JPS62134496A - Boiling heat transfer tube - Google Patents

Abstract

PURPOSE:To increase the capacity of a heat transfer tube, by spirally forming a number of projections, of which cross sections are parallelogram, on the inside wall of a heat transfer tube, by inclining those projections to the upstream side of a main flow, and by providing spiral channels, of which sections are in the shape of 'U' of 'V', on the top and the bottom areas of those projections formed on the inside wall of a heat exchanger. CONSTITUTION:Projections 3, of which cross sections are parallelogram, are provided on the inside wall of a heat transfer tube, forming a number of spiral rows, and spiral channels 6, of which sections are in the shape of 'U', and which are inclined to the upstream side of main flow, are formed between those rows. A fluid in the neighborhood of a tube wall flows, circling the inside of a tube along the inclined spiral channels 6 of which sections are in the shape of 'U'. Since fine 'U' shaped or 'V' shaped spiral channels 7 are provided on the top area of spiral projections 3 and the bottom parts of spiral channels of which sections are in the shape of 'U', capillary effect is produced and the fluid in the bottom part of a tube is raised up to the top of it. In addition, the heat transfer area in a tube is greatly increased, because the width of spiral channels 7 of which sections are in the shape of 'U' of 'V' can be made vary small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to boiling of fluids, such as evaporators of air conditioners.
This invention relates to heat exchanger tubes used in heat exchangers that involve evaporation.

2. Description of the Related Art Conventionally, this type of boiling heat exchanger tube is known, for example, from the Japanese Patent Publication Show ω-279.
As shown in Publication No. 17, it had a structure as shown in FIG. That is, the heat transfer performance was improved by carving a plurality of spiral grooves 2 having a U-shaped or ■-shaped cross section and having an inclination angle of β with respect to the tube axis on the heat transfer groove inside the heat transfer tube 1.

Problems to be Solved by the Invention Due to such a configuration, the heat transfer performance within the tube increases due to the spiral grooves 2 carved on the inner wall of the tube, and the fluid flowing near the tube wall is disturbed. The heat transfer performance inside the pipe is improved. However, if the spiral grooves 2 with uniformly small groove depth h and groove width W are carved on the pipe inner wall surface over the entire surface of the pipe inner wall, the fluid flowing near the pipe wall will not be able to pass along the pipe inner wall surface which is received from the spiral grooves 2. The turning force becomes very small.

Further, turbulence in the fluid flowing near the pipe wall is also reduced.

On the other hand, if the groove depth h and the groove width W are set too large, the capillary force that tries to pull up the liquid at the bottom of the tube to the tubes becomes small, and a liquid film is not formed in the tubes. Become. In this way, in the structure shown in FIG. 4, there is a usable range for the dimensions of the spiral groove 2. It has been impossible to significantly increase the heat transfer area within the tube compared to that of a smooth tube by reducing the groove width W of the grooves 2 and increasing the number of grooves. For the above reasons, the conventional boiling heat exchanger tube 1 could not fully utilize the heat transfer promoting effect of the spiral grooves 2.

The present invention solves the above-mentioned conventional problems, and uses the swirling motion of the fluid inside the tube due to the spiral protrusion on the wall surface, the capillary force due to the narrow spiral groove with a U-shaped or ■-shaped cross section, and an increase in the heat transfer area inside the tube. The present invention provides a boiling heat transfer tube that effectively utilizes the heat transfer promotion effect and has excellent heat transfer performance.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a flow path for a fluid that changes the metallic phase inside the heat exchanger tube, and a protrusion having a parallelogram cross section on the inner wall surface of the heat exchanger tube. A large number of spiral projections are formed in a spiral shape, the spiral projections are inclined toward the upstream direction of the mainstream, and spiral grooves with a U-shaped or V-shaped cross section are provided on the upper surface of the spiral projections and on the inner wall surface of the heat exchanger tube between the spiral projections. be.

For production The effect of this technical means is as follows.

The protrusions having a parallelogram cross section and protruding from the inner wall of the heat exchanger tube form a number of spiral rows, and between the rows, spiral grooves having a corner-shaped cross section that are inclined toward the upstream direction of the main flow are formed. Therefore, the fluid flowing near the tube wall swirls inside the tube along the spiral groove with the inclined cross-section. In addition, since a fine spiral groove with a U-shaped or V-shaped cross section is provided on the upper surface of this helical protrusion and the bottom of the helical groove with an α-shaped cross section, capillary force is generated, and the liquid at the tube bottom flows into the tube top 1. be lifted up. Furthermore, since the groove width of the spiral groove having a U-shaped or V-shaped cross section can be made very small, it is possible to significantly increase the inner surface area of the pipe.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

As shown in FIG. 1, the spiral protrusion 3 whose cross section is a parallelogram forms an angle α (arrow 4
(Angle made in the upstream direction of the main stream flowing as shown in )
A large number of protrusions are provided on the inner wall surface of the heat exchanger tube 6 so that the angles are obtuse. Therefore, between one spiral projection 3a and the adjacent spiral projection 3b, a spiral groove 6 having an α-shaped cross section tilted in the upstream direction of the mainstream is formed. Furthermore, the upper surface of the spiral protrusion 3 whose cross section is a parallelogram and α
At the bottom of the spiral groove 6 which has a shaped cross section, a spiral link having a square cross section and which has a groove width that is much smaller than the width of the spiral groove 6 is provided.

Next, the operation of the configuration of this embodiment will be explained.

The spiral protrusions 3 having a parallelogram cross section form a large number of helical grooves 6 having a helical cross section tilted in the upstream direction of the main stream on the inner wall surface of the pipe between the rows thereof, so that when the fluid velocity in the main flow section is small, As shown in FIG. 2, the liquid near the upper surface of the protrusion 3 flows along the protrusion 3 and the groove 6 while gently swirling inside the tube as shown by the arrow 8. On the other hand, when the fluid velocity in the main flow part is high, the liquid near the top surface of the protrusion 3 does not flow into the groove 6, as shown in FIG. It flows slidingly over the upper part of the groove 6 (the flow direction is indicated by an arrow 9). As a result, a clockwise circulating vortex 10a is generated in the spiral groove 6, and the circulating vortex 10a is dragged by the liquid near the top surface of the protrusion 3, that is, the liquid in the main part of the tube, and moves inside the spiral groove 6 as shown by the arrow. It flows as shown at 10b. That is, the liquid circulating within the groove 6 moves in a circular motion within the pipe along the spiral groove 6 while circulating. The vortex strength of the circulating vortex 10a is very strong because the angle α where the center line of the protrusion 3 intersects with the tube axis is greater than 900°, and the strength of the vortex is very strong, and
The amount of heat transferred to the liquid within is very large. Furthermore, since the liquid in the groove 6 exchanges heat with the liquid in the main stream near the top of the groove 6, the amount of heat transferred from the heat transfer surface to the liquid in the main stream is very large. As described above, by protruding the helical protrusion 3 with a parallelogram cross section and forming the thick helical groove 6 with a recessed cross section, regardless of the flow in the main flow section, the The liquid performs a swirling motion along the inner wall surface of the tube. As a result, the flow near the wall surface is disturbed and the amount of heat transfer increases.

In addition, the helical groove 7 with a fine V-shaped cross section and a very small groove width provided on the upper surface of the helical protrusion 3 whose cross section is a parallelogram and the bottom of the helical groove 6 with an α-shaped cross section allows the bottom of the tube to be Capillary forces are created which tend to pull the liquid up to the top of the tube. Therefore, it is not the case that liquid accumulates at the bottom of the tube and no liquid exists at the top of the tube, and a force acts to make the liquid film uniform over the entire surface of the tube.

Therefore, the liquid film becomes thinner and heat transfer is promoted.

Furthermore, since a large number of spiral grooves 7 having a fine V-shaped cross section and a very small groove width are provided as described above, the inner surface area of the tube can be significantly increased. Therefore, the amount of heat transfer within the tube increases.

Note that even if the angle α at which the center line of the spiral protrusion 3 intersects with the tube axis and the width or height of the helical protrusion 3 are different for each protrusion, the same effect as described above can be obtained. Further, a large number of helical protrusions 3 having a parallelogram cross section are protruded from the inner wall surface of the heat transfer tube 6, and a fine helical groove having a V-shaped cross section is formed on the upper surface of the protrusions 3 and the bottom of the helical groove 6 having a shaped cross section. After carving 7, if the inside of the tube is subjected to sandblasting or etching to make the inside surface rough, the turbulence of the flow near the heat transfer surface will further increase, and the heat transfer performance will further increase. It turns out.

Effects of the Invention As described above, the boiling heat exchanger tube of the present invention uses the inside of the heat exchanger tube as a flow path for a phase-changing fluid, and has spiral protrusions having a parallelogram cross section on the inner wall surface of the heat exchanger tube. a large number of spiral projections are formed, and the spiral projections are tilted in the upstream direction of the mainstream,
Since a spiral groove with a U-shaped or V-shaped cross section is provided on the upper surface of the spiral protrusion and on the inner wall surface of the heat transfer tube between the spiral protrusions, the fluid flowing near the tube wall has a flow inside the helical groove with an α-shaped cross section. In addition to promoting circulation motion and swirling motion along the inner wall of the tube, it is possible to equalize the thickness of the liquid film inside the tube and increase the heat transfer area by the capillary force of the spiral groove with a narrow U-shaped or V-shaped cross section. The heat transfer performance of boiling heat transfer tubes can be significantly improved. Therefore, the present invention is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a boiling heat exchanger tube according to an embodiment of the present invention, FIGS. 2 a, b and 3 a, b are enlarged vertical cross-sectional views of main parts of FIG. . FIG. 1b is a vertical cross-sectional view and a cross-sectional view of a conventional boiling heat exchanger tube, respectively. 3...--Spiral projection, 5... Heat exchanger tube,
6... Spiral groove with a shaped cross section, A... Spiral groove with a fine V-shaped cross section. Name of agent: Patent attorney Toshio Nakao Haga 1 person No. 4
Figure (b)

Claims (1)

[Claims] A large number of protrusions having a parallelogram cross section are formed in a spiral shape on the inner wall surface of the heat exchanger tube, and the helical protrusions are tilted in the upstream direction of the mainstream, and the upper surface of the helical protrusions and the interior of the heat exchanger tube between the helical protrusions are A boiling heat exchanger tube with a U-shaped or V-shaped spiral groove on the wall.