Annular shell and tube heat exchanger

Abstract

The present invention provides a shell and tube heat exchanger, which includes an outer shell and an internal flow channel. The inner wall is circular, the outer wall is octagonal, and an internal flow channel is formed between the inner wall and the outer wall. A plurality of annular dividing pieces are arranged in the internal flow channel, so that the internal flow channel is divided into a plurality of annular flow channels in the axial direction. The inlet and outlet of the annular flow channel are respectively arranged at opposite ends, so that the annular flow channel is a U-shaped structure, which is formed by connecting the flow channels on both sides in parallel; fish fin-shaped bionic fins are arranged in the annular flow channel, and the protrusion directions of the fish scale bionic fins in adjacent flow channels are opposite when viewed along the axial direction. The present invention designs a shell and tube heat exchanger with a new annular outer shell, which integrates the U-shaped parallel flow channel and the fish fin-shaped bionic fin. Compared with the traditional spiral and S-shaped series flow channels, the U-shaped parallel flow channel can reduce the pressure drop and has better temperature uniformity performance. The fish fin-shaped bionic fins are staggered in the flow channel to enhance the flow around.

Description

Technical Field

[0001] The invention relates to a shell and tube heat exchanger, in particular to a shell and tube heat exchanger with an annular structure. Background Art

[0002] Shell and tube heat exchangers are widely used in industries such as chemical, petroleum, refrigeration, nuclear energy and power. Due to the global energy crisis, in order to reduce energy consumption, the demand for heat exchangers in industrial production is increasing, and the quality requirements for heat exchangers are also getting higher and higher. In recent decades, although compact heat exchangers (plate, plate-fin, press-welded plate heat exchangers, etc.), heat pipe heat exchangers, direct contact heat exchangers, etc. have developed rapidly, shell and tube heat exchangers still dominate production and usage due to their high reliability and wide adaptability. According to relevant statistics, the use of shell and tube heat exchangers in industrial devices still accounts for about 70% of all heat exchangers.

[0003] Shell and tube heat exchanger is one of the types of partition heat exchanger. It has a simple structure, is easy to manufacture, install, clean and maintain, is inexpensive, and is particularly suitable for cooling and condensing high-pressure fluids, so it is still widely used today.

[0004] In recent years, in order to meet the heat exchange requirements, research on indirect liquid cooling systems has been carried out, involving many aspects such as cold plate structure, refrigerant selection, and pipeline layout. It is found that the air-cooled plate structure has a particularly significant impact on the heat exchange and power consumption of the liquid cooling system. In the indirect liquid cooling solution, an air-cooled plate-shaped shell and tube heat exchanger is used for heat exchange. The air-cooled plate is a metal heat exchange device with a flow channel structure, usually made of copper or aluminum. The heat exchange fluid is directly in contact with the bottom surface of the air-cooled substrate, and the heat is transferred to the air-cooled plate, and then the air-cooled plate and the internal refrigerant conduct convection heat exchange to take away the heat. The entire liquid cooling system uses a pump to provide power for the circulation of the working fluid. Compared with the air-cooled system, the liquid cooling system has a more compact structure. Moreover, the refrigerants used are mostly deionized water compatible with the cold plate material, a specified percentage of ethylene glycol-deionized water, nanofluids and other media, which have higher specific heat capacity and thermal conductivity than air, and are better than air cooling in heat dissipation effect. In addition, compared with the air-cooled system, the noise level of the indirect liquid cooling system is significantly reduced.

[0005] The air cooling plate can generally be divided into three parts: base plate, flow channel and cover plate. There is no unified standard for the cover plate and hose connector. Different manufacturers have different structural forms. The base plate and flow channel can be configured in various ways according to the equipment and thermal design power consumption, which is also the main factor affecting the heat dissipation performance of the air cooling plate.

[0006] Adding fins to the flow channel helps increase the heat exchange area and enhance the disturbance of the flow field. Intensifying heat exchange by adding fins has been widely used in heat exchangers. However, this design cannot only consider the heat dissipation effect, but also should try to avoid the situation where the pressure drop increases sharply after adding fins and the heat dissipation improvement effect is minimal. Considering that the temperature at the refrigerant inlet is relatively lower, the fins should be reasonably designed in the center and the periphery. Moreover, the current fin design adopts conventional design, and it is necessary to consider improving the heat transfer from the fin design.

[0007] Moreover, air-cooled plate and tube heat exchangers generally adopt a flat plate structure or a conventional shell and tube heat exchanger structure, and therefore also need further improvement.

[0008] In view of the above problems, the present invention provides a new shell and tube heat exchanger with an annular structure, which improves the structure, fluid flow and fin design of the heat exchanger, thereby solving the problem of insufficient heat exchange capacity of the current shell and tube heat exchanger. Summary of the invention

[0009] The present invention provides a new shell and tube heat exchanger with an annular structure, which improves the heat exchanger and solves the above-mentioned technical problems.

[0010] In order to achieve the above object, the technical solution of the present invention is as follows:

[0011] A shell and tube heat exchanger, the heat exchanger comprises an outer shell and an internal flow channel, the outer shell is provided with a fluid inlet and a fluid outlet, the outer shell comprises an inner wall and an outer wall, the inner wall is circular, the outer wall is octagonal or circular, the center of the inner wall and the center of the outer wall are the same point; an internal flow channel is formed between the inner wall and the outer wall, a plurality of annular dividing pieces are arranged in the internal flow channel, so that the internal flow channel is divided into a plurality of annular flow channels in the axial direction, the inlet and the outlet of the annular flow channel are respectively arranged at opposite ends, so that the annular flow channel is a U-shaped structure, which is formed by connecting the flow channels on both sides in parallel; an opening is arranged on the annular dividing piece, so that two adjacent annular flow channels form a series structure through the opening; fish fin-shaped bionic fins are arranged in the annular flow channel, and the protrusions of the fish scale bionic fins in adjacent flow channels are in opposite directions when viewed along the axial direction.

[0012] In one option, the fluid inlet and the fluid outlet are disposed at a top end of the housing.

[0013] In one option, the fish scale bionic fins are arranged on the inner wall, extending from the inner wall toward the outer wall.

[0014] In one option, the fish scale bionic fin includes a first curved wall and a second curved wall connected to each other, wherein the length of the first curved wall is greater than the length of the second curved wall, and the bending radius of the first curved wall is smaller than the bending radius of the second curved wall.

[0015] One option is to provide a circle of circumferential center fins located in the center of the flow channel and two circles of side fins located on both sides of the center fins in the annular flow channel, the height of the center fins is the same as the height of the side fins, and the width of the center fins is 1.5-2.5 times the width of the side fins.

[0016] As an option, the center fins and the side fins are staggered.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1) The present invention designs a new type of shell and tube heat exchanger with an annular shell, which integrates U-shaped parallel flow channels and fish-fin-shaped bionic fins. Compared with traditional spiral and S-shaped series flow channels, U-shaped parallel flow channels can reduce pressure drop and have better temperature uniformity performance.

[0019] 2) The fish-fin-shaped bionic fins are arranged in a staggered manner in the flow channel to enhance the flow and increase the effective heat exchange area. The flatter side of the fish-fin-shaped bionic fins is opposite to the flow direction of the working fluid, which has a better flow effect and a larger heat dissipation area than ordinary rectangular fins. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a cross-sectional view of the flow channel of the casing of the present invention.

[0021] Figure 2 Schematic diagram of the fluid channel of the present invention.

[0022] Figure 3 It is a schematic diagram of a fish-fin-shaped bionic fin in a single flow channel of the present invention. DETAILED DESCRIPTION

[0023] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0024] In this article, unless otherwise specified, “ / ” represents division, and “×” and “*” represent multiplication.

[0025] The left and right sides of the present application are viewed from the direction of the fluid inlet 2-3 to the direction of the fluid outlet 2-4, with the plane where the connecting line between the fluid inlet 2-3 and the center of the inner wall 1-1 extends along the axis of the inner wall as the center, and the left and right sides of the plane are respectively the left and right sides.

[0026] Figure 1-3 A shell and tube heat exchanger is shown. Figure 1As shown, the heat exchanger includes a shell 1 and an internal flow channel 2. The shell 1 is provided with a fluid inlet 2-3 and a fluid outlet 2-4. The shell 1 includes an inner wall 1-1 and an outer wall 1-2. The inner wall is a circular structure, and the outer wall is a polygon, preferably an octagon with more than eight sides. Preferably, the center of the circle is the center of the polygon; or the outer wall is a circle, and the inner wall circle and the outer wall circle have the same center; the internal flow channel 2 is formed between the inner wall and the outer wall. Figure 2 As shown, a plurality of annular dividing pieces 2-1 are arranged in the internal flow channel, so that the internal flow channel is divided into a plurality of annular flow channels 2-2 in the axial direction, and the fluid inlet 2-3 and the fluid outlet 2-4 of the annular flow channel are respectively arranged at opposite ends, so that the annular flow channel is a U-shaped structure, and each annular flow channel is formed by two side channels (left side channel 2-5 and right side channel 2-6) connected in parallel; an opening 2-7 is arranged on the annular dividing piece, so that two adjacent annular flow channels form a series structure through the opening, and fish fin-shaped bionic fins 2-8 are distributed in the annular flow channel.

[0027] The present invention designs a new type of shell and tube heat exchanger with an annular shell, which integrates U-shaped parallel flow channels and fish-fin-shaped bionic fins. Compared with traditional spiral and S-shaped series flow channels, U-shaped parallel flow channels can reduce pressure drop by more than 60%, while having better temperature uniformity. The fish-fin-shaped bionic fins are staggered in the flow channel to enhance the flow, increase the effective heat exchange area by 21%, and improve the convective heat transfer coefficient by 26%.

[0028] The annular flow channel is provided with fish-fin-shaped bionic fins. When viewed axially, the protrusions of the fish-scale-shaped bionic fins in adjacent flow channels are in opposite directions. Through this design, the fluid can continue to be subjected to the same turbulence effect when flowing in the U-shaped flow channel, thereby reducing the increase in flow resistance.

[0029] As an option, the heat exchanger is arranged in an up-down direction, a preferred embodiment, such as Figure 2 As shown, the fluid inlet 2-3 and the fluid outlet 2-4 are arranged at the top of the shell. Through such arrangement, the fluid can flow in the flow channel by gravity and the fluid is fully in contact with the wall surface.

[0030] As an improvement, the openings 2-7 are arranged at the upper or lower part of the internal flow channel. By being arranged at the upper or lower part, the fluid flows from the top end to the bottom end, or from the bottom end to the top end, so that the fluid can flow in the flow channel by gravity and make the fluid fully contact with the wall surface; or flow by anti-gravity, so that the fluid can fully exchange heat during the flow.

[0031] In one option, the fish scale bionic fins are arranged on the inner wall, extending from the inner wall toward the outer wall.

[0032] One option is that the fish scale bionic fin includes a first curved wall and a second curved wall connected to each other, wherein the length of the first curved wall is greater than the length of the second curved wall, and the bending radius of the first curved wall is less than the bending radius of the second curved wall. The first curved wall is located upstream of the fluid flow, and the second curved wall is located downstream of the fluid flow. The bending radius and length of the second curved wall arranged downstream are smaller than the first curved wall, and the fluid preferentially contacts the first curved wall when flowing in the U-shaped flow channel. Because the slope of the first curved wall is relatively gentle and the contact surface with the fluid is large, the fluid can fully contact and exchange heat with the bionic fin under relatively small resistance. The second curved wall increases the heat exchange area, and the heat exchange area of ​​the second curved wall of the same length increases, because the flow resistance located downstream is basically not increased, so by setting the size of the first curved wall and the second curved wall and the change of the bending radius, the heat exchange area can be increased while maintaining the same resistance, the heat exchange effect is improved, and the distribution area of ​​the fin is saved, saving costs.

[0033] One option is to provide an annular flow channel with a circle of circumferential center fins located at the center of the flow channel and two circles of side fins located at the center fins. The height of the center fins is the same as the height of the side fins. The thickness of the center fins is 1.5-2.5 times the thickness of the side fins, preferably twice. During the heat dissipation process, the thicker center fins can fully conduct heat, and the thinner side fins can reserve sufficient channels for the fluid while ensuring heat conduction, so as not to cause excessive resistance. The above-mentioned ratio of the thickness of the center fins to the thickness of the side fins is also the best relationship obtained through experiments and numerical simulations, and the best heat exchange effect is achieved while ensuring resistance.

[0034] As an option, the center fins and the side fins are staggered.

[0035] like Figure 2 As shown, the fish scale bionic fin is perpendicular to the axis of the inner wall and parallel to the direction of fluid flow. As an improvement, the fish scale bionic fin is inclined to the axis of the inner wall, that is, the angle is less than 90°, that is, it is inclined to the direction of fluid flow. When the fluid in the annular flow channel flows from the top to the bottom, the angle between the fish scale bionic fin and the axis of the inner wall becomes smaller and smaller, that is, the angle of inclination with the direction of fluid flow becomes larger and larger, that is, the inclination of the fish scale bionic fin to the fluid flow becomes larger and larger. The main reason is that the cold fluid flows faster and faster due to gravity, so it is inevitable to slow down its flow speed so that it can reach a uniform flow. Therefore, the change of the inclination angle can make the fluid flow as uniform as possible, thereby improving the heat exchange effect.

[0036] As an improvement, when the fluid in the annular flow channel flows from the top to the bottom, the angle between the fish scale bionic fin and the axis of the inner wall becomes smaller and smaller, that is, the angle between the fish scale bionic fin and the flow direction of the fluid becomes larger and larger. Because with the acceleration of gravity, the flow rate will increase. Such a setting can further improve the heat exchange effect.

[0037] As an improvement, the distribution density of the fish scale bionic fins in the annular flow channel where the fluid flows from the upper part to the lower part is greater than the distribution density of the annular flow channel where the fluid flows from the lower part to the upper part. That is, when the inlet of the annular flow channel is located at the upper part (top end), the inlet of the adjacent annular flow channel is located at the lower part (bottom end), and the distribution density of the fish scale bionic fins whose inlet is located at the upper part of the annular flow channel is greater than that whose inlet is located at the lower part. Because when the upper part flows downward with the help of gravity, the flow resistance is small, and when it flows from the bottom to the top, the flow resistance is large, so by setting the fin density, uniform flow is achieved through the change of flow resistance, and pressure is balanced, thereby promoting heat exchange.

[0038] As an improvement, the heat exchanger is used as a radiator. The inner ring formed by the inner wall is a heat source, and the heat source dissipates heat outward through the internal flow channel. The cold fluid in the internal flow channel is air or water.

[0039] As a preference, an observation hole is provided on the outer wall, such as Figure 1 As shown, it is used to observe the internal fluid flow conditions.

[0040] As an improvement, the heat exchanger of the present invention is applied to heat dissipation of a motor. The motor is arranged in the inner ring formed by the inner wall.

[0041] Existing motor cooling systems are mainly divided into air cooling and water cooling systems. Air cooling systems do not require too complicated auxiliary facilities, but cannot meet the heat dissipation requirements of high power density motors. Liquid cooling systems mostly rely on liquids with physical parameters superior to gases, such as water, oil, etc., and can produce very good cooling effects with the help of auxiliary settings. Traditional liquid cooling methods usually set evaporators or flow channels outside the casing, and the coolant is far away from the heat source, which has poor heat dissipation effects for the rotor and stator. Another way is to insert cooling pipes on the stator, such as inserting cooling pipes into the stator slots and stator yokes. Although this cooling method shortens the distance to the heat source, the cooling pipes in the slots take up a lot of space and are not suitable for motors with multi-slot stators. The structure is complex and the assembly is difficult. Another way is for the coolant to directly contact the heat source inside the motor. Although this cooling method has a better effect, it has high requirements for sealing, many cooling device components, complex cooling structure, high cost, and the cooling medium can only be oil.

[0042] The heat exchanger of the present application is used to dissipate heat from the motor. The bottom of the casing is directly bonded to the stator through heat-conducting material. The heat emitted by the stator is conducted from the bottom of the casing to the internal flow channel wall and the fish-fin-shaped bionic fins. At the same time, the fluid flows in from the inlet on the top of the casing, and then is split under the action of gravity, flowing downward through the right flow channel and the left flow channel respectively, and then intersects at the bottom, and enters the next annular flow channel through the bottom opening channel. Under the action of pressure, the fluid is split upward again and intersects at the top, and enters the next annular flow channel through the top opening channel again. The flow is repeated and finally flows out at the outlet on the top of the casing. During the flow process, the working medium conducts convection heat exchange with the bottom of the flow channel and the fish-fin-shaped bionic fins distributed in the flow channel, and takes away the heat of the heat-generating components such as the stator bonded to the bottom of the casing.

[0043] like Figure 1 As shown, the two-phase heat dissipation housing comprises an outer shell 1 and an internal flow channel 2, and the outer shell 1 is provided with a fluid inlet 2-3 and a fluid outlet 2-4. Figure 2 As shown, the internal flow channel 2-2 is a U-shaped structure, which is formed by the left flow channel 2-5 and the right flow channel 2-6 connected in parallel. The internal flow channel is provided with fish fin-shaped bionic fins 2-8, and the protrusions of the fish fin-shaped bionic fins in adjacent flow channels are in opposite directions.

[0044] like Figure 2 As shown, the fluid inlet 2-3 and the fluid outlet 2-4 of the internal flow channel are arranged at the top of the heat dissipation housing. Through such arrangement, the fluid can flow in the flow channel by gravity and make the fluid fully contact with the wall surface.

[0045] Flow channel structure Figure 2 As shown, it is divided into multiple annular flow channels 2-2 by an annular partition 2-1, and each annular flow channel is formed by a left flow channel 2-5 and a right flow channel 2-6 connected in parallel. Preferably, the width (length along the axial direction of the inner wall) of each flow channel is 12mm to 13mm, and the height (height along the radial direction of the inner wall) is 5mm to 6mm. The ratio of the two is required to be between 2 and 3, so as to ensure that the fluid has sufficient contact area with the flow channel near the inner wall. The thickness of the annular partition is 3.5mm to 4.5mm, and each annular partition is provided with an opening, and the circumferential span of each opening is 29° to 31°, so that the fluid in the parallel flow channels will have a small change in flow velocity when they meet and re-divided, so as to meet the optimal requirements of flow resistance and heat exchange.

[0046] like Figure 3As shown in the figure, fin-shaped bionic fins are distributed in each annular flow channel, and the middle fins and the side fins are staggered along the circumferential direction with an interval of 2.5° - 3.5°. The middle fins are located in the center of the flow channel, with a thickness of 1.5 - 1.8 mm. The side fins are symmetrically distributed on both sides of the middle plane of the flow channel. Axially, the center distance between the two side fins is 5 mm - 6 mm, and the thickness of each is 0.7 - 0.9 mm. The circumferential span of each fin is 14.5° - 15.5°, and the protrusion height at the top of the fin is 3.2 mm - 3.4 mm. The curvature radius of the first bending wall of the fin is 14 mm - 17 mm, and the corresponding arc length is 9 mm - 11 mm. The curvature radius of the second bending wall is 26 mm - 29 mm, and the corresponding arc length is 4 mm - 6 mm. The above optimal dimensions are the preferred dimensions obtained through a large number of numerical simulations and experimental studies, and can meet the best heat transfer requirements with a flow resistance of (600 - 700 pa).

[0047] It is found in experiments and numerical simulations that the protrusion height H at the top of the fin, the spacing of the fins, and the circumferential span of the fins cannot be too large or too small, otherwise the heat transfer effect will be poor or the resistance will be too large. Based on a large number of numerical simulations and experiments, the present invention has carried out the following optimizations to ensure the best heat transfer effect under the condition of a small increase in flow resistance:

[0048] As Figure 3 , assuming that the protrusion height at the top of the fin is H, the axial spacing of the side fins is S, and the circumferential span angle of the fins is A, the following requirements are satisfied: sinA = a - b*ln(H / S), where a and b are parameters, satisfying 0.1880 < a < 0.1890, 0.135 < b < 01.40, A is 14.5° - 15.5°, H is 3.2 mm - 3.4 mm, and S is 5 mm - 6 mm.

[0049] Preferably, a = 0.1884 and b = 0.138.

[0050] Through the above optimization design, the best heat transfer effect is achieved when the flow resistance is 600 - 700 Pa.

[0051] As Figure 2 shown, the fluid working medium flows in from the fluid inlet 2 - 3 at the top of the casing, and then is divided under the action of gravity, flowing downward through the left flow channel 2 - 5 and the right flow channel 2 - 6 respectively, and then converging at the bottom, entering the next annular flow channel through the bottom opening channel. Under the action of pressure, the fluid is divided upward again and converges at the top, and then enters the next annular flow channel through the top opening channel again. This repeated flow finally flows out from the fluid outlet 2 - 4 at the top of the casing. During the flow process, the working medium conducts convective heat transfer with the bottom of the flow channel and the fin-shaped bionic fins distributed in the flow channel, taking away the heat of the stator and other heating components in contact with the bottom of the casing.

[0052] Although the present invention has been disclosed as above with preferred embodiments, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. An annular shell and tube heat exchanger, the heat exchanger comprises an outer shell and an internal flow channel, the outer shell is provided with a fluid inlet and a fluid outlet, the outer shell comprises an inner wall and an outer wall, the inner wall is circular, the outer wall is polygonal or circular, the center of the inner wall and the center of the outer wall are the same point; an internal flow channel is formed between the inner wall and the outer wall, a plurality of annular dividing pieces are arranged in the internal flow channel, so that the internal flow channel is divided into a plurality of annular flow channels in the axial direction, the inlet and the outlet of the annular flow channel are respectively arranged at opposite ends, so that the annular flow channel is a U-shaped structure, each annular The flow channel is formed by connecting the flow channels on both sides in parallel; an opening is arranged on the annular dividing piece, so that two adjacent annular flow channels form a series structure through the opening; a fish fin-shaped bionic fin is arranged in the annular flow channel, and the fish fin-shaped bionic fin is arranged on the inner wall and extends from the inner wall to the outer wall; the fish fin-shaped bionic fin includes a first curved wall and a second curved wall connected to each other, wherein the length of the first curved wall is greater than the length of the second curved wall, and the bending radius of the first curved wall is smaller than the bending radius of the second curved wall; viewed along the axial direction, the protrusions of the fish fin-shaped bionic fins in adjacent flow channels are in opposite directions.

2. The shell and tube heat exchanger according to claim 1, characterized in that: The fluid inlet and the fluid outlet are arranged at the top end of the housing.

3. The shell and tube heat exchanger according to claim 1, characterized in that: A circle of circumferential center fins located in the center of the flow channel and two circles of side fins distributed on both sides of the center fins are arranged in the annular flow channel. The height of the center fin is the same as that of the side fins, and the width of the center fin is 1.5-2.5 times the width of the side fins.

4. The shell and tube heat exchanger according to claim 3, characterized in that: The center fins and side fins are staggered.

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