A microchannel heat exchanger with uniform tube-side flow distribution

Abstract

The present invention provides a microchannel heat exchanger with uniform tube-side flow distribution. Inner fins are arranged on the inner wall surface of the heat exchange tubes, and the inner fins protrude from the inner wall surface of the heat exchange tubes; the distribution densities of the inner fins in different flat tubes are different; as the distance of the flat tube from the inlet is farther, the distribution density of the inner fins in the flat tube is smaller. The present invention can make the fluid distribute uniformly in the tube side through the change of the distribution density of the inner fins, and enhances heat transfer.

Description

Technical Field

[0001] The present invention relates to a heat exchanger, belonging to the technical field of heat exchangers, in particular to a microchannel heat exchanger with uniform tube-side flow distribution. Background Art

[0002] Heat exchangers are extremely common in industrial production. For example, they play an important role in various industrial sectors such as chemical industry, power, metallurgy, construction, machinery manufacturing, food, medicine, and aerospace. Therefore, it is necessary for industries using heat exchangers to optimize the design of heat exchangers to improve heat transfer efficiency. For the automotive industry, it is also an urgent problem to optimize the design of automotive engine exhaust gas recirculation coolers, improve heat transfer efficiency to reduce nitrogen oxide emissions, and make the exhaust gas emissions meet the increasingly stringent exhaust emission standards.

[0003] Due to limitations in manufacturing processes and technical levels, early heat exchangers could only adopt simple structures, with small heat transfer areas, large volumes, and being bulky, such as coil heat exchangers. With the development of manufacturing processes, shell-and-tube heat exchangers have a relatively large heat transfer area per unit volume and good heat transfer effects, and have long been a typical heat exchanger in industrial production. Plate heat exchangers emerged in the 1920s and were applied to the food industry. Heat exchangers made of plates instead of tubes are structurally compact and have good heat transfer effects. After the 1980s, a large number of enhanced heat transfer elements were introduced to the market, and the manufacturing processes of heat exchangers such as plate-and-shell heat exchangers were further improved, thus promoting the vigorous development and wide application of compact heat exchangers.

[0004] The types of heat exchangers used in industrial production are diverse, and they need to be selected according to actual situations during use. Plate-and-shell heat exchangers have a wide range of applications, strong adaptability, simple structures, and low costs, and have great advantages in terms of both quality and compactness. Flat tubes have been widely used in automotive air conditioning units and residential or commercial air conditioning heat exchangers in recent years. Such flat tubes have a large heat transfer area and can thus greatly improve the heat transfer effect.

[0005] A microchannel heat exchanger is a heat exchanger with a channel equivalent diameter in the range of 10 - 1000 μm, consisting of two headers, multiple flat tubes, and fins. There are dozens of fine channels inside the flat tubes, and both ends of the flat tubes are connected to circular headers. The headers are generally placed vertically, and horizontal partitions are provided inside the headers to divide the heat exchanger channels into several passes.

[0006] In the heat exchangers of the prior art, the fluids in the shell side all pass horizontally through the flat surfaces of the flat tubes, so they flow perpendicular to the fluids in the flat tubes. This flow causes uneven distribution of the fluids in the shell side, resulting in some areas outside the flat tubes not participating in heat exchange or participating little in heat exchange, causing heat transfer short - circuit in some areas. Moreover, the distance between the header inlet and the heat exchange tubes also affects the fluid distribution in the tube side. The closer the heat exchange tube is to the inlet tube, the more fluid flow in the heat exchange tube, and the farther the heat exchange tube is from the inlet tube, the less fluid flow in the heat exchange tube. Therefore, the present invention designs a new type of heat exchanger to improve the structure of the traditional plate - shell heat exchanger to achieve the purpose of enhancing heat transfer. Summary of the Invention

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

[0008] A micro - channel heat exchanger with uniform tube - side flow distribution, the shell - and - tube heat exchanger includes a tube side, the tube side includes an inlet header, an outlet header, tube sheets and heat exchange tubes. The two ends of the heat exchange tubes are fixedly installed on the tube sheets. The tube - side fluid enters the heat exchange tubes from the inlet header and then flows out from the outlet header. The inlet header is provided with a tube - side fluid inlet, and the outlet header is provided with a tube - side fluid outlet. It is characterized in that inner fins are provided on the inner wall surface of the heat exchange tubes, and the inner fins protrude from the inner wall surface of the heat exchange tubes. The distribution density of the inner fins in different flat tubes is different. As the distance of the flat tube from the inlet is farther, the distribution density of the inner fins in the flat tube is smaller.

[0009] As the distance from the inlet is farther, the amplitude of the decrease in the distribution density of the inner fins in the flat tube becomes larger and larger.

[0010] The distribution density of the fins in the heat exchange tube closest to the inlet is 1.8 - 2.0 times that of the fins in the heat exchange tube farthest from the inlet.

[0011] The distribution density of the fins in the heat exchange tube closest to the inlet is 1.9 times that of the fins in the heat exchange tube farthest from the inlet.

[0012] The heat exchanger includes a shell side, the shell side includes a shell body. The shell - side fluid enters from the shell - side inlet on the shell body, and then exchanges heat with the tube - side fluid and flows out from the shell - side outlet on the shell body. It is characterized in that the heat exchange tubes are flat tubes, the flat tubes include a first flat tube and a second flat tube, the shell body 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. The length direction of the first flat tube extends from the first wall surface of the shell body to the second wall surface, having a first gap with the second wall surface. The length direction of the second flat tube extends from the second wall surface of the shell body to the first wall surface, having a second gap with the first wall surface. The first flat tube and the second flat tube are arranged alternately.

[0013] The tube sheet is arranged horizontally, and the tube-side fluid in the heat exchange tubes flows in the up-down direction.

[0014] The inlet of the shell-side fluid is arranged on one 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.

[0015] The outlet of the shell-side fluid is arranged on one 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.

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

[0017] Through the variable layout of the internal fins in the present invention, the closer to the inlet, the greater the resistance to fluid flow due to the more internal fins arranged, so that the fluid flows into the heat exchange tubes with less flow resistance, and the fluid flows into the heat exchange tubes at positions farther away from the inlet, thereby making the fluid distribution uniform, enabling the tube-side fluid to uniformly pass through all areas of the flat tube, and improving the heat exchange effect of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 2 is a schematic diagram of the flat tube arrangement structure of the heat exchanger of the present invention;

[0020] Figure 3 is a schematic diagram of the front structure of the flat tube arrangement of the heat exchanger of the present invention observed from one side of the flat surface of the flat tube.

[0021] Figure 4 is a schematic diagram of the internal fin arrangement structure of the flat tube of the heat exchanger of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] In this article, if not otherwise specified, for formulas, " / " represents division, and "×", "*" represent multiplication.

[0023] In the description of the present invention, the expressions of the terms "left" and "right" are based on the position or orientation relationship shown in the drawings, and do not indicate or imply the specific installation and operation orientations that the described device or element must have, and therefore should not be construed as a limitation to the present invention.

[0024] Next, the technical solutions in the embodiments of the present invention will be further described in conjunction with the drawings in the embodiments of the present invention.

[0025] Figures 1-3 A shell-and-tube heat exchanger is disclosed. Among them Figure 2 is Figure 1 a transverse cross-section ( Figure 1 the horizontal cross-section in Figure 1Schematic 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 header 1, an outlet header 2, a tube sheet 3, and heat exchange tubes 4. Both ends of the heat exchange tubes 4 are fixedly installed on the tube sheet 3. The tube-side fluid enters the flat tubes 4 from the inlet header 1 and then flows out from the outlet header 2. The shell side includes a shell 5. The shell-side fluid enters from the shell-side inlet 6 on the shell and then exchanges heat with the tube-side fluid and flows out from the shell-side outlet 7 on the shell.

[0026] The inlet header is provided with a tube-side fluid inlet 12, and the outlet header is provided with a tube-side fluid outlet 13. As an improvement, internal fins 14 are provided on the inner wall surface of the flat tubes 4, and the internal fins 14 protrude outward from the inner wall surface of the flat tubes 4. By providing the internal fins, the heat transfer area is increased and the heat transfer inside the tubes is strengthened.

[0027] As an improvement, the distribution density of the internal fins in different flat tubes is different. As the distance of the flat tube from the inlet 12 is closer, the distribution density of the internal fins in the flat tube is greater. By setting it like this, the closer to the inlet 12, the more internal fins are arranged, resulting in a greater resistance to fluid flow. Thus, the fluid flows into the heat exchange tubes with less flow resistance, and the fluid flows into the heat exchange tubes at positions farther from the inlet, so that the fluid distribution is uniform.

[0028] As an improvement, as the distance from the inlet 12 is closer, the amplitude of the increasing distribution density of the internal fins in the flat tube becomes larger and larger. Through experiments, it is found that by increasing the amplitude of the increasing distribution density, the fluid distribution can be made more uniform.

[0029] As an improvement, the distribution density of the fins in the heat exchange tubes closest to the inlet 12 is 1.8 - 2.0 times, preferably 1.9 times, that of the fins in the heat exchange tubes farthest from the inlet 12.

[0030] As an improvement, the outward protruding heights of the internal fins in different flat tubes are different. As the distance of the flat tube from the inlet 12 is closer, the outward protruding height of the internal fins in the flat tube is greater. By setting it like this, the closer to the inlet 12, the greater the outward protruding height of the internal fins, resulting in a greater resistance to fluid flow. Thus, the fluid flows into the heat exchange tubes with less flow resistance, and the fluid flows into the heat exchange tubes at positions farther from the inlet, so that the fluid distribution is uniform.

[0031] As an improvement, as the distance from the inlet 12 is closer, the amplitude of the increasing outward protruding height of the internal fins in the flat tube becomes larger and larger. Through experiments, it is found that by increasing the amplitude of the increasing outward protruding height, the fluid distribution can be made more uniform.

[0032] As an improvement, the height of the outward protrusion of the fins inside the heat exchange tube closest to the inlet 12 is 1.7 - 2.0 times, preferably 1.85 times, the height of the outward protrusion of the fins inside the heat exchange tube farthest from the inlet 12.

[0033] As Figures 2-3 shown, the heat exchange tube is a flat tube, preferably a microchannel flat tube. The flat tube includes a first flat tube 41 and a second flat tube 42. The housing includes a first wall surface 8 and a second wall surface 9, and the first wall surface 8 and the second wall surface 9 are arranged opposite to each other. The length direction of the first flat tube extends from the first wall surface 8 of the housing to the second wall surface 9, having a first gap with the second wall surface. The length direction of the second flat tube extends from the second wall surface of the housing to the first wall surface, having a second gap with the first wall surface. The first flat tube and the second flat tube are arranged alternately. The flow direction of the fluid in the shell side is along the flat plane direction of the flat tube.

[0034] In the present invention, the fluid in the shell side flows along the length (height) of the flat tube, and the flow directions of the fluid in the tube side and the shell side are parallel flows. Since the first and second flat tubes are arranged at intervals, the fluid flows along a bent path in the housing, enabling the fluid to pass through all areas of the flat tube and improving the heat exchange effect of the heat exchanger.

[0035] The flat tube includes a first plane and a second plane, and 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.

[0036] As an improvement, the tube sheet is arranged horizontally, and the fluid in the tube side of the heat exchange tube flows in the up - down direction. The headers 1 and 2 also adopt the up - down direction, and the fluid in the tube side can flow in from the upper part and out from the lower part or flow in from the lower part and out from the upper part.

[0037] As an improvement, the inlet header 1 is located in the upper part, the outlet header 2 is located in the lower part, and the inlets 6 and outlets 7 of the shell side are located on the left and right parts. Cross - flow between the fluids is formed.

[0038] As an improvement, the lengths of the first gap and the second gap are 68 - 84% of the distance between the first wall surface and the second wall surface. If the gap is too short, the flow resistance will be too large. If it is too long, it will also affect the heat pipe heat exchange efficiency and reduce the heat exchange area. If the penetration depth exceeds 84%, the flow resistance will increase greatly, resulting in cost increase.

[0039] As an improvement, the lengths of the first gap and the second gap are 75 - 80% of the distance between the first wall surface and the second wall surface. Through the optimization of the above dimensions, the heat exchange efficiency can be further increased while meeting the resistance requirements.

[0040] As an improvement, the inlet of the shell-side fluid is arranged on one 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. As an improvement, the outlet of the shell-side fluid is arranged on one 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. Through the above-mentioned cooperative arrangement, the shell-side fluid can be guided to fully pass through the flat surface of the flat tube for heat exchange.

[0041] As an improvement, the tube-side fluid is a liquid and the shell-side fluid is a gas.

[0042] As an improvement, the tube-side fluid is water and the shell-side fluid is waste gas.

[0043] As an improvement, the tube sheet is arranged vertically, and the tube-side fluid in the heat exchange tubes flows horizontally. The headers 1 and 2 are also in the left-right direction, and the tube-side fluid can flow in from the left and out from the right or flow in from the left and out from the right. The first wall surface 8 is located at the upper part, and the second wall surface 9 is located at the lower part. The inlet header and the outlet header are located on the left and right. The fluid in the shell-side is a gas, and along the flow direction of the fluid in the shell-side, the length of the first gap gradually increases, and the length of the second gap gradually decreases.

[0044] During the research process, it is found that the heat exchange on the cross-section of the flat tube in the fluid flow direction is uneven. As the distance from the inlet is farther, the gas density in the shell-side is small, so the gas flows upward, resulting in a significant increase in the upper gas. Therefore, it is necessary to design a heat exchange structure for improvement. In the present invention, along the flow direction of the gas, the lengths of the first gap and the second gap change, so that the gas in the shell-side gradually moves less upward as it flows, and stays in the middle and lower parts for more time, strengthening the heat exchange of the heat exchange tubes around the shell center and the lower part, changing the past heat exchange method, enhancing the heat exchange efficiency at different positions, making the overall heat exchange uniform, and further achieving the purpose of strengthening heat transfer.

[0045] As an improvement, along the flow direction of the fluid in the shell-side, the increasing amplitude of the length of the first gap gradually increases, and the decreasing amplitude of the length of the second gap gradually increases. Through the change of the above amplitudes, the overall heat exchange can be further made uniform, and the purpose of strengthening heat transfer is further achieved.

[0046] As an improvement, along the direction from the inlet to the outlet in the shell, from the inlet of the shell to the middle position of the shell, the distance between adjacent flat tubes continuously increases. Then from the middle position of the shell to the outlet of the shell, the distance between adjacent flat tubes continuously decreases. Because in the heat exchange process, the heat exchange amount between the hot and cold fluids is relatively evenly arranged in the flow direction, and the overall heat exchange effect is the best. However, it is found in experiments and simulations that the heat exchange amount in the middle is significantly greater than that at the inlet and the outlet. Therefore, by changing the distance between the flat tubes, the heat exchange area also changes regularly, so as to compensate for the uneven heat exchange amount through the area change, thereby further improving the heat exchange efficiency.

[0047] As an improvement, from the inlet of the housing to the middle position of the housing, the amplitude of the continuous increase in the spacing between adjacent flat tubes increases continuously. Then, from the middle position of the housing to the outlet of the housing, the amplitude of the continuous decrease in the spacing between adjacent flat tubes decreases continuously. The change in the above amplitude can make the heat exchange amount per unit area of the entire fluid motion more uniform, further improving the heat exchange efficiency.

[0048] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and the protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A microchannel heat exchanger with uniform distribution of tube-side flow rate. The heat exchanger includes a tube side, which comprises an inlet header, an outlet header, tube sheets and heat exchange tubes. The two ends of the heat exchange tubes are fixedly installed on the tube sheets. The tube-side fluid enters the heat exchange tubes from the inlet header and then flows out from the outlet header. The inlet header is provided with a tube-side fluid inlet, and the outlet header is provided with a tube-side fluid outlet. It is characterized in that, Internal fins are provided on the inner wall surface of the heat exchange tube, and the internal fins protrude from the inner wall surface of the heat exchange tube; the distribution density of the internal fins in different flat tubes is different; as the distance of the flat tube from the inlet is farther, the distribution density of the internal fins in the flat tube is smaller; the heat exchange tube is a 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 oppositely, wherein the length direction of the first flat tube extends from the first wall surface of the shell to the second wall surface, and there is a first gap with the second wall surface, the length direction of the second flat tube extends from the second wall surface of the shell to the first wall surface, and there is a second gap with the first wall surface, and the first flat tube and the second flat tube are arranged alternately; the tube sheet is arranged vertically, the tube-side fluid in the heat exchange tube flows horizontally, the inlet header and the outlet header are located on the left and right, and the tube-side fluid can flow in from the left and out from the right or flow in from the left and out from the right; the first wall surface is located at the upper part, the second wall surface is located at the lower part, the fluid in the shell side is a gas, and along the flow direction of the fluid in the shell side, 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, characterized in that, As the distance from the inlet is farther, the amplitude of the decrease in the distribution density of the internal fins in the flat tube becomes larger and larger.

3. The heat exchanger according to claim 1, characterized in that, The distribution density of the fins in the heat exchange tube closest to the inlet is 1.8 - 2.0 times that of the fins in the heat exchange tube farthest from the inlet.

4. The heat exchanger according to claim 1, characterized in that, The distribution density of the fins in the heat exchange tube closest to the inlet is 1.9 times that of the fins in the heat exchange tube farthest from the inlet.

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

6. The heat exchanger according to claim 1, characterized in that, The inlet of the shell-side fluid is arranged on one 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.

7. The heat exchanger according to claim 1, characterized in that, The outlet of the shell-side fluid is arranged on one 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.

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