82700995.

[0022] Preferably, the fitting function for the outer curve to the right of the y-axis is:

[0023] y∈[-13.925, 9.616], z=0;

[0024] Wherein: p1=11.75807878; p2=40.46398810; p3=479.99198908; p4=-7.52840350; p5=-86.31530268; p6=0.40277937; p7=3.65362208; p8=-0.00722865; p9=0.01186214; p10=0.00015071.

[0025] Preferably, the fitting function for the inner curve to the left of the y-axis is:

[0026] x = p1 + p2y + p3y 2 +p4y 3 +p5e y , y∈[-14.359, 0.672], z=0;

[0027] Where: p1 = -3.13903571; p2 = 0.31272311; p3 = 0.05808469; p4 = 0.00215792; p5 = 1.43523125.

[0028] Preferably, the fitting function for the inner curve to the right of the y-axis is:

[0029] x = p1 + p2y + p3y 2 +p4y 3 +p5y 4 +p6y 5 +p7y 6 +p8y 7 +p9y 8 y∈

[0030] [-14.359, 0.672], z = 0;

[0031] Where: p1 = 1.47560970; p2 = -1.65134560; p3 = -0.82440002; p4 = -0.24321825; p5 = -0.04474540; p6 = -0.00509385; p7 = -0.00034745; p8 = -1.29485907E-5; p9 = -2.01839406E-7.

[0032] Beneficial effects

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention provides a structure and method for reducing pressure drop in a U-shaped tube in a cooling channel. By optimizing the geometric curve of the U-shaped tube, the pressure drop is reduced. Especially for cases with a small radius ratio, the flow of fluid in the U-shaped tube can be better controlled, and the generation of vortices can be effectively reduced, thereby reducing its resistance loss and pressure drop. This effectively reduces the pressure loss and energy loss of the U-shaped tube, and improves its heat transfer performance and flow control accuracy. Attached Figure Description

[0035] Figure 1 This is a two-dimensional planar schematic diagram of a U-shaped tube under standard geometric conditions;

[0036] Figure 2 A two-dimensional schematic diagram of an optimized design method for reducing the pressure drop of U-shaped bends in cooling channels;

[0037] Figure 3 This is a design method and a three-dimensional structural schematic diagram of a U-shaped bend in a cooling channel to reduce pressure drop, as well as the coordinate system.

[0038] Figure 4 The normalized turbulent kinetic energy contour map obtained through numerical simulation at Z / Dh = 0.5. Figure 4 (a) is a U-shaped tube with standard geometry. Figure 4 (b) shows the optimized U-shaped tube;

[0039] Figure 5 The normalized average velocity field obtained through numerical simulation at Z / Dh = 0.5. Figure 5 (a) is the cloud diagram of a U-shaped tube under standard geometric conditions. Figure 5 (b) is the optimized U-shaped tube cloud map;

[0040] Figure 6 A comparison of standard static pressure drops before and after structural optimization to reduce pressure drop in U-shaped bends in cooling channels;

[0041] In the figure, 11 is an optimized U-shaped tube, 1 and 2 are both external curves, and 3 and 4 are both internal curves. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The U-shaped bend of this invention reduces the pressure drop in a pipeline system by changing the shape of the inner and outer curves of the bend, without altering the velocity, temperature, or other physical properties of the fluid inside the pipe.

[0044] Since there are no changes to external fluid parameters or the material of the bend, the effect of this invention on the pressure drop of the U-shaped bend cooling channel is limited. It is a method that has a certain effect but is not the most cost-effective. Therefore, it is possible to decide whether to use it independently, use multiple sections in parallel, or combine it with existing technologies, depending on the pipe section. For example, in complex piping systems with multiple loops, the method can be combined by changing the pipe material and adding guide vanes. In simpler pipes with large pressure drop, the U-shaped bend can be used alone.

[0045] In this invention, without considering the pipe wall thickness, the side of the U-shaped bend with a larger radius of curvature facing outward is called the outer curved surface of the pipe, and the side with a smaller radius of curvature is called the inner curved surface of the pipe. In the following text, they are simply referred to as the outer curved surface or the inner curved surface.

[0046] The U-shaped tube is the end part of the cooling pipe. It guides the airflow from one straight pipe section to the adjacent straight pipe section and further turns the airflow. Before optimization, the bend consists of two semicircles with different radii of curvature and a straight pipe extending below them.

[0047] Based on the direction of airflow, straight pipe sections in a pipeline system can be divided into upstream straight pipe sections of the U-shaped pipe in the direction of airflow inflow and downstream straight pipe sections of the U-shaped pipe in the direction of airflow outflow. For pipeline systems with two or more U-shaped pipes, a straight pipe section can be referred to as the downstream straight pipe section of the preceding U-shaped pipe or the upstream straight pipe section of the following U-shaped pipe. In this invention, only one bend is selected for optimization study; therefore, it is divided into only one upstream straight pipe section and one downstream straight pipe section.

[0048] It should be noted that the curves that make up the U-shaped tube have the same curve function form in the radial direction. Therefore, all the curved surfaces of this device can be regarded as curved surfaces swept with one curve (or straight line) as the starting line and another curve as the guide line.

[0049] In this invention, the outer and inner curved surfaces of the U-shaped tube are three-dimensional curved surfaces formed by sweeping a straight line with a specific slope as the starting line and a curve formed by the intersection of four curves as the guide line, resulting in a flat surface with a specific slope. Sweeping is a common term in surface modeling, used to create large-area curved surfaces. This can be done using SpaceClaim software, which can generate both curved surfaces and solids. The surface is swept along a spatial path, where the sweep path is called the guide line, used to control the orientation and size of the curve.

[0050] In this invention, such as Figure 3The outer curved surface of the U-shaped tube is a straight three-dimensional curved surface formed by sweeping the curve formed by splicing the outer curve 1 and the outer curve 2 to the outer curved surface end line. Similarly, the inner curved surface of the bent tube is a curved surface formed by sweeping the curve formed by splicing the inner curve 3 and the inner curve 4 to the inner curved surface end line.

[0051] In this invention, the domain is three-dimensional, but there is no shape change in the z-direction. Simultaneously, the pipe dimension in the z-direction is also Dh, meaning the considered pipe has a square cross-section, and the two inflow and outflow directions are connected by a simple 180° semi-circular curve. The left side of the U-shaped pipe is defined as the airflow inflow direction, and the right side as the outflow direction. Its diameter Dh is defined as 7.5 cm.

[0052] The shapes of the inner and outer curves can be changed, but must remain within acceptable limits. Figure 2 The bounding box shown restricts possible changes to the height and width to account for structural constraints. The distance between the two cooling channels and the channel diameter are not affected by the optimization.

[0053] Furthermore, this involves forming an upstream straight pipe section, an optimized U-shaped pipe section, and a downstream straight pipe section.

[0054] A structured mesh was constructed using Gambit software, with a mesh size of 855,000. Local refinement was performed in high-curvature regions as required, and the boundary layer was also refined. The maximum value of y+ did not exceed 2.2. Convergence studies were conducted on finer meshes, with a maximum y+ value of 0.9. Since no change was observed in the results, a coarser mesh was used.

[0055] The standard k-ε turbulence model was used for calculations. The inlet was defined as a velocity inlet boundary condition, with a fully developed velocity profile applied at the inlet. A uniform inlet velocity of U0 = 8.4 m / s was considered, with a turbulence intensity of 5% and a Reynolds number of 40,000. The k and ε values ​​of the turbulence model were also determined. The outlet was defined as a pressure outlet condition. The wall was a no-slip wall condition, and the pipe wall thickness was not considered in the simulation. The convergence criterion for the simulation was that all parameter residuals were less than 10⁻⁶.

[0056] exist Figure 1 Fitting is performed in the coordinate system shown. The origin of the coordinate system is the center point of the bend of the original U-shaped tube. The inner curve and the outer curve form the U-shaped tube in the coordinate system. The outer curve and the inner curve of the U-shaped tube to be optimized are divided into four curves by the y-axis, namely outer curve 1 on the left side of the y-axis, outer curve 2 on the right side of the y-axis, inner curve 3 on the left side of the y-axis, and inner curve 4 on the right side of the y-axis.

[0057] Each curve is defined by a polynomial with several parameters;

[0058] The outer curved surface of the U-shaped pipe is obtained by sweeping the curve formed by splicing two outer curves to the end line of the outer curved surface.

[0059] The inner curved surface of the U-shaped pipe is obtained by sweeping the curve formed by splicing two inner curves to the end line of the inner curved surface.

[0060] The outer curved surface and the inner curved surface are combined to form a three-dimensional optimized U-shaped tube, and the optimized U-shaped tube in the cooling channel is obtained based on this optimized U-shaped tube.

[0061] The fitting function for external curve 1 is:

[0062] y∈[-13.925, 9.616], z=0;

[0063] Where: p1 = -11.59744363; p2 = -0.01409116; p3 = 1.32042011; p4 = -0.19860287; p5 = 6.78044764E-8; p6 = -1.82700995.

[0064] The fitting function for external curve 2 is:

[0065] y∈[-13.925, 9.616], z=0;

[0066] Wherein: p1=11.75807878; p2=40.46398810; p3=479.99198908; p4=-7.52840350; p5=-86.31530268; p6=0.40277937; p7=3.65362208; p8=-0.00722865; p9=0.01186214; p10=0.00015071.

[0067] The fitting function for inner curve 3 is:

[0068] x = p1 + p2y + p3y 2 +p4y 3 +p5e y , y∈[-14.359, 0.672], z=0;

[0069] Where: p1 = -3.13903571; p2 = 0.31272311; p3 = 0.05808469; p4 = 0.00215792; p5 = 1.43523125.

[0070] The fitting function for inner curve 4 is:

[0071] x = p1 + p2y + p3y 2 +p4y 3 +p5y 4 +p6y 5 +p7y 6 +p8y 7 +p9y 8 y∈

[0072] [-14.359, 0.672], z = 0;

[0073] Where: p1 = 1.47560970; p2 = -1.65134560; p3 = -0.82440002; p4 = -0.24321825; p5 = -0.04474540; p6 = -0.00509385; p7 = -0.00034745; p8 = -1.29485907E-5; p9 = -2.01839406E-7.

[0074] Although only the shape of the U-bend was optimized, the effects of geometric changes on the flow field can extend to more distant downstream regions. Therefore, it is insufficient to consider only the impact of pressure drop on airflow performance at the bend. Figure 3 The locations of the cross-sections used to assess the pressure drop are shown. The upstream static pressure measurement plane is located 5Dh from the bend, and the downstream static pressure measurement plane is located 11Dh from the bend. The location of the inlet velocity profile coincides with the location of the inlet static pressure measurement.

[0075] like Figure 4 The diagram shows the turbulent kinetic energy contour map obtained from CFD numerical simulation at Z / Dh = 0.5. Figure 4 (a) is a U-shaped tube with standard geometry. Figure 4 (b) is the optimized U-shaped tube. The formula for calculating turbulent kinetic energy is as follows:

[0076]

[0077] In the formula, u and v are the fluctuations of velocity along the X and Y axes, respectively, and the upper horizontal line represents the average of 1000 data points.

[0078] Within a standard U-bend, when fluid enters the bend, the bending and frictional resistance cause the fluid to rotate and bend, generating turbulent motion. At this point, the turbulent kinetic energy increases significantly, reaching a relatively high value. In the middle section of the bend, due to the interaction of friction between the fluid and the pipe wall and the inertial force of the flow, the turbulent kinetic energy undergoes periodic fluctuations, but the overall trend remains upward. As the fluid exits the U-bend, the change in pipe geometry causes the fluid to re-enter the straight section, where the flow becomes more stable, and the turbulent kinetic energy gradually decreases, returning to the level before entering the bend.

[0079] Compared to the velocity field of a standard circular bend, the flow acceleration along the inner convex wall is more moderate. This is due to the local curvature of the inner wall, rather than a sudden change from zero to its final value, but a smooth change along the wall profile. The reduction in the local curvature of the inner wall in the first part of the bend has a less pronounced suppressive effect on the turbulence level compared to a standard U-bend. The intensity and extension of the TKE peak at separation are also significantly reduced due to limited recirculation.

[0080] The velocity distribution of this invention at the same cross-section was compared with that of a traditional pipe bend, such as... Figure 5 The figure shows the normalized average velocity field obtained from computational fluid dynamics when Z / Dh = 0.5. Figure 5 (a) is a U-shaped tube with standard geometry. Figure 5 (b) shows the optimized U-shaped tube. The formula for calculating the normalized velocity field is as follows:

[0081]

[0082] pass Figure 5 A comparison of the calculated flow characteristics of the two geometries reveals that in a standard U-shaped pipe, when fluid enters the bend, it rotates due to changes in pipe geometry and friction, resulting in a drastic change in the fluid velocity field. In the later section of the bend, the velocity field fluctuates periodically due to friction and inertia from the pipe wall. Multiple vortex structures of varying sizes form between the inner and outer walls of the bend, with the vortex phenomenon being particularly pronounced at the tail of the inner bend. As the fluid exits the U-shaped bend, the velocity field gradually stabilizes due to changes in pipe geometry and friction.

[0083] Optimized U-bend designs improve hydrodynamic performance by reducing acceleration and recirculation area along the inner wall. This is achieved by reducing the recirculation area generated along the latter half of the inner wall. A larger radius of curvature limits flow acceleration in the first half of the bend and reduces the likelihood of vortex separation. As the fluid travels a nearly straight section at the apex of the bend, it is rapidly diverted downstream, avoiding impact on the outer wall. The design of the outer wall bend directs airflow downwards (i.e., in the negative Y direction). Furthermore, the duct cross-section contracts at the final portion of the bend, limiting the spread of vortex separation, particularly in the lateral direction. The profile of the outer wall of the bend also contributes to increasing the cross-section around the bend and reducing the velocity level and radial pressure gradient.

[0084] In addition, the standard static pressure drop can be obtained by calculating the numerical simulation results using the following formula.

[0085]

[0086] Where P1 and P2 are respectively Figure 3 The static pressure at the upstream and downstream measurement sections is Pa; U0 is the fluid velocity measured at the section defining the Reynolds number is m / s.

[0087] Numerical simulation results show that the ΔP of the U-shaped tube under standard geometric conditions is... * The value is 1.01, while the new U-shaped tube ΔP optimized by curve fitting is... * The value is 0.63, meaning that the total pressure loss of the new U-shaped tube is reduced by 37.6% compared to the original standard shape. The before-and-after comparison is shown below. Figure 6 This effect will have wide applications in the field of gas or liquid transportation. This innovation solves the problem of significant pressure loss during transportation using traditional U-tubes, and is expected to improve the transportation efficiency of pipeline systems and reduce energy consumption costs.

[0088] The preferred embodiments and examples of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0089] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0090] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content of this disclosure.

[0091] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A structure for reducing the pressure drop of a U-bend tube in a cooling passage, characterized by, The optimized U-shaped tube is composed of an outer curved surface and an inner curved surface; The outer curved surface contains two outer curves, and the inner curved surface contains two inner curves; The fitting is performed in a coordinate system, the coordinate origin is the center point of the bend of the original U-shaped tube, the outer curves and the inner curves form a U-shaped tube in the coordinate system, and the outer curves and the inner curves of the U-shaped tube to be optimized are divided into four curves by the y-axis, which are the outer curve on the left side of the y-axis, the outer curve on the right side of the y-axis, the inner curve on the left side of the y-axis and the inner curve on the right side of the y-axis; Each curve is defined by a polynomial of a plurality of parameters; The outer curved surface of the bend tube is taken as a starting curve, the curve formed by splicing the two outer curves is taken as a guide curve, and the outer curved surface of the U-shaped tube is obtained by sweeping to the outer curved surface termination line; The inner curved surface of the bend tube is taken as a starting curve, the curve formed by splicing the two inner curves is taken as a guide curve, and the inner curved surface of the U-shaped tube is obtained by sweeping to the inner curved surface termination line; The outer curved surface and the inner curved surface are combined into a three-dimensional optimized U-shaped tube, and the optimized U-shaped tube in the cooling channel is processed according to the optimized U-shaped tube; The fitting function of the outer curve on the left side of the y-axis is: y e [-13.925, 9.616], z = 0; Wherein: p1=-11.59744363; p2=-0.01409116; p3=1.32042011; p4=-0.19860287; p5=6.78044764E-8; p6=-1.82700995; The fitting function of the inner curve on the right side of the y-axis is: y e [-14.359, 0.672], z = 0; Wherein: p1=1.47560970; p2=-1.65134560; p3=-0.82440002; p4=-0.24321825; p5=-0.04474540; p6=-0.00509385; p7=-0.00034745; p8=-1.29485907E-5; p9=-2.01839406E-7; The fitting function of the outer curve on the right side of the y-axis is: y e [-13.925, 9.616], z = 0; Wherein: p1=11.75807878; p2=40.46398810; p3=479.99198908; p4=-7.52840350; p5=-86.31530268; p6=0.40277937; p7=3.65362208; p8=-0.00722865; p9=0.01186214; p10=0.00015071; The fitting function of the inner curve on the left side of the y-axis is: y e [-14.359, 0.672], z = 0; Wherein: p1=-3.13903571; p2=0.31272311; p3=0.05808469; p4=0.00215792; p5=1.43523125.

2. A structure for reducing pressure drop in a U-tube in a cooling passage according to claim 1, characterized by The U-shaped tube is connected with an upstream straight tube section and a downstream straight tube section at two ends respectively.

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