JP2690817B2 - Heat transfer tube with internal groove - Google Patents

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 for a heat exchanger, a heat pipe, etc., and more particularly to an improvement for increasing heat transfer efficiency when used as a condenser.

[0002]

2. Description of the Related Art Conventionally, there has been known a heat transfer tube in which a large number of spiral or linear grooves are formed on the inner surface of a tubular body made of copper or the like by rolling or drawing. As a result, the following effects are obtained.

A. When this heat transfer tube is used as a condensing tube, the steam of the heat medium flowing in the condensing tube is made turbulent by the ridges between the grooves, and the ridges serve as condensation nuclei to enhance the condensation effect of the heat medium vapor. , Promote liquefaction. In addition, the condensed heat medium liquid efficiently flows in the longitudinal direction of the heat transfer tube due to the surface tension in the groove, and the reflux effect is increased.

B. When used as an evaporation tube, the edge of the groove of the evaporation tube serves as an evaporation nucleus for generating bubbles, promotes boiling, and improves the vaporization efficiency of the heat medium liquid supplied into the heat transfer tube. Further, due to the surface tension in the groove, the heat medium liquid flows in the longitudinal direction of the heat transfer tube and is uniformly dispersed on the inner surface of the heat transfer tube.

By the way, in order to improve the performance of such a heat transfer tube with a groove, it is considered effective to narrow the opening width of the groove so that it becomes closer to a tubular shape. According to such a tubular groove, when used as, for example, an evaporation tube, bubbles are likely to be generated inside the groove, and the bubbles serve as nuclei to promote evaporation of the heat medium and further improve vaporization efficiency. . Further, since the surface tension in the groove is improved, it is considered that the transport efficiency of the heat medium due to the surface tension is increased and the overall heat transfer performance is improved.

Therefore, the inventors of the present invention successively form two kinds of spiral grooves intersecting with each other on the inner surface of the metal tube,
Experiments were conducted from the viewpoint that a tubular part with a relatively narrow opening width could be formed between the intersections of these grooves, and as a result, when the intersection grooves were formed as described above, It has been found that the formed groove (main groove) is intermittently narrowed in opening width by the groove (sub groove) formed next, and the tubular portion as described above can be formed.

[0007]

However, in the heat transfer tube having the cross groove and the tubular portion, the cross-section of the tubular portion is narrower than the other portions, so that the capillary force of the tubular portion is increased. Although the liquid transport efficiency by the method is good, the liquid resistance along the inner surface of the heat transfer tube is inevitably large. Therefore, when the transfer speed of the heat transfer liquid in the heat transfer tube is high, the flow velocity near the inner surface of the heat transfer tube becomes considerably slower than the flow velocity near the center of the heat transfer tube, and the heat transfer tube as a whole does not The pressure loss cannot be ignored, and the heat transfer efficiency may be reduced due to the pressure loss.

When the heat transfer tube is used as a condenser, the produced liquid spreads over the entire inner surface of the heat transfer tube due to the excellent capillary action of the tubular portion, so that the amount of liquid is retained only in the intersecting groove. When the amount exceeds the limit, the liquid overflows from the groove and the entire metal surface is covered with the liquid film. Further, due to this liquid film, there is a problem that the heat transfer efficiency between the heat transfer tube and the heat medium vapor is reduced, and the condensation efficiency is reduced.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a plurality of parallel to each other extending in a direction inclined with respect to the axial direction of the metal pipe is provided on the inner peripheral surface of the metal pipe. A main groove and a large number of sub-grooves having a V-shaped cross section which are parallel to each other and form a constant angle with the main groove are sequentially formed, and the main grooves are provided between the intersections of the main grooves and the sub-grooves. Along the groove, a tubular portion whose opening width is narrower than the inner width of the main groove is formed, and between the tubular portions arranged along the same main groove, the opening width of the tubular portion is smaller than that of the tubular portion. And a liquid flow groove extending in the axial direction and intersecting both the main groove and the sub groove is formed on the inner surface of the metal pipe. To do.

[0010]

According to this heat transfer tube with an inner groove, the tubular portion formed by the intersecting groove can achieve a good evaporation promoting effect and an improvement in the liquid transport efficiency due to the surface tension, while the heat transfer liquid in the heat transfer tube is prevented. Even when the flow velocity is high, these liquids mainly concentrate in the liquid flow grooves that extend in the axial direction and flow efficiently, so that the increase in liquid flow resistance near the inner surface of the heat transfer tube due to the tubular portion is mitigated, It is possible to prevent an increase in pressure loss and a decrease in heat transfer efficiency due to the liquid resistance.

Further, even when this heat transfer tube is used as a condenser, since the main groove and the sub groove are divided by the liquid flow groove, the spread of the heat medium liquid along the main groove and the sub groove will flow. The groove prevents the liquid film from spreading on the entire inner surface of the heat transfer tube and covering the entire metal surface. Therefore,
It is possible to prevent a decrease in heat transfer efficiency between the heat transfer tube and the heating medium vapor due to the spread of the liquid film, and it is possible to always maintain a good heat exchange capacity.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the heat transfer tube according to the present invention will be described in detail below with reference to FIGS. As shown in FIG. 1 and FIG. 2, the heat transfer tube of this embodiment has a large number of parallel spiral-shaped main pipes formed on the inner surface of the metal tube 1 having a circular cross section at an angle to the axial direction of the metal tube 1. Groove 2 and a number of parallel spiral sub-grooves 3 that intersect these main grooves 2 at a constant angle.
And a plurality of liquid flow grooves 5 (four in this example) extending in the axial direction of the metal tube 1 are formed. The material of the metal tube 1 may be any conventionally used material such as copper, copper alloy, and aluminum, and the thickness and diameter thereof are determined according to the application of the heat transfer tube.

As shown in FIGS. 2 and 3 to 7, the both side walls of each main groove 2 are inclined to the inside of the main groove 2 between the intersections of the main groove 2 and the sub groove 3, respectively. The opening width of the groove 2 is narrowed to form a tubular portion 4 having a trapezoidal cross section. In addition, as shown in FIG. 1, one band-shaped welded portion 1A extending in the axial direction is formed on a part of the inner surface of the metal tube 1.

The main groove 2 is in a state before the sub groove 3 is formed.
As shown in FIG. 11, the cross-sectional angle of the bottom portion is a substantially U-shaped cross section. The closer to the U-shape, the narrower the opening width of the main groove 2 and the easier it is to form a tubular shape. The inner width W1 of the main groove 2 is the depth D
1 to 40 to 140%, preferably 80 to 120%. If it is less than 40%, the main groove 2 is likely to be crushed due to the formation of the sub groove 3, and the processing is also difficult. Further, if it is larger than 140%, the opening width of the tubular portion 4 cannot be narrowed sufficiently.

The interval P1 between the main grooves 2 is 1.5 to the inner width W1.
3 times, and preferably 1.8 to 2.2 times. If it is less than 1.5 times, when the sub-groove 3 is formed, the projecting ridge portion between the main grooves 2 collapses and it becomes difficult to form the tubular portion 4. On the other hand, if it is more than 3 times, the formation density of the main grooves 2 becomes small, and the effect of improving the heat transfer performance decreases. Specifically, in the case of a normal heat transfer tube,
The depth D1 of the main groove 2 is 0.2 to 0.3 and the width W1 is 0.2 to
0.5, P1 = 0.4 to 1.5, and the cross-sectional angle of the bottom is preferably about 75 ° or more.

On the other hand, the sub groove 3 has a V-shaped cross section. The distance P2 between the sub-grooves 3 may be equal to the distance P1 between the main grooves 2, but does not necessarily have to be equal to the main groove 2. Width W of sub groove 3
2 is 25 to 90% of the opening width W3 of the main groove, preferably 50
~ 70%. If it is less than 25%, the opening width of the tubular portion 4 cannot be sufficiently narrowed, and if it is more than 90%, the opening portion of the tubular portion 4 may be closed. Further, the depth D2 of the sub groove 3 is 50 to 100% of the depth D1 of the main groove, preferably 8
It is set to 0 to 100%. If it is less than 50%, the opening width of the tubular portion 4 cannot be narrowed sufficiently, and if it is more than 100%, the opening portion of the tubular portion 4 may be closed. Specifically, in the case of a normal heat transfer tube, the depth D2 of the auxiliary groove 3 is 0.15.
˜0.3, the interval P2 = 0.4 to 1.5, and the V-shaped cross-section angle is preferably about 45 to 90 °.

The intersection angle α between the main groove 2 and the sub groove 3 is 20 to 60.
It is desirable that the angle is 0 °, particularly 30 to 40 °. 20-6
If it goes out of the range of 0 °, it becomes difficult to form the tubular portion 4.
Further, the main groove 2 is preferably within 30 ° with respect to the axial direction of the metal tube 1. If it is larger than this, the flow of the heat medium liquid in the axial direction of the metal tube 1 becomes poor.

By forming the main groove 2 and the sub groove 3 as described above, the minimum opening width of the tubular portion 4 is narrowed to 75% or less of the width W1 of the main groove 2. If it is more than 75%, the effect of generating bubbles is lowered, and the effect of improving heat transfer performance is lower than that of the conventional grooved heat transfer tube.

On the other hand, a plurality of liquid flow grooves 5 are formed at intervals in the circumferential direction of the inner surface of the metal pipe 1. In the illustrated example, the liquid flow grooves 5 are formed at equal intervals in the circumferential direction, but the present invention is not limited thereto, and the liquid flow grooves 5 may be formed at different intervals.

Although the number of the liquid flow grooves 5 is set to four in the figure, it may be one to three or five or more. However,
If the number is too large, the distribution density of the tubular portion 4 is correspondingly reduced, so in practice about 4 to 8 pieces are preferable. In addition, the width W4 and the depth D3 of the liquid flow groove 5 should be determined according to the outer diameter and application of the heat transfer tube and the type of heat medium.

Specifically, in the heat transfer tube of the normal size, the width W4 of the liquid flow groove 5 is 1 to 2 of the width W1 of the main groove 2.
It is desirable that the depth D3 is about double and the depth D3 is about 0.8 to 1 times the depth D1 of the main groove 2. If the width W4 is less than 1 time the width W1, the liquid diffusion preventing effect is reduced, and if it is more than 2 times the liquid diffusion preventing effect is not obtained, and the distribution density of the tubular portion 4 is relatively reduced, which is wasteful. Is. Further, when the depth D3 is less than 0.8 times the depth D1, the liquid diffusion preventing effect decreases,
Even if it is more than 1 time, a further liquid diffusion preventing effect cannot be obtained, and the strength of the metal tube 1 is lowered, which is not preferable.

Next, a method of manufacturing this heat transfer tube will be described.
First of all, as shown in FIG.
1, the auxiliary groove forming roll R2, and the diffusion preventing groove forming roll R3 are successively and continuously rolled to obtain the main groove 2, the auxiliary groove 3, and the liquid flowing groove 5.
Are formed in this order.

On the outer peripheral surface of the main groove forming roll R1, as shown in FIG. 9, a large number of projecting ridges 10 having a U-shaped cross section are formed in parallel with each other while being inclined at a constant angle with respect to the circumferential direction of the roll R1. As a result, a main groove 2 having a U-shaped cross section that is inclined with respect to the longitudinal direction is formed on the surface of the plate material 1 as shown in FIG.

Further, on the outer peripheral surface of the auxiliary groove forming roll R2,
As shown in FIG. 10, a large number of protrusions 11 having a V-shaped cross section are formed in parallel. These ridges 11 are inclined in the direction opposite to the main groove forming roll R1 with respect to the circumferential direction of the roll R2, and therefore the plate material 1 is fixed to the main groove 2 as shown in FIG. A large number of parallel sub-grooves 3 having a V-shaped cross section are formed so as to intersect at an angle α.

On the other hand, on the outer peripheral surface of the liquid flow groove forming roll R3, a plurality of protrusions (not shown) having a shape complementary to the liquid flow groove 5 are formed in the circumferential direction of the outer peripheral surface. By these ridges, each liquid flow groove 5 is further formed on the surface where the main groove 2 and the sub groove 3 are formed.

Next, after the rolling of the grooves 2, 3, 5 is completed, the plate material 1 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 strip 1 is rolled in the width direction, and finally both side edges of the strip are welded to form a circular pipe shape. A commonly used ERW device may be used, and the ERW conditions may be the same as those of normal processing. Thereafter, if necessary, the welded portion on the outer peripheral surface of the tube is shaped and then wound into a roll or cut at a predetermined length to obtain a long heat transfer tube.

According to the heat transfer tube having the above structure, the tubular portion 4 formed by the cross groove (the main groove 2 and the sub groove 3) can improve the liquid transport efficiency by the favorable evaporation promoting action and the surface tension. On the other hand, even when the flow velocity of the heat transfer liquid in the heat transfer tube is high, these liquids mainly concentrate in the liquid flow groove 5 extending in the axial direction and efficiently flow, so that the inner surface of the heat transfer tube by the tubular portion 4 It is possible to mitigate the increase in the liquid flow resistance in the vicinity, and prevent an increase in pressure loss and a decrease in heat transfer efficiency due to the liquid flow resistance.

Further, even when this heat transfer tube is used as a condenser, since the main groove 2 and the sub groove 3 are divided at a plurality of points by each liquid flow groove 5, the main groove 2 and the sub groove 3 are separated from each other. The flow of the heat medium liquid along the liquid flow groove 5 is prevented, and the liquid film does not spread over the entire inner surface of the heat transfer tube to cover the entire metal surface. Therefore, it is possible to prevent a decrease in heat transfer efficiency between the heat transfer tube and the heat transfer medium vapor due to the spread of the liquid film, and it is possible to always maintain a good heat exchange capacity.

When the cooling fin is attached to the outer peripheral surface of the heat transfer tube, the heat transfer tube is passed through the insertion hole of the cooling fin, and then the plug is inserted inside the heat transfer tube to increase the outer diameter of the heat transfer tube. Just fix the fins. At that time, in the heat transfer tube of the present invention, it is desirable to set the expansion amount of the heat transfer tube by the plug to 10% or less of the outer diameter, preferably 7% or less. If the expansion amount exceeds 10%, the tubular portion 4 may be closed and the evaporation efficiency may be reduced. When proper pipe expansion processing is performed, the opening width of the sub-groove 3 is appropriately widened, the opening width of the tubular portion 4 of the main groove 2 is narrowed, and the tube shape can be made closer to the above-mentioned bubble forming action. It is possible to promote and improve the evaporation efficiency.

In the above embodiment, the heat transfer tube has a circular cross section. However, the present invention is not limited to a circular shape, and may be an elliptical cross section or a flat tubular section. Further, in the above-described manufacturing method, the liquid flow groove 5 is formed by the roll R3, but instead of rolling by the roll R3, the liquid flow groove 5 is formed by passing the groove forming plug through the tubular body that has been subjected to the electric resistance sewing process. You may form.

[0031]

As described above, according to the inner grooved tube of the present invention, when it is used as an evaporation tube, inside the tubular portion formed between the intersections of the main groove and the auxiliary groove. Bubbles are generated vigorously, and these bubbles are quickly discharged from the open end of the tubular portion without remaining in the tubular portion, so that a good evaporation promoting action is obtained and the tubular portions are intermittently arranged. As a result, liquid transport efficiency due to surface tension can be improved, and even when the flow velocity of the heat transfer liquid in the heat transfer tube is high, these liquids mainly concentrate in the liquid flow grooves extending in the axial direction and efficiently flow. Therefore, it is possible to mitigate the increase in the liquid flow resistance in the vicinity of the inner surface of the heat transfer tube due to the tubular portion, and to prevent the increase in pressure loss and the decrease in heat transfer efficiency due to the liquid flow resistance.

Further, even when this heat transfer tube is used as a condenser, since the main groove and the sub groove are divided by the liquid flow groove, the spread of the heat medium liquid along the main groove and the sub groove flows. The groove prevents the liquid film from spreading on the entire inner surface of the heat transfer tube and covering the entire metal surface. Therefore,
It is possible to prevent a decrease in heat transfer efficiency between the heat transfer tube and the heating medium vapor due to the spread of the liquid film, and it is possible to always maintain a good heat exchange capacity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a heat transfer tube with an inner groove of the present invention.

FIG. 2 is an enlarged view showing an inner surface property of the above embodiment.

3 is an enlarged view of a cross section taken along the line AA in FIG.

FIG. 4 is an enlarged view of a cross section taken along the line BB in FIG.

5 is an enlarged view of a cross section taken along the line C-C in FIG. 2.

FIG. 6 is an enlarged view of a cross section taken along line DD in FIG.

FIG. 7 is an enlarged view of a cross section taken along line EE in FIG.

FIG. 8 is a schematic view showing a manufacturing method of the above-mentioned embodiment.

FIG. 9 is a cross-sectional view of a main groove forming roll used in the above manufacturing method.

FIG. 10 is a cross-sectional view of a sub groove forming roll used in the above manufacturing method.

FIG. 11 is an explanatory diagram showing a formation state of each of a main groove and a sub groove.

[Explanation of symbols]

 1 Metal Pipe 2 Main Groove 3 Sub Groove 4 Tubular Section 5 Flow Liquid Groove

Claims (1)

(57) [Claims] 1. A large number of parallel main grooves extending in a direction inclined with respect to the axial direction of the metal tube and a large number of parallel cuts forming a constant angle with the main groove on the inner peripheral surface of the metal tube.
A surface V-shaped sub-groove is sequentially formed, and an opening width is narrower than an inner width of the main groove along each of the main grooves between each intersection of the main groove and the sub-groove. Between the tubular portions formed along the same main groove as the tubular portion formed is formed.
Is a part with an opening width larger than the opening width of the tubular part.
A heat transfer tube with an inner surface groove, wherein the inner surface of the metal tube is formed with a liquid flow groove extending in the axial direction and intersecting both the main groove and the sub groove.