JPH06101985A - Heat exchanger tube with grooved internal wall - Google Patents

Abstract

PURPOSE:To prevent a heating medium liquid from spreading along a spiral groove and increase contact frequency between heating medium steam and a metal surface, thereby enhancing the condensation efficiency. CONSTITUTION:A large number of spiral grooves, which are installed in parallel with each other at an angle of 10 deg. to 20 deg. to a pipe axis, are formed on an inner surface of a metal pipe. One spiral-shaped projected part 4 or at least two projected parts 4, which intersect the grooves 2 and are installed in parallel with each other at an angle of 2 deg.-6 deg. to the pipe axis, are formed on the inner surface with a span provided in the circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner grooved heat transfer tube used in a heat exchanger or the like, and more particularly to an improvement for increasing condensation efficiency.

[0002]

2. Description of the Related Art A heat transfer tube with an inner groove of this type is mainly used as an evaporation tube or a condensation tube in a heat exchanger such as an air conditioner or a refrigerator, and recently, it has a spiral shape over the entire inner surface. Heat transfer tubes having grooves are widely available on the market. The spiral angle of the groove of a general heat transfer tube with internal groove is about 15 to 20 degrees,
Most of the grooves have a depth of about 0.15 to 0.20 mm.

[0003]

By the way, when the heat transfer tube with the spiral groove as described above is used as a condensing tube, heat medium vapor is introduced from one end of the heat transfer tube and condensed while releasing the heat, The heat transfer liquid is discharged from the end.At this time, the heat transfer liquid is lifted up along the spiral groove by the wind pressure of the heat transfer vapor inside the heat transfer tube, and most of the inner surface of the heat transfer tube is covered with the condensate. It is inevitable to be told.

As described above, when most of the inner surface of the heat transfer tube is covered with the heat transfer medium liquid, the metal surface forming the heat transfer tube is shielded by the heat transfer medium liquid and does not come into direct contact with the heat transfer medium vapor, so that the heat transfer tube is not directly contacted. However, there is a problem that the heat transfer efficiency between the heat transfer medium and the heat medium vapor decreases, and the condensation efficiency decreases. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an inner grooved heat transfer tube that can prevent the heat transfer liquid from spreading along the inner surface of the heat transfer tube.

[0005]

A heat transfer tube with an inner groove according to the present invention has an angle of 10 to 2 with respect to the tube axis on the inner surface of a metal tube.
A large number of parallel spiral grooves of 0 ° are formed, and the spiral grooves intersect with each other and have an angle of 2 to 2 with respect to the tube axis.
It is characterized in that one or two or more 6-degree spiral protrusions are formed at intervals in the circumferential direction of the inner surface of the pipe.

[0006]

According to this heat transfer tube with internal groove, the spiral groove formed over almost the entire inner surface of the tube is divided to form a spiral protrusion having an angle of 2 to 6 ° with respect to the tube axis. Since one or several tubes are formed, when used as a condenser tube, the heat medium liquid is prevented from spreading along the spiral groove by being blocked by these protruding portions. Therefore, it is possible to increase the ratio of the metal exposed surface that is not covered with the heat medium liquid, increase the contact area between the heat medium vapor and the metal surface, and improve the condensation efficiency.

Further, since the spiral angle of the ridge is set to 2 to 6 °, if the arrangement angle around the axis of the heat transfer tube is adjusted appropriately, the liquid level of the heat transfer medium liquid when used as a condensation tube It is possible to position the ridges substantially parallel to the liquid surface along a position at a substantially constant height from the liquid surface, as the height increases from the upstream side to the downstream side of the pipe.
It is possible to effectively prevent the heat medium liquid from spreading over most of the ridges.

[0008]

1 and 2 show an embodiment of a heat transfer tube with an inner groove according to the present invention. FIG. 1 is an axial sectional view,
FIG. 4 is a diametrical cross-sectional view.

The heat transfer tube 1 is a metal tube having a circular cross section,
The angle α with respect to the tube axis is 1 over almost the entire inner surface.
A large number of parallel spiral grooves 2 of 0 to 20 ° are formed, and a ridge portion 3 is formed between the spiral grooves 2.
Further, the angle β with respect to the pipe axis is 2 to 2 as it intersects with the spiral groove 2.
One or two or more spiral protrusions 4 having a 6 ° angle,
It is formed at intervals in the circumferential direction. The spiral groove 2 and the ridge portion 4 may have the same spiral direction, or may have opposite spiral directions as shown in the drawing.

The number of the ridges 4 is preferably about 1 to 4. If the number is more than four, the effect of turbulent flow generation of the heat medium by the spiral groove 2 is reduced, and the heat exchange efficiency between the heat medium and the heat transfer tube 1 may be reduced.

The spiral angle α of the spiral groove 2 is less than 10 ° (minimum 0
)), The effect of generating turbulent flow of the heat medium by the spiral groove 2 becomes poor, and the condensation and evaporation performance deteriorates. The liquid tends to spread on the inner surface of the heat pipe 1 and the pressure loss becomes too large, which is not preferable.

The spiral angle β of the protrusion 4 is determined for the following reason. As shown in FIG. 4, when the heat transfer tube 1 is used in a horizontal state as a condensing tube, a flow of the condensed heat medium liquid occurs inside the heat transfer tube 1, and the height of the liquid level L is It gradually increases from the upstream side to the downstream side of the medium flow.
The inventors of the present invention have studied in detail the behavior of the heat transfer liquid inside the condensing tube with respect to a general heat exchange device, and as a result, the inclination angle of the liquid surface L is generally within the range of 2 to 6 °. I found a new fact.

Therefore, when the spiral angle β of the ridge portion 4 according to the present invention is 2 to 6 °, the ridge portion 4 is shown in FIG. 4 as the liquid level L increases toward the downstream side. Liquid level L as shown
Since it is possible to position along a substantially constant height from above, it is possible to effectively prevent the heat medium liquid from spreading over most of the lengthwise direction of the ridge portion 4. is there.

On the other hand, if the ridge 4 is parallel to the pipe axis, the position of the ridge 4 is too higher than the liquid level L on the upstream side, and the effect of preventing the spread of the liquid is not exerted, or on the downstream side. In this case, the ridge 4 is buried in the heat medium liquid, and the problem that the liquid spreading prevention effect is not exerted occurs. Therefore, the proportion of the portion of the ridge 4 that has a good liquid spreading preventing effect is small. Become.

As shown in FIG. 3, the upper end of the protruding portion 4 is set to be substantially aligned with the upper end of the protruding portion 3 between the spiral grooves 2. Specifically, the amount of protrusion of the protrusion 4 from the bottom surface of the spiral groove 2 is preferably about 70 to 100% of the amount of protrusion of the protrusion 3. If it is less than 70%, the effect of preventing the spread of the heat transfer liquid is poor, and if it is more than 100%, it is difficult to form it, and the outer surface does not become a circle in the pipe expanding step when it is adhered to the aluminum fins, and it is easy to buckle. Causes the problem.

The heat transfer tube 1 of this example is formed by electro-stitching a strip material. Therefore, although not shown, a part of the inner peripheral surface of the heat transfer tube 1 is A welding line extending in the pipe axis direction is formed over the entire length thereof, and the spiral groove 2 is also divided by this welding line. The material of the heat transfer tube 1 may be any conventionally used material such as copper, copper alloy, aluminum, aluminum alloy and the like, and the wall thickness and diameter thereof are determined according to the application.

To give a concrete example of dimensions, in a general heat transfer tube with an inner groove having a diameter of about 1 cm, the width of the spiral groove 2 is 0.
20-0.25 mm, the depth of the spiral groove 2 is 0.20
About 0.30 mm, the width of the ridge portion 3 is 0.2 to 0.25 m
It is preferably about m. It has been confirmed by the present inventors that the condensation performance and the evaporation performance are good with respect to a general heat medium within the range.

In order to manufacture the heat transfer tube 1 as described above, first, a strip-shaped metal plate material is continuously rolled by a rolling roll,
The spiral groove 2 and the protrusion 4 are formed at the same time. A ridge for forming the spiral groove 2 and a groove for forming the ridge portion 4 are integrally formed in advance on the outer peripheral surface of the rolling roll.

After the rolling process of the spiral groove 2 and the ridge portion 4 is completed, the plate material is set in the electric sewing machine with the groove forming surface facing the inner surface side, and the plate material is passed between the forming rolls in multiple stages. The material is rolled in the width direction, and finally both side edges of the plate material are welded to form a circular pipe shape. The electric resistance sewing machine may be a commonly used one, and the electric resistance sewing conditions may be the same as those for normal processing. Then, if necessary, the welded portion on the outer peripheral surface of the pipe is shaped, and then wound into a roll or cut into a predetermined length to obtain a long heat transfer pipe.

According to the heat transfer tube having the above structure, the spiral groove 2 formed over almost the entire inner surface of the heat transfer tube is divided,
Since one or several spiral ridges 4 having an angle of 2 to 6 ° with respect to the tube axis are formed, when used as a condenser tube, these ridges 4 block the spiral grooves. Two
Spreading of the heat carrier liquid along is prevented. Therefore, it is possible to increase the exposed area of the metal that is not covered with the heat medium liquid, improve the heat transfer efficiency between the heat medium vapor and the metal surface, and improve the condensation efficiency.

Further, since the spiral angle of the ridge 4 is set to 2 to 6 °, the liquid level L of the heat transfer medium is adjusted by adjusting the arrangement angle around the axis of the heat transfer tube 1 appropriately. As the height increases from the upstream side to the downstream side, it is possible to position the ridge portion 4 substantially parallel to the liquid surface L along a position having a substantially constant height. Therefore, the ridge portion 4
It is possible to effectively prevent the spread of the heat transfer liquid over a large proportion of the length of the heat transfer liquid.

In the above embodiment, the shape of the heat transfer tube was circular in cross section, but the present invention is not limited to circular shape, and can be embodied as an elliptical cross section, a flat tubular shape, or the like, and the spiral groove 2 or protrusion. The cross-sectional shape of the ridges 3 and 4 may be changed arbitrarily. It is also possible to fix the fins to the outer circumference of the heat transfer tube 1.

[0023]

[Experimental Example] Next, the effect of the present invention will be demonstrated with reference to an experimental example. (Experiment 1) A heat transfer tube in which only a large number of spiral grooves are formed on the inner surface of a copper tube having an outer diameter of 9.52 mm (without a ridge), and in addition to the spiral groove, one ridge has a plurality of spiral angles. The heat transfer tubes formed in Step 1 were created and their condensation performances were compared. The dimensions of the main part are as follows. Width of spiral groove: 0.20 mm Depth of spiral groove: 0.20 mm Pitch of spiral groove: 0.50 mm Height of protrusion from bottom of spiral groove: 0.2 mm

The results of Experiment 1 are shown in FIG. The vertical axis of the graph shows the condensation performance ratio for a simple grooved tube having no ridge. As is clear from FIG. 5, the condensation performance is high when the spiral angle of the ridge is 2 to 6 °.

(Experiment 2) A heat transfer tube in which a large number of spiral grooves are formed on the inner surface of a copper tube having an outer diameter of 9.52 mm (without a ridge),
And, in addition to the above-mentioned spiral groove, a heat transfer tube was formed by forming 1 to 6 ridges at a spiral angle of 4 °, and the respective condensation performances were compared. The dimensions of the main part are as follows. Width of spiral groove: 0.20 mm Depth of spiral groove: 0.20 mm Pitch of spiral groove: 0.50 mm Height of protrusion from bottom of spiral groove: 0.2 mm

The results of Experiment 2 are shown in FIG. The vertical axis of the graph shows the condensation performance ratio for a simple grooved tube having no ridge. As is clear from FIG. 6, the number of ridges is 1
When it is about 4 or so, the condensation performance is improved, but when it is 5 or more, the condensation performance is rather deteriorated.

[0027]

As described above, according to the heat transfer tube with the inner surface groove of the present invention, the spiral groove formed over almost the entire inner surface of the heat transfer tube is divided to form an angle of 2 to 6 with respect to the tube axis. Since one or several spiral protrusions having a degree of 0 are formed, when used as a condenser tube, these protrusions prevent the heat medium liquid from spreading along the spiral groove. Therefore, the exposed area of the metal that is not covered with the heat medium liquid can be increased without impeding the heat exchange promoting effect of the spiral groove itself, and the contact frequency between the heat medium vapor and the metal surface is increased to improve the condensation efficiency. be able to.

Further, since the spiral angle of the ridge is set to 2 to 6 °, if the arrangement angle of the heat transfer tube around the axis is adjusted appropriately, the liquid level of the heat transfer medium liquid when used as a condenser tube As the height increases from the upstream side to the downstream side of the pipe, the ridge can be positioned almost parallel to the liquid surface along a position at a substantially constant height from the liquid surface, The spread of the liquid medium can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view taken along the tube axis of an embodiment of a heat transfer tube with an inner groove according to the present invention.

FIG. 2 is an enlarged view of the heat transfer tube in a diameter direction.

FIG. 3 is a perspective view showing the shapes of spiral grooves and ridges.

FIG. 4 is a perspective view showing an action of a ridge portion 4 of the heat transfer tube.

FIG. 5 is a graph showing the effect of the experimental example of the present invention.

FIG. 6 is a graph showing the effect of an experimental example of the present invention.

[Explanation of symbols]

 1 heat transfer tube 2 spiral groove 3 ridge between spiral grooves 4 ridge L Liquid level of heat transfer liquid

Claims (1)

[Claims] 1. An inner surface of a metal tube having an angle of 10 with respect to the tube axis.
A large number of ˜20 ° parallel spiral grooves are formed, and one or more spiral ridges intersecting these spiral grooves and forming an angle of 2 to 6 ° with the tube axis are formed. An inner grooved heat transfer tube characterized in that it is formed at intervals in the circumferential direction of the inner surface of the tube.