Full-flow-channel zero-bypass concentric sleeve reverse flow type heat exchanger
With the full-flow-channel zero-bypass concentric shell counter-flow heat exchanger, the fluid flows purely axially within the closed pipe, completely eliminating bypass and dead zones. This solves the problems of low efficiency and complex structure of traditional shell-and-tube heat exchangers, achieving efficient and precise heat transfer and counter-flow heat exchange.
Patent Information
- Application Number
- CN202511794774.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-01-09
AI Technical Summary
Traditional shell-and-tube heat exchangers suffer from problems such as low utilization of heat transfer temperature difference due to shell-side bypass flow, complex and bulky structure, small heat transfer area per unit volume, and complex and error-prone calculation of heat transfer and resistance. Existing technologies cannot completely eliminate bypass flow.
The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger consists of concentric tube units, tube sheets, tube boxes, inlet/outlet pipes and end caps. The fluid flows purely axially within the closed pipes. Counter-flow heat exchange is achieved by rationally arranging the fluid flow direction, completely eliminating bypass and dead zones.
It achieves 100% fluid participation in effective heat exchange, significantly improves heat transfer efficiency, reduces pressure, has a simple and compact structure, is accurately designed and calculated, adapts to multi-media and multi-process heat exchange, and has a wide range of applications.
Smart Images
Figure CN121297541A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of heat exchange equipment, and particularly relates to a full-flow zero-bypass concentric double-pipe counterflow heat exchanger. BACKGROUND
[0002] The shell-and-tube heat exchanger is the most widely used heat exchange equipment in the industry. However, the conventional shell-and-tube heat exchanger, whether adopting the segmental baffle, the helical baffle or the rod support structure, has inherent and difficult-to-overcome structural defects, mainly including:
[0003] 1. Shell-side bypass flow: Fluid inevitably forms multiple bypass flows in the gaps between the baffle and the inner wall of the shell, the tube bundle and the inner wall of the shell, and the tube bundle and the tube hole of the baffle. Studies have shown that the flow not participating in effective heat exchange accounts for 10% to 40% of the total flow, significantly reducing the efficiency of the heat exchanger.
[0004] 2. Complex structure and high manufacturing cost: In order to suppress the above-mentioned bypass flow, the prior art usually needs to set up complex sealing structures such as sealing strips, lining tubes and bypass baffles, which not only increases the complexity of the structure, but also increases the manufacturing, installation and maintenance costs.
[0005] 3. Large pressure drop and fluid-induced vibration: The baffle causes the shell-side fluid to repeatedly scour the tube bundle transversely, resulting in a large pressure loss and easily inducing tube bundle vibration, leading to tube material fatigue damage and noise.
[0006] 4. Low utilization rate of heat transfer temperature difference: The existence of bypass flow and cross flow makes the flow mode of the shell-side fluid unable to achieve pure counterflow, resulting in a logarithmic mean temperature difference (LMTD) correction coefficient F usually less than 0.8, causing irreversible thermodynamic loss.
[0007] 5. Difficulty in design calculation: Due to the complexity and uncertainty of the shell-side bypass flow, it brings great difficulty to the accurate design and performance prediction of the heat exchanger, and the design result often has a large error.
[0008] Although the prior art attempts to "reduce" bypass by improving the baffle form or adding sealing elements, it cannot "eliminate" bypass. The fundamental reason is that the "shell side" structural concept itself means that there are geometric gaps that cannot be eliminated. Therefore, there is an urgent need in the field for a new heat exchanger structure that can fundamentally eliminate fluid bypass, short circuit and dead zone. SUMMARY
[0009] The purpose of this invention is to provide a full-flow-channel zero-bypass concentric tube counter-flow heat exchanger, so as to completely solve a series of difficult problems existing in traditional shell-and-tube heat exchangers, such as low heat transfer temperature difference utilization rate due to shell-side bypass, complex structure, bulky, small heat transfer area per unit volume, complex heat transfer and resistance calculation, and large error.
[0010] To achieve the above objectives, the present invention adopts the following technical solution: a full-flow-channel zero-bypass concentric tube counter-flow heat exchanger, comprising concentric tube units, tube sheets, tube boxes, inlet / outlet pipes, and end caps at both ends of the heat exchanger, etc. The concentric tube unit is composed of at least two coaxially nested heat exchange tubes of different diameters and lengths, forming a circular and multi-layered annular flow channel; the innermost central heat exchange tube constitutes the first layer of flow channel, and from the inside out, the annular channels formed between every two layers of heat exchange tubes successively constitute the second layer of flow channel, the third layer of flow channel, etc.; the space outside the outermost heat exchange tube can also be used as a flow channel for a fluid. Several concentric tube units are arranged in parallel. The ends of several heat exchange tubes in each flow channel of each concentric tube unit are connected to the corresponding tube sheet. The tube sheet can be a circular or square tube sheet with flanges, or a circular or square tube sheet without flanges. Adjacent tube sheets are connected by a tube box, isolating each flow channel into its own independent heat exchange chamber. The tube box can be a circular or square cylinder, or a cylinder with a circular or square flange at one end or both ends. Fluid inlet / outlet pipes are arranged on the tube box. Each stream of fluid participating in heat exchange enters its corresponding chamber through the inlet / outlet pipes and flows axially within its independent flow channel. Indirect heat exchange is achieved between the fluids through the tube walls. By rationally arranging the fluid flow direction, counter-current heat exchange between two or more complex streams can be achieved. Since all fluids flow within a completely closed, single pipe, the possibility of any geometric bypass, short circuit, or flow dead zone is fundamentally eliminated.
[0011] Furthermore, the heat exchange tubes of the concentric tube unit can be plain tubes, finned tubes, corrugated tubes, threaded tubes, composite high-throughput sintered tubes, or grooved tubes of various shapes, or scientifically combined with each other, or longitudinal fins can be set on the surface of the inner and outer plain tube heat exchange tubes or in the annular channel formed by their nesting; the fin shape can be straight, straight perforated, corrugated, serrated, etc.; the outer surface of the outermost heat exchange tube can also be arranged with transverse circular or square fins.
[0012] Furthermore, one or more baffles are installed within each tube sheet or end cap. These baffles divide the heat exchange chamber into multiple independent sub-channel chambers, each equipped with inlet / outlet pipes to achieve heat exchange for multiple media, multiple fluids, or multiple flow paths. Further, the innermost central heat exchange tubes are divided into two or more groups, separated by baffles. Each group of heat exchange tubes extends from the end cap, further dividing the first-layer flow path into several independent sub-channels. Each group of sub-channels is then connected to a corresponding tube sheet, with end caps equipped with inlet / outlet pipes on the tube sheet, achieving heat exchange for multiple media, multiple fluids, or multiple flow paths. This structure is more suitable for heat exchange conditions where cross-leakage between fluids is strictly prevented.
[0013] Furthermore, the connection between the two ends of several heat exchange tubes in each flow channel of each concentric tube unit and the corresponding tube sheet can be welding, expansion joint, or a combination of expansion and welding. Each layer of heat exchange tubes can also be tightly sealed to the corresponding tube sheet with nuts. Further, each layer of heat exchange tubes in several concentric tube units is arranged with perforated bridges on the corresponding tube sheet and welded to the tube sheet; the outermost outer tubes can also be arranged closely tangentially without perforated bridges, and the outermost outer tubes are directly welded to the tube sheet with honeycomb perforations. The gaps between adjacent outer tubes are sealed by welding and / or filling to form a self-supporting honeycomb structure. Regardless of the arrangement, the pressure inside the tubes is borne by the outer tubes, eliminating the need for a traditional shell-and-tube heat exchanger shell. Alternatively, a traditional shell can be retained if necessary.
[0014] Furthermore, when the heat exchanger retains the shell of a traditional shell-and-tube heat exchanger, the space inside the shell and outside the outer tube can also serve as a shell-side flow channel for the heat exchange fluid, making full use of the outer surface area of the outer tube and further improving the compactness of the heat exchanger and the heat exchange efficiency of the fluid.
[0015] Furthermore, the heat exchanger can be designed as a fixed tube sheet structure, or as a floating tube sheet structure with a stuffing box seal for compensating for thermal expansion and / or for ease of maintenance and repair. The heat exchanger can be round, square, or other shapes that meet the requirements.
[0016] Beneficial effects
[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0018] 1. Zero bypass, high heat transfer efficiency: Since all fluids flow in a completely closed pipe, 100% of the fluids participate in effective heat exchange, completely eliminating the existence of bypass flow, short circuit and dead zone, and greatly improving heat transfer efficiency.
[0019] 2. The fluid flows purely axially within each channel, achieving pure countercurrent heat exchange through reasonable arrangement. The temperature difference is fully utilized, making the logarithmic mean temperature difference correction coefficient F approach 1, maximizing the utilization of the heat transfer temperature difference and reducing irreversible losses.
[0020] 3. Simple and compact structure with low material consumption: It eliminates the shell, which is the most consumable material in the heat exchanger, as well as complex internal components such as baffles, tie rods, spacers, sealing strips, and baffles. It also eliminates the material waste caused by the artificially increased heat exchange area due to the bypass.
[0021] 4. Low pressure drop, no flow-induced vibration, and low temperature stress: The fluid flows in laminar or turbulent axial direction, avoiding lateral scouring, resulting in low flow resistance and low pressure drop; the heat exchanger tube bundle has low temperature stress because it is not constrained by the shell; and the outermost heat exchange tubes support each other, making the structure robust and fundamentally eliminating fluid-induced vibration of the tube bundle, ensuring safe and reliable operation and long service life.
[0022] 5. Accurate and reliable design calculations: The flow channel geometry is regular and well-defined, with no uncertain bypass flow. Heat transfer and resistance calculations can be based on classical in-pipe flow formulas, resulting in accurate design results with small errors.
[0023] 6. High flexibility and modularity: By increasing or decreasing the number of concentric sleeve layers and the baffles inside the tube box, multiple chambers can be formed to adapt to multi-flow and complex flow heat exchange; through modular combination, it is easy to realize micro-channel, large-scale, high temperature and high pressure conditions; maintenance and cleaning are also more convenient and flexible.
[0024] 7. The heat exchanger described in this invention combines the advantages of traditional tubular heat exchangers, plate-fin heat exchangers, shell-and-plate heat exchangers, finned heat exchangers, and coaxial heat exchangers, while overcoming their shortcomings, and is suitable for heat exchange of various media and complex working conditions. Attached Figure Description
[0025] Figure 1 This is a structural diagram of a double-layer concentric sleeve unit according to an embodiment of the present invention, wherein longitudinal fins are arranged in the annular channel.
[0026] Figure 2 yes Figure 1 A top view; the arrows indicate the direction of fluid flow.
[0027] Figure 3 This is a structural diagram of a three-layer concentric tube unit according to an embodiment of the present invention, wherein longitudinal fins are arranged in the annular channel and transverse fins are arranged on the outermost heat exchange tube.
[0028] Figure 4 yes Figure 3 A top view; the arrows indicate the direction of fluid flow.
[0029] Figure 5 This is a cross-sectional view of the assembly structure of a heat exchanger of the present invention, which has two streams, a fixed tube sheet, countercurrent heat exchange, and no shell, according to an embodiment of the present invention.
[0030] Figure 6 yesFigure 5 ee sectional view.
[0031] Figure 7 This is another embodiment of the present invention: a four-flow, shell-less, floating tube sheet type heat exchanger.
[0032] Figure 8 yes Figure 7 The top view shows that the heat exchanger has a square shape.
[0033] Figure 9 yes Figure 7 The SS cross-sectional view shows the second layer (B) flow channel heat exchange tubes arranged in a honeycomb pattern with closely tangential triangular bridges on a square tube sheet. It also shows the outermost outer tubes directly welded to the square tube sheet with honeycomb-shaped perforations. Adjacent outer tubes are arranged closely and tangentially, and the gaps between the outer tubes are sealed by welding and / or filling to form a self-supporting honeycomb structure.
[0034] Figure 10 This is a heat exchanger with three streams, a fixed tube sheet, and a traditional shell, implemented in an embodiment of the present invention.
[0035] Figure 11 yes Figure 10 The ff sectional view shows the inner tube connected to the tube sheet with nuts and washers. Detailed Implementation
[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0037] Example 1
[0038] like Figure 1 , Figure 2 As shown, the concentric tube unit (1) of the present invention consists of two heat exchange tubes of different diameters and lengths nested together to form a circular channel (A) and an annular channel (B). Longitudinal heat exchange fins are arranged in the annular channel. Figure 5 The embodiment shown is a two-stream, fixed tube sheet, shell-less, full-flow-channel, zero-bypass concentric tube counter-flow heat exchanger, consisting of a tube unit (1), tube sheet (2), tube box (3), inlet and outlet pipes (4), end caps (5), and several tubes. Figure 1 , Figure 2The concentric tube units (1) shown are arranged in parallel. The two ends of the heat exchange tubes of the first flow channel (A) are welded to the corresponding tube sheets (2). The outer heat exchange tubes of the second flow channel (B) are arranged closely and tangentially, and are also welded to the corresponding tube sheets (2) at both ends. The gap between the outer tubes is sealed and welded. The adjacent tube sheets (2) at both ends are welded to the tube box (3). The two tube boxes are equipped with inlet / outlet pipes (4). The tube sheets (2) at both ends of the heat exchanger are equipped with end caps (5). The end caps (5) are arranged with inlet / outlet pipes (4). The two tube boxes form a fixed tube sheet, shell-less, full-flow-channel zero-bypass concentric tube counter-flow heat exchanger. One fluid enters flow channel (A) from the inlet pipe (4) of one end cap (5) of the heat exchanger and exits from the outlet pipe (4) of the other end cap (5). The other fluid enters flow channel (B) from the inlet pipe of one end tube box (3) of the heat exchanger and exits from the outlet pipe (4) of the other end tube box (3). The fluids flow in a counter-current arrangement, achieving pure counter-current heat exchange between the two fluids. (Appendix) Figure 6 It is attached Figure 5 The cross-sectional view shows the heat exchange tubes of the second flow channel (B) arranged closely and tangentially, forming a honeycomb-shaped self-supporting structure. Longitudinal fins are arranged between the inner and outer heat exchange tubes. The structure is compact, with a large heat exchange area per unit volume and a robust structure. It is particularly suitable for heat exchange between clean gases or lubricating oil and water with large differences in heat release coefficients on both sides.
[0039] Example 2
[0040] like Figure 7 The figure shows a cross-sectional view of a four-flow, shell-less, floating tube sheet type full-flow-channel zero-bypass concentric tube counter-flow heat exchanger. The difference between this embodiment 2 and embodiment 1 is that, in order to compensate for thermal expansion caused by temperature difference or for convenient inspection and maintenance, the tube sheets (2) at both ends of the heat exchanger are designed as floating tube sheet structures, and the dynamic sealing connection between the end cover (5), floating tube sheet (2), and tube box (3) is achieved through the stuffing box (6). The end cover (5) and tube box (3) can be disassembled. In order to realize heat exchange between the four fluids, a partition (7) is set in the end cover (5) and tube box (3). The partition (7) isolates the several first flow channels (A) and (B) fixed on the tube sheet (2) into two groups of A1, A2: B1, B2 sub-flow channel chambers respectively. An inlet / outlet pipe (4) is set on each sub-chamber. The four different fluids enter the A1, A2; B1, B2 sub-flow channels respectively. The fluid flow direction is arranged in counterflow, realizing the complex heat exchange of four fluids in the full-flow zero-bypass concentric tube counterflow heat exchanger of this invention. Since the end cap (5) and tube box (3) can be disassembled, they are suitable for occasions where the heat exchange medium has a lot of dirt, needs to be cleaned regularly, or the temperature difference between the fluids on both sides is large.
[0041] Figure 8 yes Figure 7 The top view shows that the heat exchanger has a square shape.
[0042] Figure 9 yes Figure 7 The cross-sectional view of the SS shows that the heat exchange tubes of the second flow channel (B) are arranged in a triangular, non-porous bridge arrangement on the square tube sheet. The outermost tube is directly welded to the square tube sheet with honeycomb holes. The gaps between the outer tubes are bonded by sealing welding and / or filling to form a self-supporting honeycomb structure.
[0043] Example 3
[0044] like Figure 10 The figure shows a cross-sectional view of a three-flow, fixed tube sheet, concentric tube (1) counter-flow heat exchanger with detachable inner tubes and zero bypass. The outer tube heat exchange tube of the concentric tube unit (1) is arranged in a hole bridge on the tube sheet (2), and its two ends are welded and sealed to the corresponding tube sheet (2). It is installed into the conventional tube heat exchange shell (8) and sealed and welded. Then, the two tube sheets (2) to be connected to the two ends of the inner tube are welded to the two ends of the shell (8). The inner tube is concentrically inserted into the outer tube through the hole of the tube sheet (2) and comes out from the tube hole of the other end of the tube sheet (2). The two ends of the inner tube heat exchange tube are threaded, and the two ends of the inner tube are locked and sealed to the tube sheet (2) by means of nuts and washers. To fully utilize the heat exchange area outside the outer tube, the space outside the outer tube and inside the shell (8) is used as a shell-side flow channel for the heat exchange fluid. Fluid inlet / outlet pipes (4) are added to the shell (8). To increase the length and turbulence of the shell-side fluid flow channel, a traditional spiral baffle component is added to the shell side. The heat exchange area outside the outer tube is fully utilized, further improving the compactness of the heat exchanger and the heat exchange efficiency of the fluid. End caps (5) are fitted at both ends of the heat exchanger to realize the full-channel zero-bypass concentric tube counter-flow heat exchanger of this invention. This type of heat exchanger is suitable for heat exchange in conditions where the two heat exchange media have many impurities, are prone to scaling, and are prone to coking, such as heat exchangers for crude oil, residue oil, and recycled oil in oil refineries. It can significantly improve the heat exchange efficiency and service life of the heat exchanger. It also greatly reduces the difficulty of heat exchanger maintenance and cleaning. Figure 11 yes Figure 10 The ff sectional view shows the sealing connection diagram of the inner tube and the tube sheet (2) with nuts and gaskets.
[0045] The above-described embodiments are merely examples of specific implementations of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A full-flow-channel zero-bypass concentric tube counter-flow heat exchanger, comprising a concentric tube unit (1), a tube sheet (2), a tube box (3), inlet and outlet pipes (4), and end caps (5), characterized in that, The concentric tube unit (1) consists of at least two coaxially nested heat exchange tubes of different diameters and lengths, forming a circular and multi-layered annular flow channel; the innermost central heat exchange tube constitutes the first flow channel (A), and from the inside out, the annular channels formed between every two layers of heat exchange tubes successively constitute the second flow channel (B), the third flow channel (C), and the space outside the outermost heat exchange tube can also be used as a fluid flow channel; several concentric tube units (1) are arranged in parallel, and the two ends of several heat exchange tubes in each flow channel are respectively connected to the tube sheet (2) of the corresponding layer; the tube sheet (2) can It can be a round or square tube sheet with flanges, or a round or square tube sheet without flanges; two adjacent tube sheets (2) are connected by a tube box (3); the tube box (3) can be a round or square cylinder, or a cylinder with a round or square flange at one end or with round or square flanges at both ends, which isolates each flow channel into its own independent heat exchange chamber; fluid inlet / outlet pipes (4) are arranged on the tube box (3); end caps (5) are arranged on the tube sheets (2) at both ends of the heat exchanger to form a fixed tube sheet type or stuffing box sealed floating head type full flow channel zero bypass concentric sleeve counterflow heat exchanger.
2. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claim 1, characterized in that, The heat exchange tubes of the concentric tube unit (1) are plain tubes, finned tubes, corrugated tubes, threaded tubes, composite high-throughput sintered tubes, or tubes with grooves of various shapes or scientific combinations thereof; or longitudinal fins are provided on the inner and outer surfaces of the inner and outer plain tube heat exchange tubes or in the annular channel formed by their nesting, or transverse circular or square fins are provided on the outermost heat exchange tube.
3. The concentric tube unit (1) according to claim 2, wherein longitudinal fins are provided on the surfaces of the inner and outer smooth tube heat exchange tubes or within the annular channel formed by their nesting, characterized in that, The shape of the fins can be straight, straight with holes, corrugated, or serrated longitudinal fins, etc.
4. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claim 1, characterized in that, One or more baffles (7) are provided inside the tube box (3) and end cap (5). The baffles (7) divide the flow channels of several heat exchange chambers in this layer into multiple independent sub-flow channel chambers such as A1, A2, B1, B2... Each sub-flow channel chamber is equipped with inlet / outlet pipes to realize heat exchange of multiple media, multiple streams of fluid, or multiple processes.
5. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claim 1, characterized in that, The first flow channel (A) of the innermost central heat exchange tube of several tube units (1) is divided into two or more groups. Each group is led out from the end cap (5) and connected to the corresponding tube sheet (2). The A flow channel is divided into several A1, A2... multiple sub-flow channels.
6. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claim 1, characterized in that, The heat exchange tubes of multiple concentric tube units (1) are welded to the corresponding tube sheets, and are connected by expansion joint or expansion welding combination; the heat exchange tubes of each flow channel can also be locked and sealed to the corresponding tube sheet with nuts and washers. The two ends of the heat exchange tubes in this structure are threaded.
7. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claim 1, characterized in that, Each layer of heat exchange tubes in several concentric tube units (1) is arranged in a perforated bridge pattern on the corresponding tube sheet (2); the outermost heat exchange tubes can also be arranged tangentially and sealed and welded to the tube sheet (2), with the gaps between the tubes sealed by welding and / or filled to form a self-supporting honeycomb structure. Regardless of the arrangement, when the pressure inside the tubes is borne by the outer tubes, the shell of the traditional shell-and-tube heat exchanger (8) can be eliminated, or the shell of the traditional shell-and-tube heat exchanger (8) can be retained as needed.
8. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claims 1 and 7, characterized in that, The heat exchanger retains the shell (8) of the traditional shell-and-tube heat exchanger as needed. Outside the outer tube, the shell can also serve as a shell-side flow channel for fluid.
9. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claims 1 and 8, characterized in that, The heat exchanger can be a fixed tube sheet type at one end and a floating tube sheet type at the other end; it can also be a heat exchanger structure with fixed tube sheets at both ends or floating tube sheets at both ends, etc.
10. The full-flow-channel zero-bypass concentric tube counter-flow heat exchanger according to claims 1, 7, 8, and 9, characterized in that, The heat exchanger is in a shape suitable for manufacturing and installation, such as round or square.