A twisted interleaved interrupted helical finned tube heat exchanger

Abstract

The application provides a twisted staggered intermittent helical fin type sleeve heat exchange device, belonging to the field of heat exchange intensification and heat exchange equipment, comprising an outer sleeve, an inner base pipe, and twisted staggered intermittent helical fins arranged on the ring side between the inner pipe and the outer sleeve, wherein the continuous helical fins are equidistantly slotted to form a fan shape, and the top end of the fan shape helical fin is twisted at an angle β The twisted staggered intermittent helical fins are formed. The twisted staggered intermittent helical fins arranged on the ring side of the sleeve heat exchange device can well constrain the fluid to flow in a spiral shape, increase the mixing of near-wall flow and main flow. At the same time, the small jet flow at the twisted gap not only forms a secondary flow at the center of the ring side spiral channel, enhances the disturbance at the center of the ring side fluid, and improves the field synergy of the temperature field and the velocity field, but also effectively reduces the flow and heat exchange dead zone at the leeward surface of the helical fin, thereby intensifying the heat transfer. The heat transfer performance of the twisted staggered intermittent helical fin type sleeve heat exchange device under unit pump power consumption is significantly enhanced. The application has the characteristics of high heat exchange efficiency, low initial investment, low pump power consumption under the same heat exchange capacity, compact structure, long service life, and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of heat exchange enhancement and heat exchanger, mainly applied in the industries of energy power, petroleum chemical industry and heating ventilation air conditioning chemical industry, and relates to a twisted staggered intermittent helical fin double-pipe heat exchange device. BACKGROUND

[0002] The double-pipe heat exchanger is widely used in chemical industry, energy, power, machinery and other industries due to its simple structure, wide working range, convenient realization of the interwall heat exchange of fluid medium, high heat transfer coefficient on both sides of the heat transfer surface. In the double-pipe heat exchanger, the high-temperature medium and the low-temperature medium can realize the heat transfer in the same direction and the heat transfer in the opposite direction through the inner pipe wall to achieve the purpose of heat exchange. However, the inner pipe and the outer pipe of the conventional double-pipe heat exchanger are both smooth round pipes, the effective heat exchange stroke of the annular side flow channel formed between the inner pipe and the outer pipe is short, and there is lack of turbulence elements between the inner pipe and the outer pipe, so that the fluid flow is fast and the heat exchange is not sufficient, resulting in low heat transfer efficiency. In addition, due to the change of heat flow on the pipe wall, impurities and minerals in the fluid often form scale on the pipe wall, causing the problem of scale deposition on the outer wall of the inner pipe and the inner wall of the outer pipe, further affecting the heat exchange, and also easily damaging the heat exchanger, reducing the service life of the equipment and increasing the production cost.

[0003] Especially when the heat transfer coefficient of the double-pipe heat exchanger ring side is much smaller than that of the pipe side, it is very important to take the heat transfer enhancement technology measures. For the traditional continuous single helical fin strengthened double-pipe heat exchanger ring side heat exchange, affected by the centrifugal force, the secondary flow at the center of the ring side spiral channel is weakened, and flow and heat transfer dead zones appear near the leeward area of the helical fin, forming a local high temperature area, which is not conducive to the flow and heat transfer. SUMMARY

[0004] The twisted staggered intermittent helical fin double-pipe heat exchange device and its design and manufacturing method are proposed to solve the above technical problems, aiming to inhibit the formation of scale in the heat exchanger, strengthen the flow and heat transfer, and improve the heat exchange efficiency of the heat exchanger.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A torsionally intermittent spiral blade heat exchanger is provided, the structure of which is a heat exchanger body consisting of an outer tube and an inner tube concentrically nested together; wherein, there is an annular channel between the outer tube and the inner tube, and a tube-side channel inside the inner tube; both ends of the inner tube extend beyond the corresponding end faces of the outer tube, one end of the inner tube is the tube-side inlet, and the other end of the inner tube is the tube-side outlet; the outer tube has a left end plate near the tube-side inlet of the inner tube, and a right end plate near the tube-side inlet of the inner tube. The end plates, specifically the left and right end plates of the outer sleeve, seal both ends of the annular channel. An annular outlet is located on the outer sleeve side near the left end plate, and an annular inlet is located on the outer sleeve side near the right end plate. The annular channel is provided with intermittently twisted spiral fins formed by equidistantly spaced, continuous single straight spiral blades. These intermittently twisted spiral blades extend along a spiral line, with the lower end of the spiral blades perpendicularly attached to the outer wall of the inner tube and the upper end close to the inner wall of the outer sleeve, thus forming an approximately spiral-shaped flow channel and increasing the flow rate of the fluid medium on the annular side.

[0006] The fins of the twisted, intermittent spiral blades are evenly distributed along the spiral line on the outer wall of the inner tube at their base.

[0007] The slit depth h of the torsionally intermittent spiral blade is 1 / 3 to 1 of the height H of the intermittent spiral blade; the number of slits n per unit pitch of the torsionally intermittent spiral blade is 1 to 20.

[0008] The torsion angle β of the torsionally intermittent spiral blade is 0° to 90°.

[0009] The circular base tube is a pressure-resistant base tube, which can be a steel pipe or a copper pipe.

[0010] The spiral blades are made of a material with good flexibility and high thermal conductivity, such as aluminum or copper.

[0011] The first fluid medium enters through the inlet of the outer tube, passes through the spiral channel formed by the outer tube, the inner tube, and the torsion intermittent spiral blades, presents a spiral piston flow, and flows out through the outlet of the outer tube; the second fluid medium enters through the inlet of the inner tube and flows out through the outlet of the inner tube.

[0012] The design, fabrication, and processing method of the aforementioned torsionally intermittent spiral blades:

[0013] A rectangular metal plate of width W is asymmetrically extruded or stretched on both sides using a specialized machine tool, and then rolled into a continuous single straight spiral blade with a helix angle α. The outer and inner edge unfolding lengths of the spiral blade are a and b, respectively.

[0014] a 2 =(πD1) 2 +(mP) 2

[0015] b 2 =(πD2) 2 +(mP) 2

[0016] W = (D1 - D2) / 2

[0017]

[0018] H = W = (D1 - D2) / 2

[0019] In the formula, D1 and D2 are the diameters of the outer tube and inner tube of the shell-and-tube heat exchanger, respectively; m is the number of spiral blade pitches within the effective heat exchange length of the shell-and-tube heat exchanger; and P is the pitch of the spiral line L on the outer wall of the inner tube of the shell-and-tube heat exchanger.

[0020] Then, using a lathe, equidistant vertical cuts are made from the top of a continuous single straight spiral blade to obtain a fan-shaped discontinuous spiral blade, with a cut depth of h and a cut spacing of S. Further, using the vertical center line of the fan-shaped discontinuous spiral blade as an axis, its top is twisted in the same direction at a twist angle of β, forming a twisted intermittent spiral blade. Finally, the entire twisted intermittent spiral blade is seamlessly welded along the spiral line L on the outer wall of the inner tube.

[0021]

[0022] In the formula, n is the number of slots per unit pitch.

[0023] The continuous constraint of the intermittently twisted spiral blades forms a rectangular spiral channel with gaps. The fluid on the annular side exhibits a spiral piston flow, continuously and obliquely scouring the walls of the inner tube and spiral blades, thinning the flow boundary layer and promptly carrying away heat dissipation. The main spiral stream generates jets at the torsional gaps between the intermittently twisted spiral blades. Small streams of fluid flow at high speed through these gaps, creating a flow effect similar to an "inlet effect," and mix with the main spiral stream within the next pitch, forming a secondary flow at the center of the rectangular spiral channel. This enhances the disturbance at the center of the rectangular cross-section spiral channel and strengthens the heat transfer at the center. When the small jets of the main spiral stream flow at high speed through the intermittently twisted spiral blades, they not only thin the fluid boundary layer on the windward wall of the spiral blades but also effectively improve the flow and heat transfer dead zone in the leeward area of ​​the spiral fins, increasing the temperature gradient at the spiral blade wall and improving the heat transfer coefficient. The pulsating flow generated by the small jets of the main spiral stream flowing at high speed through the intermittently twisted spiral blades enhances the turbulence at the center of the channel, improves the synergy between the temperature and velocity fields, and strengthens heat transfer.

[0024] The beneficial effects of this invention are that the device employing a torsionally intermittent spiral blade to enhance heat transfer increases the heat exchange area of ​​the annular fluid medium, improves the effective heat transfer area per unit mass of the heat exchanger, and effectively saves on the cost of heat exchange equipment; the fluid in the annular channel mainly flows in a spiral shape, extending the flow path and heat exchange time of the heat exchange medium; under the influence of centrifugal force, this spiral flow structure causes radial flow of the annular fluid, thereby promoting thorough mixing of the main fluid and the boundary layer fluid of the inner and outer sleeve walls, thinning the fluid boundary layer of the inner and outer sleeve walls, improving the heat transfer coefficient, and increasing the heat transfer capacity; the annular... Under the constraint of tightly connected, intermittently twisted spiral fins, the fluid medium mainly flows in a spiral pattern along the rectangular spiral channel, enhancing heat transfer between the fluid and the wall. Small leaks mix with the main spiral flow, increasing turbulence in the middle of the rectangular channel, improving the synergy between the temperature and velocity fields, and enhancing convective heat transfer between fluids within the rectangular channel. At each torsional gap, a flow similar to an "inlet effect" is formed, increasing the fluid velocity at the spiral fin wall, enhancing turbulence across the spiral fins, and increasing the temperature gradient of the fluid on the fin wall. Compared with traditional equipment, the torsional intermittently twisted continuous spiral fin heat exchanger tube of this invention significantly enhances the heat transfer effect of finned tubes, increasing the heat transfer coefficient by approximately 10.7%-15.4% and reducing the drag factor by an average of 8.2%-55.3%. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the outer tube;

[0026] Figure 2 Schematic diagram of the inner tube with intermittently twisted spiral blades;

[0027] Figure 3 Partial view of the inner tube of the torsionally intermittent spiral blades;

[0028] Figure 4 Schematic diagram of interlaced, twisted, discontinuous spiral blades;

[0029] Figure 5 A schematic diagram of a continuous single straight spiral plate;

[0030] Figure 6 A schematic diagram of obtaining a fan-shaped discontinuous spiral blade by cutting a slit in a continuous single straight spiral blade;

[0031] Figure 7 A three-dimensional schematic diagram of a torsionally intermittent spiral blade heat exchanger;

[0032] Figure 8 Schematic diagram of the cross section of a torsion interlaced discontinuous spiral blade heat exchanger;

[0033] In the diagram: 1. Outer tube inlet; 2. Outer tube outlet; 3. Inner tube inlet; 4. Inner tube outlet; 5. Inner tube; 6. Twisted, intermittent spiral blade; 7. Outer tube; 8. Left end plate of outer tube; 9. Right end plate of outer tube; 10. Continuous single straight spiral blade; 11. Fan-shaped spiral blade; Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings.

[0035] See Figure 1 , Figure 2 and 7 As shown, a torsionally intermittent spiral finned heat exchanger includes an outer tube 7, an inner tube 5, and torsionally intermittent spiral fins 6 connected circumferentially to the outer wall of the inner tube 5. The torsionally intermittent spiral fins 6 are based on a continuous single straight spiral fin 10, with equidistant vertical cuts made from the top of the continuous single straight spiral fin 10 to form fan-shaped spiral fins 11. Then, a parallel torsion angle β is made with the vertical center line of the fan-shaped spiral fins 11 as the axis. The cut depth is h, the spacing is S, and the number of cuts per unit pitch is n.

[0036]

[0037] In the formula, P is the helical pitch.

[0038] The first fluid medium enters through the outer tube inlet 1, flows through the intermittently twisted spiral blades located on the annular side, and, constrained by the spiral blades and subjected to centrifugal force, exhibits a spiral piston flow, continuously moving forward, and finally flows out through the outer tube outlet 2. The second medium enters through the inner tube inlet 3 and flows out through the inner tube outlet 4.

[0039] Under the continuous constraint of the intermittently twisted spiral blades 6 on the annular side, the fluid forms a spiral flow through the rectangular cross-section spiral channel, continuously and obliquely scouring the heat exchange wall of the inner tube 5 and the spiral blades 6, and promptly carrying away the heat dissipation; in addition, the centrifugal force generated by the spiral flow causes the radial flow of the fluid on the annular side, thereby promoting the full mixing of the main fluid with the boundary layer fluid on the wall of the inner tube 5 and the outer tube 7, and thinning the fluid boundary layer on the tube wall.

[0040] Due to the influence of the torsional gaps between the intermittently twisted spiral blades 6, the main flow of the spiral flow on the annular side successively leaks at the gaps, with a small portion of fluid flowing at high speed through the torsional gaps, forming a flow effect similar to the "inlet effect". This flow mixes with the main flow of the spiral flow in the next pitch, forming a secondary flow at the center of the rectangular spiral channel, enhancing the disturbance at the center of the rectangular cross-section spiral channel and strengthening the heat transfer of the fluid at the center of the channel. In addition, when the small stream of leaking fluid flows at high speed through the intermittently twisted spiral blades 6, it not only thins the fluid boundary layer on the windward side of the spiral blades 6, reducing the flow and heat transfer dead zone on the leeward side of the intermittently twisted spiral blades 6, and increasing the temperature gradient at the spiral blade wall, thus increasing the heat transfer coefficient, but also generates a pulsating flow from the small stream of high-speed fluid, improving the synergy between the temperature field and the velocity field, thereby enhancing heat transfer.

[0041] The inner tube's outer wall surface is provided with intermittently arranged, twisted spiral blades along a spiral line, forming a narrow rectangular spiral channel with twisted gaps on the circumferential side between the inner and outer tubes. This causes the fluid in the circumferential channel to flow primarily in a spiral shape, extending the flow path of the heat exchange medium and the heat exchange time. In addition, under the influence of centrifugal force, this spiral flow structure causes radial flow of the fluid on the circumferential side, thereby promoting thorough mixing of the main fluid and the boundary layer fluid on the inner and outer tube walls, thinning the fluid boundary layer on the inner and outer tube walls, improving the heat transfer coefficient, and increasing the amount of heat exchanged. Under the constraint of tightly connected, intermittently twisted spiral blades, the fluid medium on the annular side mainly flows in a spiral shape along the rectangular spiral channel, obliquely scouring the heat exchange wall, thinning the flow boundary layer, and enhancing the heat transfer between the fluid and the wall. Meanwhile, due to the influence of the torsional gaps between the spiral blades, small streams of fluid leak out at high speed, flowing through the gaps into the rectangular spiral channel of the next pitch, mixing with the mainstream spiral flow, enhancing the turbulence of the fluid in the middle of the rectangular channel, improving the synergy between the temperature and velocity fields, and enhancing convective heat transfer between the fluids within the rectangular channel. As the mainstream spiral flow continues, fluid continuously flows at high speed through the torsional gaps, forming a flow similar to an "inlet effect" at each gap, increasing the fluid velocity at the spiral blade wall, enhancing the turbulence of the fluid sweeping across the spiral blades, and increasing the temperature gradient of the fluid on the fin wall. Furthermore, due to the existence of the torsion angle, a wave-like structure is formed between the connected spiral blades, causing the passing fluid to pulsate, further enhancing heat transfer.

Claims

1. A torsionally intermittent spiral blade heat exchanger, comprising an outer tube (7) and an inner tube (5), characterized in that: The heat exchanger body is formed by concentrically fitting an outer tube and an inner tube together. An annular channel connects the outer and inner tubes, while a tube-side channel runs inside the inner tube. Both ends of the inner tube extend beyond the corresponding end faces of the outer tube; one end of the inner tube is the tube-side inlet, and the other end is the tube-side outlet. The outer tube has a left end plate near the tube-side inlet of the inner tube and a right end plate near the tube-side inlet of the inner tube. These left and right end plates seal off both ends of the annular channel. The outer tube is positioned near the left end plate of the outer tube. The outer tube has an annular outlet on one side and an annular inlet on the side of the outer tube near the right end plate of the outer tube; the annular side between the outer tube and the inner tube is provided with a twisted interlaced helical fin formed by equidistant slits of continuous single straight helical blades and twisting them, and the twist angle of the twisted interlaced helical blades (6) is β; the twisted interlaced helical blades extend along the helical line, with the lower end of the helical blades perpendicularly close to the outer wall of the inner tube and the upper end close to the inner wall of the outer tube, forming an approximately spiral flow channel in the annular side channel; The continuous single straight spiral blade has n = 1 to 20 equidistant slits per unit pitch, slit depth h = 1 / 3H to 1H, where H is the height of the discontinuous spiral blade, and slit distance S > 0. The torsion angle β of the torsionally intermittent spiral blades is 0° to 90°; The first fluid flows into the ring side through the inlet (1) of the outer tube and flows out of the ring side through the outlet (2) of the outer tube, realizing the ring side flow and presenting a spiral piston flow; the second fluid flows in through the inlet (3) of the inner tube and flows out through the outlet (4) of the inner tube, realizing the flow inside the tube.

2. The torsion interlaced discontinuous spiral blade heat exchanger according to claim 1, characterized in that: The twisted intermittent spiral blade is based on a continuous single straight spiral blade (8) rolled by a special machine tool. It is formed by vertically cutting slits with equal distances of S to form a fan-shaped intermittent spiral blade (9). It is obtained by twisting the fan-shaped spiral blade with the vertical center line as the axis by an angle β. ； Where P is the helical pitch, D1 is the outer diameter of the inner tube, and n is the number of slots per unit pitch.

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