JPH01102295A - Heat transmission pipe externally exchanging heat - Google Patents

Abstract

PURPOSE:To provide a heat transmission pipe which excels both in boiling and condensing performances by providing the heat transmission pipe with fins and spiral grooves, and performing the condensing on the fin side and the boiling with the spiral grooves and boiling enhancing nuclei disposed in the bottom of the groove. CONSTITUTION:At the time of condensing, fins 10 which cover most of the outer surface of a heat transmission pipe 5 have much chance of contact with the vaporized heating medium, and promote the nucleated condensation with their tips as nuclei. At the time of boiling, on the other hand, the liquid heating medium is in contact with the entire outer surface of the heat transmission pipe 5, and is most actively boiled in the bottom 13 of spiral grooves 11 where the temperature is higher than the fins 10 because of the closeness to the heat source flowing through the pipe. Since boiling enhancing nuclei 15 are formed in the groove bottom 13 with fine ribs 14, the nucleated boiling of heating medium can be physically enhanced in addition to the temperature condition. Further, as air bubbles generated at the groove bottom 13 rise because of their buoyancy, they contact the surface of the fin 10 adjacent to the spiral groove 11 to disturb the liquid film, improving the heat transmission through the fins 10.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a heat transfer tube applied to a heat exchanger such as a refrigerator or an air conditioner, in which heat exchange is performed by bringing a heat medium into contact with the outer surface of the tube. Regarding things of form.

(Prior Art) Conventionally, in order to particularly improve the boiling performance of this type of heat exchanger tube, one in which corrugated fins are wrapped around the outer surface of the wood tube is known (Japanese Utility Model Publication No. 170460/1983). The corrugated fins are formed by forming a large number of cuts at minute intervals in a strip-shaped thin metal plate, and further deforming the plate surface into a wave shape to form voids for boiling bubble nuclei between adjacent peaks of the fins.

In addition, in a heat transfer tube in which the inside of the tube is used as a heat medium passage, two systems of spiral grooves in opposite directions that intersect with each other are formed adjacent to each other in a group on the inner wall of the tube, and the groove depths of the trapezoids are varied to increase the protrusion height. It is well known to have a row of pyramidal protrusions with different numbers (Japanese Patent Publication No. 6, 1983).
1-32599).

This is intended to improve the heat transfer coefficient between the heat medium and the heat transfer tube by the group of protrusions.

(Problems to be Solved by the Invention) As described above, in order to improve the boiling performance or condensing performance of heat transfer tubes, many heat transfer surface structures that match each phenomenon have been proposed. However, even though conventional heat transfer tubes are excellent in either boiling performance or condensing performance, they cannot satisfy both performances at the same time. There was a difference in heat exchange ability depending on the case. Therefore, for example, if the conventional heat transfer tubes described above are applied to the heat exchanger of a heat pump type air conditioner, either the cooling capacity or the heating capacity will be insufficient, and it is necessary to compensate for this lack of capacity. The upper heat exchanger had become larger.

In addition, when trying to increase the heat exchange capacity by increasing the diameter of the heat exchanger tube, it is possible to increase the heat exchange capacity by increasing the diameter of the heat exchanger tube.
It was difficult to sufficiently improve the heat transfer coefficient even if the heat transfer surface structure intended for heat transfer tubes of 2000 to 30000 was applied as it was. For example, when condensation is performed by forming two types of pyramid-shaped protrusion rows on the surface of an external heat exchange type heat transfer tube with a diameter exceeding 100 mm, as in the conventional example, the condensate flows down the tube. The condensate layer becomes thicker toward the bottom, making it impossible to obtain sufficient condensing performance. This is because there is a large difference between the amount of heat medium to be boiled or condensed and the processing capacity of the specified heat transfer surface structure, and even if the heat transfer surface structure is scaled up in response to a change in diameter. Even if this is the case, it is presumed that this is because performance cannot necessarily be improved.

The present invention has been proposed in view of the above, and is a heat transfer tube using an extra-tube heat exchange method, which has a heat transfer surface structure that can be adapted to both boiling and condensation functions, thereby achieving both boiling performance and condensation performance. The purpose is to obtain heat exchanger tubes that are corroded by corrosion.

Another object of the present invention is to realize miniaturization of a heat exchanger in an air conditioner for both cooling and heating by applying heat exchanger tubes having excellent boiling and condensing performance to the heat exchanger.

(Means for solving the problem) The heat transfer tube of the present invention has a heat transfer surface structure that is mainly effective for boiling and a heat transfer surface structure that is mainly effective for condensation, respectively, corresponding to boiling action and condensation action. This improves both boiling and condensing performance in a well-matched manner.

In other words, we aim to roughly differentiate the heat transfer functions regarding both boiling and condensation actions.

Specifically, as shown in FIG. 1, condensation is mainly performed by fins (10) formed on the outer peripheral surface of the tube body (5a), and the fins (10) are divided into groups at multiple points in the circumferential direction. A boiling accelerating nucleus (15) effective for boiling action is formed at the groove bottom (13) of the spiral groove (11). The fin (10
) is integrally formed with the tube body (5a) so as to surround the outer peripheral surface of the tube body (5a) and continue in a chevron shape along the tube axis.

Further, the spiral groove (11) is arranged such that the groove bottom (13) is located radially inside the virtual cylindrical surface (12) connecting the base parts (10a) of the fins (10).
) formed on the outer peripheral surface. That is, adjacent fins (10)
The full depth of the spiral groove (11) is set larger than that of the fin groove formed therebetween.

Here, the boiling accelerating nucleus (15) is provided with a large number of minute protrusions (14) on the groove bottom (13), and between adjacent minute protrusions (14), as shown in FIG. A branch groove (16) is formed which opens into the groove, and the cross section of the branch groove (16) is formed in an inverted Ω-shape so that the opening is the narrowest.

(Function) Accordingly, in the present invention, during condensation, the fins (10) occupying most of the outer surface of the heat transfer tube (5) have many opportunities to come into contact with the heat medium in the vapor state, and the tip of the fin (10) has many opportunities to come into contact with the heat medium in the vapor state. Promote condensation. The droplets condensed on the fins (10) gradually grow and flow down along the outer surface of the fins (10) in the direction of gravity. At this time, the fin (10) has a spiral groove (
11), the condensate quickly flows through the fin grooves between the fins (10) and into the spiral grooves (11).
It falls from the lower end in the direction of gravity. In other words, the condensate is quickly removed from the fins (10) or fin grooves to prevent accumulation, the fins (10) are maintained below the steam saturation temperature, and the cooling energy of the fins (10) is taken away by the condensate. to prevent

On the other hand, during boiling, the liquid heat medium is in contact with the entire outer surface of the heat transfer tube (5), but the spiral groove (11) is closest to the heat source passing through the tube and has a higher profile than the fins (10). It boils actively at the bottom of the groove (13).

Furthermore, the groove bottom (13) is formed of, for example, minute protrusions (14). l! ! Since the promoting nuclei (15) are provided, in addition to the above-mentioned temperature conditions, nucleate boiling of the heating medium can be physically promoted. Furthermore, when the bubbles generated at the groove bottom (13) rise due to their buoyancy, they come into contact with the surface of the fin (10) adjacent to the spiral groove (11), disturbing the 'a membrane and causing the fin (10) to can improve heat transfer.

(First Embodiment) FIGS. 1 to 5 show a first embodiment in which the present invention is applied to a heat exchanger in a heat pump type air conditioner for both cooling and heating.

In Fig. 2, the heat exchanger (1) has an inlet ice chamber (3) and an outlet ice chamber (4) partitioned on the left and right sides of a sealed tank body (2), and the space between the two ice chambers (3) and (4) is divided. Many heat exchanger tubes (5)
Both Himuro (3) are connected.

(4) A heat exchange chamber (6) is separated between the two.

An inlet (7) is opened on the peripheral wall side of the heat exchange chamber (6), and the heat medium supplied from the inlet (7) exchanges heat while contacting the heat transfer tube (5). It is sent out from an outlet (8) opened on the other side of the peripheral wall. Said entrance ice room (3)
An inlet (3a) and an outlet (4a) are also provided to the and outlet ice chamber (4), respectively, and the outlet (4a) is connected from the inlet (3a) to the outlet (4a).
The system provides water that is regulated for

In FIGS. 3 and 4, the outer peripheral surface of the heat exchanger tube (5) facing the heat exchange chamber (6) has fins (10) and spiral grooves (1
A heat transfer surface structure consisting of 1) is provided. fin(
10) is integrally formed with the tube body (5a) so as to surround the outer peripheral surface of the tube body (5a) and continue in a chevron shape along the tube axis. Specifically, for example, the tube body (5a) is cut to form continuous chevron-shaped fins (10). The fins (10) may be separated each time they go around the tube body (5a), or may be continuous like a single or multi-thread thread.

The spiral groove (11) is formed so as to gently turn right in the tube axis direction while intersecting the fin (10). 10) is divided at multiple points in the circumferential direction. In other words, every time the fin (10) goes around the tube body (5a), the fin (
10) is divided into equal numbers due to the spiral groove (11).

As shown in FIG. 1, the groove depth of the spiral groove (11) is set larger than the depth of the fin groove between adjacent fins (10). Specifically, with reference to the virtual cylindrical surface (12) connecting the bases (10a) of the fins (10), the grooves are formed so that the groove bottom (13) of the spiral groove (11) is located radially inward from this. Set depth.

Then, a boiling promoting core (15) consisting of a large number of minute protrusions (14) is formed on the groove bottom (13). As shown in FIG. 5(b), the minute protrusions (14) are formed in a series along the spiral groove (11), and a branch groove (16) opening outward is formed between each adjacent portion. It is formed. This branch groove (16
) is formed in an inverted Ω-shape in cross section, and its opening width is the narrowest compared to other parts.

FIGS. 5(a) and 5(b) show an example of processing the boiling accelerating nucleus (15). In this case, after forming continuous mountain-shaped minute protrusions (14) on the groove bottom (13), the roller (14) is attached to the tip of each protrusion.
7) and crush the top to form an inverted Ω-shaped branch groove (16).
form. Figure 5(b) shows the fin (10) and the spiral 1i.
The main dimension symbols of l ('11) and boiling accelerated nucleus (15) are shown, and the details are as follows.

Projection height (Fr) of fin (10) = 1.0~3WIW+ Width of spiral groove (11) (W>=2~4+nyn Spiral groove (1
1) Total depth (E) = 2~5ynv Total depth of nuclear groove (16) (G) = 0.4~1.0 However, in this case, the diameter (outer diameter) of the heat exchanger tube (5) is 10
0 to 300+ nm.

According to the heat exchanger tube (5) configured as above, the condensing action is mainly performed by the group of fins (1o), and the boiling action is mainly performed by the boiling accelerating core (15) provided in the spiral groove (11), The heat medium can be efficiently processed in both cases of boiling and condensation.

During condensation, the fin (1o) with the largest surface area has many opportunities to come into contact with the heat medium vapor, and nuclear condensation occurs at its tip. The droplets condensed on the fins (10) gradually grow and flow down along the fins (10) or along the fin grooves between adjacent fins in the direction of gravity. And the spiral that divides the fin (10) @ (11)
and flows down along this groove (11) into the heat exchanger tube (
5) Fall from the bottom side. In this way, the fin (10
) is quickly guided to the spiral grooves (11) at multiple points in the circumferential direction of the fins (10).
By preventing the condensate from accumulating in the fins (10) and preventing the outer surface from being covered with a condensate film, the fins (10) can be kept in constant contact with the heat medium vapor and condensation can be carried out efficiently. In addition, due to the presence of a condensate film, fins (10
) can also eliminate the decrease in the heat transfer coefficient from the steam to the steam.

By feeding the heat medium liquid to the heat exchange chamber (6), boiling occurs in each heat transfer tube (5). Heat exchanger tube (
5) The temperature distribution on the outer surface of the spiral groove (
The heat flux is high at the groove bottom (13) of 11) and becomes lower toward the tip of the fin (10), increasing the heat flux on the groove bottom (13) side. Furthermore, boiling promoting nuclei (15) are formed in the groove bottom (13), and the conditions for bubble generation are much better than in the fins (10). Therefore, most of the boiling action is actively carried out within the spiral groove (11), and boiling can be carried out efficiently. Further, when the bubbles generated at the groove bottom (13) float up, the bubbles come into contact with the fins (10) located above the area where the bubbles are generated, and displace or disturb the heat transfer liquid on the surface thereof. This allows the fin (10
) As the temperature rises or fluctuations occur, bubbles are more likely to be generated, further promoting boiling.

Therefore, in the heat exchanger (1) to which the heat transfer tube (5) is applied, heat exchange can be performed without creating a difference between the cooling capacity and the heating capacity, so an additional device is provided to compensate for the difference in capacity. It is also possible to reduce the size of the heat exchanger (1) by eliminating waste such as performance setting being performed on the low capacity side while the heat exchange action on the high capacity side is not utilized. In particular, in the case of a large-diameter heat exchanger tube (5) with a large heat exchange capacity, the amount of heat based on the difference in ability between boiling and condensation is large, so to compensate for this, an additional device that produces a considerable amount of heat is required. This is advantageous in that the necessity of additional equipment affects the size of the heat exchanger (1).

In addition, a performance comparison was made regarding the heat transfer coefficient between the heat transfer tube (5) of the above example and the comparative example, but when the comparative example is taken as 1,
The condensing heat transfer coefficient of the example was about 2.5 times, and the boiling heat transfer coefficient was about 2.0 times. The heat exchanger tube of the comparative example has only screw-shaped fins formed on the outer surface of the tube.

(Second Example) Figures 6(a), (b) to 8 show boiling accelerated nuclei (15
) shows a second embodiment. In FIGS. 6(a) and (b), the boiling promoting nuclei (15) are formed by forming minute protrusions (14) with a metal wire material such as copper having excellent thermal conductivity, and each protrusion (
14) A vertically collapsed inverted Ω-shaped branch groove (16) is formed in between. In this case, as shown in FIG.
9) and (19), and cut grooves (2
0) is formed, a large number of these are arranged and fixed in parallel to the groove bottom (13) to form minute protrusions (14). Moreover, instead of the kerf (20), as shown in FIG.
(14a) may be transformed into a continuous waveform to form minute protrusions (14).

Note that the wire diameter of the metal wire (14a) is 0.3 to 0.5.
Let it be mm.

(Third Embodiment) Figure 9 shows a third embodiment of the boiling accelerating nucleus (15), in which a porous layer (21) is formed at the groove bottom (13) to form the boiling accelerating nucleus (15). do.

This porous layer (21>) is formed by sintering metal powder or by spraying metal.

The number of spiral grooves (11) may be determined depending on the usage conditions of the heat exchanger (1) or the heat flux conditions at the groove bottom (13).

(Effects of the Invention) As explained above, in the heat transfer tube of the present invention, the fins (10) and the spiral grooves (11) are provided as the heat transfer surface structure, and the condensation action is mainly performed on the fin (10) side. Spiral groove (1
1) and the boiling accelerating nucleus (15) provided at the groove bottom (13).
), the boiling action is mainly carried out, and the functions of boiling and condensation are roughly differentiated.
Both the boiling performance and condensing performance of the heat exchanger tube (5) can be simultaneously improved with good consistency.

This not only allows the same heat transfer tube to be used in both the evaporator and the condenser, but also eliminates the difference in cooling and heating capacity when used in a heat exchanger for both cooling and heating. Since there is no need to add a device to compensate for this, it is advantageous in that the heat exchanger can be made smaller accordingly.

[Brief explanation of the drawing]

1 to 5 (a) and (b) show a first embodiment of the present invention, in which FIG. 1 is a partial sectional view of a heat exchanger tube, FIG. 2 is a schematic sectional view of a heat exchanger, and FIG. FIG. 4 is a perspective view of a heat transfer tube, FIG. 4 is a perspective view of a heat transfer surface structure, and FIGS. 5(a) and 5(b) are cross-sectional views showing the processing procedure for boiling promoting nuclei. Figure 6 (a
), (1+) to FIG. 8 show the second embodiment of the boiling accelerating nucleus, and FIG. 6(a) is a plan view of the boiling accelerating nucleus, and FIG.
b) is a cross-sectional view of the same, FIG. 7 is a front view showing an example of processing of minute protrusions, and FIG. 8 is a plan view showing a deformed form of boiling accelerating nuclei. FIG. 9 is a sectional view showing a third embodiment of the boiling accelerating nucleus. (5a)...Pipe body, (10)...Fin, (1
0a)...Basal part, (11)...Spiral groove, (12)
... Virtual cylindrical surface, (13) ... Groove bottom, (14) ...
・Minute ridges, (15)... Boiling accelerating nuclei, (16)...
- Branch groove, (21)... Porous layer.

Claims (3)

[Claims] (1) Fins (10
) is formed integrally with the tube body (5a), and the fins (10)
A group of spiral grooves (11) that intersect with the fins (10) and divide the fins (10) at multiple points in the circumferential direction are formed on the outer circumferential surface of the tube body (5a), and connect the base portions (10a) of the fins (10). With reference to the virtual cylindrical surface (12), the spiral groove (11)
The groove depth of the spiral groove (11) is set so that the groove bottom (13) is located radially inward from the virtual cylindrical surface (12). Nucleus (1
5) An extratubular heat exchange type heat transfer tube characterized by forming the following. (2) A large number of minute protrusions (14) are provided on the groove bottom (13),
A nuclear groove that opens outward between adjacent microridges (14)
16), and the cross-sectional shape of the core groove (16) is set in an inverted Ω shape where the opening is the narrowest, thereby configuring the boiling accelerating core (15). The external heat exchange type heat transfer tube described. (3) The external heat exchange type heat transfer tube according to claim (1), wherein a porous layer (21) is formed on the groove bottom (13) to serve as boiling promoting nuclei (15).