JPH0854158A - Heat exchanger for absorption type refrigerating machine - Google Patents

Abstract

PURPOSE:To improve the wetting property of a lower stage side heat transfer tube, in which the transfer liquid is effected in later half after receiving the liquid from an upper stage side by a plurality of times and wetting is readily becomming uneven generally while bad effect due to the vertical deviation of the axis of tube is readily generated. CONSTITUTION:A pair tube, having a flat surface 3, is employed for heat transfer tubes 1A-1J positioned at an upper stage side among 20 pieces of heat transfer tubes 1A-1J provided in an evaporator 5 or an absorber 6 while a shot- blasted tube, on the surface of which a non-directional rough surface 4, produced by shot-blasting treatment for spreading dropped liquid into four directions, is formed, is employed for heat transfer tubes 1K-1T positioned at a lower stage side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for an absorption refrigerator used as an evaporator or an absorber of an absorption refrigerator.

[0002]

2. Description of the Related Art Conventionally, a heat exchanger for an absorption refrigerating machine of this type has been disclosed in Japanese Patent Laid-Open No. 3-255862 and FIG.
As shown in, heat transfer tubes A, B, ... M extending horizontally vertically over a plurality of stages are provided below the sprayer V for spraying the liquid, and the liquid sprayed from the upper side is sequentially transferred to the lower side. The surface of each heat transfer tube A, B, ... M is wetted with a liquid so that the liquid exchanges heat with the fluid flowing in the heat transfer tube. Specifically, in the evaporator, water that serves as a refrigerant is sprayed on the surface of the heat transfer tube to remove the heat of evaporation from the cooling water flowing in the heat transfer tube, and in the absorber, it is absorbed on the surface of the heat transfer tube. A solution of lithium bromide, which is a solution, is sprayed to give absorption heat to the cooling water flowing in the heat transfer tube.

[0003] Then, a ridge X extending along the tube axis is provided on the surface of each of the heat transfer tubes A to F and HM located on the upper side and the lower side, and the liquid adhering to the tube surface is called Marangoni convection. In addition to causing vigorous convection, a spiral ridge Y having a helix angle with respect to the tube axis direction is provided in the heat transfer tube G located in the middle stage to disperse the liquid in the longitudinal direction of the tube axis and Improving the wetting characteristics of the lower heat transfer tubes H to M that are likely to be partially non-uniform with respect to the tube axis, and preventing the lower heat transfer tubes H to M from forming non-wetting regions, As a whole, it aims to improve the heat transfer characteristics.

[0004]

However, the Marangoni convection is an effect obtained by adding an alcohol component to the absorbing solution without any special provision of the ridge X along the tube axis direction. . Further, the liquid is to be dispersed in the tube axial direction along the spiral ridge Y provided in the middle heat transfer tube G, but the tube axis between the middle heat transfer tube G and the upper heat transfer tube F is Assuming that the liquid perfectly falls in the vertical direction and always falls on the top of the heat transfer tube G in the middle stage, as shown in FIG. 7, the tube axes of the respective stages ... F, g, h.・
Usually, j, k, ... Deviate due to an assembly error in the manufacturing process, a heat cycle, etc., and when the liquid W drops to a position outside the top of the heat transfer tube G in the middle stage, The liquid is gathered only on one side, the right side or the left side in the tube axis direction along the spiral ridge Y, and the wetting area of the lower heat transfer tubes H ... Happens. Further, in the lower heat transfer tubes H to M, the liquid flow amount in the tube axial direction tends to be partially non-uniform, and in the portion where the liquid flow amount is small, the top and bottom of the heat transfer tube K are displaced by the vertical pipe axis deviation. If the liquid falls to a position outside the area, there is a problem that the liquid does not fill the entire outer circumference of the pipe and only half of the liquid gets wet.

Therefore, the above problems have a problem that the heat transfer characteristics are not sufficiently improved although the structure of the heat transfer tube is complicated and the cost is high.

In the present invention, the liquid is delivered in the latter half after the liquid has been handed over from the upper stage a plurality of times, and generally, the wetting is likely to be non-uniform, and in addition, the adverse effect due to the vertical displacement of the pipe axis is caused. Focusing on the lower heat transfer tube that is easy to come out and improving the wettability of this lower heat transfer tube, it is possible to make the surface of the upper heat transfer tube from the upper step to the lower step overall wet at low cost. In addition, it is an object of the present invention to provide a heat exchanger for an absorption refrigerator, which can improve the heat transfer characteristics.

[0007]

Therefore, in order to achieve the above object, an absorption provided with heat transfer tubes 1A, 1B, ... In the heat exchanger for a refrigerator, bare tubes having a flat surface 3 are used for the heat transfer tubes 1A to 1J located on the upper stage side, and the dripping liquid is applied to the surfaces of the heat transfer tubes 1K to 1T located on the lower stage side. The non-directional rough surface 4 that spreads in all directions was formed.

[0008]

The upper heat transfer tubes 1A to 1J in which the number of times of delivering liquid is small and the amount of liquid flowing in the tube axial direction is relatively uniform are
Since the bare tube having the flat surface 3 is used, the cost can be reduced accordingly. Liquid transfer is via the upper heat transfer tube 1A
It was done in the latter half after passing the liquid inheritance from ~ 1J multiple times,
Since the non-directional rough surface 4 that spreads the dripping liquid in all directions is formed on the surface of the heat transfer tubes 1K to 1T on the lower stage side where the liquid flow amount tends to be non-uniform in the tube axis direction, The liquid film can be spread over a wide area in the longitudinal direction, and the liquid flow rate in the pipe axis direction can be made uniform, which allows the transfer of the lower stage side regardless of the deviation of the pipe axis in the vertical direction. A wet region can be formed on the entire surface of each of the heat tubes 1K to 1T. Thus, the heat transfer characteristics can be improved at the minimum cost.

[0009]

FIG. 3 shows an absorption refrigerator having an evaporator 5 and an absorber 6 which constitute a heat exchanger for an absorption refrigerator according to the present invention. The evaporator 5 and the absorber 6 are provided adjacent to each other inside the same container 50 with the eliminator 51 interposed therebetween, and below the sprayer 2 for spraying the liquid, a plurality of vertically, for example, 20 horizontal stages. Heat transfer tube 1
A, 1B ... In the evaporator 5, water serving as a refrigerant is sprayed from the sprayer 2 and the heat transfer tubes 1A, 1B ...
..Take off heat of evaporation from cooling water flowing to
Then, the lithium bromide aqueous solution as an absorbing solution is sprayed from the sprayer 2 to give absorption heat to the cooling water flowing through the heat transfer tubes 1A, 1B ....

In FIG. 3, 71 is a refrigerant pump, 72 is a solution pump, 73 is a low temperature heat exchanger, 74 is a high temperature heat exchanger, and 81.
Is a high temperature generator that uses the burner 82 as a heat source to generate a refrigerant from a dilute solution containing a large amount of refrigerant in the absorber 6, 83 is a heat transfer tube group 84 through which the refrigerant vapor generated in the high temperature generator 81 flows.
And the high temperature heat exchanger 74 generated by the high temperature generator 81.
The low-temperature generator that generates a refrigerant from the intermediate-concentration solution after passing through the condenser 85 is a condenser that condenses the refrigerant vapor generated in the low-temperature generator 83 by the cooling water pipe 86 that is continuously provided after the heat transfer pipe 1A of the absorber 6. It is a vessel.

In the above-mentioned structure, as shown in FIGS. 1 and 2, the evaporator 5 and the absorber 6 are respectively provided with 20.
Among the heat transfer tubes 1A to 1T, 10 heat transfer tubes 1A to 1J located on the upper stage side are bare tubes made of a copper tube or an iron tube having a flat surface 3 and are located on the lower stage side.
In the heat transfer tubes 1K to 1T of the book, on the surface of the tube material 10 made of a copper tube, an iron tube or the like, by the shot blasting treatment described below,
A shot blast tube is used which has a large number of random scratches with a depth of about 0.5 to 1000 microns and which has a non-directional rough surface 4 that spreads the dropped liquid in all directions.

In FIGS. 1 and 2, reference numeral 21 is a spray tray of the sprayer 2, 22 is a refrigerant or solution outlet, and 23 is a dispersion plate.

In the shot blasting treatment, as a blasting material, silica sand having a particle diameter of 0.005 mm to 3.0 mm or non-metallic sand such as alumina is used, and as a treatment method, it is moved while rotating as shown in FIG. 0.5 kgf / cm ² from the nozzle 9 toward the tube material 10 to be made to move with an air compressor or the like.
A direct pressure type in which a blast material is injected together with compressed air pressurized to ˜20 kgf / cm ² is adopted. However, it is also possible to use a metal material such as a cast iron grid, a copper slab, or a nickel slab as the blast material. As a processing method, a rotor type in which the blast material is projected onto the rotor blades and scattered by centrifugal force is adopted. It is also possible.

Incidentally, the pipe material 10 has a diameter of 15 mm,
Table 1 shows the results of the direct pressure treatment using a non-metallic blast material having an average particle diameter of 0.5 mm, using a copper tube having a length of 300 mm.
Table 2 shows the results of rotor-type processing using a cast iron grid with an average particle size of 0.7 mm.

[0015]

[Table 1]

[0016]

[Table 2]

As is clear from Tables 1 and 2, the direct pressure type can deepen the scratch and can effectively improve the wettability as compared with the rotor type. In addition, since the non-metallic blast material is used, dissimilar metals do not remain on the surface of the heat transfer tube, the potential on the surface of the heat transfer tube can be prevented from becoming non-uniform, and the cause of corrosion can be eliminated.

With the above structure, as shown in FIG. 1, the liquid is delivered in the latter half after the liquid is passed from the upper heat transfer tubes 1A to 1J a plurality of times, and the liquid flow amount in the axial direction of the pipe is increased. On the surface of the heat transfer tubes 1K to 1T on the lower side where the liquid tends to be non-uniform, a non-directional rough surface 4 formed by shot blast that spreads the dropped liquid in all directions is formed. Since the film W (hatched portion) can be widened in a wide range, a region Z of a nest where a little wetting does not occur at both ends in the axial direction of the heat transfer tube 1J located at the lowermost side of the upper stage and in the middle thereof. Even if there is a tendency to occur, such growth of the nest Z can be prevented, and the liquid flow amount in the pipe axis direction can be made uniform. As a result, as shown in FIG. 2, even if the pipe axis is deviated in the vertical direction, a wetted region can be entirely formed on the surfaces of the lower heat transfer tubes 1K to 1T regardless of the deviation. You can do it.

In the above, the non-directional rough surface 4 was formed by shot blasting. However, as shown in FIG. 5, the minute projections 41 having a size of about 1 mm to 3 mm are formed on the surface of the tube material 10. The non-direction rough surface 4 may be formed by providing a large number in the tube axis direction and the circumferential direction. For a tube having such microscopic projections 41,
The tube commercially available from Kobe Steel, Ltd. under the product name Top Cross CT can be used as it is. Even with such minute projections 41, as in the case of the above-mentioned shot blasting treatment, the dripping liquid can be spread in four directions in the tube axial direction and the circumferential direction without any direction, and the heat transfer tubes 1K to 1T on the lower stage side can be spread. Can improve wettability,
The same effect as above can be obtained.

In the embodiment described above, the heat transfer tubes 1A-1
T was set to 20 stages, 10 stages on the upper stage side were used as bare pipes, and non-directional rough surfaces 4 were formed on the 10 stages on the lower stage side, but it is not necessary to divide them into halves, for example, 8 stages on the upper stage side. In the bare tube,
The non-directional rough surface 4 may be formed in the lower 12 steps, or the upper 12 steps may be formed as a bare tube and the lower non-directional surface 4 may be formed in the lower 8 steps. Further, the total number of stages does not have to be 20, and may be about 10 stages, or may be 20 stages or more. Generally, about 50% of the total number of upper stage heat transfer tubes are used as bare tubes. The non-directional rough surface 4 may be formed on the lower heat transfer tube of the other half.

[0021]

According to the present invention, bare tubes having a flat surface 3 are used for the upper heat transfer tubes 1A to 1J in which the number of times of delivery of liquid is small and the liquid flow amount in the pipe axial direction is relatively uniform. Therefore, the cost can be reduced accordingly, the liquid is delivered in the latter half, and the amount of liquid flowing in the tube axial direction tends to be non-uniform. Since the non-directional rough surface 4 that expands is formed, the liquid film can be widely spread in the circumferential direction and the longitudinal direction of the pipe, and the liquid flow amount in the pipe axial direction can be made uniform,
As a result, even if the pipe axis is deviated in the vertical direction, it is possible to form a wetted region on the entire surface of the lower heat transfer tubes 1K to 1T regardless of the deviation, resulting in the minimum cost. Thus, the heat transfer characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a side view of a heat exchanger for an absorption refrigerator according to the present invention.

FIG. 2 is a sectional view of the heat exchanger.

FIG. 3 is a piping diagram of an absorption refrigerator having the same heat exchanger.

FIG. 4 is a diagram illustrating a process of manufacturing a non-directional rough surface by the same shot blasting.

FIG. 5 is an enlarged view of a main part showing another embodiment of the same non-directional rough surface.

FIG. 6 is a side view of a conventional heat exchanger for an absorption refrigerator.

FIG. 7 is a cross-sectional view illustrating a conventional problem.

[Explanation of symbols]

1A to 1T; heat transfer tube, 2; spreader, 3; flat surface, 4;
Non-directional rough surface

Claims (1)

[Claims] 1. Below a sprayer (2) for spraying liquid,
Heat transfer tubes (1A, 1
In the heat exchanger for the absorption refrigerating machine provided with B ...), a flat surface (3) is provided on the heat transfer tubes (1A to 1J) located on the upper side.
Is used, and a non-directional rough surface (4) that spreads the dripping liquid in all directions is formed on the surface of the heat transfer tube (1K to 1T) located on the lower side. Heat exchanger for absorption refrigerator.