JPH02180601A - Falling liquid film type evaporator - Google Patents

Abstract

PURPOSE:To achieve uniform distribution of liquid and formation of liquid film by providing a plurality of evaporating tubes having a large number of longitudinal grooves formed on their outer circumferential surfaces, a first distributing body for distributing liquids to be treated, and a second distributing body for dispersing the liquids to be treated, disposed close to the underside of the first distributing body. CONSTITUTION:A falling liquid film type evaporator 1 has a plurality of evaporating tubes 10 having large number of longitudinal grooves 10a formed on their outer circumferential surfaces. And the evaporator 1 is provided with a first distributing body 12 for distributing liquids to be treated 11 introduced into the evaporator 1 to the evaporating tubes 10 and with a second distributing body 13 for dispersing the liquids 11 having been distributed in a direction of the evaporating tubes 10, wherein the second distributing body 13 is disposed close to the underside of the first one 12. Further, by providing a pair of another distributing bodies 12'-13', etc., in addition to a pair of bodies 12-13, the evaporator 1 can be formed into a multistage construction. With this construction, breakage of liquid film, while the liquid is falling over the evaporating tubes 10, can be avoided. And it is preferable that the first distributing body 12 is a nozzle type tube plate and the second body 13 is a slit type tube plate.

Description

Detailed Description of the Invention "Industrial Application Field" The great invention is to evaporate at least a part of the liquid while filtering the liquid to be treated in a film form along the circumferential surface of the evaporation tube, and to remove the latent heat of boiling. This invention relates to a falling film evaporator used as a heat exchanger, liquid concentrator, etc.

``Prior Art'' Liquid film evaporators, especially falling film evaporators, have been widely used because they have relatively large processing capacity, simple structure, and easy control. When used as a heat exchanger that constitutes a system, the heat exchange temperature difference can be reduced by reducing thermal resistance by thinning the film and promoting heat and mass transfer by interfacial disturbance, which can improve the coefficient of performance of the heat pump. It's good to be able to do it.

However, this device requires a liquid circulation pump to re-introduce the refrigerant that remains at the bottom of the device due to heat exchange on the circumferential surface of the evaporator tube to the upper end of the evaporator tube. The more the liquid circulation pump power increases, the more the efficiency of the system as a whole may decrease.

``Problem to be Solved by the Invention'' For this reason, in boat fishing, the flow rate of liquid supplied to the evaporator tube is reduced to reduce as much as possible the accumulation of liquid after flowing down the evaporator tube. If this configuration is adopted, the uniform distribution of liquid to each evaporator tube and the formation of a stable liquid film will be hindered, resulting in the formation of a dry surface on a part of the circumferential surface of the evaporator tube and a decrease in heat transfer performance. There may be cases where

For example, when forming a liquid film on the outer surface of a vertical evaporation tube, liquid distribution methods include using a slit-type distributor with a slit space around the evaporation tube, or using a nozzle to spray liquid onto the periphery of the evaporation tube. There are nozzle-type distributors, but slit-type distributors require a fairly small gap between them and the evaporation tube to enable low flow rate supply, so the machining accuracy of the slit and the gap between the evaporation tube and the slit must be kept very small. Due to variations in assembly accuracy, it is difficult to form a stable and uniform liquid film in the circumferential direction.

In the case of a nozzle-type distributor, liquid distribution in the winding tubes of the evaporator tube group can be achieved relatively evenly even in a low flow rate range, but liquid distribution in the circumferential direction of the tubes is uneven due to the influence of the nozzle jet. If the number of nozzles is increased in order to avoid this, the nozzle diameter must be made smaller accordingly, and as with the slit type, nozzle processing accuracy becomes a problem.

Therefore, in any of the above methods, it is difficult to form a stable liquid film when the flow rate of the liquid to be treated is reduced.
In particular, in the case of the above-mentioned evaporator, the liquid film becomes thinner as it flows down the evaporation tube, so the liquid film tends to break near the bottom of the tube.For this reason, in a normal evaporator, the ratio of the amount of liquid supplied to the amount of evaporation is is made large to make it difficult for the liquid film to break, but with this configuration, the excess refrigerant will accumulate at the bottom of the evaporator, and the power of the liquid circulation pump to circulate it will inevitably increase. , reducing the overall efficiency of the system.

For this reason, a device with a multi-stage structure in which the evaporation tube is divided into a plurality of parts and a liquid supply JI41 is provided between them has also been developed (Japanese Patent Application Laid-Open No. 138201/1982), but the evaporation pipe Since it is not possible to flow water, etc. as a heat source into the evaporator by dividing the evaporator, it is possible to apply it as an inner tube type falling film evaporator in which steam, etc. as a heat source is brought into contact with the outer periphery. However, it is impossible to apply this method to an apparatus in which a liquid to be treated flows in a film along the outer peripheral surface of an evaporation tube as in the present invention.

In view of the drawbacks of the prior art, the present invention has been developed to provide a flow rate that can form a stable liquid film over the entire surface of the evaporation tube, even when the flow rate of the liquid to be treated to be supplied to the evaporation tube is reduced. The purpose is to provide a liquid film type evaporator.

Another object of the present invention is that it is possible to easily create a multi-stage structure in a device that allows the liquid to be processed to flow in a film along the outer circumferential surface of the evaporation tube, thereby preventing the liquid film from breaking while flowing down the evaporation tube. The purpose of this invention is to provide a falling film type evaporator that can

"Means for Solving the Problems" The present invention aims to smoothly achieve the above technical problems by effectively combining the nozzle type and slit type distributors, and its features are shown in Figure 1. As shown in FIG. a first distributor 12 that distributes the introduced liquid to be treated 11 to each of the evaporation tubes 10; and a first distributor 1.
The second distributor 13 is configured to disperse the liquid to be treated 11 distributed by 2 in the circumferential direction of the evaporation tube 10, and the second distributor 13 is disposed close to the lower side of the first distributor 12. The main point is that a liquid distribution mechanism is provided.

Preferably, the first distributor 12 includes a nozzle 121
The second distributor 13 is configured as a nozzle-type tube plate 12 that sprays liquid onto the second distributor 13, and the second distributor 13 is configured as a slit-type tube plate with a slit space 131 provided around the evaporation tube 10. , but is not necessarily limited to this.

"Function" A. As described above, in the present invention, the advantages of the nozzle type and the slit type are utilized exclusively, and the flow rate of the liquid to be treated 11 is regulated by the nozzle type tube plate 12 while the After being distributed to each evaporation tube 10, the distributed liquid to be treated 11 is dispersed in the circumferential direction of the evaporation tube 10 by the slit type tube plate 13, so that when the flow rate of the liquid to be treated 11 is reduced, It also enables uniform liquid distribution and liquid film formation.

In other words, since the present invention employs a two-stage distribution structure, the above effects can be smoothly achieved even when the flow rate is reduced. , it becomes possible to effectively bring out the advantages of the bipartite bodies 12 and 13.

That is, the nozzle jet from the nozzle-type tube plate 12 is not used to attach the liquid to be treated 11 to the evaporation tube 10 as in the prior art, but the receiver is used as a second distributor 1 that functions as a plate.
Since the purpose is to inject and supply a predetermined amount to 3 evaporation tubes, there is no need to increase the number of nozzles, and one nozzle 121 per 10 evaporation tubes is sufficient, so the nozzle diameter can be increased. As a result, processing becomes easier and there is no need to worry about clogging.

In addition, since the nozzle 121 only needs to inject onto the slit type tube plate 13 which functions as a tray, there is no need to set an inclination angle and the nozzle 121 can be formed perpendicular to the tube plate 13. As a result, the nozzle processing accuracy becomes loose.

In addition, since excess liquid 11 to be treated is not supplied to the slit type tube plate 13 which serves as a tray, the evaporation tube 1
0 and slit! 31, it is easy to form a stable and uniform liquid film in the circumferential direction, and thereby the above effect can be smoothly achieved.

In this case, in a preferred embodiment of the invention:
Said pickpocket 7) Since the annular 1g133 is provided on the upper surface side of the tube plate 13 so as to surround 131, the nozzle +21
The ejected liquid to be treated U can be smoothly spread in the circumferential direction of the pipe, and the above effect is further improved.

Also, there is an annular groove on the bottom side of the tube plate 13! By providing the slit 34, the liquid to be treated 11 attached to the evaporation tube 10 from the slit 131 is prevented from being unevenly distributed and spread in the circumferential direction of the tube, and the liquid is prevented from being attached to a part of the evaporation tube 10. To further facilitate the formation of a stable and circumferentially uniform liquid film.

B. By the above method, it is possible to form a liquid film near the evaporation tube 10 directly below the slit type tube plate 13, but since the liquid film accompanies evaporation, the liquid film becomes thinner as it flows down the tube, and especially The evaporator tube 1 has a structure in which the liquid film formed directly below the slit type tube plate 13 is maintained over the entire length of the tube, since the liquid film is likely to break at low flow rates.
It is necessary to use 0.

Therefore, in the present invention, since the evaporation tube 1G (hereinafter referred to as a flute tube) in which a large number of vertical grooves 10a are formed on the outer circumferential surface is used, the liquid can be successfully distributed directly under the slit-type tube plate 13 according to the above-mentioned component (2). By allowing the liquid to flow through all of the vertical grooves 10a, it is possible to maintain this state over the entire length of the pipe up to a considerably low flow rate region.

In such a case, the liquid film will not be uniform in the circumferential direction of the tube, and the vertical groove 1
It is thick at the 0a part and becomes thinner at the mountain part, but a dry surface is unlikely to occur.Even if a dry surface occurs in one vertical groove 10a, it will not affect the surrounding vertical grooves 10a, so the dry surface will not spread or cause any problems. It doesn't become like a streaky flow.

C9 Furthermore, when the evaporation tube IO is formed of a bare tube,
Structurally, there is a tube plate 12° as described above in the middle of the tube 10.

Providing the tube plates 12', 13° and 14 as described above disturbs the liquid film, which is not preferable, but when using the flute tube in a low flow range, when the tube plates 12', 13° and 14 as described above are installed, Also, no disturbance of the liquid film occurs.

In addition, since the tube plates 12', 13', and 14 also function as intermediate support plates, they can prevent the evaporator tube lO from wobbling and deflecting, and the one or more tube plates 12', 13 degrees.

By arranging intermediate distribution bodies consisting of 14 in a multi-stage manner and configuring the liquid to be treated 11 to be supplied to each of the intermediate distribution bodies 12°, 13°, and 14, the liquid film thinned by the evaporation can be sequentially removed. A stable and uniformly formed liquid film can be maintained over the entire length of the pipe, and breakage of the liquid film near the lower end of the pipe 10 can also be prevented.

D. Now, in the falling liquid film type evaporator 1, the peripheral surface of the evaporation tube 10 is still dry at the initial stage of startup when the liquid to be treated 11 is supplied. It is necessary to create a state where it is easy to form.

Therefore, in a preferred embodiment of the present invention, the liquid pipe 60 leading from the processing liquid pump 6 to the evaporator 1 is branched, and the liquid to be processed is placed on the nozzle type tube plate 12 as well as on the slit type tube plate 13. With this structure, the flow rate can be easily increased by feeding the liquid 11 to be treated onto the slit type tube plate 13 as well as the nozzle type tube plate 12 at the time of startup, thereby eliminating the above-mentioned drawbacks. It is possible to aim for

"Embodiments" Hereinafter, preferred embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. It's nothing more than that.

FIG. 4 shows a heat pump system incorporating a falling film type evaporator M1 according to an embodiment of the present invention, in which a screw compressor 3 connected to a motor 2, a condensing vessel 4, liquid separator and refrigerant tank 5. An evaporator 1 is installed, and a refrigerant 11 compressed by a compressor 3 is condensed and liquefied by a condenser 4, and then stored in a refrigerant tank 5, and then pumped into the evaporator 1 by a refrigerant liquid circulation pump 6. An evaporation tube l introduced and vertically installed in the evaporator 1
While the refrigerant liquid flows in a film shape along the outer peripheral surface, it is heated and evaporated by the water flowing through the inside thereof, and the vaporized refrigerant is passed through the liquid separator and refrigerant tank 5 again to the compression y1.
The unevaporated refrigerant liquid in the evaporator 1 and the refrigerant liquid separated by the liquid separator 5a are stored in the refrigerant tank 5 again, and this cycle is repeated. There is.

Next, the internal structure of the evaporator 1 will be explained in detail.

The evaporator 1 consists of a vertical large-diameter cylindrical container 20 with a water groove outlet 21 and an inlet 22 opened at both upper and lower ends, and the upper and lower head plate portions of the internal space are partitioned by partition plates 23, 24 to form a water retention chamber 25. 28 and the partition plates 23 and 24
In the central space 19 sandwiched between the
+3° groups are arranged vertically in multiple stages at predetermined intervals to divide into a plurality of sections.

Furthermore, a plurality of evaporation tubes 10 are installed in the central space 19 so as to penetrate through the divided compartments, and both ends thereof are opened to the water retention chambers 25 and 28.

On the other hand, the discharge pipe 60 from the liquid circulation pump 6 has its tip branched into four branches, and these branch pipes 61 to 64 are connected to the nozzle-type tube plate 12 and the slit-type tube plate 13 via on-off valves 65, respectively.
Open at the top. A refrigerant gas return pipe 51 is provided between the space below the slit tube plate 13 and a position directly below the liquid separator 5a of the refrigerant tank 5, and a refrigerant gas return pipe 51 is provided between the lower end of the central space 19 near the lower partition plate and the bottom of the refrigerant tank 5. A liquid return pipe 52 is connected to each.

Next, the structure of the evaporator tube 10 and tube plates 12', 13', and 14 will be explained in detail based on FIGS. 2 and 3.

The evaporation tube 10 is a metal tube with good thermal conductivity along the axial direction.
It is formed of a flute tube with a large number of vertical grooves 10a evenly formed on the inner and outer circumferential surfaces.

The nozzle type tube plate 12 is configured to fit tightly around the outer periphery of the evaporation tube 10, and the nozzle type tube plate 12 is constructed using a nozzle 121 formed by perpendicularly perforating a through hole in the vicinity of the evaporation tube 10. The refrigerant accumulated above can be injected onto the circular recess 132 of the slit tube plate 13 located below. The slit-type tube plate 13 has a through hole slightly larger than the outer diameter of the evaporation tube 10, and forms a ring-shaped slit gap 131 with a very small gap width between it and the circumferential surface of the evaporation tube 10. A circular recess 13 is formed around the outer periphery of the void 131.
2 is recessed so that the refrigerant injected from the nozzle 121 can be stored therein. Ring-shaped rings tR133 and 134 having semicircular cross sections are formed on both upper and lower sides of the circular recess 132 to perform the above-described function.

Then, the pair of tube sheets 12' and 13' are
As shown in the figure, it may be arranged at a central position below the predetermined interval, or as shown in Fig. 2, the slit space +31
The intermediate tube sheet 14 having only the pair of tube sheets 12', 1
It may be placed instead of 3 degrees.

Next, since the operation based on this embodiment has already been explained in detail in the section of the operation of the invention, it will be briefly explained.
The liquid circulation pump 6 is driven while flowing the refrigerant 11 into the nozzle type tube plate 12 and the slit type tube plate 13 respectively.
is supplied to temporarily increase the liquid supply flow rate to form a uniform liquid film on the still dry peripheral surface of the evaporation tube 10.

After the liquid film is formed, the flow rate of the refrigerant liquid 11 from the nozzle 121 is regulated by stopping the supply of the refrigerant 11 from above the slit type tube plate 13 and supplying the refrigerant 11 only from above the nozzle type tube plate 12. However, the refrigerant liquid can be distributed to the circular concave portion 132 of the slit type tube plate 13 surrounding each evaporation tube 10, and after that, the distributed refrigerant liquid is distributed in the circumferential direction of the evaporation tube 10, and then evaporated from the slit gap 131. tube 10
A liquid film can be formed on the peripheral surface. Note that the refrigerant liquid 11
The flow rate is regulated by the nozzle 121 diameter and slit type tube plate 13
It can be easily controlled by changing or selecting the upper refrigerant liquid height H.

In this embodiment, tube sheets 12', +
3', intermediate tube sheet 14 with group or slit cavities 131;
It has a multi-stage structure, and the intermediate tube plate 12°, 1
Since the refrigerant liquid is configured to be able to be supplied to each stage, it is possible to sequentially replenish the liquid film that has become thin due to the evaporation, as well as the unevaporated refrigerant remaining at each stage, making it possible to maintain a stable and A uniformly formed liquid film can be maintained over the entire length of the tube.

"Effects" As described above, according to the present invention, by combining the two-stage distribution structure and the fluted flute tube, uniform liquid distribution and liquid film formation are possible even at low flow rates.
This eliminates the need to supply excess refrigerant liquid, making it possible to reduce the power of the liquid circulation pump and improve heat transfer performance.

Furthermore, the use of vertically grooved evaporation tubes expands the evaporation surface area and reduces the number of evaporation tubes installed, resulting in space savings.

In particular, by using a vertically grooved evaporator tube in a low flow rate range, the present invention can easily have a multi-stage structure even in a device that flows a refrigerant liquid in a film along the outer circumferential surface of the evaporator tube. This not only prevents the liquid film from breaking while flowing down the evaporation tube, but also prevents the evaporation tube from shaking or bending.

Furthermore, using a multi-stage structure using a liquid distribution mechanism consisting of the first distribution body and the second distribution body means that the liquid is held and redistributed at each stage of the distribution mechanism, so that liquid distribution is unevenly distributed at the top. Even if the temperature is lowered, the next stage can achieve uniformity and other effects.

It has various effects such as

[Brief explanation of the drawing]

1 to 4 each show an evaporator according to an embodiment of the present invention, FIG. 1 is an overall view, FIG. 2 is a detailed view of the main internal parts, and FIG. 3 is a cross-sectional view of FIG. 2. The plan view and FIG. 4 are overall schematic diagrams of a heat pump system using the evaporator. Patent applicant: Maekawa Seisakusho Co., Ltd.

Claims (1)

[Scope of Claims] 1) A flow-down system configured to allow at least a portion of the liquid to be evaporated while flowing the liquid to be treated in a film form along the outer peripheral surface of the evaporation tube vertically installed in the evaporation container. In a liquid film evaporator, a plurality of evaporation tubes each having a large number of vertical grooves formed on the outer circumferential surface;
a first distribution body that distributes the liquid to be treated introduced into the evaporator to each of the evaporation tubes; and a second distribution body that disperses the liquid to be treated distributed by the first distribution body in the circumferential direction of the evaporation tube. 2) A falling liquid film type evaporator according to claim 1), characterized in that the second distributor is disposed close to the lower side of the first distributor. In a film evaporator, the liquid pipe leading from the liquid pump to the evaporator is branched,
3) A falling liquid according to claim 1) or 2), characterized in that the liquid to be treated can be supplied onto the second distribution body as well as on the first distribution body. In the film-type evaporator, one or more intermediate distributors are disposed at a predetermined interval at least below the second distributor in the evaporator pipe installed vertically in the evaporator, and each intermediate distributor on the intermediate distributor 4) A falling liquid film type evaporator characterized in that the liquid to be treated can be supplied to the liquid to be treated. 5) The falling liquid film type evaporator according to claim 1), 2) or 3), wherein the second distributor is a slit type tube plate having a slit space around the evaporation tube.5) The falling liquid film type evaporator according to claim 4) A falling liquid film type evaporator characterized in that an annular groove is provided on both upper and lower sides of the tube plate so as to surround the slit of the slit type tube plate.