JPH09138086A - Heat transfer tube for absorption refrigerator - Google Patents

Abstract

(57) [Abstract] [Problem] The structure became complicated when trying to increase the absorption capacity. SOLUTION: Six ridges are formed in the longitudinal direction of the tube surface on the outer surface of the heat transfer tube, and the ridges are 0.18 degrees / mm or more and 0.72 degrees / mm or less with respect to the tube axis. A heat transfer tube for an absorption refrigerator, which is spirally arranged with a specific twist angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube used in a heat exchanger using an absorption refrigeration cycle such as an absorption refrigerator, an absorption chiller-heater, or an absorption heat pump, and more particularly to a heat transfer tube for an absorption refrigerator having improved performance. It is about.

[0002]

2. Description of the Related Art An absorber used in equipment using an absorption refrigeration cycle, such as an absorption refrigerator, an absorption chiller-heater, and an absorption heat pump, is constructed by arranging a large number of heat transfer tubes horizontally or vertically in a closed container. To be done. In this case, in the case of using the lithium bromide (LiBr) monoaqueous system which is most often used in Japan as the absorbent-refrigerant, a high-concentration LiBr aqueous solution is made to flow down from the upper part to the outer surface of the heat transfer tube, and then the film is formed in the evaporator. It is usual that the generated water vapor of the refrigerant is absorbed by the absorption liquid and at the same time, the latent heat at the time of absorption is removed by the cooling water flowing in the pipe.

Absorption is caused by a pressure difference between the evaporation pressure in the evaporator and the saturated vapor pressure of the absorbing liquid flowing down on the surface of the heat transfer tube. If this pressure difference is large, the absorption capacity is improved. Further, the lower the temperature or the higher the concentration of the absorbing liquid, the lower the saturated vapor pressure and the larger the pressure difference, which contributes to the improvement of the absorbing capacity. On the other hand, looking at the behavior on the outer surface of the heat transfer tube, the mass transfer in which the condensed water diffuses into the absorbing liquid and the heat transfer for the generation and removal of heat coexist, showing a very complicated aspect. However, the current situation is that the phenomenon has not been fully clarified yet. That is,
In order to improve the performance of the heat transfer tube, it is necessary to improve both of the above-mentioned mass transfer and heat transfer, but from the viewpoint of the absorption capacity, the heat transfer is improved and the mass transfer performance is improved. Is more important. However, the heat transfer tube for improving the mass transfer is expensive for its performance, and the heat transfer tube for the absorber is mainly a smooth tube. computer,
In the equipment industry, application to a large number of pins can be considered.

On the other hand, as a conventional absorber or heat transfer pipe, an absorber in which a large number of spiral grooves having an inclination angle of 15 ° to 45 ° are engraved on the outer surface of the heat transfer pipe (Actual Publication 64). -4051), a heat transfer tube formed by alternately arranging a plurality of peaks and valleys having a twist angle of 3 degrees or more on the outer surface of the tube in a spiral shape (JP-A-2-71062), the central axis of the tube body. Direction of the heat transfer tube and the longitudinal tube axial direction 15
A heat transfer tube having a plurality of ridges having a twist angle of not more than 3 degrees (Japanese Patent Application Laid-Open No. H3-236565), a valley portion toward the central axis of the tubular body, and a mountain portion protruding in the radial direction of the central axis are surrounded. A heat transfer pipe having a plurality of pleats alternately provided in the direction (Japanese Patent Laid-Open No. 5-39990) is known, but none of them has yet reached the satisfactory performance in terms of characteristics.

[0005]

The technical problems in the conventional heat transfer tube will be described. The current solution flow-down method is a method of flowing a solution in the form of a thin film, and the heat transfer resistance is further reduced to improve the efficiency of the equipment. For this reason, there is a trend toward more thin layers. In addition, as mentioned above, in order to improve the absorption capacity, it is a priori decided to promote mass transfer rather than heat transfer, but for that purpose, let's solve those problems. Since the structure of the heat transfer tube is inevitably complicated, the processing cost at the time of manufacturing is high and it is not yet in practical use. In particular, there is also a method in which a large amount of a surfactant such as n-octyl alcohol or diethylhexanol is added to cause severe interfacial disturbance based on the so-called Marangoni effect in the solution at the time of absorption to improve the absorption capacity. In this case, the structure of the heat transfer tube has not yet been industrially satisfied, and there is a strong demand for structural improvement of the heat transfer tube from this aspect.

Therefore, it is an object of the present invention to provide a heat transfer tube for an absorption refrigerator, which can more effectively develop heat transfer and mass transfer peculiar to the absorption phenomenon.

An object of the present invention is to provide a heat transfer tube for an absorption chiller in which two phenomena, heat transfer and mass transfer, are remarkably improved and the absorption capacity is dramatically improved.

Another object of the present invention is to provide at low cost a heat transfer tube for an absorption refrigerating machine having a simple structure, more effectively promoting heat transfer and mass transfer, and having improved absorption capacity. .

Another object of the present invention is that the structure is simple, the manufacturing process is easy, and the heat transfer and mass transfer peculiar to the absorption phenomenon in the tube outer surface tube longitudinal direction of the heat transfer tube for the absorption refrigerator. It is to provide a heat transfer tube that improves the above two phenomena economically and inexpensively.

[0010]

In order to achieve the above-mentioned object, the present invention forms a liquid film of the absorbing liquid on the outer surface of the pipe by dropping or spraying the absorbing liquid on the outer surface of the heat transfer pipe. In a heat transfer tube for an absorption refrigerating machine that transfers heat through the liquid film, a non-deformable portion is provided in the longitudinal direction of the outer surface of the tube to form six ridges. Provided is a heat transfer tube for an absorption refrigerating machine, wherein the parts are spirally arranged with a specific twist angle of 0.18 degrees / mm or more and 0.72 degrees / mm or less with respect to the tube axis.

In a heat transfer tube for an absorption refrigerator in which an absorbing liquid is dropped or sprayed on the outer surface of the heat transfer tube to form a liquid film of the absorbing liquid on the outer surface of the heat transfer tube and heat is transferred through the liquid film. The outer surface of the pipe has six ridges formed in the longitudinal direction of the pipe axis, and these ridges are 0.18 degrees / mm with respect to the pipe axis.
As described above, by arranging spirally with a specific twist angle of 0.72 degrees / mm or less to form a heat transfer tube for an absorption refrigerator, both heat transfer and mass transfer peculiar to the absorption phenomenon in the heat transfer tube can be performed. I am trying to improve it.

Further, the six convex ridges arranged spirally in the longitudinal direction of the tube outer surface of the heat transfer tube for the absorption chiller are formed to be concave on the inner surface of the tube. The liquid film of the absorbing liquid on the outer surface of the tube and the heat transfer on the inner surface of the tube are efficiently performed.

Furthermore, the outer surface of the heat transfer tube for the absorption refrigerator is 0.18 degrees / mm or more with respect to the tube axis in the tube axis longitudinal direction.
The heat transfer tube having six ridges arranged spirally with a specific twist angle of 72 degrees / mm or less is made of metal such as copper or copper alloy. Examples of copper include electrolytic copper and oxygen-free copper, and examples of copper alloys include copper and tin, copper and zirconium, and copper and silver. Thereby, the liquid film of the absorbing liquid on the outer surface of the tube and the heat transfer on the inner surface of the tube are configured to be performed very efficiently.

The outer surface of the heat transfer tube for an absorption refrigerating machine has six ridges arranged spirally with respect to the tube axis in the longitudinal direction of the tube axis, and the specific twist angle is 0.18 degrees / mm or less. In such a case, the absorbing liquid spreads in the lateral direction, but cannot pass over the ridges, and the absorbing liquid forms a thick film between the ridges, which hinders heat transfer, and improvement in absorption performance cannot be expected. on the other hand,
When the specific twist angle is 0.72 degrees / mm or more, the absorbing liquid flows down in the circumferential direction, the stirring effect of the absorbing liquid cannot be expected, and improvement in absorption performance cannot be expected. Therefore, in the present invention, the six ridges formed spirally with respect to the tube axis have a specific twist angle of 0.18 degrees / mm to 0.72 degrees / mm, which is characteristic of the absorption phenomenon in the heat transfer tube. This is the most appropriate area to improve both the two phenomena of heat transfer and mass transfer.

[0015]

1 is a cross-sectional view of a heat transfer tube according to an embodiment of the present invention, and FIG. 2 is an external view of the heat transfer tube according to an embodiment of the present invention. FIG. 3 is an explanatory view showing an example of a method for manufacturing the heat transfer tube according to the present invention, FIG. 4 is a front view of a processing die used for manufacturing the heat transfer tube according to the present invention, and FIG. 5 is another embodiment of the heat transfer tube according to the present invention. It is a form and is an external view of a heat transfer tube. 1, which shows an embodiment of the heat transfer tube of the present invention, a ridge 12 having a predetermined pitch and a twist angle is provided on the outer surface of the heat transfer tube body 10. 11 is a smooth part. Specifically, the ridges 12 are formed in six rows on the periphery of the heat transfer tube body 10, and the ridges 12 are formed on the heat transfer tube body 1
No. 0 outer surface of the tube relative to the longitudinal axis of the tube relative twist angle 0.3
It is arranged with a slight twist of 6 degrees / mm.
In the heat transfer tube according to the embodiment shown in FIG. 1, a concave streak portion 13 is formed inside the heat transfer tube main body 10 in which the convex streak portion 12 is formed.

The ridge portion 12 of the heat transfer tube according to the embodiment of the present invention shown in FIG. 1 acts to spread the absorbing liquid dropped or sprinkled from the upper portion on the outer surface of the tube, particularly on the surface of the heat transfer tube in the axial direction of the tube. To do. As a result, the absorbing liquid becomes a thin liquid film and covers the surface of the heat transfer tube to increase the heat transfer coefficient, and at the same time, it is possible to improve the mass transfer characteristic of the absorption phenomenon by the flow in the tube axial direction, thereby improving the absorption performance. is there. On the other hand, the inner surface of the tube of the ridge 12 is a ridge 13. The cooling water flowing in the pipe is disturbed by the recessed portion 13, and as a result, the heat transfer performance inside the heat transfer tube is improved, and the heat transfer performance of the heat transfer tube as a whole is improved.

In the embodiment of the heat transfer tube shown in FIG. 2, the outer surface of the heat transfer tube body 20 is provided with the ridge portion 22 having a predetermined pitch and a twist angle. 21 is a smooth part. Specifically, the ridges 22 are formed in six rows on the periphery of the heat transfer tube body 20, and the ridges 22 have a specific twist angle with respect to the tube axis in the tube outer surface tube axis longitudinal direction of the heat transfer tube body 20. It is arranged with a gentle twist of 0.28 degrees / mm. Also in the embodiment of the heat transfer tube shown in FIG. 2, the ridge portion 22 acts on the outer surface of the tube so as to spread the absorbing liquid dropped or sprinkled from the upper part particularly on the surface of the heat transfer tube in the tube axial direction. As a result, the absorbing liquid becomes a thin liquid film and covers the surface of the heat transfer tube to increase the heat transfer coefficient, and at the same time, the mass transfer characteristic of the absorption phenomenon is improved by the flow in the tube axial direction to improve the absorption performance.

FIG. 3 is a schematic view showing an embodiment of a method for manufacturing a heat transfer tube of the present invention. In the processing die 32, 12 protrusions 42 having a predetermined pitch and height are provided on the inner surface of the die body 41 shown in FIG. The processing die 3
2 is fixed to a rotating device 33 located outside of FIG. 3 and is rotatably attached. Since the heat transfer tube for absorption type is not so high in working pressure, a relatively thin copper tube or the like is used. The convex tube portion 12 or 22 can be formed on the outer surface of the tube 31 having a circular cross-section, such as a thin copper tube, by performing drawing while passing the rotating processing die 32. In this case, six recesses 13 are formed on the inner surface of the pipe.

FIG. 5 shows a heat transfer tube according to another embodiment of the present invention. In this embodiment, the diameter of the raw pipe having a circular cross section such as a thin copper pipe is made larger than the height of the protruding portion 52. The six ridge portions 52 arranged and formed spirally with respect to the tube axis of the heat transfer tube have a width of 0.18 degrees / mm or more to 0.
It is formed so as to have a specific twist angle of 72 degrees / mm or less. This is to improve both the two phenomena, heat transfer and mass transfer, which are peculiar to the absorption phenomenon in the heat transfer tube. In addition, in order to improve the absorption performance, a groove 51 perpendicular to the tube axis direction may be formed in the lengthwise direction in the smooth portion between the six ridges 52. Furthermore, even if the heat transfer tube has a small thickness, fine grooves can be formed on the inner surface of the heat transfer tube. By providing such grooves 51 perpendicular to the tube axis direction or fine grooves on the inner surface of the heat transfer tube, the absorbing liquid becomes a thin liquid film and has the effect of improving the heat transfer coefficient covering the surface of the heat transfer tube. As a result, the characteristics of mass transfer peculiar to the absorption phenomenon due to the flow in the axial direction of the tube are improved, and the absorption performance can be improved.

[0020]

As an effect of the present invention, it is possible to provide a heat transfer tube for an absorption refrigerating machine capable of efficiently advancing heat transfer and mass transfer peculiar to an absorption phenomenon.

Another advantage of the present invention is to provide a heat transfer tube for an absorption refrigerator, which has a simple structure and which remarkably improves two phenomena of heat transfer and mass transfer and has dramatically improved absorption capacity. You can

Further, as an effect of the present invention, it is possible to economically provide a heat transfer tube for an absorption refrigerator, which has a simple structure, efficiently promotes heat transfer and mass transfer, and has improved absorption capacity at low cost. Can be done.

Another advantage of the present invention is that the structure is simple, the manufacturing process is easy, and the heat transfer characteristic of the absorption phenomenon in the longitudinal direction of the tube outer surface of the heat transfer tube for the absorption refrigerator is achieved. It is possible to economically and inexpensively provide a heat transfer tube in which two phenomena called mass transfer are improved.

Another advantage of the present invention is that, in addition to improving the absorption performance, it does not require a special apparatus and can be processed at high speed by a general drawing manufacturing apparatus, so that it can be used at a low cost for a high-performance absorption refrigerator. A heat transfer tube can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heat transfer tube according to an embodiment of the heat transfer tube of the present invention.

FIG. 2 is an external view of a heat transfer tube according to the embodiment of the heat transfer tube of the present invention.

FIG. 3 is an explanatory view showing an example of a method for manufacturing a heat transfer tube according to the present invention.

FIG. 4 is a front view of a processing die used for manufacturing the heat transfer tube according to the present invention.

FIG. 5 is an external view of a heat transfer tube according to another embodiment of the heat transfer tube of the present invention.

[Explanation of symbols]

 10 heat transfer tube main body 11 smooth section 12 convex streak section 13 concave streak section 20 heat transfer tube main body 21 smooth section 22 convex streak section 31 element pipe 32 processing die 33 rotating device 41 die body 42 projection 51 groove 52 convex streak section

Claims (2)

[Claims] Claim: What is claimed is: 1. A transfer for an absorption refrigerating machine, wherein an absorbing liquid is dropped or sprinkled on the outer surface of a heat transfer pipe to form a liquid film of the absorbing liquid on the outer surface of the heat transfer pipe, and heat is transferred through the liquid film. In the heat pipe, a non-deformable portion is provided in the longitudinal direction of the outer surface of the tube to form six ridges, and the ridges are 0.18 degrees / mm or more with respect to the tube axis, and are 0. A heat transfer tube for an absorption refrigerator, which is spirally arranged with a specific twist angle of 72 degrees / mm or less. 2. The heat transfer tube for an absorption refrigerating machine according to claim 1, wherein the six ridges are formed in a concave shape on the inner surface of the tube.