A small temperature difference membrane evaporation device

Abstract

A kind of small temperature difference membrane evaporator, including evaporator, heat exchanger, heat exchanger is rotatably arranged in evaporator, heat exchanger includes heat exchange tube group, steam inlet cavity and condensate cavity, heat exchange tube group is horizontally arranged and two ends are communicated steam inlet cavity and condensate cavity respectively, evaporator lower part is set to liquid distribution groove, heat exchange tube group includes several heat exchange tubes, the cross section of heat exchange tube is spirally arranged, heat exchanger rotates and makes heat exchange tube enter liquid distribution groove in turn.The utility model discloses through the horizontal arrangement and rotation of heat exchange tube group, and the liquid distribution groove formed dynamic liquid distribution system on the rotation track of heat exchange tube group, realize the uniform distribution and periodic renewal of liquid film, prevent pipe wall scale, break through the restriction of traditional falling-film evaporator vertical installation, greatly improve the flexibility of equipment layout.Compared with prior art, the small temperature difference membrane evaporator of the utility model not only can realize small temperature difference heat transfer evaporation, but also lower manufacturing difficulty and manufacturing cost, and equipment layout flexibility is higher.

Description

Technical Field

[0001] This utility model relates to the field of evaporation, and in particular to a small temperature difference film evaporation device. Background Technology

[0002] Evaporation equipment widely used in industrial applications primarily employs two heat transfer methods: shell-and-tube heat exchange structures and falling film evaporation technology. Traditional shell-and-tube heat exchangers utilize a shell-and-tube layout, where steam circulates within the pipes or shell space. These devices require a temperature difference of at least 5°C to ensure heat transfer efficiency, making it difficult to effectively utilize low-grade heat sources (such as industrial waste heat), thus limiting energy efficiency. Furthermore, uneven liquid film distribution leading to thickness fluctuations increases thermal resistance, easily causing localized dry areas and scaling, severely impacting the continuous and stable operation of the equipment.

[0003] To address the issue of temperature difference limitations, falling film evaporators are also used in industry. This technology relies on gravity to allow the liquid to form an evaporation film along the vertical tube wall. However, it not only requires extremely high uniformity of liquid distribution, necessitating a sophisticated liquid distribution system to ensure a uniform and stable thin film, significantly increasing manufacturing difficulty, but also requires a continuous downward flow of liquid to refresh the film, resulting in substantial water energy consumption. Using water circulation equipment would further increase manufacturing costs. Furthermore, such equipment must be installed vertically, imposing strict requirements on installation height and limiting the flexibility of equipment layout.

[0004] Based on the above, the existing evaporation equipment needs further improvement. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of existing evaporation devices and provide a small temperature difference film evaporation device. By arranging heat exchange tubes horizontally and spirally, the heat exchange tubes are immersed in the solution in turn as they rotate. Under the action of centrifugal force, the solution is evenly distributed on the tube wall, which not only achieves the effect of periodically renewing the liquid film, but also reduces the manufacturing difficulty and cost by rotating vertically, and the equipment layout is more flexible.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a small temperature difference film evaporation device, comprising an evaporator and a heat exchanger, wherein the heat exchanger is rotatably disposed within the evaporator, the heat exchanger comprising a heat exchange tube assembly, a steam inlet chamber and a condensate chamber, the heat exchange tube assembly being arranged horizontally and having its two ends connected to the steam inlet chamber and the condensate chamber respectively, the lower part of the evaporator being provided with a liquid distribution tank, the heat exchange tube assembly comprising a plurality of heat exchange tubes, the heat exchange tubes having a spiral cross-section, and the heat exchanger being rotated to allow the heat exchange tubes to sequentially enter the liquid distribution tank.

[0007] This invention utilizes a horizontal arrangement and rotation of heat exchange tubes, along with a liquid distribution trough positioned along the tubes' rotation path, to form a dynamic liquid distribution system. It fully leverages the immersion-type natural film-forming mechanism and rotational motion, combined with the centrifugal force generated by the spiral arrangement, to ensure the solution naturally and evenly adheres to the tube walls, achieving uniform liquid film distribution. Simultaneously, the periodic nature of the rotational motion ensures periodic renewal of the liquid film, preventing scaling on the tube walls. This overcomes the limitation of traditional falling film evaporators, which require vertical installation to form a uniform flowing liquid film, significantly improving the flexibility of equipment layout and substantially reducing manufacturing difficulty and cost. Compared to existing technologies, this invention's small-temperature-difference film evaporation device not only achieves small-temperature-difference heat exchange evaporation but also boasts lower manufacturing difficulty and cost, and greater flexibility in equipment layout.

[0008] Preferably, the end of the heat exchange tube connected to the steam inlet chamber is designated as the first connection end, and the end of the heat exchange tube connected to the condensate chamber is designated as the second connection end. The height of the first connection end of the plurality of heat exchange tubes is greater than the height of the second connection end. Since the steam enters from the steam inlet chamber and exits from the condensate chamber, setting the height difference between the first connection end and the second connection end conforms to the law of gravity, accelerates the discharge of steam condensate, and prevents condensate accumulation from increasing thermal resistance.

[0009] Preferably, the inner wall of the heat exchange tube is provided with spiral microgrooves arranged from the first connection end to the second connection end to promote the directional discharge of steam condensate and reduce liquid film thermal resistance.

[0010] Preferably, the spiral microgroove has a groove depth of 0.2-0.5 mm and a pitch of 5-10 mm.

[0011] Preferably, it also includes a driving device, which drives the heat exchanger to rotate through a transmission structure so that the heat exchange tubes enter the liquid distribution tank in turn. When the heat exchange tube group rotates, since the cross-section of the heat exchange tubes is spirally distributed, it can avoid violent fluctuations in the liquid surface caused by multiple tubes entering the water at the same time. At the same time, the spirally arranged heat exchange tube group generates a slight centrifugal force when rotating, which forces the liquid film to stick tightly to the tube wall and prevents uneven film thickness caused by gravity drooping, so as to achieve the effect of natural film formation, uniform film formation, and thin film formation.

[0012] Preferably, the driving device is a low-speed rotation driving device; the heat exchange tube group rotates at low speed to ensure that the solution is in full contact with the tube wall, and adheres tightly to the tube wall by centrifugal force, preventing the liquid film from being thrown off the heat exchange tube due to excessive rotation speed. The rotation speed is adjusted by calculating the centrifugal force required to form the liquid film thickness, so that the liquid film thickness is just right to adhere to the tube wall.

[0013] Preferably, the heat exchanger is mounted inside the evaporator via a sealing element, which passes through the outer wall of the evaporator and is disposed on the side of the steam inlet chamber and the side of the condensate chamber.

[0014] Preferably, the transmission structure is located on the side of the seal away from the heat exchanger, and the transmission structure is connected to the heat exchanger in a transmission manner.

[0015] Preferably, it also includes a steam inlet pipe and a drain pipe. The steam inlet pipe passes through a seal and communicates with the steam inlet chamber, and the drain pipe passes through a seal and communicates with the condensate chamber. Steam enters the heat exchanger through the steam inlet pipe, and steam condensate is quickly discharged through the condensate chamber, the inclined heat exchange tube, and the spiral microgroove.

[0016] Preferably, the heat exchange tube forms an angle of 2°-5° with the horizontal plane. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the cross-sectional arrangement of the heat exchange tubes.

[0019] Figure 3 This is a cross-sectional view of the heat exchanger tube.

[0020] Label Explanation:

[0021] Small temperature difference film evaporator 1, evaporator 2, liquid distribution tank 21, heat exchanger 3, heat exchange tube group 31, heat exchange tube 311, first connecting end 3111, second connecting end 3112, spiral micro groove 3113, steam inlet chamber 32, condensate chamber 33, drive device 4, transmission structure 5, sealing element 6, steam inlet pipe 7, drain pipe 8. Detailed Implementation

[0022] In the description of this utility model, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "horizontal", "inner", and "outer" is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing this utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this utility model.

[0023] See Figures 1 to 3This embodiment discloses a small temperature difference film evaporation device 1, including an evaporator 2 and a heat exchanger 3. The heat exchanger 3 is rotatably disposed inside the evaporator 2. The heat exchanger 3 includes a heat exchange tube group 31, a steam inlet chamber 32, and a condensate chamber 33. The heat exchange tube group 31 is arranged horizontally and its two ends are respectively connected to the steam inlet chamber 32 and the condensate chamber 33. The lower part of the evaporator 2 is provided as a liquid distribution tank 21. The heat exchange tube group 31 includes a plurality of heat exchange tubes 311. The cross-section of the heat exchange tubes 311 is arranged in a spiral shape. The heat exchanger 3 rotates so that the heat exchange tubes 311 enter the liquid distribution tank 21 in sequence. The heat exchange tubes 311 in this design are arranged in a spiral cross-section. This avoids drastic fluctuations in the liquid surface caused by multiple tubes entering the water simultaneously. On the other hand, it generates a slight centrifugal force when the heat exchange tube bundle 31 rotates, so that the liquid film adheres tightly to the tube wall, maintaining a small and uniform liquid film thickness and preventing uneven film thickness due to gravity. At the same time, the inclined spiral arrangement of the horizontal tube bundle and the low-speed rotation drive device 4 are designed to control the rotation of the heat exchange tube bundle 31 in a coordinated manner. The thickness of the liquid film can be adjusted by adjusting the centrifugal force on the tube wall through the rotation speed.

[0024] The end of the heat exchange tube 311 connected to the steam inlet chamber 32 is designated as the first connection end 3111, and the end of the heat exchange tube 311 connected to the condensate chamber 33 is designated as the second connection end 3112. The height of the first connection end 3111 of the plurality of heat exchange tubes 311 is greater than the height of the second connection end 3112. In this design, the first connection end 3111 and the second connection end 3112 form an inclined angle, with the steam inlet end being higher and the drain end being lower. This height difference is more conducive to the discharge of condensate.

[0025] To facilitate the directional drainage of condensate and reduce thermal resistance, the inner wall of the heat exchange tube 311 is provided with spiral microgrooves 3113 arranged from the first connecting end 3111 to the second connecting end 3112. In this design, the spiral microgrooves 3113 work synergistically with the external dynamic liquid distribution groove 21 to enhance heat transfer.

[0026] The spiral microgroove 3113 has a groove depth of 0.2-0.5 mm and a pitch of 5-10 mm.

[0027] To provide rotational power to the heat exchange tubes 311, a drive device 4 is also included. The drive device 4 drives the heat exchanger 3 to rotate through the transmission structure 5 so that the heat exchange tubes 311 enter the liquid distribution tank 21 in turn.

[0028] The driving device 4 is a low-speed rotational driving device. Specifically, the rotational speed of the driving device 4 is 10-60 rpm. In this scheme, the driving device 4 drives the heat exchange tube assembly 31 to rotate at a low speed, so that a uniform liquid film is formed on the tube wall, avoiding the liquid film being thrown off the tube wall due to excessive rotational speed and excessive centrifugal force. The heat exchange tube assembly 31 and the driving device 4 form a dynamic liquid distribution system. The driving device 4 drives the heat exchange tube assembly 31 to rotate at a low speed through the liquid distribution tank 21, so that the solution is fully in contact with the heat exchange tube 311 and evenly coated on the outer wall of the tube, forming a thin liquid film of 0.1-0.3 mm.

[0029] The heat exchanger 3 is mounted inside the evaporator 2 via a sealing element 6. The sealing element 6 passes through the outer wall of the evaporator 2 and is located on one side of the steam inlet chamber 32 and the other side of the condensate chamber 33. In this design, the sealing element elevates the heat exchanger to a certain height, working in conjunction with the drive device to achieve rotation of the heat exchanger 3 within the evaporator 2. This replaces the existing falling film evaporator's method of achieving uniform film formation through dynamic liquid with a method using dynamic heat exchange tubes, significantly reducing the equipment's requirements for liquid flow and simplifying its structure.

[0030] The transmission structure 5 is located on the side of the seal 6 away from the heat exchanger 3, and the transmission structure 5 is connected to the heat exchanger 3 in a transmission manner.

[0031] It also includes a steam inlet pipe 7 and a drain pipe 8. The steam inlet pipe 7 passes through the sealing element 6 and communicates with the steam inlet chamber 32, and the drain pipe 8 passes through the sealing element 6 and communicates with the condensate chamber 33. In this scheme, the steam inlet pipe 7 is used to input steam. After the steam enters the steam inlet chamber 32, it is evenly distributed to each heat exchange tube 311 and flows along the heat exchange tube 311 to the condensate chamber 33 for discharge.

[0032] Specifically, the steam introduced into the steam inlet pipe 7 is low-pressure steam (pressure ≤ 0.1 MPa).

[0033] The heat exchange tube 311 forms an angle of 2°-5° with the horizontal plane.

[0034] The workflow of this invention is as follows:

[0035] (1) Liquid film formation stage: The driving device drives the heat exchange tube group to rotate so that the heat exchange tubes enter the liquid distribution tank in turn. When the heat exchange tube rotates to below the liquid surface of the liquid distribution tank, the solution is evenly attached to the outer wall of the tube to form an initial liquid film.

[0036] (2) Evaporation stage: When the heat exchange tube rotates to the top of the liquid surface, the steam inside the tube condenses and releases latent heat, which heats the liquid film through the tube wall. The liquid film evaporates rapidly under the low temperature difference (≤3℃).

[0037] (3) Steam condensate discharge stage: The spiral micro-grooves on the inner wall guide the steam condensate to flow along the pipe wall to the outlet end, avoiding the accumulation of liquid and the thickening of thermal resistance.

[0038] (4) Dynamic renewal to prevent scaling: The rotating cycle renews the liquid film to prevent solute deposition, while centrifugal force assists in the removal of crystallized substances.

[0039] This invention utilizes the horizontal arrangement and rotation of heat exchange tubes 31, along with a liquid distribution trough 21 positioned along the rotation trajectory of the tubes 31, to form a dynamic liquid distribution system. It fully leverages the immersion-type natural film-forming mechanism and rotational motion, combined with the centrifugal force generated by the spiral arrangement, to ensure the solution naturally and uniformly adheres to the tube walls, achieving a uniform liquid film distribution. Simultaneously, the periodic nature of the rotational motion enables periodic renewal of the liquid film, preventing scaling on the tube walls. This overcomes the limitation of traditional falling film evaporators, which require vertical installation to form a uniform flowing liquid film, significantly improving the flexibility of equipment layout and substantially reducing manufacturing difficulty and cost. Compared to existing technologies, this invention's small-temperature-difference film evaporation device 1 not only achieves small-temperature-difference heat exchange evaporation but also boasts lower manufacturing difficulty and cost, and greater equipment layout flexibility.

[0040] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, this utility model is not limited to the specific embodiments disclosed and described above, and some modifications and changes to this utility model should also fall within the protection scope of the claims of this utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this utility model.

Claims

1. A small temperature difference film evaporation device, characterized in that, The device includes an evaporator (2) and a heat exchanger (3). The heat exchanger (3) is rotatably disposed inside the evaporator (2). The heat exchanger (3) includes a heat exchange tube assembly (31), a steam inlet chamber (32), and a condensate chamber (33). The heat exchange tube assembly (31) is arranged horizontally and its two ends are respectively connected to the steam inlet chamber (32) and the condensate chamber (33). The lower part of the evaporator (2) is provided as a liquid distribution tank (21). The heat exchange tube assembly (31) includes a plurality of heat exchange tubes (311). The cross-section of the heat exchange tubes (311) is arranged in a spiral shape. The heat exchanger (3) rotates so that the heat exchange tubes (311) enter the liquid distribution tank (21) in sequence.

2. The evaporation apparatus according to claim 1, characterized in that, The end of the heat exchange tube (311) connected to the steam inlet chamber (32) is designated as the first connection end (3111), and the end of the heat exchange tube (311) connected to the condensate chamber (33) is designated as the second connection end (3112). The height of the first connection end (3111) of the plurality of heat exchange tubes (311) is greater than the height of the second connection end (3112).

3. The evaporation apparatus according to claim 2, characterized in that, The heat exchange tube (311) has spiral microgrooves (3113) arranged along the first connecting end (3111) to the second connecting end (3112) on its inner wall.

4. The evaporation apparatus according to claim 3, characterized in that, The spiral microgroove (3113) has a groove depth of 0.2-0.5 mm and a pitch of 5-10 mm.

5. The evaporation apparatus according to claim 1, characterized in that, It also includes a drive device (4), which drives the heat exchanger (3) to rotate through a transmission structure (5) so that the heat exchange tubes (311) enter the liquid distribution tank (21) in turn.

6. The evaporation apparatus according to claim 5, characterized in that, The driving device (4) is a low-speed rotation driving device.

7. The evaporation apparatus according to claim 5, characterized in that, The heat exchanger (3) is mounted inside the evaporator (2) by a sealing element (6), which passes through the outer wall of the evaporator (2) and is located on one side of the steam inlet chamber (32) and the other side of the condensate chamber (33).

8. The evaporation apparatus according to claim 7, characterized in that, The transmission structure (5) is located on the side of the seal (6) away from the heat exchanger (3), and the transmission structure (5) is connected to the heat exchanger (3) in a transmission manner.

9. The evaporation apparatus according to claim 7, characterized in that, It also includes a steam inlet pipe (7) and a drain pipe (8), wherein the steam inlet pipe (7) passes through the seal (6) and communicates with the steam inlet chamber (32), and the drain pipe (8) passes through the seal (6) and communicates with the condensate chamber (33).

10. The evaporation apparatus according to claim 2, characterized in that, The heat exchange tube (311) forms an angle of 2°-5° with the horizontal plane.

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