CN212881078U - Spiral flat pipe with rough wall surface and falling film evaporator with horizontal pipe - Google Patents

Abstract

The utility model discloses a rough wall spiral flat tube and a horizontal tube falling film evaporator, wherein the cross section of the rough wall spiral flat tube is oval, the flat tube is hollow, and the exterior of the flat tube presents a periodically changing spiral shape; the outer wall surface of the flat pipe is provided with a plurality of ribs, and a plurality of grooves are formed between the ribs. The horizontal tube falling-film evaporator comprises a cylinder, a plurality of rough wall surface spiral flat tubes, an inlet pipeline, a liquid distribution device and a liquid accumulating device; the plurality of rough-wall spiral flat tubes are placed in the cylinder, the inlet pipeline and the liquid distribution device are arranged at the upper ends of the rough-wall spiral flat tubes, the liquid distribution device is arranged at the bottom of the inlet pipeline, and the liquid inlet is arranged at the upper end of the inlet pipeline; the left end and the right end of the cylinder body are respectively provided with a heating medium inlet and a heating medium outlet, the upper end of the cylinder body is provided with a steam outlet, the lower end of the cylinder body is provided with a liquid accumulator, and the lower end of the liquid accumulator is provided with a liquid outlet. The utility model relates to a heat transfer apparatus technical field.

Description

Spiral flat pipe with rough wall surface and falling film evaporator with horizontal pipe

Technical Field

The utility model relates to a heat transfer equipment technical field, in particular to coarse wall spiral flat tube and horizontal pipe falling film evaporation ware.

Background

The evaporator is mainly used for evaporation, concentration and crystallization in the industries of chemical industry, energy, refrigeration and air conditioning and the like. With the continuous development of economy, the domestic requirements on environmental protection, green agriculture and comprehensive resource utilization are higher and higher. In the field of environmental protection, the treatment of heavy sewage is one direction from waste water treatment to waste water treatment, the best treatment method of waste water rich in non-volatile salts and organic matters is evaporation concentration, and the traditional evaporator has high temperature difference loss, large heat transfer temperature difference and low heat transfer coefficient, so that very important energy consumption is caused, and the waste water treatment operation cost is high and the waste water cannot be treated. The method has the same extensive requirements in the field of comprehensive utilization of agricultural resources, such as: some low-concentration agricultural product juice (such as green orange pulp juice, the content of soluble nutrients is between 2 and 5 percent), the juice cannot be directly applied due to low content, if the juice is not treated, not only expensive resources are wasted, but also the environment (surface water, soil and atmosphere) is damaged, and if a traditional evaporation concentration method is adopted, the operation cost is high, and the effective nutrients are easy to damage. Therefore, there is a strong need for new concentration techniques.

At present, an evaporation and concentration technology called Mechanical Vapor Recompression (MVR) is gradually pushed away, but in the MVR technology, an evaporator plays a crucial role, the effect and the operating cost of evaporation and concentration are not only directly influenced, but also secondary pollution of condensed water can be caused, and therefore, in the MVR technology, an evaporation device with high efficiency, low heat transfer temperature difference, good gas-liquid separation effect and compact structure is urgently needed.

At present, 90 percent of evaporators in the industrial production and civil fields are vertical tube evaporators, and have two main types of falling film type and rising film type, the proportions of which are basically close, and the evaporators of the vertical tube rising film type and the vertical tube falling film type have the following problems: large temperature difference loss (boiling point rise caused by static pressure difference), low heat transfer coefficient (because the cloth film is thicker), easy scaling and even blockage of pipelines, difficult gas-liquid separation, large liquid entrainment amount and large equipment volume (large volume of unit heat transfer area or large volume of unit treatment capacity).

At present, the most application fields of falling film evaporators are solution concentration and crystallization, and most of the falling film evaporators adopt vertical tube falling film evaporators, so that the heat transfer temperature difference of the evaporators is large, the maximum effect number provided in multi-effect evaporation is very limited, the energy consumption is generally large, and low-temperature waste heat cannot be used generally.

At present, some horizontal tube falling-film evaporators are available, but the number of horizontal tube falling-film evaporators really applied to real-world production is small, and only a few evaporators used for seawater desalination and central air conditioning are available (the two types of evaporators have low solution concentration and have small requirements on liquid distribution). Most horizontal tube falling film evaporators simply adopt common steel tubes (round without surface treatment), so that the liquid is unevenly distributed outside the tubes, and a dry area (namely, a part of the outside of the tubes is not distributed with the liquid) is formed on the outer surface of the tubes, so that the dry area is completely ineffective or is easy to crystallize. Although most of the current treatments for ameliorating this problem are to change the way the film is applied, the results are marginal.

SUMMERY OF THE UTILITY MODEL

The utility model aims to overcome prior art's defect and not enough, provide the flat pipe of coarse wall spiral, can make liquid even at this heat-transfer pipe surface distribution, avoid appearing "dry district".

Another object of the utility model is to provide a horizontal pipe falling film evaporator, the temperature difference loss is little, and heat transfer coefficient is high.

The purpose of the utility model can be realized by the following technical scheme: the cross section of the flat pipe is oval, the flat pipe is hollow, and the outside of the flat pipe is in a periodically-changed spiral shape; the outer wall surface of the flat pipe is provided with a plurality of ribs, and a plurality of grooves are formed between the ribs.

Preferably, the ratio of the major diameter to the minor diameter of the elliptical cross-section is in the range of 1.2 to 2.5.

As the preferred technical scheme, the rough wall surface spiral flat pipe is obtained by pressing a circular base pipe, and the ratio of the pitch of the flat pipe to the outer diameter of the circular base pipe ranges from 2 to 10.

Preferably, the height difference between the ribs and the grooves ranges from 0.2mm to 1mm, the width of each rib and each groove ranges from 0.5mm to 2mm, and the distance between each adjacent rib and each adjacent groove ranges from 1mm to 3 mm.

The utility model discloses another purpose can be realized through following technical scheme: the horizontal tube falling-film evaporator comprises a cylinder, a plurality of rough wall surface spiral flat tubes, an inlet pipeline, a liquid distribution device and a liquid accumulating device; the plurality of rough-wall spiral flat tubes are horizontally arranged in the cylinder, the inlet pipeline and the liquid distribution device are arranged at the upper ends of the rough-wall spiral flat tubes, the liquid distribution device is arranged at the bottom of the inlet pipeline, and the liquid inlet is arranged at the upper end of the inlet pipeline; the left end and the right end of the cylinder body are respectively provided with a heating medium inlet and a heating medium outlet, the upper end of the cylinder body is provided with a steam outlet, the lower end of the cylinder body is provided with a liquid accumulator, and the lower end of the liquid accumulator is provided with a liquid outlet.

As a preferred technical scheme, the arrangement mode of the plurality of rough wall surface spiral flat tubes is regular triangle arrangement or regular quadrilateral arrangement.

According to the preferable technical scheme, the rough wall surface spiral flat tubes are obtained by pressing a circular base tube, and the distance range between the rough wall surface spiral flat tubes is 1.3 times to 2.5 times of the outer diameter of the circular base tube.

The steam-water separator comprises a cylindrical shell, a cylindrical baffle arranged in the center of the shell, and a plurality of spiral continuous blades arranged between the shell and the baffle. The water vapor further separates a small amount of liquid foam entrained in the steam through the gas-liquid separation device, and the phenomenon of liquid foam entrainment is reduced.

Preferably, the inner wall surface of the housing is provided with a vertical groove. The spiral blade is provided with a plurality of small holes. The separated liquid may be forced to move downward.

Compared with the prior art, the utility model, following advantage and beneficial effect have:

1. the utility model discloses a coarse wall spiral flat tube, flat tube surface are equipped with a large amount of vertically and horizontally staggered's groove and rib, provide a large amount of vaporization cores for the evaporation heat transfer, consequently this heat-transfer pipe the heat transfer difference in temperature little, heat transfer coefficient is high. And the grooves and the ribs excite the disturbance of surface fluid in a micro-area, so that the scale formation and crystallization on the surface of the flat tube are reduced to the maximum extent. The liquid is redistributed on the surface of the flat tube in the longitudinal direction, the transverse direction and the micro-region for many times, so that the liquid is uniformly distributed on the surface of the flat tube, and the effect that the surface of the heat transfer tube has no dry region is achieved.

2. The utility model discloses a horizontal pipe falling film evaporator, because in the flat tub of surface vaporization process of coarse wall spiral on the one hand, gas-liquid contact time is short, makes the liquid foam smuggle suddenly and reduces secretly, and the gas-liquid separation who installs simultaneously in the evaporimeter top has further reduced the liquid foam and has smugglied the phenomenon secretly, and liquid foam entrainment volume falls to below 0.05%.

Drawings

Fig. 1 is a schematic structural view of a rough-wall spiral flat tube in an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken at A-A in FIG. 1;

FIG. 3 is a cross-sectional view taken at B-B of FIG. 1;

fig. 4 is a schematic cross-sectional view of a rough-wall spiral flat tube in an embodiment of the present invention;

fig. 5 is a schematic longitudinal sectional view of the rough-wall spiral flat tube in the embodiment of the present invention;

fig. 6 is a schematic structural diagram of a horizontal tube falling film evaporator in the embodiment of the present invention.

Wherein: 1: inlet line, 11: liquid inlet, 2: liquid distribution device, 3: rough wall surface spiral flat tube, 31: rib, 32: groove, 4: heating medium outlet, 5: liquid accumulator, 6: liquid outlet, 7: heating medium inlet, 8: steam outlet, 9: gas-liquid separation device, 10: and (4) a cylinder body.

Detailed Description

The present invention will be described in further detail with reference to the following examples and drawings, but the present invention is not limited thereto.

As shown in fig. 1 to 3, the rough-walled spiral flat tube is a heat transfer tube element, and the cross section of the flat tube is oval, the inside is hollow, the outside is in a spiral shape with a periodic change, and the spiral pitch is denoted by t in the figure. The elliptical major radii are designated as a and the elliptical minor radii are designated as b. As shown in fig. 4-5, the outer wall surface of the flat tube is provided with a plurality of ribs, and a plurality of grooves are formed between the ribs. The height difference between the ribs and the grooves ranges from 0.2mm to 1mm, the width of the ribs and the grooves is basically maintained between 0.5mm and 2mm, and the distance between the adjacent ribs and the adjacent grooves is approximately between 1mm and 3 mm.

The processing steps of the rough wall surface spiral flat pipe are as follows: the outer surface of a heat transfer pipe with a general circular cross section is processed into grooves and ribs which are staggered longitudinally and transversely through a plurality of modes such as roller gate operation and the like through a special die. The round base pipe with the rough wall surface is pressed through a special die to form the heat transfer pipe with the oval section with the special length-diameter ratio s (s is a/b). One of the characteristic parameters of the oval heat transfer tube is the length to diameter ratio s, which can be controlled to be between 1.2 and 2.5. The heat transfer pipe knob with the elliptic section is a heat transfer pipe with a rough outer surface with a periodically changed spiral elliptic section. The periodic spiral pitch t is one of the main control parameters of the heat transfer pipe, the characteristic parameter of the heat transfer pipe is also the pitch diameter ratio r, namely r is t/d, d is the outer diameter of the circular base pipe, and the r value can be controlled between 2 and 20 generally. The processing steps of the spiral flat pipe with the rough wall surface can be divided into multiple times of processing and one-time forming processing.

As shown in fig. 6, the horizontal tube falling-film evaporator includes a cylinder, a plurality of spiral flat tubes with rough wall surfaces, an inlet pipeline, a liquid distribution device, a liquid accumulation device, and a gas-liquid separation device. The plurality of rough-wall spiral flat tubes are placed in the cylinder, the inlet pipeline and the liquid distribution device are arranged at the upper ends of the rough-wall spiral flat tubes, the liquid distribution device is arranged at the bottom of the inlet pipeline, and the liquid inlet is arranged at the upper end of the inlet pipeline; the left end and the right end of the cylinder body are respectively provided with a heating medium inlet and a heating medium outlet, the upper end of the cylinder body is provided with a steam outlet, the lower end of the cylinder body is provided with a liquid accumulator, and the lower end of the liquid accumulator is provided with a liquid outlet. The gas-liquid separation device is arranged at the lower end of the steam outlet and comprises a shell, a baffle plate and blades. The cylindrical baffle is arranged at the central position inside the cylindrical shell. The blades are a plurality of spiral continuous blades and are arranged between the shell and the baffle. The inner wall of the shell is provided with a small number of longitudinal grooves, and the spiral blade is provided with a plurality of small holes which can promote the separated liquid to move downwards.

The spiral flat pipes with rough wall surfaces form an array according to a certain arrangement mode, and can adopt a regular triangle arrangement mode or a regular quadrilateral arrangement mode which rotates for a certain angle. The interval range between the spiral flat pipes with rough wall surfaces is 1.3 times to 2.5 times of the outer diameter of the circular base pipe. The spiral flat pipes with rough wall surfaces are arranged in the cylinder body in the horizontal direction.

The working principle of the horizontal tube falling-film evaporator is as follows:

the preheated raw material liquid and part of circulating concentrated solution returned from the bottom of the evaporator are fully mixed and enter the evaporator from a liquid inlet of an inlet pipeline, the inlet pipeline of the evaporator is connected with a liquid distribution device into a whole, the liquid is dispersed into liquid particles with certain particle size through the liquid distribution device, and the liquid particles are uniformly distributed above the spiral flat tubes with rough wall surfaces.

Liquid particles from the liquid distribution device land on the surface of the spiral flat pipe with the rough wall surface after reaching the basic uniformity through a section of space, and the liquid is distributed for one time along the radial direction because the liquid is simultaneously subjected to the combined action of the self gravity of liquid drops and the interfacial tension of the liquid and the surface of the flat pipe; similarly, due to the adoption of the periodic spiral elliptical flat tubes, liquid can be axially secondarily distributed along a spiral path; in addition, the surface of the flat pipe is provided with criss-cross raised ribs and concave grooves, so that fluid is promoted to be distributed on the surface of the flat pipe for three times, and liquid is uniformly distributed on the spiral flat pipe with the rough wall surface, and the requirement that the surface of the heat transfer pipe has no dry area is met.

When the liquid is uniformly distributed on the outer surface of the heat transfer pipe, the heating medium (such as water vapor) enters the system from the heating medium inlet and enters the heat transfer pipe, the sensible heat or latent heat of the heating medium is continuously transferred to the liquid outside the pipe through the wall surface of the heat transfer pipe, the liquid outside the pipe receives the heat transferred in the pipe, the temperature of the liquid rises and is vaporized and boiled on the outer surface of the pipe, a large amount of steam is generated, the generated steam moves in the direction opposite to the liquid away from the surface of the heat transfer pipe, and simultaneously the temperature of the heating medium in the heat transfer pipe is continuously reduced or directly condensed into the liquid due to continuous heat release, and the liquid is discharged out.

After partial evaporation, the liquid on the surface of the heat transfer pipe drops into or flows into the next row of rough wall surface spiral flat pipes, the liquid distribution is repeated again, the heat transfer process is repeated again, and the process is repeated in this way until the last row of rough wall surface spiral flat pipes completely separate the initial liquid into steam and concentrated solution.

The concentrated liquid passing through the last row automatically flows into the liquid accumulating device through the bottom of the evaporator, the liquid accumulating device is a simple container with a certain depth, can be integrated with the evaporator into a whole, and can also exist independently, and the purpose is to collect the concentrated liquid and ensure the normal and stable operation of subsequent liquid conveying equipment (pump). The liquid can be partially discharged from the evaporator after being pressurized by the pump through the liquid outlet and is treated as a product or waste, and part of the liquid can be circulated to the liquid inlet for recycling, so that the liquid in the evaporator reaches a certain flow rate, and the stability of the evaporator is ensured.

The steam separated from the surface of the spiral flat pipe with the rough wall surface can carry a part of liquid foam in the steam, the carrying amount of the liquid foam is closely related to the surface tension, the liquid density, the viscosity and the gas flow of the liquid, the part of the carried liquid can carry a part of the components of the concentrated solution, and the existence of the liquid foam can seriously pollute the purity of the water vapor and further pollute the environment on one hand, and on the other hand, the yield of the concentrated solution can be reduced due to the carrying of the water vapor, and the yield of the product can be influenced. Therefore, the gas primarily separated on the surface of the spiral flat tube with the rough wall surface is collected above the device and enters the gas-liquid separation device, the vapor is further separated from a small amount of liquid foam carried in the vapor through the gas-liquid separation device, the liquid returns and enters the liquid accumulator, and the pure vapor is discharged from the vapor outlet discharge system and is further utilized or directly condensed into water to be discharged.

The spiral continuous blade of the gas-liquid separation device divides a flow channel of gas into a spiral upward flow channel, the central baffle plate enables the gas to move upwards only along the spiral channel, the vapor carrying a small amount of liquid makes spiral motion in the spiral channel and is acted by centrifugal force, the centrifugal force borne by the liquid is far larger than the gas due to the fact that the density difference of the liquid and the gas is very large (for the vapor, the density difference is more than thousand times), the liquid is slowly close to the inner wall surface of the cylinder and flows downwards along the inner wall liquid flow channel, and the gas continuously flows upwards and is finally discharged.

The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims (10)

1. The rough wall surface spiral flat pipe is characterized in that the cross section of the flat pipe is oval, the flat pipe is hollow inside, and the outside of the flat pipe is in a periodically changing spiral shape; the outer wall surface of the flat pipe is provided with a plurality of ribs, and a plurality of grooves are formed between the ribs.

2. The rough-walled helical flat tube according to claim 1, wherein the ratio of the major diameter to the minor diameter of the elliptical cross-section is in the range of 1.2 to 2.5.

3. The rough-wall spiral flat tube according to claim 1, wherein the rough-wall spiral flat tube is obtained by pressing a circular base tube, and the ratio of the flat tube pitch to the outer diameter of the circular base tube is in the range of 2 to 10.

4. A rough-walled spiral flat tube according to any one of claims 1 to 3, wherein the difference in height between the ribs and grooves is in the range of 0.2mm to 1mm, the width between the ribs and grooves is in the range of 0.5mm to 2mm, and the pitch between adjacent ribs and adjacent grooves is in the range of 1mm to 3 mm.

5. The horizontal tube falling-film evaporator is characterized by comprising a cylinder, a plurality of rough wall surface spiral flat tubes, an inlet pipeline, a liquid distribution device and a liquid accumulator; the plurality of rough-wall spiral flat tubes are horizontally arranged in the cylinder, the inlet pipeline and the liquid distribution device are arranged at the upper ends of the rough-wall spiral flat tubes, the liquid distribution device is arranged at the bottom of the inlet pipeline, and the liquid inlet is arranged at the upper end of the inlet pipeline; the left end and the right end of the cylinder body are respectively provided with a heating medium inlet and a heating medium outlet, the upper end of the cylinder body is provided with a steam outlet, the lower end of the cylinder body is provided with a liquid accumulator, and the lower end of the liquid accumulator is provided with a liquid outlet.

6. The horizontal tube falling film evaporator of claim 5, wherein the arrangement of the plurality of rough-wall spiral flat tubes is regular triangle arrangement or regular quadrilateral arrangement.

7. The horizontal tube falling film evaporator of claim 6, wherein the rough wall surface spiral flat tubes are obtained by pressing a round base tube, and the distance between the rough wall surface spiral flat tubes ranges from 1.3 times to 2.5 times of the outer diameter of the round base tube.

8. The horizontal tube falling film evaporator according to claim 5, further comprising a gas-liquid separating device provided at a lower end of the vapor outlet, comprising a cylindrical shell, a cylindrical baffle installed at the center inside the shell, and a plurality of spiral continuous blades installed between the shell and the baffle.

9. The horizontal tube falling film evaporator of claim 8, wherein a longitudinal groove is provided on an inner wall surface of the shell.

10. The horizontal tube falling film evaporator of claim 8 wherein the helical vanes are perforated with a plurality of small holes.

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