A flat tube microchannel heat exchanger

Abstract

The present invention provides a flat tube microchannel heat exchanger, wherein the heat exchange tubes are flat tubes, comprising a first flat tube and a second flat tube. The housing comprises a first wall surface and a second wall surface, the first wall surface and the second wall surface being arranged opposite each other. The first flat tube extends longitudinally from the first wall surface of the housing toward the second wall surface, with a first gap therebetween. The second flat tube extends longitudinally from the second wall surface of the housing toward the first wall surface, with a second gap therebetween. The first and second flat tubes are arranged alternately. The present invention enables fluid to pass through all flat areas of the heat exchange tubes even at low flow rates, thereby increasing the heat exchange flow area and enhancing heat transfer.

Description

Technical Field

[0001] The invention relates to a heat exchanger, belonging to the technical field of heat exchangers, in particular to the field of flat tube microchannel heat exchangers. Background Art

[0002] Heat exchangers are widely used in industrial production, playing a vital role in various sectors, including chemical, power, metallurgy, construction, machinery manufacturing, food, medicine, and aerospace. Therefore, optimizing heat exchanger design to improve heat transfer efficiency is essential for these industries. For the automotive industry, optimizing the design of exhaust gas recirculation coolers to improve heat transfer efficiency and reduce nitrogen oxide emissions, ensuring that exhaust emissions meet increasingly stringent emission standards, is a pressing issue.

[0003] Due to limitations in manufacturing processes and technological advancements, early heat exchangers, such as coiled-tube heat exchangers, could only adopt simple structures, resulting in small heat transfer areas, large volumes, and heavy weight. With the advancement of manufacturing processes, shell-and-tube heat exchangers have a larger heat transfer area per unit volume and better heat transfer performance, and have long been a typical heat exchanger in industrial production. Plate heat exchangers appeared in the 1920s and were used in the food industry. Heat exchangers constructed with plates instead of tubes offer a compact structure and excellent heat transfer performance. Since the 1980s, a large number of enhanced heat transfer components have been introduced to the market, and manufacturing processes for heat exchangers such as plate and shell heat exchangers have been further refined, driving the rapid development and widespread application of compact heat exchangers.

[0004] The variety of heat exchangers used in industrial production is vast, requiring careful selection based on practical application. Plate and shell heat exchangers offer a wide range of applications, strong adaptability, simple structure, and low cost, offering significant advantages in both quality and compactness. Flat tube heat exchangers have been widely used in automotive air conditioning units and residential and commercial air conditioning heat exchangers in recent years. These flat tubes offer a large heat transfer area, significantly improving heat transfer efficiency.

[0005] A microchannel heat exchanger (MCHE) has channels with an equivalent diameter of 10-1000μm. It consists of two manifolds, multiple flat tubes, and fins. The flat tubes contain dozens of microscopic channels, each connected to a circular manifold at each end. The manifolds are typically placed vertically, with horizontal baffles installed inside to separate the heat exchanger's flow paths into several separate flow paths.

[0006] In conventional plate and shell heat exchangers, the shell-side fluid flows transversely across the flat surfaces of the flat tubes, thus flowing perpendicularly to the fluid within the tubes. This flow pattern causes some areas outside the flat tubes to not participate in heat exchange or to participate only slightly due to uneven fluid distribution within the shell, resulting in heat short-circuiting in some areas. Therefore, the present invention designs a new heat exchanger that improves the structure of traditional plate and shell heat exchangers to enhance heat transfer. Summary of the Invention

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] A flat tube microchannel heat exchanger, the shell and tube heat exchanger includes a tube side and a shell side, the tube side includes an inlet head, an outlet head, a tube sheet and a heat exchange tube, both ends of the heat exchange tube are fixedly mounted on the tube sheet, the tube side fluid enters the flat tube from the inlet head and then flows out from the outlet head; the shell side includes a shell, the shell side fluid enters from the shell side inlet on the shell, and then flows out from the shell side outlet on the shell after heat exchange with the tube side fluid; it is characterized in that the heat exchange tube is a microchannel flat tube, the flat tube includes a first flat tube and a second flat tube, the shell includes a first wall surface and a second wall surface, the first wall surface and the second wall surface are arranged opposite to each other, wherein the length direction of the first flat tube starts from the first wall surface of the shell and extends to the second wall surface, with a first gap between the first flat tube and the second wall surface, the length direction of the second flat tube starts from the second wall surface of the shell and extends to the first wall surface, with a second gap between the first flat tube and the first wall surface, and the first flat tube and the second flat tube are alternately arranged in the flow direction of the shell side fluid.

[0009] As an improvement, the tube sheet is arranged horizontally, and the tube-side fluid in the heat exchange tube flows in the up-down direction.

[0010] As an improvement, the inlet head is located at the upper part, the outlet head is located at the lower part, and the inlet and outlet of the shell side are located at the left and right parts.

[0011] As an improvement, the length of the first gap and the second gap is 68-84% of the distance between the first wall and the second wall.

[0012] As an improvement, the inlet for the shell-side fluid is arranged on a side of the shell close to the first wall surface, and the first flat tube is close to the inlet for the shell-side fluid.

[0013] As an improvement, the outlet of the shell-side fluid is arranged on a side of the shell close to the second wall surface, and the second flat tube is close to the outlet of the shell-side fluid.

[0014] As an improvement, the tube-side fluid is liquid and the shell-side fluid is gas.

[0015] As an improvement, the tube-side fluid is water and the shell-side fluid is exhaust gas.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] In the present invention, the shell-side fluid flows along the length (height) of the flat tubes, and the flow directions of the tube-side fluid and the shell-side fluid are parallel. Because the first and second flat tubes are arranged at intervals, a similar baffle effect is formed, so that the fluid flows along a tortuous path in the shell, allowing the fluid to pass through all areas of the flat tubes, thereby improving the heat exchange effect of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a schematic diagram of the overall structure of the heat exchanger of the present invention;

[0019] Figure 2 yes Figure 1 Schematic diagram of the flat tube arrangement structure viewed from above in a transverse section;

[0020] Figure 3 It is a schematic structural diagram of the flat tube arrangement of the heat exchanger of the present invention as viewed from the flat side. DETAILED DESCRIPTION

[0021] In this article, unless otherwise specified, “ / ” represents division, and “×” and “*” represent multiplication.

[0022] In the description of the present invention, the terms "left" and "right" are used based on the position or orientation relationship shown in the accompanying drawings, and do not indicate or imply that the described device or element must have a specific installation and operating orientation, and therefore cannot be understood as a limitation of the present invention.

[0023] The technical solutions in the embodiments of the present invention will be supplemented below with reference to the accompanying drawings in the embodiments of the present invention.

[0024] Figure 1-3 A flat tube shell and tube heat exchanger is disclosed. Figure 2 yes Figure 1 Transverse section ( Figure 1 Horizontal section in the Figure 1 Schematic diagram of the flat tube arrangement structure observed from above. The shell and tube heat exchanger includes a tube side and a shell side. The tube side includes an inlet head 1, an outlet head 2, a tube sheet 3 and a heat exchange tube 4. Both ends of the heat exchange tube 4 are fixedly mounted on the tube sheet 3. The tube side fluid enters the flat tube 4 from the inlet head 1 and then flows out from the outlet head 2. The shell side includes a shell 5. The shell side fluid enters from the shell side inlet 6 on the shell, and then flows out from the shell side outlet 7 on the shell after heat exchange with the tube side fluid. Figure 2-3As shown, the heat exchange tubes are flat tubes, preferably microchannel flat tubes. The flat tubes include a first flat tube 41 and a second flat tube 42. The shell includes a first wall 8 and a second wall 9, which are arranged opposite each other. The first flat tubes extend longitudinally from the first wall 8 to the second wall 9, with a first gap between them. The second flat tubes extend longitudinally from the second wall to the first wall, with a second gap between them. The first and second flat tubes are arranged alternately. The fluid in the shell side flows along the flat surfaces of the flat tubes.

[0025] In the present invention, the shell-side fluid flows along the length (height) of the flat tubes, and the flow directions of the tube-side fluid and the shell-side fluid are parallel. Because the first and second flat tubes are arranged at intervals, the fluid flows along a tortuous path in the shell, allowing the fluid to pass through all areas of the flat tubes, thereby improving the heat exchange effect of the heat exchanger.

[0026] The flat tube includes a first plane and a second plane, wherein a fluid flow cavity is formed between the first plane and the second plane. The distance between the first plane and the second plane is 5-70 microns, preferably 20-40 microns.

[0027] As an improvement, the tube sheet is arranged horizontally, and the tube-side fluid in the heat exchange tube flows in an up-down direction. The heads 1 and 2 are also arranged in an up-down direction, and the tube-side fluid can flow in from the top and out from the bottom, or flow in from the bottom and out from the top.

[0028] As an improvement, the inlet head 1 is located at the top, the outlet head 2 is located at the bottom, and the shell side inlet 6 and outlet 7 are located at the left and right, forming a cross flow between the fluids.

[0029] As an improvement, the length of the first gap and the second gap is 68-84% of the distance between the first wall and the second wall. If the gap is too short, the flow resistance will be too large. The length will also affect the heat transfer efficiency of the heat pipe and reduce the heat transfer area. If the depth exceeds 84%, the flow resistance will increase significantly, leading to higher costs.

[0030] As an improvement, the length of the first gap and the second gap is 75-80% of the distance between the first wall and the second wall. The above-mentioned optimization of the size can further increase the heat exchange efficiency while meeting the resistance requirement.

[0031] As an improvement, the shell-side fluid inlet is located on the side of the shell near the first wall, with the first flat tube located near the shell-side fluid inlet. As an improvement, the shell-side fluid outlet is located on the side of the shell near the second wall, with the second flat tube located near the shell-side fluid outlet. This coordinated arrangement allows the shell-side fluid to fully pass through the flat surfaces of the flat tubes for heat exchange.

[0032] As an improvement, the tube-side fluid is liquid and the shell-side fluid is gas.

[0033] As an improvement, the tube-side fluid is water and the shell-side fluid is exhaust gas.

[0034] As an improvement, the tubesheet is arranged vertically, and the tube-side fluid in the heat exchange tubes flows horizontally. Headers 1 and 2 also adopt a left-right orientation, allowing the tube-side fluid to flow in from the left and out from the right, or vice versa. The first wall 8 is located at the top, and the second wall 9 is located at the bottom. The inlet and outlet heads are located on the left and right. The shell-side fluid is a gas. Along the flow direction of the shell-side fluid, the length of the first gap gradually increases, while the length of the second gap gradually decreases.

[0035] During the research process, it was discovered that the heat exchange in the flat tubes was uneven across the cross-section in the direction of fluid flow. As the distance from the inlet increased, the gas density in the shell side decreased, causing the gas to flow upward, resulting in a significant increase in the gas volume in the upper portion. Therefore, it was necessary to design an improved heat exchange structure. The present invention varies the lengths of the first and second gaps along the direction of gas flow, causing the gas in the shell side to gradually decrease and move toward the upper portion as it flows, spending more time in the middle and lower portions. This enhances heat exchange in the center of the shell and the surrounding heat exchange tubes in the lower portion of the shell, changing the previous heat exchange method and increasing the heat exchange efficiency at different locations. This results in uniform heat exchange overall, further achieving the goal of enhanced heat transfer.

[0036] As an improvement, along the flow direction of the fluid in the shell side, the first gap length gradually increases in amplitude, while the second gap length gradually decreases in amplitude. By changing the amplitude, the overall heat exchange can be further uniformed, further achieving the purpose of enhanced heat transfer.

[0037] As an improvement, the spacing between adjacent flat tubes increases from the inlet to the center of the shell, along the direction from the inlet to the outlet. Then, the spacing between adjacent flat tubes decreases from the center to the outlet. This is because during heat exchange, the heat transfer between the hot and cold fluids is relatively uniform along the flow direction, resulting in the best overall heat transfer effect. However, experiments and simulations have found that the heat transfer in the center is significantly greater than that at the inlet and outlet. Therefore, by varying the spacing between the flat tubes, the heat transfer area also changes regularly. This area variation compensates for the uneven heat transfer, further improving heat transfer efficiency.

[0038] As an improvement, the spacing between adjacent flat tubes increases from the shell inlet to the middle. Then, the spacing decreases from the middle to the shell outlet. This variation in spacing makes the heat transfer per unit area of the entire fluid flow more uniform, further improving heat transfer efficiency.

[0039] The inlet end cap is provided with a tube-side fluid inlet 12, and the outlet end cap is provided with a tube-side fluid outlet 13. As an improvement, internal fins are provided on the inner wall of the flat tube, projecting outward from the inner wall of the flat tube. The internal fins increase the heat exchange area and enhance heat exchange within the tube.

[0040] As an improvement, the inner fins are distributed at different densities within different flat tubes. The closer the flat tube is to the inlet 12, the greater the density of the inner fins within the flat tube. This arrangement increases the resistance to fluid flow as the inner fins are more numerous the closer the flat tube is to the inlet 12. This forces the fluid to flow toward the heat exchange tubes with less resistance, and toward the heat exchange tubes farther from the inlet, resulting in even fluid distribution.

[0041] As an improvement, the distribution density of the inner fins in the flat tube increases as the distance from the inlet 12 increases. Experiments have shown that increasing the distribution density can make the fluid distribution more uniform.

[0042] As an improvement, the distribution density of the fins in the heat exchange tube closest to the inlet 12 is 1.8-2.0 times, preferably 1.9 times, the distribution density of the fins in the heat exchange tube farthest from the inlet 12 .

[0043] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A flat tube microchannel heat exchanger, comprising a tube side and a shell side, wherein the tube side comprises an inlet head, an outlet head, a tube sheet, and heat exchange tubes, both ends of the heat exchange tubes being fixedly mounted on the tube sheet, and the tube side fluid enters the flat tubes from the inlet head and then flows out from the outlet head; the shell side comprises a shell, and the shell side fluid enters from a shell side inlet on the shell, exchanges heat with the tube side fluid, and then flows out from a shell side outlet on the shell; characterized in that: The heat exchange tubes are microchannel flat tubes, which include a first flat tube and a second flat tube. The shell includes a first wall and a second wall. The first wall and the second wall are arranged opposite to each other, wherein the length direction of the first flat tube extends from the first wall of the shell to the second wall, and has a first gap with the second wall. The length direction of the second flat tube extends from the second wall of the shell to the first wall, and has a second gap with the first wall. The first flat tube and the second flat tube are alternately arranged in the flow direction of the shell-side fluid; the tube sheet is arranged in a vertical direction, and the tube-side fluid in the heat exchange tube flows in a horizontal direction. The inlet head and the outlet head are located on the left and right, and the tube-side fluid can flow from the left into the right and out, or from the left into the right and out; the first wall is located at the upper part, and the second wall is located at the lower part. The fluid in the shell is gas. Along the flow direction of the shell-side fluid, the length of the first gap gradually increases, and the length of the second gap gradually decreases.

2. The heat exchanger according to claim 1, wherein The tube sheet is arranged horizontally, and the tube-side fluid in the heat exchange tube flows in the up-down direction.

3. The heat exchanger according to claim 1, wherein The inlet head is located at the upper part, the outlet head is located at the lower part, and the inlet and outlet of the shell side are located on the left and right parts.

4. The heat exchanger according to claim 1, wherein The inlet of the shell-side fluid is arranged on a side of the shell close to the first wall surface, and the first flat tube is close to the inlet of the shell-side fluid.

5. The heat exchanger according to claim 1, wherein The outlet of the shell-side fluid is arranged on a side of the shell close to the second wall surface, and the second flat tube is close to the outlet of the shell-side fluid.

6. The heat exchanger according to claim 1, wherein The tube-side fluid is liquid and the shell-side fluid is gas.

7. The heat exchanger according to claim 6, characterized in that The tube-side fluid is water and the shell-side fluid is exhaust gas.

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