CN112033209B - A columnar fin falling film evaporation heat exchange tube - Google Patents
A columnar fin falling film evaporation heat exchange tube Download PDFInfo
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- CN112033209B CN112033209B CN202011036396.7A CN202011036396A CN112033209B CN 112033209 B CN112033209 B CN 112033209B CN 202011036396 A CN202011036396 A CN 202011036396A CN 112033209 B CN112033209 B CN 112033209B
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- heat exchange
- exchange tube
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- groove
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F1/00—Tubular elements; Assemblies of tubular elements
- F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
- F28F1/42—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being both outside and inside the tubular element
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- Engineering & Computer Science (AREA)
- Geometry (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
Abstract
The invention discloses a columnar fin falling film evaporation heat exchange tube, wherein rectangular columnar fins are uniformly arranged on the outer surface of the columnar fin falling film evaporation heat exchange tube, gaps between adjacent columnar fins form axial and circumferential grooves to form a flow network favorable for uniform distribution of liquid, in order to prevent splashing generated when the liquid of an upper heat exchange tube drops onto the surface of a lower heat exchange tube and change the surface morphology, the top of each columnar fin is designed to be an inclined surface, a plurality of micro-inclined grooves are arranged at the bottom of each circumferential groove, so that the wetting angle is improved, the comprehensive effect of the micro-inclined grooves at the bottom of each groove and the inclined tops of the columnar fins increases the hydrophobicity of the surface, the state of the surface reaches the Cassie state of a rough surface, the flow resistance of the liquid is reduced, the spreading performance of the liquid is improved, the thickness of the liquid film is thinned, the composite boundary formed by solid-liquid-vapor is also formed, the number of gasification cores is increased, and the evaporation heat exchange coefficient is increased.
Description
Technical Field
The invention relates to a columnar fin falling film evaporation heat exchange tube, belongs to the technical field of heat exchangers, and is particularly suitable for falling film evaporators, and comprises an absorber in an absorption heat pump system.
Background
The falling film evaporator is widely used in evaporators in central air conditioning systems at present and comprises an evaporator and an absorber of a lithium bromide absorption heat pump, and the specific working mode is that the refrigerant is sprayed onto heat exchange tubes which are horizontally arranged through a spraying device at the top, part of liquid generates steam through heat exchange with hot fluid in the heat exchange tubes, and the other part of non-evaporated liquid drops onto the tubes arranged below along the radial direction of the heat exchange tubes. Because the liquid sprayed by the sprayer and the liquid dropped by the high heat exchange tube basically take the shape of drops or columns, the thickness of the local liquid film at the drop is larger than that of other places, so that the liquid film on the surface of the heat exchange tube is uniform and cannot be dried, and the liquid on the surface of the heat exchange tube needs to flow along the axial flow path and capacity. Although the heat exchange area can be greatly improved by the conventionally used spiral fins, the convex radial fins block the axial flow of the liquid, when the liquid film is unevenly distributed, the requirement of the liquid on the axial flow cannot be met, and once the liquid film is locally dried, the effective evaporation heat exchange area is greatly reduced. In order to solve the problem, chinese patent publication No. CN 201034434Y proposes a pitted surface tube, specifically, a plurality of notches are machined on an axially extending spiral fin along the radial direction of the outer edge of the fin to form circumferential teeth, a plurality of prismatic table-shaped fins and flow passages along the axial direction and the radial direction are manufactured, and the spray liquid on the surface of the heat exchange tube is promoted to be rapidly and uniformly diffused under the action of capillary force, and experiments show that the heat exchange efficiency of the tube type is improved. However, during use, this type of heat exchange tube is found to have room for improvement in its performance. In a falling film evaporator, liquid is generally supplied to a heat exchange tube by a spray device at the top and the heat exchange tube at a high position in such a manner that the liquid is continuously dropped. However, when the liquid dropped from the high place hits the surface of the heat exchange tube below, the splashing phenomenon can occur, and the splashed liquid can be directly dropped on the bottom of the heat exchanger through gaps between the heat exchange tubes, can not participate in evaporation, or can be randomly carried away by steam, so that the local liquid distribution is uneven, the heat exchange efficiency of the evaporator can be seriously affected, and even the evaporator is flushed out to endanger the safety of connected equipment.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a falling film evaporation heat exchange tube with inclined top columnar fins.
The invention provides a cylindrical fin falling film evaporation heat exchange tube which comprises two parts, namely an optical section and an evaporation surface section, wherein the evaporation surface section is a heat exchange surface, the evaporation surface section comprises a heat exchange tube body and fins which are arranged on the outer surface of the heat exchange tube body and are spirally distributed along the axis of the heat exchange tube, the cylindrical fin falling film evaporation heat exchange tube is characterized in that the fins are composed of uniformly arranged rectangular cylindrical fins, the top surfaces of the rectangular cylindrical fins are inclined surfaces, the inclined surfaces face the axial direction of the heat exchange tube, axial gaps between adjacent rectangular cylindrical fins form axial grooves, circumferential gaps between adjacent rectangular cylindrical fins form circumferential grooves 7), the axial grooves and the circumferential grooves form staggered net-shaped grooves, a plurality of micro-inclined grooves which are uniformly distributed are arranged at the bottom of the circumferential grooves, and two ends of the micro-inclined grooves extend to the root parts of the rectangular cylindrical fins.
Further, the normal cross section perpendicular to the micro-diagonal grooves is triangular.
Further, the included angle between the micro-chute and the axis of the heat exchange tube body is 20-60 degrees, the depth of the micro-chute is 0.03-0.10 mm, the upper opening is 0.03-0.3 mm, and 60-100 micro-chutes are arranged along the circumferential direction of the heat exchange tube body.
Further, the included angle between the micro-chute and the axis of the heat exchange tube body is 45 degrees, the depth of the micro-chute is 0.05mm, the upper opening is 0.15mm wide, and 70 micro-chutes are arranged along the circumferential direction of the heat exchange tube body.
Further, 8-40 triangular grooves 5 with the spiral angle of 20-60 degrees are formed in the inner surface of the heat exchange tube body, and the depth is 0.10-0.45 mm.
Further, the included angle between the rectangular columnar fin and the gravity direction is 30-45 degrees.
Further, 144 rectangular columnar fins are arranged per inch along the axial direction.
Further, the height of the rectangular columnar fin is 0.15-0.5 mm, and the length-width ratio of the columnar section is (1.1-4): 1.
Further, the height of the rectangular columnar fin is 0.35mm, the length of the columnar section is 0.57mm, and the width is 0.45mm.
Further, the axial groove width is 0.1-1.0 mm, and the circumferential groove width is 0.3-0.8 mm.
The beneficial effects of the invention are as follows:
1. In a falling film evaporator, the liquid on the surface of the heat exchange tube is provided by the way the liquid drops from the heat exchange tube above. The impact of the dropped liquid with the solid plane creates a break-up of the liquid and rebound to form liquid splatter. In addition, the result of numerical calculation shows that the steam speed between the heat exchange tubes can reach more than 10m/s, splashed liquid is immediately carried by steam after leaving the solid surface, and the flow of the steam carrying splashed liquid drops in the evaporator is uneven, so that the flow of the steam carrying splashed liquid drops is random with the adhesion of the surfaces of the heat exchange tubes, the non-uniformity of liquid distribution is aggravated, and sometimes the splashed liquid drops to the bottom of the heat exchanger directly through gaps between the heat exchange tubes without contacting the heat exchange tubes, so that the yield of the steam is reduced. Droplets entrained in the steam cannot be discharged from the evaporator, otherwise, the next-stage equipment, i.e., the compressor, is damaged. In summary, how to reduce the liquid splashing, even eliminate the liquid splashing, is an important way to improve the heat exchange efficiency. The splashing of the liquid is related to the initial velocity of the liquid, namely, the kinetic energy of the liquid striking the wall surface, and is also related to the striking angle of the liquid (the striking angle: the angle between the dropping direction of the liquid drop and the surface), when the striking angle is smaller than 90 DEG, the momentum of the falling liquid drop can be decomposed into two parts of momentum vertical to the wall surface and along the wall surface, and obviously, the inclined surface can weaken the kinetic energy of rebound, thus reducing the probability of rebound of the liquid drop. In the experiment, the photo taken at high speed shows that as the impact angle is reduced, the critical speed (the speed of the liquid drops generating the splashing phenomenon) is increased until the impact angle is reduced to 30 degrees, and the speed of the liquid drops is continuously increased, so that the splashing phenomenon does not occur. Simultaneously, along with the reduction of the impact angle, the flow speed of the liquid film on the inclined plane is gradually increased, and the thickness of the liquid film on the surface is obviously reduced.
2. When the tops of the rectangular columnar fins are inclined surfaces, the crushing and splashing of liquid dripping from high positions are eliminated, and more liquid flows into the grooves at the root parts along the columnar fins. The thickness of the liquid film is a main factor influencing the evaporation heat transfer process, and in order to avoid the liquid forming a thick film in the groove, the invention optimizes by regulating and controlling the hydrophilic and hydrophobic properties of the solid surface. The specific method is that a plurality of micro-inclined grooves are arranged at the bottom of the radial groove, two ends of each micro-inclined groove extend to the root of each column fin, and the clamp angle of each micro-inclined groove and the heat exchange tube axis is 45 degrees. From experimental observations and tests, it was found that a surface with a plurality of micro-diagonal grooves resulted in a regular rough surface, which could alter the wettability of the surface. Measurement of the smooth surface showed that the contact angle between the surface and the liquid was around 80 °, but the contact angle of the surface was changed to 105 to 135 ° after the surface was provided with a plurality of micro-inclined grooves. It is well known that when the contact angle is less than 90 deg., the surface is defined as a hydrophilic surface, and when the contact angle is greater than 90 deg., the surface is defined as a hydrophobic surface. Therefore, when the surface is provided with micro-grooves, the surface changes from hydrophilic to hydrophobic. When the bottom of the groove forms a hydrophobic surface, the liquid tends to form a bead or rope shape thereon, thereby reducing the flow resistance, improving the flow speed and reducing the thickness of the liquid film. On the other hand, when the bottom surface of the groove is covered with a liquid, the liquid cannot completely fill the micro chute due to poor wettability of the hydrophobic surface, and air is present therein, and at this time, the surface forms a composite boundary of solid-liquid-gas composition, i.e., a Cassie state called a rough surface. The composite boundary can provide more vaporization cores, strengthen boiling heat exchange efficiency and improve evaporation heat exchange coefficient.
Thirdly, the rectangular columnar fin has the advantages that the processing die is simple and convenient to manufacture, and the processing of the inclined top of the fin and the micro-chute on the bottom surface of the groove is convenient.
In addition, the spiral triangular channels are arranged on the inner surface of the heat exchange tube to improve the convection heat transfer coefficient in the tube, and according to experiments, the evaporation heat transfer coefficient outside the tube is improved by more than 40% compared with that of a light tube, and is improved by about 10% compared with that of a pitted surface tube provided in Chinese patent application No. CN 201034434Y. Meanwhile, the spreading diameter of the liquid drop on the surface of the heat exchange tube is increased by more than 13% compared with that of the surface of a pitted surface tube provided by Chinese patent publication No. CN 201034434Y.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic longitudinal cross-sectional view of an evaporation surface section according to the invention;
FIG. 3 is a schematic cross-sectional view of an evaporation surface section according to the invention
FIG. 4 is a cross-sectional view of a rectangular columnar fin of the present invention;
FIG. 5 is a cross-sectional view of a micro-groove in the normal direction of the present invention;
FIG. 6 is a graph showing the comparison of heat exchange experimental data between a light pipe type falling film evaporation tube and a conventional micro columnar falling film evaporation heat exchange tube.
The symbols in the drawings illustrate:
the evaporation heat exchange coefficient of the light pipe type falling film evaporation tube (calculated according to a test association formula);
the heat exchange coefficient (calculated according to a test association formula) of the conventional miniature columnar falling film evaporation heat exchange tube;
the invention relates to a heat exchange coefficient test point of a columnar fin falling film evaporation heat exchange tube.
Detailed Description
The following detailed description of specific embodiments of the invention refers to the accompanying drawings:
as shown in FIGS. 1-6, a falling film evaporation heat exchange tube with columnar fins is The tube fitting comprises a light section 1 and an evaporation surface section, wherein the evaporation surface section is a heat exchange surface, the evaporation surface section comprises a heat exchange tube body and fins which are arranged on the outer surface of the heat exchange tube body and are distributed spirally along the axis of the heat exchange tube, each fin consists of rectangular columnar fins 2 which are uniformly arranged, 144 rectangular columnar fins 2 are arranged along the axial direction per inch, the height of each rectangular columnar fin 2 is 0.15-0.5 mm (preferably 0.35 mm), the length-width ratio of each columnar section is (1.1-4): 1, and the length and width of each columnar section of each rectangular columnar fin 2 are preferably 0.57mm and 0.45mm. The top surface 3 of the rectangular columnar fin 2 is an inclined surface, the included angle between the inclined surface and the gravity direction is 30-45 degrees, and the inclined surface faces the axial direction of the heat exchange tube. The axial gaps between the adjacent rectangular columnar fins 2 form axial grooves 6, the circumferential gaps between the adjacent rectangular columnar fins 2 form circumferential grooves 7, the axial grooves 6 and the circumferential grooves 7 form mesh grooves which are staggered axially and circumferentially, the width of the axial grooves 6 is 0.1-1.0 mm, and the width of the circumferential grooves 7 is 0.3-0.8 mm. The bottom of the circumferential groove 7 is provided with a plurality of micro-inclined grooves 4 which are uniformly distributed, two ends of each micro-inclined groove 4 extend to the root of the rectangular columnar fin 2, the normal section perpendicular to the micro-inclined groove 4 is triangular, the included angle between the micro-inclined groove 4 and the axis of the heat exchange tube body is 20-60 degrees (preferably 45 degrees), the depth of each micro-inclined groove 4 is 0.03-0.10 mm (preferably 0.05 mm), the upper opening width is 0.03-0.3 mm (preferably 0.15 mm), and 60-100 (preferably 70) micro-inclined grooves are arranged along the circumferential direction of the heat exchange tube body. 8-40 (preferably 25) triangular channels 5 with the spiral angle of 20-60 degrees (preferably 43 degrees) are arranged on the inner surface of the heat exchange tube body, and the depth is 0.10-0.45 mm (preferably 0.3 mm).
It should be understood that parts of the present specification not specifically described are prior art. The above examples are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solution of the present invention should fall within the scope of protection defined by the claims of the present invention without departing from the spirit of the design of the present invention.
Claims (8)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011036396.7A CN112033209B (en) | 2020-09-28 | 2020-09-28 | A columnar fin falling film evaporation heat exchange tube |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011036396.7A CN112033209B (en) | 2020-09-28 | 2020-09-28 | A columnar fin falling film evaporation heat exchange tube |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112033209A CN112033209A (en) | 2020-12-04 |
| CN112033209B true CN112033209B (en) | 2025-04-04 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011036396.7A Active CN112033209B (en) | 2020-09-28 | 2020-09-28 | A columnar fin falling film evaporation heat exchange tube |
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Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113566454B (en) * | 2021-08-16 | 2024-10-11 | 珠海格力电器股份有限公司 | Falling film evaporating pipe, heat exchanger and air conditioning unit |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101004335A (en) * | 2007-01-15 | 2007-07-25 | 高克联管件(上海)有限公司 | Evaporation and condensation combined type heat-transfer pipe |
| CN101813433A (en) * | 2010-03-18 | 2010-08-25 | 金龙精密铜管集团股份有限公司 | Enhanced heat transfer tube for condensation |
| CN212458084U (en) * | 2020-09-28 | 2021-02-02 | 山东恒辉节能技术集团有限公司 | Columnar fin falling film evaporation heat exchange tube |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0961080A (en) * | 1995-08-21 | 1997-03-07 | Hitachi Ltd | Turbo refrigerator |
| CN100365369C (en) * | 2005-08-09 | 2008-01-30 | 江苏萃隆铜业有限公司 | Evaporator heat exchange tube |
| JP2012167854A (en) * | 2011-02-14 | 2012-09-06 | Hitachi Cable Ltd | Heat transfer tube for falling liquid film evaporator, and turbo refrigerator using the same |
-
2020
- 2020-09-28 CN CN202011036396.7A patent/CN112033209B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101004335A (en) * | 2007-01-15 | 2007-07-25 | 高克联管件(上海)有限公司 | Evaporation and condensation combined type heat-transfer pipe |
| CN101813433A (en) * | 2010-03-18 | 2010-08-25 | 金龙精密铜管集团股份有限公司 | Enhanced heat transfer tube for condensation |
| CN212458084U (en) * | 2020-09-28 | 2021-02-02 | 山东恒辉节能技术集团有限公司 | Columnar fin falling film evaporation heat exchange tube |
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| CN112033209A (en) | 2020-12-04 |
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