CN109612320B - Turbulent flow element and turbulent flow pipe for reducing turbulence critical Reynolds number - Google Patents

Abstract

The application discloses a turbulence element and a turbulence tube for reducing turbulence Reynolds number, wherein the turbulence element comprises at least two support rods and a plurality of rib plates which are arranged in parallel; the rib plates are fixed between two adjacent support rods and keep a certain angle with the support rods, and each rib plate is arranged in a scattered manner along the length direction of the support rods; the supporting rod rotates into a multicycle spiral shape according to a certain spiral rate Y, and the rib plates fixed on the supporting rod rotate into an arc shape along with the supporting rod. The application generates high-strength longitudinal vortex in the fluid by the induction of the inclined rib plates, and improves the mixing degree of a near wall area and a core flow area in the tube because the rotation direction of the vortex is parallel to the tube axis, damages the development of a boundary layer, improves the heat flow density of the tube wall, and is further beneficial to improving the heat transfer rate. The application can reduce the critical turbulence Reynolds number of the fluid in the pipe by enhancing the heat transfer of the fluid, thereby obviously improving the comprehensive heat transfer performance of the fluid in the pipe at low Reynolds number.

Description

Spoiler element and spoiler tube for reducing turbulent critical Reynolds number

technical field

The invention relates to the technical field of enhanced heat transfer of heat exchangers, in particular to a spoiler element and a spoiler tube for reducing the critical Reynolds number of turbulent flow.

Background technique

As a common flow condition in heat exchangers, laminar flow has a low Reynolds number, the fluid particles do not collide with each other and do not mix with each other, and there is a regular parallel flow along the tube axis. Especially high viscosity fluids, in many working conditions, are in laminar flow. As a common tube type for heat exchangers, smooth tubes have less disturbance to the fluid and a lower heat transfer rate when laminar heat transfer is applied; turbulent flow has stronger momentum and heat exchange than laminar flow. Therefore, in order to improve Heat transfer efficiency, conventional practice is to convert laminar flow into turbulent flow. But to achieve turbulent flow, the Reynolds number needs to reach more than 4000, and the power consumption is relatively large.

In view of the low Reynolds number conditions in the tube, strengthening elements such as displacement devices or twisted bands are often used in the industry to reduce the critical Reynolds number of turbulent flow in the tube, promote the flow state in the tube to reach turbulent flow in advance, and improve the mixing capacity and heat transfer rate in the tube. However, in many cases, the mixing uniformity of the flow field in the tube is not enough, the eddy current intensity is low, the frictional resistance or shape resistance is large, the increase of the heat transfer rate in the tube is limited, and the overall heat transfer performance is not good under constant power consumption.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention provides a spoiler element and a spoiler tube for reducing the Reynolds number of turbulent flow. The strengthening element generates a high-intensity longitudinal vortex in the fluid through the induction of the inclined rib. The direction is parallel to the tube axis, which improves the mixing degree of the near-wall area and the core flow area in the tube, destroys the development of the boundary layer, increases the heat flux density of the tube wall, and is conducive to improving the heat transfer rate. The invention can reduce the critical turbulent Reynolds number of the fluid in the tube by enhancing the heat transfer of the fluid, and further significantly improve the comprehensive heat transfer performance of the fluid in the tube at a low Reynolds number.

In order to achieve the above purpose, one aspect of the present invention provides a spiral fin reinforced heat transfer element,

A spoiler element for reducing the critical Reynolds number of turbulent flows,

Including at least two supporting rods arranged in parallel and multiple ribs;

The ribs are fixed between two adjacent support rods, and maintain a certain angle with the support rods, and each rib is scattered along the length direction of the support rods;

The support rod rotates according to a certain helical rate Y into a multi-period helical shape, and the ribs fixed on the support rod then rotate into an arc shape.

Preferably, there are two support rods, and the two ends of the ribs are respectively fixed on the two support rods.

Preferably, the ribs are provided with several through holes for reducing the backflow vortex on the leeward side of the ribs.

Preferably, the through hole is a circular hole.

Preferably, before the support rod rotates into a helical shape, each adjacent rib plate is distributed in parallel on the support rod.

Preferably, before the support rod rotates into a helical shape, the staggered angle between adjacent ribs is 15°-75°.

Preferably, before the support rod rotates into a helical shape, each adjacent rib is symmetrically distributed on the support rod.

Preferably, the helix rate Y=2-8.

Preferably, the included angle between the support rod and the rib is 15°-75°.

Another aspect of the present invention provides a turbulence tube, which includes a tube body and the above-mentioned turbulence element, the turbulence element is built in the tube body along the longitudinal direction of the tube body, and the turbulence element Through its multi-period helical structure and the arc-shaped ribs fixed between the helical structures, the element guides the fluid in the pipe body to generate multiple longitudinal vortices along the way.

Compared with prior art, the beneficial effect of the present invention is:

1) The present invention provides a spoiler element with a helical structure with arc-shaped ribs. Through the spoiler element, the fluid is guided along its flow direction to generate a plurality of longitudinal vortices along the route, which can effectively homogenize the flow field and improve the flow rate. The temperature gradient into the wall surface improves the heat transfer efficiency. In the invention, the large-scale mixing of the longitudinal vortex is generated by guiding the fluid in the turbulence tube, and the mixing ability is stronger than that of the transverse vortex turbulence tube, and the heat transfer efficiency is higher.

2) Compared with the typical torsion belt, due to the relay along the longitudinal vortex and the opening of the spiral rib, part of the fluid passes through the round hole and merges with the fluid behind the inclined rib, which can significantly reduce the backflow vortex on the leeward side of the inclined rib, and further The body resistance is reduced, and the comprehensive heat transfer performance is better.

3) The reinforcing element is easy to process and easy to install, and can be used in the design of new heat exchangers and the upgrade of old heat exchangers. At the same time, because it guides the fluid to generate eddy currents, it can significantly reduce the fouling of high-viscosity fluids in the tube.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and not to limit the present application.

Fig. 1 is the front view of the rib plate of Embodiment 1 of the present invention;

Fig. 2 is a side view of Embodiment 1 of the present invention before rotating into a helical structure;

Fig. 3 is a top view of Embodiment 1 of the present invention before being rotated into a helical structure;

Fig. 4 is a schematic diagram of the three-dimensional structure of Embodiment 1 of the present invention after being rotated into a helical structure;

Fig. 5 is a front view of Embodiment 1 of the present invention after being rotated into a helical structure;

Fig. 6 is a top view of Embodiment 1 of the present invention after being rotated into a helical structure;

Fig. 7 is a side view of Embodiment 2 of the present invention before rotating into a helical structure;

Fig. 8 is a top view of Embodiment 2 of the present invention before rotating into a helical structure;

Fig. 9 is a schematic diagram of the three-dimensional structure of Embodiment 2 of the present invention after being rotated into a helical structure;

Fig. 10 is a side view of Embodiment 3 of the present invention before rotating into a helical structure;

Fig. 11 is a top view of Embodiment 3 of the present invention before rotating into a helical structure;

Fig. 12 is a schematic perspective view of the third embodiment of the present invention after being rotated into a helical structure.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

As mentioned in the background technology, in view of the low Reynolds number working conditions in the heat exchange tube, strengthening elements such as displacement devices or twisted bands are often used in the industry to reduce the critical Reynolds number of turbulent flow in the tube, promote the flow state in the tube to reach turbulent flow in advance, and improve the mixing capacity and heat transfer rate. However, in many cases, the mixing uniformity of the flow field in the tube is not enough, the eddy current intensity is low, the frictional resistance or shape resistance is large, the increase of the heat transfer rate in the tube is limited, and the overall heat transfer performance is not good under constant power consumption. Based on this, specific embodiments of the present invention are described in detail:

A turbulence element for reducing the critical Reynolds number of turbulence, including several ribs, and two parallel support rods used to fix the ribs, wherein, as shown in Figure 1, the two ends of the ribs are respectively fixed on There are round holes on the two support rods, and the ribs are scattered along the length direction of the support rods (that is, the direction of fluid flow). Generally, the ribs can be arranged in parallel (as shown in Figure 2) or crossed Layout (as shown in Figure 5). The value range of the height H of the rib is: H=3～20mm, the value range of the length L of the rib is: L=10～40mm, correspondingly, the value range of the diameter D of the round hole is: D=2 ~15mm, the inclination angle a between the longitudinal direction of the ribs and the longitudinal direction of the support bar is 15°~75°, and the range of the distance P between two adjacent ribs is: P=10~40mm. In addition, the value range of the diameter d of the support rod is: d=2-5mm, and the intersection angle between adjacent ribs is 15°-75°. After the rib plate and the support rod are integrally fixed and formed, they are rotated according to the helix rate Y to obtain the helical spoiler. Here, it needs to be explained that the value range of the helix rate Y is: Y=2~8, and the helix rate is defined as : the ratio of the length S of the support rod after helical 360° to the width B of the helical rod (as shown in Figure 5 and Figure 6).

In the following, in combination with the structure of the above-mentioned embodiment, the structural parameter combination schemes of three groups of spiral ribs are listed for further description of the present invention, wherein each embodiment needs to be combined with the above-mentioned structure, and the embodiment of the present invention is not limited thereto. Simple modifications or changes to the essence of the present invention all belong to the scope of the technical solution of the present invention. In addition, in order to evaluate the performance of each embodiment, the comprehensive heat transfer performance is defined as:

PEC = (Nu/Nu ₀ )/(f/f ₀ ) ^(1/3) ;

Among them, PEC represents the comprehensive heat transfer performance, that is, the performance evaluation criterion (PEC), Nu ₀ and Nu represent the dimensionless heat transfer rate (ie Nusselt number) of the light pipe and the enhanced pipe respectively, f ₀ and f represent The dimensionless pressure drop of the light pipe and the reinforced pipe is the friction factor. Under the same power consumption, if the PEC is greater than 1, it means that the overall heat transfer performance is improved compared with the light pipe, and vice versa.

Example 1

As shown in Figure 1 and Figure 2, the height of the ribs is H=4mm, the length L=19mm, and the thickness of the ribs is t=4mm. Each rib is arranged in parallel on the support rod, and there are 3 round holes scattered on the rib. , the diameter of the round hole D=2mm, the distance between the round holes A1=3.5mm, the distance between the support rod and the round hole A2=3mm, the inclination a=60°, the pitch P=20mm, the diameter of the support rod is d=2mm, The twist rate Y=4 of the spiral rib.

Its application method is:

The rib plate is fixed on the support rod, and the support rod fixed with the rib plate is spiraled according to the spiral rate Y, thereby forming a multi-cycle spiral spoiler element (as shown in Fig. 3, Fig. 4, Fig. 5 and Fig. 6). The spoiler element is built into the spoiler tube and fixed by spot welding for easy disassembly and assembly. In use, the fluid enters from one end of the spoiler tube, and under the induction of the spoiler element, a longitudinal vortex along the fluid flow direction is generated, and the vortex scours the tube wall, driving the mixing of high-temperature fluid and low-temperature fluid, reducing the velocity vector and the low-temperature fluid in the tube. The included angle between the temperature gradient vectors, the volume-weighted average synergy angle is lower than the angle between the two in the light pipe, which is close to 90°, which improves the coordination of the temperature field and the velocity field. Compared with the light pipe, the fluid replacement intensity in the pipe is greatly improved, reducing thinning the boundary layer. Due to the periodicity of the helical structure of the spoiler element, the longitudinal vortex is formed repeatedly, which is not easy to attenuate, and a cooperative relay is formed in the middle of each pitch with low resistance, so as to obtain a better heat transfer rate. Under common working conditions, compared with traditional smooth tubes, the critical Reynolds number is lower than 1000, and the heat transfer rate is increased by more than 100%. Under the same power consumption, the comprehensive heat transfer performance PEC can reach more than 2.

Example 2

As shown in Figure 7 and Figure 8, the difference between this embodiment and Embodiment 1 is that there are differences in the layout of the ribs on the support rods, the intersection angle of two adjacent ribs along the flow direction is 60°, and the two are opposite To arrange, become left-right symmetry, after support rod drives rib plate to spiral, its structural diagram is as shown in Figure 9, and other structures are the same as embodiment 1, and application method is also the same as embodiment 1.

Example 3

As shown in Figure 10, Figure 11 and Figure 12, the height of the ribs is H=6mm, the length L=25mm, the thickness of the ribs is t=6mm, the adjacent ribs are parallel to each other, and there are 3 ribs Round hole, the diameter of the round hole D=3mm, the distance between adjacent round holes A1=3.5mm, the distance between the support rod and the round hole A2=3mm, the inclination angle a=45°, the pitch P=20mm, the diameter of the support rod For d=2mm, the torsion rate Y=4 of the spiral rib. Under normal working conditions, compared with the traditional smooth tube, the critical Reynolds number is lower than 1000, and the heat transfer rate is increased by more than 150%. Under the same power consumption, the comprehensive heat transfer performance reaches more than 2.5, and its application method is the same as that of Example 1.

The turbulence element provided by the present invention utilizes the inclination angle between the rib plate spiraled into an arc and the fluid flow direction to induce longitudinal vortices in the flow field, and then the rib plate is screwed according to a certain helical rate under the fixation of the support rod. Under the double function of the spiral, the strength and influence area of the longitudinal vortex are further improved, the fluid replacement capacity is greatly improved in the core area of the mainstream and the wall area, the collision of fluid particles is strengthened, the uniformity of the flow field and temperature field is improved, and the pipe wall is improved. Heat flux. Of course, the turbulence element is not only suitable for circular channels, but also for rectangular channels. Since the critical Reynolds number of turbulent flow can be reduced, a higher degree of turbulence can be obtained at a lower flow rate, so the turbulence element is not only suitable for low Reynolds number flow of high-viscosity fluid, but also suitable for low-viscosity fluid flow. Reynolds number flow. By arranging several ribs in the flow direction and opening holes in the ribs, the resistance is actively regulated, so that at a low Reynolds number, it can not only ensure a large heat transfer rate, but also pay a small fluid power consumption, so that the overall Low-resistance and high-efficiency enhanced comprehensive heat transfer performance can be obtained.

The above is only one embodiment of the present invention, and those skilled in the art should understand that the embodiments of the present invention may be provided as methods, systems or computer program products. Accordingly, the present invention can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects.

In addition, it should be noted that:

Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "one embodiment" or "an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment.

While preferred embodiments of the present invention have been described, additional changes and modifications can be made to these embodiments by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it is not a limitation to the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (8)

1. A spoiler element for reducing the critical Reynolds number of turbulence, characterized in that, Including at least two supporting rods arranged in parallel and multiple ribs; The ribs are fixed between two adjacent support rods, and maintain a certain angle with the support rods, and each rib is scattered along the length direction of the support rods; The support rod rotates into a multi-period spiral shape according to a certain spiral rate Y, and the rib plate fixed on the support rod then rotates into an arc shape; There are two support rods, and the two ends of the ribs are respectively fixed on the two support rods; The ribs are provided with several through holes for reducing the backflow vortex on the leeward side of the ribs. 2 . The turbulence element for reducing the critical Reynolds number of turbulent flow according to claim 1 , wherein the through hole is a round hole. 3 . 3 . The turbulence element for reducing the critical Reynolds number of turbulence according to claim 1 , characterized in that, before the support rod rotates into a spiral shape, each adjacent rib is distributed in parallel on the support rod. 4 . 4. A turbulence element for reducing the critical Reynolds number of turbulent flow according to claim 3, characterized in that, after the support rod is rotated into a spiral shape, the staggered angle between adjacent ribs is 15°-75° °. 5 . The turbulence element for reducing the critical Reynolds number of turbulent flow according to claim 1 , wherein, before the support rod rotates into a spiral shape, each adjacent rib is symmetrically distributed on the support rod. 6 . 6 . The flow turbulence element for reducing the critical Reynolds number of turbulent flow according to claim 1 , wherein the spiral rate Y=2-8. 7 . 7 . The spoiler element for reducing the critical Reynolds number of turbulent flow according to claim 1 , wherein the angle between the support rod and the rib plate is 15°-75°. 8. A turbulence tube, characterized in that it comprises a tube body and the turbulence element according to any one of claims 1-7, the turbulence element is built into the tube body along the longitudinal direction of the tube body, so The flow turbulence element guides the fluid in the pipe body to generate multiple longitudinal vortices through its multi-period helical structure and the arc-shaped ribs fixed between the helical structures.